Central and Eastern United States 

Seismic Source Characterization 

for Nuclear Facilities 

Volume 5: Appendices C to F

U.S. Department of Energy

1000 Independence Avenue SW

Washington, DC 20585

Report # DOE/NE-0140

Electric Power Research Institute

3420 Hillview Avenue

Palo Alto, CA 94304

Report # 1021097

U.S. Nuclear Regulatory Commission

Offi ce of Nuclear Regulatory Research

Washington DC 20555

NUREG-2115

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Central and Eastern United States 

Seismic Source Characterization for 

Nuclear Facilities

Cosponsors

U.S. Department of Energy

1000 Independence Avenue SW

Washington, DC 20585

R. H. Lagdon, Jr.

Chief of Nuclear Safety

Office of the Under Secretary for Nuclear Security, S-5 

M.E. Shields

Project Manager

Office of Nuclear Energy, NE-72

Electric Power Research Institute

3420 Hillview Avenue

Palo Alto, CA 94304

J. F. Hamel 

Program Manager 

Advanced Nuclear Technology 

U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research

Washington DC 20555

R.G. Roche-Rivera

NRC Project Manager
DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES

EPRI DISCLAIMER

THIS DOCUMENT WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED OR 

COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEITHER 

EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR BELOW, NOR ANY PERSON ACTING ON 

BEHALF OF ANY OF THEM:

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) 

WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR 

SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS 

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(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER 

(INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE 

HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR 

SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, 

PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT.

DOE DISCLAIMER

THIS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED BY AN AGENCY OF 

THE UNITED STATES GOVERNMENT. NEITHER THE UNITED STATES GOVERNMENT NOR ANY 

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NRC DISCLAIMER

THIS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED BY AN AGENCY OF THE 

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. 
This publication is a corporate document that should be cited in the literature in the following 

manner:

Technical Report: Central and Eastern United States Seismic Source Characterization for 

Nuclear Facilities. EPRI, Palo Alto, CA, U.S. DOE, and U.S. NRC: 2012. 

iii

SPONSORS’ ACKNOWLEDGMENTS 

The project sponsors would like to acknowledge the following individuals for directing the 

project: 

Coppersmith Consulting, Inc. 

2121 N. California Blvd., #290 

Walnut Creek, CA 94596 

Technical Integration (TI) Lead

K.J. Coppersmith 

Savannah River Nuclear Solutions, LLC 

Savannah River Site 

Building 730-4B, Room 313 

Aiken, SC 29808 

CEUS SSC Project Manager

L.A. Salomone 

This document describes research sponsored by the Electric Power Research Institute (EPRI), 

U.S. Department of Energy (U.S. DOE) under Award Number DE-FG07-08ID14908, and the 

U.S. Nuclear Regulatory Commission (U.S. NRC) under Award Number NCR-04-09-144. 

v 

AUTHORS

This document was prepared by the following investigators: 

Technical Integration Lead Kevin J. Coppersmith

Project Manager Lawrence A. Salomone

Technical Integration Team Chris W. Fuller

Laura L. Glaser

Kathryn L. Hanson

Ross D. Hartleb

William R. Lettis

Scott C. Lindvall

Stephen M. McDuffie

Robin K. McGuire

Gerry L. Stirewalt

Gabriel R. Toro

Robert R. Youngs

Database Manager David L. Slayter

Technical Support Serkan B. Bozkurt

Randolph J. Cumbest

Valentina Montaldo Falero 

Roseanne C. Perman

Allison M. Shumway

Frank H. Syms

Martitia (Tish) P. Tuttle, Paleoliquefaction Data 

Resource

NUREG-2115 DOE/NE-0140 EPRI 1021097

vii 

This document has been

reproduced from the best available copy.

 

ix

ABSTRACT

This report describes a new seismic source characterization (SSC) model for the Central and 

Eastern United States (CEUS). It will replace the Seismic Hazard Methodology for the Central 

and Eastern United States, EPRI Report NP-4726 (July 1986) and the Seismic Hazard 

Characterization of 69 Nuclear Plant Sites East of the Rocky Mountains, Lawrence Livermore 

National Laboratory Model, (Bernreuter et al., 1989). The objective of the CEUS SSC Project is 

to develop a new seismic source model for the CEUS using a Senior Seismic Hazard Analysis 

Committee (SSHAC) Level 3 assessment process. The goal of the SSHAC process is to represent 

the center, body, and range of technically defensible interpretations of the available data, models, 

and methods. Input to a probabilistic seismic hazard analysis (PSHA) consists of both seismic 

source characterization and ground motion characterization. These two components are used to 

calculate probabilistic hazard results (or seismic hazard curves) at a particular site. This report 

provides a new seismic source model. 

Results and Findings

The product of this report is a regional CEUS SSC model. This model includes consideration of 

an updated database, full assessment and incorporation of uncertainties, and the range of diverse 

technical interpretations from the larger technical community. The SSC model will be widely 

applicable to the entire CEUS, so this project uses a ground motion model that includes generic 

variations to allow for a range of representative site conditions (deep soil, shallow soil, hard 

rock). Hazard and sensitivity calculations were conducted at seven test sites representative of 

different CEUS hazard environments. 

Challenges and Objectives

The regional CEUS SSC model will be of value to readers who are involved in PSHA work, and 

who wish to use an updated SSC model. This model is based on a comprehensive and traceable 

process, in accordance with SSHAC guidelines in NUREG/CR-6372, Recommendations for 

Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and Use of Experts. The model 

will be used to assess the present-day composite distribution for seismic sources along with their 

characterization in the CEUS and uncertainty. In addition, this model is in a form suitable for use 

in PSHA evaluations for regulatory activities, such as Early Site Permit (ESPs) and Combined 

Operating License Applications (COLAs).

Applications, Values, and Use

Development of a regional CEUS seismic source model will provide value to those who (1) have 

submitted an ESP or COLA for Nuclear Regulatory Commission (NRC) review before 2011; (2) 

will submit an ESP or COLA for NRC review after 2011; (3) must respond to safety issues 

resulting from NRC Generic Issue 199 (GI-199) for existing plants and (4) will prepare PSHAs 

to meet design and periodic review requirements for current and future nuclear facilities. This 

work replaces a previous study performed approximately 25 years ago. Since that study was 
x 

completed, substantial work has been done to improve the understanding of seismic sources and 

their characterization in the CEUS. Thus, a new regional SSC model provides a consistent, stable 

basis for computing PSHA for a future time span. Use of a new SSC model reduces the risk of 

delays in new plant licensing due to more conservative interpretations in the existing and future 

literature.

Perspective

The purpose of this study, jointly sponsored by EPRI, the U.S. Department of Energy (DOE), 

and the NRC was to develop a new CEUS SSC model. The team assembled to accomplish this 

purpose was composed of distinguished subject matter experts from industry, government, and 

academia. The resulting model is unique, and because this project has solicited input from the 

present-day larger technical community, it is not likely that there will be a need for significant 

revision for a number of years. See also Sponsors’ Perspective for more details.

Approach

The goal of this project was to implement the CEUS SSC work plan for developing a regional 

CEUS SSC model. The work plan, formulated by the project manager and a technical integration 

team, consists of a series of tasks designed to meet the project objectives. This report was 

reviewed by a participatory peer review panel (PPRP), sponsor reviewers, the NRC, the U.S. 

Geological Survey, and other stakeholders. Comments from the PPRP and other reviewers were 

considered when preparing the report. The SSC model was completed at the end of 2011. 

Keywords

Probabilistic seismic hazard analysis (PSHA)

Seismic source characterization (SSC)

Seismic source characterization model

Central and Eastern United States (CEUS)
xi 

CONTENTS

Abstract........................................................................................................................................ ix

Contents ....................................................................................................................................... xi 

List of Figures ............................................................................................................................xxv

List of Tables........................................................................................................................... lxxvii

Executive Summary ................................................................................................................lxxxv

Participatory Peer Review Panel Final Report Dated October 24, 2011 ...................................xcv

Project Acknowledgements.........................................................................................................ciii

Sponsor’s Perspective ................................................................................................................ cv

Abbreviations ..............................................................................................................................cix 

1 INTRODUCTION .................................................................................................................... 1-1 

1.1 Background and History.................................................................................................. 1-1 

1.1.1 EPRI-SOG and LLNL Projects ................................................................................ 1-2 

1.1.2 Development of the SSHAC Process ..................................................................... 1-2 

1.1.3 Implementation of the SSHAC Methodology .......................................................... 1-3 

1.1.4 Regional SSC Model for Nuclear Facilities.............................................................. 1-3 

1.1.5 Differences from USGS National Seismic Hazard Mapping Project........................ 1-4 

1.2 Purpose of the CEUS SSC Project ................................................................................. 1-5 

1.2.1 Implementation of SSHAC Level 3 Process ............................................................ 1-6 

1.2.2 Goals: Stability and Longevity ................................................................................. 1-8 

1.2.3 Interface with Ground Motion Models...................................................................... 1-8 

1.3 Study Region................................................................................................................. 1-10

1.4 Products of Project........................................................................................................ 1-10

1.4.1 Seismic Source Model for Study Region ............................................................... 1-10

1.4.2 Hazard Input Document......................................................................................... 1-12

1.4.3 Documentation of Technical Bases for All Assessments ...................................... 1-12

1.4.4 Other Key Products ............................................................................................... 1-13

1.4.4.1 Data Evaluation and Data Summary Tables.................................................. 1-13
xii 

1.4.4.2 Database of Geologic, Geophysical, and Seismological Data....................... 1-13

1.4.4.3 Earthquake Catalog with Uniform Moment Magnitudes................................. 1-13

1.4.4.4 Updated Paleoseismicity Data and Guidance................................................ 1-14

1.4.4.5 Recommendations for Future Applications of SSC Model............................. 1-14

2 SSHAC LEVEL 3 ASSESSMENT PROCESS AND IMPLEMENTATION ............................. 2-1 

2.1 Goals and Activities of a SSHAC Assessment Process.................................................. 2-2 

2.1.1 Evaluation................................................................................................................ 2-4 

2.1.2 Integration ............................................................................................................... 2-4 

2.2 Roles of CEUS SSC Project Participants........................................................................ 2-5 

2.3 CEUS SSC Project Organization .................................................................................... 2-7 

2.4 Key Tasks and Activities ................................................................................................. 2-9 

2.4.1 Database Development ........................................................................................... 2-9 

2.4.2 Identification of Significant Issues ......................................................................... 2-10

2.4.3 Workshop #1—Key Issues and Available Data ..................................................... 2-10

2.4.4 Workshop #2—Alternative Interpretations............................................................. 2-12

2.4.5 Working Meetings.................................................................................................. 2-13

2.4.6 SSC Sensitivity Model Development ..................................................................... 2-14

2.4.7 Workshop #3—Feedback ...................................................................................... 2-15

2.4.8 SSC Preliminary Model Development ................................................................... 2-16

2.4.9 Finalization and Review of SSC Draft and Final Model......................................... 2-17

2.4.10 Documentation .................................................................................................... 2-19

2.4.10.1 Development of the Hazard Input Document............................................... 2-19

2.4.10.2 Development of Earlier Draft Report............................................................ 2-19

2.4.10.3 Draft Report Review..................................................................................... 2-19

2.4.10.4 Final Report Development ........................................................................... 2-20

2.5 Participatory Peer Review Panel................................................................................... 2-20

2.5.1 Roles and Responsibilities .................................................................................... 2-20

2.5.2 Reviews and Feedback ........................................................................................ 2-20

2.5.3 Fulfillment of SSHAC-Prescribed Scope of Review of Both Technical and 

Process Issues .............................................................................................................. 2-21

2.6 Consistency of CEUS SSC Assessment Process with SSHAC Guidelines .................. 2-22

3 EARTHQUAKE CATALOG.................................................................................................... 3-1 

3.1 Goals for the Earthquake Catalog Development............................................................. 3-1 

3.1.1 Completeness.......................................................................................................... 3-1 
xiii

3.1.2 Uniformity of Catalog Processing ............................................................................ 3-2 

3.1.3 Catalog Review ....................................................................................................... 3-3 

3.2 Catalog Compilation........................................................................................................ 3-4 

3.2.1 Continental-Scale Catalogs ..................................................................................... 3-5 

3.2.2 Regional Catalogs ................................................................................................... 3-7 

3.2.3 Catalogs from Special Studies ................................................................................ 3-7 

3.2.4 Focal Depth Data..................................................................................................... 3-8 

3.2.5 Nontectonic Events.................................................................................................. 3-9 

3.2.6 Identification of Unique Earthquake Entries ............................................................ 3-9 

3.3 Development of a Uniform Moment Magnitude Earthquake Catalog............................ 3-11

3.3.1 Approach for Uniform Magnitude and Unbiased Recurrence Estimation .............. 3-11

3.3.2 Estimation of E[M] for the CEUS SSC Project Catalog ......................................... 3-19

3.3.2.1 Effect of Magnitude Rounding on Statistical Tests ........................................ 3-19

3.3.2.2 Moment Magnitude Data................................................................................ 3-20

3.3.2.3 Estimation of E[M] from Body-Wave Magnitudes .......................................... 3-22

3.3.2.4 Estimation of E[M] from ML Magnitudes......................................................... 3-28

3.3.2.5 Estimation of E[M] from MS Magnitudes ........................................................ 3-29

3.3.2.6 Estimation of E[M] from MC and MD Magnitudes............................................ 3-30

3.3.2.7 Estimation of E[M] from the Logarithm of Felt Area....................................... 3-32

3.3.2.8 Estimation of E[M] from the Maximum Intensity, I0 ........................................ 3-32

3.3.2.9 Uniform Moment Magnitude Catalog of E[M] and N* Values......................... 3-36

3.4 Identification of Independent Earthquakes.................................................................... 3-37

3.5 Catalog Completeness.................................................................................................. 3-39

4 CONCEPTUAL SEISMIC SOURCE CHARACTERIZATION FRAMEWORK........................ 4-1 

4.1 Needs for a Conceptual SSC Framework ....................................................................... 4-2 

4.1.1 Logic Tree Approach to Representing Alternatives and Assessing 

Uncertainties........................................................................................................ 4-2 

4.1.1.1 Examples of Logic Trees ................................................................................. 4-3 

4.1.1.2 Assigning Weights to Logic Tree Branches ..................................................... 4-3 

4.1.2 Data Identification and Evaluation ........................................................................... 4-5 

4.1.2.1 “Generic” Data Identification to Address Indicators of a Seismic Source ........ 4-5 

4.1.2.2 Data Evaluation for Particular Seismic Sources: Data Evaluation and 

Data Summary Tables ................................................................................................. 4-7 

4.1.3 Methodology for Identifying Seismic Sources.......................................................... 4-9 
xiv 

4.1.3.1 Hazard-Informed Approach ........................................................................... 4-11

4.1.3.2 Conclusions Regarding the Hazard Significance of Various SSC Issues...... 4-13

4.1.3.3 Criteria for Defining Seismic Sources ............................................................ 4-14

4.2 Master Logic Tree ......................................................................................................... 4-18

4.2.1 Description of Logic Tree Elements....................................................................... 4-18

4.2.2 RLME Source Logic Tree ...................................................................................... 4-20

4.2.3 Mmax Zones Logic Tree........................................................................................ 4-22

4.2.4 Seismotectonic Zones Branch............................................................................... 4-24

5 SSC MODEL: OVERVIEW AND METHODOLOGY............................................................... 5-1 

5.1 Overview of Spatial and Temporal Models...................................................................... 5-1 

5.1.1 Spatial Model Considerations.................................................................................. 5-1 

5.1.2 Considerations Regarding Temporal Models .......................................................... 5-3 

5.1.3 Perspective on CEUS SSC Models......................................................................... 5-4 

5.2 Maximum Earthquake Magnitude Assessment............................................................... 5-5 

5.2.1 Approaches to Mmax Estimation in the CEUS........................................................ 5-6 

5.2.1.1 Bayesian Mmax Approach............................................................................... 5-8 

5.2.1.2 Kijko Approach to Mmax Assessment ........................................................... 5-17

5.2.1.3 Weights for the Alternative Mmax Approaches.............................................. 5-20

5.2.1.4 Example Mmax Distributions ......................................................................... 5-20

5.2.2 Other Mmax Issues .............................................................................................. 5-21

5.3 Earthquake Recurrence Assessment............................................................................ 5-22

5.3.1 Smoothing to Represent Spatial Stationarity......................................................... 5-22

5.3.2 Smoothing Approach............................................................................................. 5-23

5.3.2.1 Development of Penalized-Likelihood Approach and Formulation ................ 5-23

5.3.2.2 Application of the Model and Specification of Model Parameters.................. 5-36

5.3.2.3 Exploration of Model Results in Parameter Space ........................................ 5-40

5.3.2.4 Consideration of Constant b-Value Kernel Approaches ................................ 5-42

5.3.2.5 Comparison to EPRI-SOG Approach............................................................. 5-45

5.3.2.6 Assessment of the Lombardi Study ............................................................... 5-46

5.3.3 Estimation of Recurrence for RLME Sources ........................................................ 5-47

5.3.3.1 Estimation of Occurrence Rates for the Poisson Model ................................ 5-48

5.3.3.2 Estimation of Occurrence Rates for a Renewal Model .................................. 5-51

5.3.3.3 Incorporating Uncertainty in the Input............................................................ 5-52

5.3.3.4 RLME Magnitude Distribution ........................................................................ 5-53
xv 

5.4 Assessment of Future Earthquake Characteristics ....................................................... 5-54

5.4.1 Tectonic Stress Regime ........................................................................................ 5-55

5.4.2 Sense of Slip/Style of Faulting............................................................................... 5-55

5.4.3 Strike and Dip of Ruptures .................................................................................... 5-55

5.4.4 Seismogenic Crustal Thickness ........................................................................... 5-56

5.4.5 Fault Rupture Area ................................................................................................ 5-57

5.4.6 Rupture Length-to-Width Aspect Ratio.................................................................. 5-57

5.4.7 Relationship of Rupture to Source Zone Boundaries ............................................ 5-58

5.5 Predicted Seismic Moment Rate................................................................................... 5-58

6 SSC MODEL: RLME SOURCES AND MMAX ZONES BRANCH......................................... 6-1 

6.1 RLME Sources ................................................................................................................ 6-1 

6.1.1 Charlevoix................................................................................................................ 6-3 

6.1.1.1 Evidence for Temporal Clustering.................................................................... 6-4 

6.1.1.2 Localizing Tectonic Features ........................................................................... 6-4 

6.1.1.3 Geometry and Style of Faulting ....................................................................... 6-5 

6.1.1.4 RLME Magnitude ............................................................................................. 6-7 

6.1.1.5 RLME Recurrence ........................................................................................... 6-8 

6.1.2 Charleston ............................................................................................................. 6-10

6.1.2.1 Evidence for Temporal Clustering.................................................................. 6-11

6.1.2.2 Localizing Feature ......................................................................................... 6-12

6.1.2.3 Geometry and Style of Faulting ..................................................................... 6-12

6.1.2.4 RLME Magnitude ........................................................................................... 6-15

6.1.2.5 RLME Recurrence ......................................................................................... 6-17

6.1.3 Cheraw Fault ........................................................................................................ 6-22

6.1.3.1 Evidence for Temporal Clustering.................................................................. 6-23

6.1.3.2 Geometry and Style of Faulting ..................................................................... 6-24

6.1.3.3 RLME Magnitude ........................................................................................... 6-25

6.1.3.4 RLME Recurrence ......................................................................................... 6-26

6.1.4 Meers Fault............................................................................................................ 6-28

6.1.4.1 Evidence for Temporal Clustering.................................................................. 6-29

6.1.4.2 Localizing Feature ......................................................................................... 6-29

6.1.4.3 Geometry and Style of Faulting ..................................................................... 6-30

6.1.4.4 RLME Magnitude ........................................................................................... 6-31

6.1.4.5 RLME Recurrence ......................................................................................... 6-34
xvi 

6.1.5 Reelfoot Rift–New Madrid Fault System ............................................................... 6-35

6.1.5.1 Evidence for Temporal Clustering.................................................................. 6-40

6.1.5.2 Geometry and Style of Faulting ..................................................................... 6-42

6.1.5.3 RLME Magnitude ........................................................................................... 6-44

6.1.5.4 RLME Recurrence ......................................................................................... 6-47

6.1.6 Reelfoot Rift—Eastern Rift Margin Fault ............................................................... 6-50

6.1.6.1 Evidence for Temporal Clustering.................................................................. 6-53

6.1.6.2 Geometry and Style of Faulting ..................................................................... 6-53

6.1.6.3 RLME Magnitude ........................................................................................... 6-54

6.1.6.4 RLME Recurrence ......................................................................................... 6-56

6.1.7 Reelfoot Rift—Marianna ....................................................................................... 6-57

6.1.7.1 Evidence for Temporal Clustering.................................................................. 6-58

6.1.7.2 Geometry and Style of Faulting ..................................................................... 6-59

6.1.7.3 RLME Magnitude ........................................................................................... 6-60

6.1.7.4 RLME Recurrence ......................................................................................... 6-61

6.1.8 Reelfoot Rift—Commerce Fault Zone .................................................................. 6-62

6.1.8.1 Evidence for Temporal Clustering.................................................................. 6-63

6.1.8.2 Geometry and Style of Faulting ..................................................................... 6-64

6.1.8.3 RLME Magnitude ........................................................................................... 6-65

6.1.8.4 RLME Recurrence ......................................................................................... 6-66

6.1.9 Wabash Valley ...................................................................................................... 6-68

6.1.9.1 Evidence for Temporal Clustering.................................................................. 6-69

6.1.9.2 Geometry and Style of Faulting ..................................................................... 6-69

6.1.9.3 RLME Magnitude ........................................................................................... 6-72

6.1.9.4 RLME Recurrence ......................................................................................... 6-73

6.2 Mmax Distributed Seismicity Source Zones.................................................................. 6-74

6.2.1 Definition of Mmax Zones ..................................................................................... 6-74

6.2.2 Criteria for Defining the MESE/NMESE Boundary ............................................... 6-75

6.3 Maximum Magnitude Distributions for Mmax Distributed Seismicity Sources............... 6-76

6.3.1 Maximum Observed Earthquake Magnitude ......................................................... 6-76

6.3.2 Mmax Distributions ................................................................................................ 6-77

6.4 Recurrence Parameters ................................................................................................ 6-78

6.4.1 Rate and b-Value Maps for Single Zone and Two Zones...................................... 6-78

6.4.2 Comparison of Recurrence Parameters to Catalog............................................... 6-79
xvii 

7 SSC MODEL: SEISMOTECTONIC ZONES BRANCH .......................................................... 7-1 

7.1 Approaches and Data Used to Define Seismotectonic Zones ........................................ 7-1 

7.2 RLME Sources in the Seismotectonic Zones Branch...................................................... 7-4 

7.3 Seismotectonic Source Zones......................................................................................... 7-4 

7.3.1 St. Lawrence Rift Zone (SLR) ................................................................................. 7-4 

7.3.1.1 Background...................................................................................................... 7-5 

7.3.1.2 Basis for Defining Seismotectonic Zone ........................................................ 7-11

7.3.1.3 Basis for Zone Geometry............................................................................... 7-12

7.3.1.4 Basis for Zone Mmax..................................................................................... 7-12

7.3.1.5 Future Earthquake Characteristics ................................................................ 7-13

7.3.2 Great Meteor Hotspot Zone (GMH) ...................................................................... 7-15

7.3.2.1 Background.................................................................................................... 7-16

7.3.2.2 Basis for Defining Seismotectonic Zone ........................................................ 7-18

7.3.2.3 Basis for Zone Geometry............................................................................... 7-19

7.3.2.4 Basis for Zone Mmax..................................................................................... 7-19

7.3.2.5 Future Earthquake Characteristics ................................................................ 7-20

7.3.3 Northern Appalachian Zone (NAP) ....................................................................... 7-21

7.3.3.1 Background.................................................................................................... 7-21

7.3.3.2 Basis for Defining Seismotectonic Zone ........................................................ 7-23

7.3.3.3 Basis for Zone Geometry............................................................................... 7-24

7.3.3.4 Basis for Zone Mmax..................................................................................... 7-24

7.3.3.5 Future Earthquake Characteristics ................................................................ 7-25

7.3.4 Paleozoic Extended Crust (PEZ)........................................................................... 7-25

7.3.4.1 Background.................................................................................................... 7-26

7.3.4.2 Basis for Defining Seismotectonic Zone ........................................................ 7-32

7.3.4.3 Basis for Zone Geometry............................................................................... 7-33

7.3.4.4 Basis for Zone Mmax..................................................................................... 7-34

7.3.4.5 Future Earthquake Characteristics ............................................................... 7-36

7.3.5 Ilinois Basin Extended Basement Zone (IBEB) ..................................................... 7-37

7.3.5.1 Background.................................................................................................... 7-38

7.3.5.2 Basis for Defining Seismotectonic Zone ........................................................ 7-38

7.3.5.3 Basis for Zone Geometry............................................................................... 7-40

7.3.5.4 Basis for Zone Mmax..................................................................................... 7-41

7.3.5.5 Future Earthquake Characteristics ................................................................ 7-41

7.3.6 Reelfoot Rift Zone (RR)......................................................................................... 7-42
xviii 

7.3.6.1 Background.................................................................................................... 7-42

7.3.6.2 Basis for Defining Seismotectonic Zone ........................................................ 7-46

7.3.6.3 Basis for Zone Geometry............................................................................... 7-46

7.3.6.4 Basis for Zone Mmax..................................................................................... 7-47

7.3.6.5 Future Earthquake Characteristics ................................................................ 7-48

7.3.7 Extended Continental Crust–Atlantic Margin Zone (ECC-AM) .............................. 7-48

7.3.7.1 Background.................................................................................................... 7-49

7.3.7.2 Basis for Defining Seismotectonic Zone ........................................................ 7-53

7.3.7.3 Basis for Geometry ........................................................................................ 7-54

7.3.7.4 Basis for Mmax .............................................................................................. 7-54

7.3.7.5 Future Earthquake Characteristics ................................................................ 7-55

7.3.8 Atlantic Highly Extended Crust Zone (AHEX)........................................................ 7-55

7.3.8.1 Basis for Defining Seismotectonic Zone ........................................................ 7-56 

7.3.8.2 Basis for Geometry ........................................................................................ 7-57

7.3.8.3 Basis for Mmax .............................................................................................. 7-57

7.3.8.4 Future Earthquake Characteristics ................................................................ 7-57

7.3.9 Extended Continental Crust–Gulf Coast Zone (ECC-GC)..................................... 7-58

7.3.9.1 Basis for Defining Seismotectonic Zone ........................................................ 7-58

7.3.9.2 Basis for Zone Geometry............................................................................... 7-59

7.3.9.3 Basis for Zone Mmax..................................................................................... 7-62

7.3.9.4 Future Earthquake Characteristics ................................................................ 7-63

7.3.9.5 Possible Paleoliquefaction Features in Arkansas, Louisiana, and 

Mississippi ................................................................................................................. 7-64

7.3.10 Gulf Coast Highly Extended Crust Zone (GHEX)................................................ 7-65

7.3.10.1 Basis for Defining Seismotectonic Zone ...................................................... 7-66

7.3.10.2 Basis for Zone Geometry............................................................................. 7-66

7.3.10.3 Basis for Zone Mmax................................................................................... 7-66

7.3.10.4 Future Earthquake Characteristics .............................................................. 7-67

7.3.11 Oklahoma Aulacogen Zone (OKA)...................................................................... 7-68 

7.3.11.1 Basis for Defining Seismotectonic Zone ...................................................... 7-69

7.3.11.2 Basis for Zone Geometry............................................................................. 7-69

7.3.11.3 Basis for Zone Mmax................................................................................... 7-70

7.3.11.4 Future Earthquake Characteristics .............................................................. 7-70

7.3.12 Midcontinent-Craton Zone (MidC) ....................................................................... 7-70

7.3.12.1 Background.................................................................................................. 7-71
xix 

7.3.12.2 Basis for Defining Seismotectonic Zone ...................................................... 7-76

7.3.12.3 Basis for Zone Geometry............................................................................. 7-77

7.3.12.4 Basis for Zone Mmax................................................................................... 7-77

7.3.12.5 Future Earthquake Characteristics .............................................................. 7-77

7.4 Maximum Magnitude Distributions for Seismotectonic Distributed Seismicity 

Sources ............................................................................................................................... 7-78

7.4.1 Maximum Observed Earthquake Magnitude ......................................................... 7-78

7.4.2 Mmax Distributions ................................................................................................ 7-79

7.5 Recurrence Parameters ................................................................................................ 7-80

7.5.1 Rate and b-Value Maps for Single Zone and Two Zones...................................... 7-80

7.5.2 Comparison of Recurrence Parameters to Catalog............................................... 7-80

8 DEMONSTRATION HAZARD CALCULATIONS................................................................... 8-1 

8.1 Background on Demonstration Hazard Calculations....................................................... 8-1 

8.2 Demonstration Hazard Calculations................................................................................ 8-2 

8.2.1 Central Illinois Site................................................................................................... 8-4 

8.2.2 Chattanooga Site..................................................................................................... 8-5 

8.2.3 Houston Site............................................................................................................ 8-6 

8.2.4 Jackson Site ............................................................................................................ 8-7 

8.2.5 Manchester Site....................................................................................................... 8-9 

8.2.6 Savannah Site ......................................................................................................... 8-9 

8.2.7 Topeka Site ........................................................................................................... 8-10

9 USE OF THE CEUS SSC MODEL IN PSHA ......................................................................... 9-1 

9.1 Overview ......................................................................................................................... 9-1 

9.2 Hazard Input Document (HID)......................................................................................... 9-2 

9.3 Implementation Instructions ............................................................................................ 9-2

9.3.1 Simplifications to Seismic Sources.......................................................................... 9-2 

9.3.1.1 Charleston RLME............................................................................................. 9-3 

9.3.1.2 Charlevoix RLME............................................................................................. 9-3 

9.3.1.3 Cheraw RLME ................................................................................................. 9-4 

9.3.1.4 Commerce Fault Zone RLME .......................................................................... 9-5 

9.3.1.5 Eastern Rift Margin North RLME ..................................................................... 9-5 

9.3.1.6 Eastern Rift Margin South RLME..................................................................... 9-5 

9.3.1.7 Marianna RLME............................................................................................... 9-6 

9.3.1.8 Meers RLME.................................................................................................... 9-6 
xx 

9.3.1.9 New Madrid Fault System RLME..................................................................... 9-7 

9.3.1.10 Wabash Valley RLME.................................................................................... 9-7 

9.3.1.11 Background Sources...................................................................................... 9-8 

9.3.2 Accessing the SSC Model and Components from the Website .............................. 9-8 

9.3.3 Accessing Project Databases.................................................................................. 9-9 

9.3.4 Use of SSC Model with Site-Specific Refinements ............................................... 9-10

9.4 Hazard Significance ...................................................................................................... 9-10

9.4.1 Data Available to Evaluate the Precision of Seismic Hazard Estimates................ 9-10

9.4.2 Observed Imprecision in Seismic Hazard Estimates............................................. 9-11

9.4.2.1 Area Seismic Sources.................................................................................... 9-11

9.4.2.2 RLME Seismic Sources ................................................................................. 9-12

9.4.2.3 Ground Motion Equations .............................................................................. 9-15

9.4.2.4 Site Response ............................................................................................... 9-19

9.4.3 Conclusions on the Precision in Seismic Hazard Estimates ................................. 9-19

10 REFERENCES ...................................................................................................................10-1 

11 GLOSSARY OF KEY TERMS ............................................................................................11-1 

A DESCRIPTION OF THE CEUS SSC PROJECT DATABASE ............................................. A-1 

A.1 Data Sources ................................................................................................................. A-2 

A.2 Project Database Design and Management .................................................................. A-3 

A.3 Workflow and Data Assessment.................................................................................... A-3 

A.3.1 Workflow ................................................................................................................ A-3 

A.3.2 Digital Data............................................................................................................. A-4 

A.3.3 Nondigital Data ...................................................................................................... A-4 

A.4 Use of Project Database in Model Development .......................................................... A-5 

A.5 Metadata........................................................................................................................ A-5 

A.6 Database Delivery Format ............................................................................................. A-6 

B EARTHQUAKE CATALOG DATABASE ............................................................................. B-1 

B.1 CEUS SSC Uniform Moment Magnitude Earthquake Catalog ...................................... B-1 

B.2 Moment Magnitude Data................................................................................................ B-2 

B.3 Approximate Moment Magnitude Data .......................................................................... B-3 

B.4 CEUS SSC Project Data................................................................................................ B-3 
xxi 

C DATA EVALUATION TABLES ............................................................................................. C-1 

Introduction .......................................................................................................................... C-2 

D DATA SUMMARY TABLES ................................................................................................. D-1 

Introduction .......................................................................................................................... D-2 

E CEUS PALEOLIQUEFACTION DATABASE, UNCERTAINTIES ASSOCIATED WITH 

PALEOLIQUEFACTION DATA, AND GUIDANCE FOR SEISMIC SOURCE 

CHARACTERIZATION.............................................................................................................. E-i

E.1 Development of the Paleoliquefaction Database........................................................... E-1 

E.1.1 Database Structure ................................................................................................ E-1 

E.1.2 Regional Data Sets ................................................................................................ E-4 

E.2 Uncertainties Associated with Paleoliquefaction Data ................................................ E-24

E.2.1 Collection of Paleoliquefaction Data ................................................................... E-24

E.2.2 Uncertainties Related to Interpretation of Paleoliquefaction Data........................ E-35

E.2.3 Recommendations for Future Research .............................................................. E-43 

 E.3 Guidance for the Use of Paleoliquefaction Data in Seismic Source

Characterization...................................................................................................................... E-44

E.4 Glossary....................................................................................................................... E-46

E.5 References .................................................................................................................. E-49

E.5.1 References Cited in Paleoliquefaction Database ................................................ E-49

E.5.2 References Cited in Appendix E .......................................................................... E-54

F WORKSHOP SUMMARIES ................................................................................................... F-1 

WORKSHOP 1: KEY ISSUES AND AVAILABLE DATA

DAY 1–TUESDAY, JULY 22, 2008 ....................................................................................... F-1 

DAY 2–WEDNESDAY, JULY 23, 2008............................................................................... F-10

REFERENCES .................................................................................................................... F-17

WORKSHOP 2: ALTERNATIVE INTERPRETATIONS

DAY 1–WEDNESDAY, FEBRUARY 18, 2009 .....................................................................F18

DAY 2–THURSDAY, FEBRUARY 19, 2009........................................................................ F-24

DAY 3–FRIDAY, FEBRUARY 20, 2009 .............................................................................. F-29

REFERENCES .................................................................................................................. F-34

WORKSHOP 3: FEEDBACK

DAY 1–TUESDAY, AUGUST 25, 2009............................................................................... F-42

DAY 2–WEDNESDAY, AUGUST 26, 2009......................................................................... F-49
xxii 

G BIOGRAPHIES OF PROJECT TEAM.................................................................................. G-1 

EPRI MANAGEMENT .......................................................................................................... G-2 

PROJECT MANAGER ......................................................................................................... G-2 

TI TEAM ............................................................................................................................... G-3 

TECHNICAL SUPPORT....................................................................................................... G-7 

DATABASE MANAGER....................................................................................................... G-9 

PARTICIPATORY PEER REVIEW PANEL.......................................................................... G-9 

SPONSOR REVIEWERS................................................................................................... G-14

H CEUS SSC MODEL HAZARD INPUT DOCUMENT (HID)................................................... H-1 

H.1 Introduction.................................................................................................................... H-1 

H.2 Seismic Source Model Structure and Master Logic Tree .............................................. H-1 

H.3 Mmax Zones Distributed Seismicity Sources ................................................................ H-2 

H.3.1 Division of Study Region ....................................................................................... H-2 

H.3.2 Location of Boundary of Mesozoic Extension ....................................................... H-2 

H.3.3 Magnitude Interval Weights for Fitting Earthquake Occurrence Parameters ........ H-2 

H.3.4 Mmax Zones ......................................................................................................... H-2 

H.3.5 Seismogenic Crustal Thickness ............................................................................ H-2 

H.3.6 Future Earthquake Rupture Characteristics .......................................................... H-3 

H.3.7 Assessment of Seismicity Rates ........................................................................... H-3 

H.3.8 Degree of Smoothing Applied in Defining Spatial Smoothing of Seismicity 

Rates ............................................................................................................................... H-3 

H.3.9 Uncertainty in Earthquake Recurrence Rates........................................................ H-3 

H.3.10 Uncertainty in Maximum Magnitude..................................................................... H-4 

H.4 Seismotectonic Zones ................................................................................................... H-4 

H.4.1 Alternative Zonation Models .................................................................................. H-4 

H.4.2 Magnitude Interval Weights for Fitting Earthquake Occurrence Parameters ......... H-4 

H.4.3 Seismotectonic Zones............................................................................................ H-5 

H.4.4 Seismogenic Crustal Thickness............................................................................. H-5 

H.4.5 Future Earthquake Rupture Characteristics .......................................................... H-5 

H.4.6 Assessment of Seismicity Rates ........................................................................... H-5 

H.4.7 Degree of Smoothing Applied in Defining Spatial Smoothing of Seismicity 

Rates .............................................................................................................................. H-5 

H.4.8 Uncertainty in Earthquake Recurrence Rates ....................................................... H-5 

H.4.9 Uncertainty in Maximum Magnitude ...................................................................... H-6 

H.5 RLME Sources ....................................................................................................H-6 
xxiii 

H.5.1 Charlevoix RLME Seismic Source Model ............................................................. H-6 

H.5.2 Charleston RLME Seismic Source Model.............................................................. H-7 

H.5.3 Cheraw RLME Seismic Source Model................................................................... H-9 

H.5.4 Meers RLME Seismic Source Model ................................................................... H-11

H.5.5 New Madrid Fault System RLME Seismic Source Model .................................... H-12

H.5.6 Eastern Rift Margin Fault RLME Seismic Source Model ..................................... H-14

H.5.7 Marianna Zone RLME Seismic Source Model ..................................................... H-15

H.5.8 Commerce Fault RLME Seismic Source Model................................................... H-16

H.5.9 Wabash Valley RLME Seismic Source Model ..................................................... H-18

I PPRP REVIEW COMMENTS................................................................................................... I-1 

CORRESPONDENCE—CONTENTS .................................................................................... I-3 

Participatory Peer Review Panel (PPRP) Letters.............................................................. I-3 

Technical Integration (TI) Team and Project Manager (PM) Response to PPRP 

Letters................................................................................................................................ I-4 

J MAGNITUDE-RECURRENCE MAPS FOR ALL REALIZATIONS AND ALL 

SOURCE-ZONE CONFIGURATIONS....................................................................................... J-1 

K SCR DATABASE USED TO DEVELOP MMAX PRIOR DISTRIBUTIONS ......................... K-1 

K.1 SCR Earthquake Catalog............................................................................................... K-1 

K.2 SCR Crustal Domains.................................................................................................... K-3 

L QUALITY ASSURANCE ........................................................................................................ L-1 

L.1 BACKGROUND............................................................................................................... L-1 

L.2 CEUS SSC PROJECT .................................................................................................... L-2 

L.2.1 Introduction.............................................................................................................. L-2 

L.3 BEST BUSINESS PRACTICES ...................................................................................... L-3 

L.3.1 General.................................................................................................................... L-3 

L.4 CEUS SSC EARTHQUAKE CATALOG DEVELOPMENT.............................................. L-3 

L.4.1 External Review of Earthquake Catalog.................................................................. L-3 

L.4.2 Simulation Testing................................................................................................... L-4 

L.4.3 Checks for Consistency in Magnitude Conversion from Intensity ........................... L-4 

L.4.4 Use of Verified Computer Programs........................................................................ L-4 

L.5 RECURRENCE ANALYSIS AND SPATIAL SMOOTHING............................................. L-4 

L.5.1 Introduction.............................................................................................................. L-4 

L.5.2 Recurrence Comparisons at the Source-Zone Level .............................................. L-5 
xxiv 

L.5.3 Recurrence Comparisons for Portions of a Source Zone ....................................... L-5 

L.5.4 Examination of Recurrence Maps .......................................................................... L-5 

L.5.5 Test with a Synthetic Catalog Homogeneous Seismicity ....................................... L-5 

L.5.6 Test for the Adequacy of Eight Maps to Represent Epistemic Uncertainty ............. L-6 

L.6 HAZARD CALCULATION SOFTWARE.......................................................................... L-6 

L.6.1 Introduction.............................................................................................................. L-6 

L.6.2 Test for the Treatment of Variable b........................................................................ L-6 

L.6.3 Test for the Treatment of Dipping Ruptures Within a Source Zone......................... L-6 

L.6.4 Tests for Treatment of Epistemic Uncertainty from Sources that Make Small 

Contribution to Hazard...................................................................................................... L-6 
xxv 

LIST OF FIGURES

Figure 1.3-1 Map showing the study area and test sites for the CEUS SSC Project............... 1-15

Figure 2.3-1 CEUS SSC Project organization ......................................................................... 2-33 

Figure 2.3-2 Lines of communication among the participants of the CEUS SSC Project........ 2-34 

Figure 2.4-1 Essential activities associated with a SSHAC Level 3 or 4 project 

(Coppersmith et al., 2010)................................................................................................ 2-35 

Figure 3.2-1 Areal coverage of the primary earthquake catalog sources. Top: GSC 

catalog (Halchuk, 2009); bottom: USGS seismic hazard mapping catalog (Petersen 

et al., 2008). Red line denotes boundary of study region. Blue line denotes portion 

of each catalog used for development of project catalog................................................. 3-57

Figure 3.2-2 Histogram of ML magnitudes from the GSC SHEEF catalog for the time 

period 1600-1899 and the region east of longitude –105° and south of latitude 53° ....... 3-58

Figure 3.2-3 Histogram of ML magnitudes from the GSC SHEEF catalog for the time 

period 1900-1929 and the region east of longitude –105° and south of latitude 53° ....... 3-59

Figure 3.2-4 Histogram of ML magnitudes from the GSC SHEEF catalog for the time 

period 1930-1979 and the region east of longitude –105° and south of latitude 53° ....... 3-60

Figure 3.2-5 Histogram of ML magnitudes from the GSC SHEEF catalog for the time 

period 1980-2007 and the region east of longitude –105° and south of latitude 53° ....... 3-61

Figure 3.2-6 Histogram of ML magnitudes from the revised catalog with GSC as the 

source for the time period 1928-1979 .............................................................................. 3-62

Figure 3.2-7 Map of the CEUS SSC Project catalog showing earthquakes of uniform 

moment magnitude E[M] 2.9 and larger. Colored symbols denote earthquakes not 

contained in the USGS seismic hazard mapping catalog. ............................................... 3-63

Figure 3.3-1 Illustration of equivalence of the M* and γ2 corrections to remove bias in 

earthquake recurrence relationships estimated from magnitudes with uncertainty ......... 3-64

Figure 3.3-2 Approximate moment magnitudes from Atkinson (2004b) compared to 

values of M given in Table B-2 in Appendix B for earthquakes in common ..................... 3-65

Figure 3.3-3 Approximate moment magnitudes from Boatwright (1994) compared to 

values of M given in Table B-2 in Appendix B for earthquakes in common ..................... 3-66

Figure 3.3-4 Approximate moment magnitudes from Moulis (2002) compared to values 

of M given in Table B-2 in Appendix B for earthquakes in common................................. 3-67

Figure 3.3-5 Difference between MN reported by the GSC and MN or mLg(f) reported by 

the Weston Observatory catalog as a function of time..................................................... 3-68

Figure 3.3-6 Spatial distribution of earthquakes with body-wave (mb, mbLg, MN) and M 

magnitudes in the CEUS SSC Project catalog for the Midcontinent region. Color 

codes indicate the source of the body-wave magnitudes................................................. 3-69

Figure 3.3-7 mb-M data for the earthquakes shown on Figure 3.3-6. Red curve shows the 

preferred offset fit M = mb – 0.28...................................................................................... 3-70
xxvi 

Figure 3.3-8 Residuals from offset fit shown on Figure 3.3-7 plotted against earthquake 

year .................................................................................................................................. 3-71

Figure 3.3-9 Spatial distribution of earthquakes with body wave (mb, mbLg, MN) and M 

magnitudes in the CEUS SSC Project catalog for the northeastern portion of the 

study region. Color codes indicate the source of the body-wave magnitudes. ................ 3-72

Figure 3.3-10 mb-M data for the earthquakes shown on Figure 3.3-9. Red curve shows 

the preferred offset fit M = mb – 0.42................................................................................ 3-73

Figure 3.3-11 Residuals from offset fit shown on Figure 3.3-10 plotted against 

earthquake year ............................................................................................................... 3-74

Figure 3.3-12 Residuals for GSC data from offset fit shown on Figure 3.3-10 plotted 

against earthquake year................................................................................................... 3-75

Figure 3.3-13 Residuals for WES data from offset fit shown on Figure 3.3-10 plotted 

against earthquake year................................................................................................... 3-76

Figure 3.3-14 Residuals for data from sources other than GSC or WES from offset fit 

shown on Figure 3.3-10 plotted against earthquake year................................................ 3-77

Figure 3.3-15 Difference between body-wave magnitudes reported by LDO and those by 

other sources as a function of year.................................................................................. 3-78

Figure 3.3-16 Spatial distribution of earthquakes with reported GSC body-wave 

magnitudes. Red and blue symbols indicate earthquakes with both mb and M 

magnitudes for mb ≥ 3.5. Dashed line indicates the portion of the study region 

considered the “Northeast” for purposes of magnitude scaling........................................ 3-79

Figure 3.3-17 M-mb as a function of time for mb data from the GSC shown on Figure 3.3-

16 ..................................................................................................................................... 3-80

Figure 3.3-18 Plot of magnitude differences mbLg – m(3 Hz) for the OKO catalog................... 3-81

Figure 3.3-19 Final mb-M data set. Vertical dashed lines indicate the magnitude range 

used to develop the scaling relationship. Diagonal line indicates a one-to-one 

correlation. ....................................................................................................................... 3-82

Figure 3.3-20 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

instrumental ML magnitudes............................................................................................. 3-83

Figure 3.3-21 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

instrumental ML magnitudes and M magnitudes .............................................................. 3-84

Figure 3.3-22 ML-M data from the CEUS SSC Project catalog and robust regression fit to 

the data ............................................................................................................................ 3-85

Figure 3.3-23 Relationship between MN and ML for the GSC data .......................................... 3-86

Figure 3.3-24 Data from the northeastern portion of the study region with ML and MC or 

MD magnitude from catalog sources other than the GSC ................................................ 3-87

Figure 3.3-25 Data from the northeastern portion of the study region with ML and M 

magnitudes from sources other than the GSC................................................................. 3-88

Figure 3.3-26 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

MS ≥ 3 magnitudes ........................................................................................................... 3-89

Figure 3.3-27 MS-M data from the CEUS SSC Project catalog and quadratic polynomial 

fit to the data .................................................................................................................... 3-90

Figure 3.3-28 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

MC ≥ 2.5 magnitudes ........................................................................................................ 3-91
xxvii 

Figure 3.3-29 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

MC ≥ 2.5 and M magnitudes ............................................................................................. 3-92

Figure 3.3-30 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

MD ≥ 3 magnitudes ........................................................................................................... 3-93

Figure 3.3-31 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

both MD and M magnitudes .............................................................................................. 3-94

Figure 3.3-32 MC-M data from the CEUS SSC Project catalog and linear regression fit to 

the data ............................................................................................................................ 3-95

Figure 3.3-33 Spatial distribution of earthquakes with reported MC and MD magnitudes......... 3-96

Figure 3.3-34 Comparison of MC and MD magnitudes for the LDO and WES catalogs ........... 3-97

Figure 3.3-35 Comparison of MC with MD for at least one of the two magnitude types 

reported in the OKO catalog ............................................................................................ 3-98

Figure 3.3-36 Comparison of MC with MD for at least one of the two magnitude types 

reported in the CERI catalog............................................................................................ 3-99

Figure 3.3-37 Comparison of MC with MD for at least one of the two magnitude types 

reported in the SCSN catalog ........................................................................................ 3-100

Figure 3.3-38 Comparison of MC with MD for at least one of the two magnitude types 

reported in other catalogs for earthquakes in the Midcontinent portion of the study 

region ............................................................................................................................. 3-101

Figure 3.3-39 Relationship between M and MC, MD, or ML for the Midcontinent portion of 

the study region.............................................................................................................. 3-102

Figure 3.3-40 Comparison of MC and MD magnitudes with ML magnitudes for the region 

between longitudes 105°W and 100°W.......................................................................... 3-103

Figure 3.3-41 Comparison of mb magnitudes with ML magnitudes for the region between 

longitudes 105°W and 100°W ........................................................................................ 3-104

Figure 3.3-42 Comparison of mb magnitudes with MC and MD magnitudes for the region 

between longitudes 105°W and 100°W.......................................................................... 3-105

Figure 3.3-43 Spatial distribution of earthquake with ln(FA) in the CEUS SSC Project 

catalog............................................................................................................................ 3-106

Figure 3.3-44 Catalog ln(FA)–M data and fitted model.......................................................... 3-107

Figure 3.3-45 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

reported values of I0 ....................................................................................................... 3-108

Figure 3.3-46 I0 and M data for earthquakes in the CEUS SSC Project catalog. Curves 

show locally weighted least-squares fit (Loess) to the data and the relationship 

published by Johnston (1996b). ..................................................................................... 3-109

Figure 3.3-47 I0 and mb data from the NCEER91 catalog. Plotted are the relationships 

between I0 and mb developed by EPRI (1988) (EPRI-SOG) and Sibol et al. (1987)...... 3-110

Figure 3.3-48 Categorical model fits of I0 as a function and M for earthquakes in the 

CEUS SSC Project catalog ............................................................................................ 3-111

Figure 3.3-49 Results from proportional odds logistic model showing the probability of 

individual intensity classes as a function of M................................................................ 3-112

Figure 3.3-50 Comparison of I0 and mb data from the CEUS SSC Project catalog for 

those earthquakes with reported values of M (M set) and the full catalog (full set). 

Locally weighted least-squares fits to the two data sets are shown along with the 
xxviii 

relationship use to develop the EPRI (1988) catalog and the Sibol et al. (1987) 

relationship used in the NCEER91 catalog. ................................................................... 3-113

Figure 3.3-51 Linear fits to the data from Figure 3.3-50 for I0 ≥ V .......................................... 3-114

Figure 3.3-52 Comparison of I0 and mb data from the project, with mb adjusted for the 

difference in mb to M scaling ......................................................................................... 3-115

Figure 3.3-53 Linear fits to the data from Figure 3.3-52 for I0 ≥ V .......................................... 3-116

Figure 3.3-54 Composite I0–M data set used for assessment of I0 scaling relationship ........ 3-117

Figure 3.3-55 Linear and inverse sigmoid models fit to the project data for I0 > IV................ 3-118

Figure 3.4-1 Illustration of process used to identify clusters of earthquakes (from EPRI, 

1988, Vol. 1): (a) local and extended time and distance windows, (b) buffer window, 

and (c) contracted window ............................................................................................. 3-119

Figure 3.4-2 Identification of secondary (dependent) earthquakes inside the cluster 

region through Poisson thinning (from EPRI, 1988, Vol. 1)............................................ 3-120

Figure 3.4-3 Comparison of dependent event time and distance windows with results for 

individual clusters in the project catalog......................................................................... 3-121

Figure 3.5-1 Earthquake catalog and catalog completeness regions used in EPRI-SOG 

(EPRI, 1988) .................................................................................................................. 3-122

Figure 3.5-2 CEUS SSC Project earthquake catalog and modified catalog completeness 

regions ........................................................................................................................... 3-123

Figure 3.5-3 Plot of year versus location for the CEUS SSC Project earthquake catalog. 

Red lines indicate the boundaries of the catalog completeness time periods................ 3-124

Figure 3.5-4 (1 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-125

Figure 3.5-4 (2 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-126

Figure 3.5-4 (3 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-127

Figure 3.5-4 (4 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-128

Figure 3.5-4 (5 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-129

Figure 3.5-4 (6 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-130

Figure 3.5-4 (7 of 7) “Stepp” plots of earthquake recurrence rate as a function of time for 

the individual catalog completeness regions shown on Figure 3.5-2 ............................. 3-131

Figure 4.1.1-1 Example logic tree from the PEGASOS project (NAGRA, 2004) showing 

the assessment of alternative conceptual models on the logic tree. Each node of 

the logic tree represents an assessment that is uncertain. Alternative branches 

represent the alternative models or parameter values, and the weights associated 

with each branch reflect the TI Team’s relative degree of belief that each branch is 

the correct model or parameter value. ............................................................................. 4-40

Figure 4.1.1-2 Example logic tree from the PVHA-U (SNL, 2008) project showing the 

treatment of alternative conceptual models in the logic tree ............................................ 4-41
xxix 

Figure 4.2.1-1 Master logic tree showing the Mmax zones and seismotectonic zones 

alternative conceptual models for assessing the spatial and temporal characteristics 

of future earthquake sources in the CEUS....................................................................... 4-42

Figure 4.2.2-1 Example of a logic tree for RLME sources. Shown is the tree for the 

Marianna RLME source. .................................................................................................. 4-43

Figure 4.2.2-2 Map showing RLME sources, some with alternative source geometries 

(discussed in Section 6.1). ............................................................................................... 4-44

Figure 4.2.3-1 Logic tree for the Mmax zones branch of the master logic tree........................ 4-45

Figure 4.2.3-2 Subdivision used in the Mmax zones branch of the master logic tree. 

Either the region is considered one zone for purposes of Mmax or the region is 

divided into two zones as shown: a Mesozoic-and-younger extension (MESE) zone 

and a non-Mesozoic-and-younger zone (NMESE). In this figure the “narrow” MESE 

zone is shown .................................................................................................................. 4-46

Figure 4.2.3-3 Subdivision used in the Mmax zones branch of the master logic tree. 

Either the region is considered one zone for purposes of Mmax or the region is 

divided into two zones as shown: a Mesozoic-and-younger extension (MESE) zone 

and a non-Mesozoic-and-younger zone (NMESE). In this figure the “wide” MESE 

zone is shown .................................................................................................................. 4-47

Figure 4.2.4-1(a) Logic tree for the seismotectonic zones branch of the master logic tree ..... 4-48

Figure 4.2.4-1(b) Logic tree for the seismotectonic zones branch of the master logic tree ..... 4-49

Figure 4.2.4-2 Seismotectonic zones shown in the case where the Rough Creek Graben 

is not part of the Reelfoot Rift (RR), and the Paleozoic Extended Zone is narrow 

(PEZ-N) ........................................................................................................................... 4-50

Figure 4.2.4-3 Seismotectonic zones shown in the case where the Rough Creek Graben 

is part of the Reelfoot Rift (RR-RCG), and the Paleozoic Extended Zone is narrow 

(PEZ-N)............................................................................................................................ 4-51

Figure 4.2.4-4 Seismotectonic zones shown in the case where the Rough Creek Graben 

is not part of the Reelfoot Rift (RR), and the Paleozoic Extended Crust is wide 

(PEZ-W) ........................................................................................................................... 4-52

Figure 4.2.4-5 Seismotectonic zones shown in the case where the Rough Creek Graben 

is part of the Reelfoot Rift (RR-RCG), and the Paleozoic Extended Crust is wide 

(PEZ-W) ........................................................................................................................... 4-53

Figure 5.2.1-1 Diagrammatic illustration of the Bayesian Mmax approach showing (a) the 

prior distribution, (b) the likelihood function, and (c) the posterior distribution. The 

posterior distribution is represented by a discrete distribution (d) for implementation 

in hazard analysis. ........................................................................................................... 5-72

Figure 5.2.1-2 Diagrammatic illustration of the Bayesian Mmax approach showing (a) the 

prior distribution, (b) the likelihood function, and (c) the posterior distribution. The 

posterior distribution is represented by a discrete distribution (d) for implementation 

in hazard analysis. ........................................................................................................... 5-73

Figure 5.2.1-3 Median values of mmax−obs as a function of maximum magnitude, mu

, and 

sample size N, the number of earthquakes ≥ M 4.5......................................................... 5-74

Figure 5.2.1-4 Histograms of mmax−obs for extended and non-extended superdomains .......... 5-75
xxx 

Figure 5.2.1-5 Histograms of mmax−obs for Mesozoic-and-younger extended (MESE) 

superdomains and for older extended and non-extended (NMESE) superdomains........ 5-76

Figure 5.2.1-6 Histograms of mmax−obs for Mesozoic-and-younger extended (MESE) 

superdomains and for older extended and non-extended (NMESE) superdomains 

using age of most recent extension for the age classification.......................................... 5-77

Figure 5.2.1-7 Histograms of mmax−obs for Mesozoic-and-younger extended (MESE) 

superdomains and for older extended and non-extended (NMESE) superdomains 

using final sets indicated by asterisks in Tables 5.2.1-1 and 5.2.1-2 ............................... 5-78

Figure 5.2.1-8 Histograms of mmax−obs for combined (COMB) superdomains using final 

sets indicated by asterisks in Table 5.2.1-3 ..................................................................... 5-79

Figure 5.2.1-9 Bias adjustments from mmax−obs to mu for the three sets of superdomain 

analysis results presented in Table 5.2.1-4 ...................................................................... 5-80

Figure 5.2.1-10 Results of simulations of estimates of Mmax using the Bayesian 

approach for earthquake catalogs ranging in size from 1 to 1,000 earthquakes. True 

Mmax is set at the mean of the prior distribution.............................................................. 5-81

Figure 5.2.1-11 Comparison of the Kijko (2004) estimates of mu for given values of 

mmax−obs and N, the number of earthquakes of magnitude ≥ 4.5. Also shown is the 

median value of mmax−obs for given mu obtained using Equation 5.2.1-2.......................... 5-82

Figure 5.2.1-12 Behavior of the cumulative probability function for mu (Equation 5.2.1-9) 

for the K-S-B estimator and a value of mmax−obs equal to 6.............................................. 5-83

Figure 5.2.1-13 Example Mmax distribution assessed for the Mesozoic-and-younger 

extended Mmax zone for the case where the zone is “narrow” (MESE-N). 

Distributions are shown for the Kijko approach and for the Bayesian approach using 

either the Mesozoic-and-younger extended prior distribution or the composite prior 

distribution. The final composite Mmax distribution, which incorporates the relative 

weights, is shown by the red probability distribution. ....................................................... 5-84

Figure 5.2.1-14 Example Mmax distribution assessed for the Northern Appalachian 

seismotectonic zone (NAP). Distributions are shown for the Kijko approach and for 

the Bayesian approach using either the Mesozoic-and-younger extended prior 

distribution or the composite prior distribution. Note that the Kijko results are shown 

in this example for illustration, even though they have zero weight. The final 

composite Mmax distribution, which incorporates the relative weights, is shown by 

the red probability distribution. ......................................................................................... 5-85

Figure 5.3.2-1 Likelihood function for rate per unit area in a Poisson process, for multiple 

values of the earthquake count N: (a) arithmetic scale, and (b) logarithmic scale 

used to illustrate decreasing COV as N increases........................................................... 5-86

Figure 5.3.2-2 Likelihood function for b-value of an exponential magnitude distribution, 

for multiple values of the earthquake count N. The value of b is normalized by the 

maximum-likelihood estimate, which is derived from Equation 5.3.2-5............................ 5-87

Figure 5.3.2-3 Histogram of magnitudes in the earthquake catalog used in this section. 

The minimum magnitude shown (M 2.9) is the lowest magnitude used in these 

recurrence calculations. ................................................................................................... 5-88
xxxi 

Figure 5.3.2-4 Objectively determined values of the penalty function for ln(rate) for Case 

A magnitude weights. Source zones are sorted from smallest to largest. See list of 

abbreviations for full source-zone names. ....................................................................... 5-89

Figure 5.3.2-5 Objectively determined values of the penalty function for beta for Case A 

magnitude weights ........................................................................................................... 5-90

Figure 5.3.2-6 Objectively determined values of the penalty function for ln(rate) for Case 

B magnitude weights........................................................................................................ 5-91

Figure 5.3.2-7 Objectively determined values of the penalty function for beta for Case B 

magnitude weights. Source zones are sorted from smallest to largest............................ 5-92

Figure 5.3.2-8 Objectively determined values of the penalty function for ln(rate) for Case 

E magnitude weights........................................................................................................ 5-93

Figure 5.3.2-9 Objectively determined values of the penalty function for beta for Case E 

magnitude weights. Source zones are sorted from smallest to largest............................ 5-94

Figure 5.3.2-10 Mean map of rate and b-value for ECC-AM calculated using Case A 

magnitude weights ........................................................................................................... 5-95

Figure 5.3.2-11 Mean map of rate and b-value for ECC-GC calculated using Case A 

magnitude weights ........................................................................................................... 5-96

Figure 5.3.2-12 Mean map of rate and b-value for ECC-AM calculated using Case B 

magnitude weights ........................................................................................................... 5-97

Figure 5.3.2-13 Mean map of rate and b-value for ECC-GC calculated using Case B 

magnitude weights ........................................................................................................... 5-98

Figure 5.3.2-14 Mean map of rate and b-value for ECC-AM calculated using Case E 

magnitude weights ........................................................................................................... 5-99

Figure 5.3.2-15 Mean map of rate and b-value for ECC-GC calculated using Case E 

magnitude weights ......................................................................................................... 5-100

Figure 5.3.2-16 Sensitivity of seismic hazard at Manchester site to the strength of the 

prior on b ........................................................................................................................ 5-101

Figure 5.3.2-17 Sensitivity of seismic hazard at Topeka site to the strength of the prior 

on b ................................................................................................................................ 5-102

Figure 5.3.2-18 Sensitivity of seismic hazard at Manchester site to the choice of 

magnitude weights ......................................................................................................... 5-103

Figure 5.3.2-19 Sensitivity of seismic hazard at Topeka site to the choice of magnitude 

weights ........................................................................................................................... 5-104

Figure 5.3.2-20 Sensitivity of seismic hazard from source NAP at Manchester site to the 

eight alternative recurrence maps for Case B magnitude weights................................. 5-105

Figure 5.3.2-21 Sensitivity of seismic hazard from source MID-C–A at Topeka site to the 

eight alternative recurrence maps for Case B magnitude weights................................. 5-106

Figure 5.3.2-22 Mean recurrence-parameter map for the study region under the highest 

weighted source-zone configuration in the master logic tree. See Sections 6.3 and 

7.5 for all mean maps..................................................................................................... 5-107

Figure 5.3.2-23 Map of the uncertainty in the estimated recurrence parameters, 

expressed as the coefficient of variation of the rate (left) and the standard deviation 

of the b-value (right) for the study region, under the highest weighted source-zone 

configuration in the master logic tree. See Appendix J for all maps of uncertainty........ 5-108
xxxii 

Figure 5.3.2-24 First of eight equally likely realizations of the recurrence-parameter map 

for the study region under the highest weighted source-zone configuration in the 

master logic tree. See Appendix J for maps of all realizations for all source-zone 

configurations................................................................................................................. 5-109

Figure 5.3.2-25 Eighth of eight equally likely realizations of the recurrence-parameter 

map for the study region under the highest weighted source-zone configuration in 

the master logic tree. See Appendix J for maps of all realizations for all source-zone 

configurations................................................................................................................. 5-110

Figure 5.3.2-26 Map of geographic areas considered in the exploration of model results..... 5-111

Figure 5.3.2-27 Comparison of model-predicted earthquake counts for the USGS 

Eastern Tennessee area using Case A magnitude weights. The error bars 

represent the 16%–84% uncertainty associated with the data, computed using the 

Weichert (1980) procedure. ........................................................................................... 5-112

Figure 5.3.2-28 Comparison of model-predicted earthquake counts for the USGS 

Eastern Tennessee area using Case B magnitude weights........................................... 5-113

Figure 5.3.2-29 Comparison of model-predicted earthquake counts for the USGS 

Eastern Tennessee area using Case E magnitude weights........................................... 5-114

Figure 5.3.2-30 Comparison of model-predicted earthquake counts for the central New 

England area using Case A magnitude weights ............................................................ 5-115

Figure 5.3.2-31 Comparison of model-predicted earthquake counts for the central New 

England area using Case B magnitude weights ............................................................ 5-116

Figure 5.3.2-32 Comparison of model-predicted earthquake counts for the central New 

England area using Case E magnitude weights ............................................................ 5-117

Figure 5.3.2-33 Comparison of model-predicted earthquake counts for the Nemaha 

Ridge area using Case A magnitude weights ................................................................ 5-118

Figure 5.3.2-34 Comparison of model-predicted earthquake counts for the Nemaha 

Ridge area using Case B magnitude weights ................................................................ 5-119

Figure 5.3.2-35 Comparison of model-predicted earthquake counts for the Nemaha 

Ridge area using Case E magnitude weights ................................................................ 5-120

Figure 5.3.2-36 Comparison of model-predicted earthquake counts for the Miami, FL, 

area using Case A magnitude weights........................................................................... 5-121

Figure 5.3.2-37 Comparison of model-predicted earthquake counts for the Miami, FL, 

area using Case B magnitude weights........................................................................... 5-122

Figure 5.3.2-38 Comparison of model-predicted earthquake counts for the Miami, FL, 

area using Case E magnitude weights........................................................................... 5-123

Figure 5.3.2-39 Comparison of model-predicted earthquake counts for the St. Paul, MN, 

area using Case A magnitude weights........................................................................... 5-124

Figure 5.3.2-40 Comparison of model-predicted earthquake counts for the St. Paul, MN, 

area using Case B magnitude weights........................................................................... 5-125

Figure 5.3.2-41 Comparison of model-predicted earthquake counts for the St. Paul, MN, 

area using Case E magnitude weights........................................................................... 5-126

Figure 5.3.2-42 Recurrence parameters for the ECC-AM, MID-C–A, and NAP 

seismotectonic source zones and Case A magnitude weights computed using an 

objective adaptive kernel approach................................................................................ 5-127
xxxiii 

Figure 5.3.3-1 Likelihood distribution for rate parameter λ derived using Equation 5.3.3-1 

for N = 2 and T = 2,000 years. Top: normalized probability density function for λ. 

Bottom: resulting cumulative distribution function. Dashed lines show the 

cumulative probability levels for the Miller and Rice (1983) discrete approximation of 

a continuous probability distribution. .............................................................................. 5-128

Figure 5.3.3-2 Uncertainty distributions for the age of Charleston RLMEs............................ 5-129

Figure 5.4.4-1 Spatial distribution of earthquakes in the CEUS SSC Project catalog. 

Solid lines indicate the boundaries of the seismotectonic source zones (narrow 

interpretation)................................................................................................................. 5-130

Figure 5.4.4-2 Spatial distribution of earthquakes in the CEUS SSC Project catalog with 

good quality depth determinations used for assessing crustal thickness. Solid lines 

indicate the boundaries of the seismotectonic source zones (narrow interpretation)..... 5-131

Figure 5.4.4-3 Distribution of better-quality focal depths in Mmax source zones................... 5-132

Figure 5.4.4-4 (1 of 3) Distribution of better-quality focal depths in seismotectonic source 

zones.............................................................................................................................. 5-133

Figure 5.4.4-4 (2 of 3) Distribution of better-quality focal depths in seismotectonic source 

zones.............................................................................................................................. 5-134

Figure 5.4.4-4 (3 of 3) Distribution of better-quality focal depths in seismotectonic source 

zones.............................................................................................................................. 5-135

Figure 6.1-1 Map showing the RLME sources characterized in the CEUS SSC model. 

Detailed alternatives to the source geometries are shown on figures associated with 

each RLME discussion................................................................................................... 6-111

Figure 6.1-2a Map showing the RLME sources and seismicity from the CEUS SSC 

earthquake catalog. Some of the RLMEs occur in regions of elevated seismicity, but 

others do not. ................................................................................................................. 6-112 

Figure 6.1-2b Close-up of the Wabash Valley and New Madrid/Reelfoot Rift RLME 

sources and seismicity from the CEUS SSC earthquake catalog. Some of the 

RLMEs occur in regions of elevated seismicity, but others do not................................. 6-113 

Figure 6.1.1-1 Logic tree for the Charlevoix RLME source.................................................... 6-114 

Figure 6.1.1-2 Seismicity and tectonic features of the Charlevoix RLME .............................. 6-115 

Figure 6.1.1-3 Magnetic and gravity anomaly maps of the Charlevoix RLME ....................... 6-116 

Figure 6.1.2-1a Logic tree for the Charleston RLME source ................................................. 6-117 

Figure 6.1.2-1b Logic tree for the Charleston RLME source ................................................. 6-118 

Figure 6.1.2-2 Charleston RLME source zones with (a) total magnetic anomaly and (b) 

residual isostatic gravity data ...................................................................................... 6-119 

Figure 6.1.2-3 Postulated faults and tectonic features in the Charleston region ................. 6-120

Figure 6.1.2-4 Postulated faults and tectonic features in the local Charleston area ............ 6-121

Figure 6.1.2-5a Postulated faults and tectonic features in the Charleston region with 

Charleston RLME source zones ................................................................................... 6-122 

Figure 6.1.2-5b Postulated faults and tectonic features in the local Charleston area with 

Charleston RLME source zones .................................................................................... 6-123 

Figure 6.1.2-6 Schematic diagram showing contemporary, maximum, and minimum 

constraining age sample locations ................................................................................. 6-124 
xxxiv 

Figure 6.1.2-7 Charleston space-time diagram of earthquakes interpreted from 

paleoliquefaction, contemporary-ages-only scenario .................................................... 6-125 

Figure 6.1.2-8 Charleston space-time diagram of earthquakes interpreted from 

paleoliquefaction, all-ages scenario ............................................................................. 6-126 

Figure 6.1.2-9 Distribution of liquefaction from earthquake A, contemporary-ages-only 

scenario ........................................................................................................................ 6-127 

Figure 6.1.2-10 Distribution of liquefaction from earthquake B, contemporary-ages-only 

scenario ........................................................................................................................ 6-128 

Figure 6.1.2-11 Distribution of liquefaction from earthquake C, contemporary-ages-only 

scenario ........................................................................................................................ 6-129 

Figure 6.1.2-12 Distribution of liquefaction from earthquake D, contemporary-ages-only 

scenario ........................................................................................................................ 6-130

Figure 6.1.2-13 Distribution of liquefaction from earthquake E, contemporary-ages-only 

scenario ........................................................................................................................ 6-131

Figure 6.1.2-14 Distribution of liquefaction from earthquake A, all-ages scenario ............... 6-132 

Figure 6.1.2-15 Distribution of liquefaction from earthquake B, all-ages scenario ............... 6-133 

Figure 6.1.2-16 Distribution of liquefaction from earthquake C, all-ages scenario ............... 6-134 

Figure 6.1.2-17 Distribution of liquefaction from earthquake D, all-ages scenario ............... 6-135 

Figure 6.1.2-18 Distribution of liquefaction from earthquake E, all-ages scenario................. 6-136 

Figure 6.1.2-19 Uncertainty distributions for the age of Charleston RLMEs.......................... 6-137 

Figure 6.1.3-1 Logic tree for the Cheraw fault RLME source................................................. 6-138 

Figure 6.1.3-2 Map (c) and hillshade relief images (a, b, and d) showing location of 

mapped Cheraw fault, possible northeast extension, and paleoseismic locality............ 6-139 

Figure 6.1.3-3 Cheraw RLME source relative to (a) total magnetic anomaly and (b) 

residual isostatic gravity data ......................................................................................... 6-140

Figure 6.1.4-1 Meers fault location ........................................................................................ 6-141

Figure 6.1.4-2 Logic tree for the Meers fault source .............................................................. 6-142 

Figure 6.1.5-1 Logic tree for the NMFS RLME source ......................................................... 6-143 

Figure 6.1.5-2 Map showing seismicity and major subsurface structural features in the 

New Madrid region ....................................................................................................... 6-144 

Figure 6.1.5-3 Map showing geomorphic and near-surface tectonic features in the New 

Madrid region and locations of NMFS RLME fault sources .......................................... 6-145 

Figure 6.1.5-4 Rupture segments (a) and models (b) for the New Madrid faults from 

Johnston and Schweig (1996) and (c) the NMFS RLME fault sources ........................ 6-146 

Figure 6.1.5-5 Map of NMSZ showing estimated ages and measured sizes of 

liquefaction features ....................................................................................................... 6-147 

Figure 6.1.5-6 Earthquake chronology for NMSZ from dating and correlation of 

liquefaction features at sites (listed at top) along N-S transect across region................ 6-148 

Figure 6.1.5-7 Probability distributions for the age of the AD 900 and AD 1450 NMFS 

RLMEs ........................................................................................................................... 6-149 

Figure 6.1.5-8 Liquefaction fields for the 1811-1812, AD 1450, and AD 900 earthquakes 

as interpreted from spatial distribution and stratigraphy of sand blows.......................... 6-150
xxxv 

Figure 6.1.6-1a Logic tree for the Reelfoot Rift–Eastern Rift Margin South RLME source. 

Two options for the southern extent of the ERM-S are considered: ERM-SCC 

includes the Crittenden County fault zone, and ERM-SRP includes the postulated 

zone of deformation based on fault picks identified in a high-resolution seismic 

profile along the Mississippi River.................................................................................. 6-151

Figure 6.1.6-1b Logic tree for the Reelfoot Rift–Eastern Rift Margin North RLME source..... 6-152 

Figure 6.1.6-2 Map showing structural features and paleoseismic investigation sites 

along the eastern margin of the Reelfoot rift. The inset map shows the locations of 

inferred basement faults that border and cross the Reelfoot rift (Csontos et al., 

2008) and the inferred Joiner Ridge–Meeman-Shelby fault (JR-MSF; Odum et al., 

2010). ............................................................................................................................ 6-153 

Figure 6.1.6-3 Maps showing surficial geology and locations of subsurface investigations 

at (a) Meeman-Shelby Forest State Park locality and (b) Union City site (MSF and 

UC on Figure 6.1.6-2). Modified from Cox et al. (2006) and Odum et al. (2010). .......... 6-154 

Figure 6.1.6-4 Figure showing the timing of events along the eastern Reelfoot rift margin. 

Modified from Cox (2009)............................................................................................... 6-155 

Figure 6.1.7-1 Logic tree for the Reelfoot rift–Marianna RLME source ................................. 6-156 

Figure 6.1.7-2 Map showing tectonic features and locations of paleoliquefaction sites in 

the vicinity of Marianna, Arkansas ................................................................................. 6-157 

Figure 6.1.7-3 Map showing liquefaction features near Daytona Beach lineament 

southwest of Marianna, Arkansas .................................................................................. 6-158 

Figure 6.1.8-1 Logic tree for the Commerce Fault Zone RLME source ................................. 6-159

Figure 6.1.8-2 Map showing tectonic features, seismicity, and paleoseismic localities 

along the Commerce Fault Zone RLME source............................................................. 6-160

Figure 6.1.8-3 Location of the Commerce geophysical lineament and Commerce Fault 

Zone RLME source relative to the (a) regional magnetic anomaly map and (b) 

regional gravity anomaly map ........................................................................................ 6-161

Figure 6.1.8-4 Space-time diagram showing constraints on the location and timing of late 

Pleistocene and Holocene paleoearthquakes that may be associated with the 

Commerce Fault Zone RLME source............................................................................. 6-162 

Figure 6.1.9-1 Logic tree for the Wabash Valley RLME source............................................. 6-163 

Figure 6.1.9-2 Map showing seismicity, subsurface structural features, paleoearthquake 

energy centers, and postulated neotectonic deformation in the Wabash Valley 

region of southern Illinois and southern Indiana .......................................................... 6-164 

Figure 6.1.9-3 Wabash Valley RLME source relative to (a) magnetic anomaly, and (b) 

residual isostatic gravity data ....................................................................................... 6-165 

Figure 6.2-1 Map showing the two Mmax zones for the “narrow” interpretation of the 

Mesozoic-and-younger extended zone .......................................................................... 6-166 

Figure 6.2-2 Map showing the two Mmax zones for the “wide” interpretation of the 

Mesozoic-and-younger extended zone .......................................................................... 6-167 

Figure 6.3.1-1 Distributions for m max-obs for the Mmax distributed seismicity source zones .. 6-168 

Figure 6.3.2-1 Mmax distributions for the study region treated as a single Mmax zone........ 6-169 

Figure 6.3.2-2 Mmax distributions for the MESE-N Mmax zone............................................ 6-170
xxxvi 

Figure 6.3.2-3 Mmax distributions for the MESE-W Mmax zone ........................................... 6-171

Figure 6.3.2-4 Mmax distributions for the NMESE-N Mmax zone ......................................... 6-172 

Figure 6.3.2-5 Mmax distributions for the NMESE-W Mmax zone ........................................ 6-173 

Figure 6.4.1-1 Mean map of rate and b-value for the study region under the source-zone 

configuration, with no separation of Mesozoic extended and non-extended; Case A 

magnitude weights ......................................................................................................... 6-174 

Figure 6.4.1-2 Mean map of rate and b-value for the study region under the source-zone 

configuration, with no separation of Mesozoic extended and non-extended; Case B 

magnitude weights ......................................................................................................... 6-175 

Figure 6.4.1-3 Mean map of rate and b-value for the study region under the source-zone 

configuration, with no separation of Mesozoic extended and non-extended; Case E 

magnitude weights ......................................................................................................... 6-176 

Figure 6.4.1-4 Mean map of rate and b-value for the study region under the source-zone 

configuration, with separation of Mesozoic extended and non-extended, narrow 

geometry for MESE; Case A magnitude weights ........................................................... 6-177 

Figure 6.4.1-5 Mean map of rate and b-value for the study region under the source-zone 

configuration, with separation of Mesozoic extended and non-extended, narrow 

geometry for MESE; Case B magnitude weights ........................................................... 6-178 

Figure 6.4.1-6 Mean map of rate and b-value for the study region under the source-zone 

configuration, with separation of Mesozoic extended and non-extended, narrow 

geometry for MESE; Case E magnitude weights ........................................................... 6-179 

Figure 6.4.1-7 Mean map of rate and b-value for the study region under the source-zone 

configuration, with separation of Mesozoic extended and non-extended, wide 

geometry for MESE; Case A magnitude weights ........................................................... 6-180

Figure 6.4.1-8 Mean map of rate and b-value for the study region under the source-zone 

configuration, with separation of Mesozoic extended and non-extended, wide 

geometry for MESE; Case B magnitude weights ........................................................... 6-181

Figure 6.4.1-9 Mean map of rate and b-value for the study region under the source-zone 

configuration, with separation of Mesozoic extended and non-extended, wide 

geometry for MESE; Case E magnitude weights ........................................................... 6-182 

Figure 6.4.2-1 Comparison of model-predicted earthquake counts for study region using 

Case A magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-183 

Figure 6.4.2-2 Comparison of model-predicted earthquake counts for study region using 

Case B magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-184 

Figure 6.4.2-3 Comparison of model-predicted earthquake counts for study region using 

Case E magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-185 

Figure 6.4.2-4 Comparison of model-predicted earthquake counts for MESE-N using 

Case A magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-186 

Figure 6.4.2-5 Comparison of model-predicted earthquake counts for MESE-N using 

Case B magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-187 
xxxvii 

Figure 6.4.2-6 Comparison of model-predicted earthquake counts for MESE-N using 

Case E magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-188 

Figure 6.4.2-7 Comparison of model-predicted earthquake counts for MESE-W using 

Case A magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-189 

Figure 6.4.2-8 Comparison of model-predicted earthquake counts for MESE-W using 

Case B magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-190

Figure 6.4.2-9 Comparison of model-predicted earthquake counts for MESE-W using 

Case E magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-191

Figure 6.4.2-10 Comparison of model-predicted earthquake counts for NMESE-N using 

Case A magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-192 

Figure 6.4.2-11 Comparison of model-predicted earthquake counts for NMESE-N using 

Case B magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-193 

Figure 6.4.2-12 Comparison of model-predicted earthquake counts for NMESE-N using 

Case E magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-194 

Figure 6.4.2-13 Comparison of model-predicted earthquake counts for NMESE-W using 

Case A magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-195 

Figure 6.4.2-14 Comparison of model-predicted earthquake counts for NMESE-W using 

Case B magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-196 

Figure 6.4.2-15 Comparison of model-predicted earthquake counts for NMESE-W using 

Case E magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure.................... 6-197 

Figure 7.1-1 Seismotectonic zones shown in the case where the Rough Creek graben is 

not part of the Reelfoot rift (RR) and the Paleozoic Extended Crust is narrow (PEZN) .................................................................................................................................... 7-83

Figure 7.1-2 Seismotectonic zones shown in the case where the Rough Creek graben is 

part of the Reelfoot rift (RR_RCG) and the Paleozoic Extended Crust is narrow 

(PEZ-N)............................................................................................................................ 7-84

Figure 7.1-3 Seismotectonic zones shown in the case where the Rough Creek graben is 

not part of the Reelfoot rift (RR) and the Paleozoic Extended Crust is wide (PEZ-W)..... 7-85

Figure 7.1-4 Seismotectonic zones shown in the case where the Rough Creek graben is 

part of the Reelfoot rift (RR_RCG) and the Paleozoic Extended Crust is wide (PEZW)..................................................................................................................................... 7-86

Figure 7.1-5 Example of comparing seismotectonic zones with magnetic map developed 

as part of the CEUS SSC Project..................................................................................... 7-87

Figure 7.1-6 Example of comparing seismotectonic zones with isostatic gravity map 

developed as part of the CEUS SSC Project . ................................................................ 7-88
xxxviii 

Figure 7.1-7 Map of seismicity based on the earthquake catalog developed for the CEUS 

SSC Project...................................................................................................................... 7-89

Figure 7.1-8 Map showing example comparison of seismotectonic zones with seismicity. 

Note the non-uniform spatial distribution of seismicity within the zones. Spatial 

smoothing of a- and b-values accounts for these spatial variations................................. 7-90

Figure 7.3-1 Logic tree for the seismotectonic zones branch of the master logic tree............. 7-91

Figure 7.3.1-1 Significant earthquakes and paleoseismology of the SLR seismotectonic 

zone ................................................................................................................................. 7-92

Figure 7.3.1-2 Tectonic features of the SLR seismotectonic zone .......................................... 7-93

Figure 7.3.1-3 Magnetic and gravity anomaly maps of the SLR seismotectonic zone ............ 7-94

Figure 7.3.2-1 Significant earthquakes and paleoseismic study area in the region of the 

GMH seismotectonic zone ............................................................................................... 7-95

Figure 7.3.2-2 Igneous rocks attributed to the GMH seismotectonic zone .............................. 7-96

Figure 7.3.2-3 Relocated hypocentral depths and crustal depth of the GMH 

seismotectonic zone......................................................................................................... 7-97

Figure 7.3.2-4 Magnetic and gravity anomaly maps of the GMH seismotectonic zone .......... 7-98

Figure 7.3.3-1 Seismicity of the NAP seismotectonic zone ..................................................... 7-99

Figure 7.3.3-2 Magnetic and gravity anomaly maps of the NAP seismotectonic zone .......... 7-100

Figure 7.3.4-1 Seismicity and tectonic features of the PEZ seismotectonic zone.................. 7-101

Figure 7.3.4-2 Magnetic and gravity anomaly maps of the PEZ seismotectonic zone .......... 7-102

Figure 7.3.5-1 Map showing seismicity, subsurface Paleozoic and basement structures, 

and postulated energy centers for prehistoric earthquakes ........................................... 7-103

Figure 7.3.5-2 Map showing alternative boundaries for Precambrian (proto-Illinois basin) 

rift basins........................................................................................................................ 7-104

Figure 7.3.5-3 Maps showing the IBEB source zone boundaries, seismicity, and 

prehistoric earthquake centers relative to (a) regional magnetic anomalies and (b) 

regional gravity anomalies ............................................................................................. 7-105

Figure 7.3.6-1 Map of seismicity and geomorphic features and faults showing evidence 

for Quaternary neotectonic deformation and reactivation. Inset map shows 

basement structures associated with the Reelfoot rift. .................................................. 7-106

Figure 7.3.6-2 Maps showing geophysical anomalies in the Reelfoot rift region ................... 7-107

Figure 7.3.7-1 Mesozoic basins within the ECC-AM zone .................................................... 7-108

Figure 7.3.7-2 Seismicity within the ECC-AM and AHEX zones............................................ 7-109

Figure 7.3.7-3 Magnetic and gravity data for ECC-AM and AHEX zones.............................. 7-110

Figure 7.3.7-4 Estimated locations of the 1755 M 6.1 Cape Ann earthquake ....................... 7-111

Figure 7.3.8-1 Correlation of interpreted transitional crust with the East Coast magnetic 

anomaly.......................................................................................................................... 7-112

Figure 7.3.9-1 The ECC-GC seismotectonic zone................................................................. 7-113

Figure 7.3.10-1 The GHEX seismotectonic zone................................................................... 7-114

Figure 7.3.11-1 The OKA seismotectonic zone and regional gravity and magnetic data ...... 7-115

Figure 7.3.12-1 Simplified tectonic map showing the distribution of principal basement 

faults, rifts, and sutures in the Midcontinent................................................................... 7-116
xxxix 

Figure 7.3.12-2 Maps showing major basement structural features relative to (a) regional 

magnetic anomalies and (b) regional gravity anomalies ................................................ 7-117

Figure 7.3.12-3 Seismic zones and maximum observed earthquakes in the MidC zone ...... 7-118

Figure 7.3.12-4 Alternative MidC source zone configurations ............................................... 7-119

Figure 7.4.1-1 (1 of 3) Distributions for mmax−obs for the seismotectonic distributed 

seismicity source zones ................................................................................................. 7-120

Figure 7.4.1-1 (2 of 3) Distributions for mmax−obs for the seismotectonic distributed 

seismicity source zones ................................................................................................. 7-121

Figure 7.4.1-1 (3 of 3) Distributions for mmax−obs for the seismotectonic distributed 

seismicity source zones ................................................................................................. 7-122

Figure 7.4.2-1 Mmax distributions for the AHEX seismotectonic zone .................................. 7-123

Figure 7.4.2-2 Mmax distributions for the ECC_AM seismotectonic zone............................. 7-124

Figure 7.4.2-3 Mmax distributions for the ECC_GC seismotectonic zone............................. 7-125

Figure 7.4.2-4 Mmax distributions for the GHEX seismotectonic zone.................................. 7-126

Figure 7.4.2-5 Mmax distributions for the GMH seismotectonic zone.................................... 7-127

Figure 7.4.2-6 Mmax distributions for the IBEB seismotectonic zone.................................... 7-128

Figure 7.4.2-7 Mmax distributions for the MidC-A seismotectonic zone................................ 7-129

Figure 7.4.2-8 Mmax distributions for the MidC-B seismotectonic zone................................ 7-130

Figure 7.4.2-9 Mmax distributions for the MidC-C seismotectonic zone................................ 7-131

Figure 7.4.2-10 Mmax distributions for the MidC-D seismotectonic zone.............................. 7-132

Figure 7.4.2-11 Mmax distributions for the NAP seismotectonic zone .................................. 7-133

Figure 7.4.2-12 Mmax distributions for the OKA seismotectonic zone .................................. 7-134

Figure 7.4.2-13 Mmax distributions for the PEZ_N seismotectonic zone .............................. 7-135

Figure 7.4.2-14 Mmax distributions for the PEZ_W seismotectonic zone.............................. 7-136

Figure 7.4.2-15 Mmax distributions for the RR seismotectonic zone..................................... 7-137

Figure 7.4.2-16 Mmax distributions for the RR_RCG seismotectonic zone........................... 7-138

Figure 7.4.2-17 Mmax distributions for the SLR seismotectonic zone................................... 7-139

Figure 7.5.1-1 Mean map of rate and b-value for the study region under the source-zone 

configuration with narrow interpretation of PEZ, Rough Creek graben associated 

with Midcontinent; Case A magnitude weights............................................................... 7-140

Figure 7.5.1-2 Mean map of rate and b-value for the study region under the source-zone 

configuration with narrow interpretation of PEZ, Rough Creek graben associated 

with Midcontinent; Case B magnitude weights............................................................... 7-141

Figure 7.5.1-3 Mean map of rate and b-value for the study region under the source-zone 

configuration with narrow interpretation of PEZ, Rough Creek graben associated 

with Midcontinent; Case E magnitude weights............................................................... 7-142

Figure 7.5.1-4 Mean map of rate and b-value for the study region under the source-zone 

configuration with narrow interpretation of PEZ, Rough Creek graben associated 

with Reelfoot rift; Case A magnitude weights................................................................. 7-143
xl 

Figure 7.5.1-5 Mean map of rate and b-value for the study region under the source-zone 

configuration with narrow interpretation of PEZ, Rough Creek graben associated 

with Reelfoot rift; Case B magnitude weights................................................................. 7-144

Figure 7.5.1-6 Mean map of rate and b-value for the study region under the source-zone 

configuration with narrow interpretation of PEZ, Rough Creek graben associated 

with Reelfoot rift; Case E magnitude weights................................................................. 7-145

Figure 7.5.1-7 Mean map of rate and b-value for the study region under the source-zone 

configuration with wide interpretation of PEZ, Rough Creek graben associated with 

Midcontinent; Case A magnitude weights ...................................................................... 7-146

Figure 7.5.1-8 Mean map of rate and b-value for the study region under the source-zone 

configuration with wide interpretation of PEZ, Rough Creek graben associated with 

Midcontinent; Case B magnitude weights ...................................................................... 7-147

Figure 7.5.1-9 Mean map of rate and b-value for the study region under the source-zone 

configuration with wide interpretation of PEZ, Rough Creek graben associated with 

Midcontinent; Case E magnitude weights ...................................................................... 7-148

Figure 7.5.1-10 Mean map of rate and b-value for the study region under the sourcezone configuration with wide interpretation of PEZ, Rough Creek graben associated 

with Reelfoot rift; Case A magnitude weights................................................................. 7-149

Figure 7.5.1-11 Mean map of rate and b-value for the study region under the sourcezone configuration with wide interpretation of PEZ, Rough Creek graben associated 

with Reelfoot rift; Case B magnitude weights................................................................. 7-150

Figure 7.5.1-12 Mean map of rate and b-value for the study region under the sourcezone configuration with wide interpretation of PEZ, Rough Creek graben associated 

with Reelfoot rift; Case E magnitude weights................................................................. 7-151

Figure 7.5.2-1 Comparison of model-predicted earthquake counts for AHEX using Case 

A magnitude weights. No earthquake counts are shown because this source zone 

contains no seismicity. . ............................................................................................... 7-152

Figure 7.5.2-2 Comparison of model-predicted earthquake counts for AHEX using Case 

B magnitude weights. No earthquake counts are shown because this source zone 

contains no seismicity.. ................................................................................................. 7-153

Figure 7.5.2-3 Comparison of model-predicted earthquake counts for AHEX using Case 

E magnitude weights. No earthquake counts are shown because this source zone 

contains no seismicity. .................................................................................................. 7-154

Figure 7.5.2-4 Comparison of model-predicted earthquake counts for ECC_AM using 

Case A magnitude weights. The error bars represent the 16%–84% uncertainty 

associated with the data, computed using the Weichert (1980) procedure. .................. 7-155

Figure 7.5.2-5 Comparison of model-predicted earthquake counts for ECC_AM using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-156

Figure 7.5.2-6 Comparison of model-predicted earthquake counts for ECC_AM using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-157

Figure 7.5.2-7 Comparison of model-predicted earthquake counts for ECC_GC using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-158

Figure 7.5.2-8 Comparison of model-predicted earthquake counts for ECC_GC using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-159

Figure 7.5.2-9 Comparison of model-predicted earthquake counts for ECC_GC using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-160
xli 

Figure 7.5.2-10 Comparison of model-predicted earthquake counts for GHEX using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-161

Figure 7.5.2-11 Comparison of model-predicted earthquake counts for GHEX using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-162

Figure 7.5.2-12 Comparison of model-predicted earthquake counts for GHEX using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-163

Figure 7.5.2-13 Comparison of model-predicted earthquake counts for GMH using Case 

A magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-164

Figure 7.5.2-14 Comparison of model-predicted earthquake counts for GMH using Case 

B magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-165

Figure 7.5.2-15 Comparison of model-predicted earthquake counts for GMH using Case 

E magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-166

Figure 7.5.2-16 Comparison of model-predicted earthquake counts for IBEB using Case 

A magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-167

Figure 7.5.2-17 Comparison of model-predicted earthquake counts for IBEB using Case 

B magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-168

Figure 7.5.2-18 Comparison of model-predicted earthquake counts for IBEB using Case 

E magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-169

Figure 7.5.2-19 Comparison of model-predicted earthquake counts for MidC-A using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-170

Figure 7.5.2-20 Comparison of model-predicted earthquake counts for MidC-A using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-171

Figure 7.5.2-21 Comparison of model-predicted earthquake counts for MidC-A using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-172

Figure 7.5.2-22 Comparison of model-predicted earthquake counts for MidC–B using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-173

Figure 7.5.2-23 Comparison of model-predicted earthquake counts for MidC-B using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-174

Figure 7.5.2-24 Comparison of model-predicted earthquake counts for MidC–B using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-175

Figure 7.5.2-25 Comparison of model-predicted earthquake counts for MidC–C using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-176

Figure 7.5.2-26 Comparison of model-predicted earthquake counts for MidC–C using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-177

Figure 7.5.2-27 Comparison of model-predicted earthquake counts for MidC–C using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-178

Figure 7.5.2-28 Comparison of model-predicted earthquake counts for MidC–D using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-179

Figure 7.5.2-29 Comparison of model-predicted earthquake counts for MidC–D using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-180

Figure 7.5.2-30 Comparison of model-predicted earthquake counts for MidC–D using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-181

Figure 7.5.2-31 Comparison of model-predicted earthquake counts for NAP using Case 

A magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-182
xlii

Figure 7.5.2-32 Comparison of model-predicted earthquake counts for NAP using Case 

B magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-183

Figure 7.5.2-33 Comparison of model-predicted earthquake counts for NAP using Case 

E magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-184

Figure 7.5.2-34 Comparison of model-predicted earthquake counts for OKA using Case 

A magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-185

Figure 7.5.2-35 Comparison of model-predicted earthquake counts for OKA using Case 

B magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-186

Figure 7.5.2-36 Comparison of model-predicted earthquake counts for OKA using Case 

E magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-187

Figure 7.5.2-37 Comparison of model-predicted earthquake counts for PEZ_N using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-188

Figure 7.5.2-38 Comparison of model-predicted earthquake counts for PEZ_N using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-189

Figure 7.5.2-39 Comparison of model-predicted earthquake counts for PEZ_N using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-190

Figure 7.5.2-40 Comparison of model-predicted earthquake counts for PEZ_W using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-191

Figure 7.5.2-41 Comparison of model-predicted earthquake counts for PEZ_W using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-192

Figure 7.5.2-42 Comparison of model-predicted earthquake counts for PEZ_W using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-193

Figure 7.5.2-43 Comparison of model-predicted earthquake counts for RR using Case A 

magnitude weights. Error bars as in Figure 7.5.2-4. ..................................................... 7-194

Figure 7.5.2-44 Comparison of model-predicted earthquake counts for RR using Case B 

magnitude weights. Error bars as in Figure 7.5.2-4. ..................................................... 7-195

Figure 7.5.2-45 Comparison of model-predicted earthquake counts for RR using Case E 

magnitude weights. Error bars as in Figure 7.5.2-4. ..................................................... 7-196

Figure 7.5.2-46 Comparison of model-predicted earthquake counts for RR_RCG using 

Case A magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-197

Figure 7.5.2-47 Comparison of model-predicted earthquake counts for RR_RCG using 

Case B magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-198

Figure 7.5.2-48 Comparison of model-predicted earthquake counts for RR_RCG using 

Case E magnitude weights. Error bars as in Figure 7.5.2-4. ......................................... 7-199

Figure 7.5.2-49 Comparison of model-predicted earthquake counts for SLR using Case

A magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-200

Figure 7.5.2-50 Comparison of model-predicted earthquake counts for SLR using Case 

B magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-201

Figure 7.5.2-51 Comparison of model-predicted earthquake counts for SLR using Case 

E magnitude weights. Error bars as in Figure 7.5.2-4. .................................................. 7-202

Figure 8.1-1 Map showing the study area and seven test sites for the CEUS SSC Project .... 8-28

Figure 8.1-2 Mean VS profile for shallow soil site.................................................................... 8-29

Figure 8.1-3 Mean VS profile for deep soil site........................................................................ 8-30
xliii

Figure 8.1-4 Mean amplification factors for shallow soil site.................................................... 8-31

Figure 8.1-5 Mean amplification factors for deep soil site........................................................ 8-32

Figure 8.2-1a Central Illinois 10 Hz rock hazard: mean and fractile total hazard..................... 8-33

Figure 8.2-1b Central Illinois 1 Hz rock hazard: mean and fractile total hazard....................... 8-34

Figure 8.2-1c Central Illinois PGA rock hazard: mean and fractile total hazard....................... 8-35

Figure 8.2-1d Central Illinois 10 Hz rock hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-36

Figure 8.2-1e Central Illinois 1 Hz rock hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-37

Figure 8.2-1f Central Illinois PGA rock hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-38

Figure 8.2-1g Central Illinois 10 Hz rock hazard: contribution by background source............. 8-39

Figure 8.2-1h Central Illinois 1 Hz rock hazard: contribution by background source............... 8-40

Figure 8.2-1i Central Illinois PGA rock hazard: contribution by background source................ 8-41

Figure 8.2-1j Central Illinois 10 Hz rock hazard: comparison of three source models............. 8-42

Figure 8.2-1k Central Illinois 1 Hz rock hazard: comparison of three source models .............. 8-43

Figure 8.2-1l Central Illinois PGA rock hazard: comparison of three source models............... 8-44

Figure 8.2-1m Central Illinois 10 Hz shallow soil hazard: total and total and contribution 

by RLME and background................................................................................................ 8-45

Figure 8.2-1n Central Illinois 1 Hz shallow soil hazard: total and contribution by RLME 

and background ............................................................................................................... 8-46

Figure 8.2-1o Central Illinois PGA shallow soil hazard: total and contribution by RLME 

and background ............................................................................................................... 8-47

Figure 8.2-1p Central Illinois 10 Hz deep soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-48

Figure 8.2-1q Central Illinois 1 Hz deep soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-49

Figure 8.2-1r Central Illinois PGA deep soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-50

Figure 8.2-1s Central Illinois 10 Hz hazard: comparison of three site conditions .................... 8-51

Figure 8.2-1t Central Illinois 1 Hz hazard: comparison of three site conditions ....................... 8-52

Figure 8.2-1u Central Illinois PGA hazard: comparison of three site conditions...................... 8-53

Figure 8.2-1v Central Illinois 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones................................................................................................................................ 8-54

Figure 8.2-1w Central Illinois 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones................................................................................................................................ 8-55

Figure 8.2-1x Central Illinois 10 Hz rock hazard: sensitivity to Mmax for source IBEB............ 8-56

Figure 8.2-1y Central Illinois 1 Hz rock hazard: sensitivity to Mmax for source IBEB.............. 8-57

Figure 8.2-1z Central Illinois 10 Hz rock hazard: sensitivity to smoothing options .................. 8-58

Figure 8.2-1aa Central Illinois 1 Hz rock hazard: sensitivity to smoothing options .................. 8-59

Figure 8.2-1bb Central Illinois 10 Hz rock hazard: sensitivity to eight realizations for 

source IBEB, Case A ....................................................................................................... 8-60
xliv

Figure 8.2-1cc Central Illinois 10 Hz rock hazard: sensitivity to eight realizations for 

source IBEB, Case B ....................................................................................................... 8-61

Figure 8.2-1dd Central Illinois 10 Hz rock hazard: sensitivity to eight realizations for 

source IBEB, Case E ....................................................................................................... 8-62

Figure 8.2-1ee Central Illinois 1 Hz rock hazard: sensitivity to eight realizations for 

source IBEB, Case A ....................................................................................................... 8-63

Figure 8.2-1ff Central Illinois 1 Hz rock hazard: sensitivity to eight realizations for source 

IBEB, Case B ................................................................................................................... 8-64

Figure 8.2-1gg Central Illinois 1 Hz rock hazard: sensitivity to eight realizations for 

source IBEB, Case E ....................................................................................................... 8-65

Figure 8.2-2a Chattanooga 10 Hz rock hazard: mean and fractile total hazard ...................... 8-66

Figure 8.2-2b Chattanooga 1 Hz rock hazard: mean and fractile total hazard......................... 8-67

Figure 8.2-2c Chattanooga PGA rock hazard: mean and fractile total hazard ........................ 8-68

Figure 8.2-2d Chattanooga 10 Hz rock hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-69

Figure 8.2-2e Chattanooga 1 Hz rock hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-70

Figure 8.2-2f Chattanooga PGA rock hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-71

Figure 8.2-2g Chattanooga 10 Hz rock hazard: contribution by background source............... 8-72

Figure 8.2-2h Chattanooga 1 Hz rock hazard: contribution by background source................. 8-73

Figure 8.2-2i Chattanooga PGA rock hazard: contribution by background source.................. 8-74

Figure 8.2-2j Chattanooga 10 Hz rock hazard: comparison of three source models............... 8-75

Figure 8.2-2k Chattanooga is 1 Hz rock hazard: comparison of three source models ............ 8-76

Figure 8.2-2l Chattanooga PGA rock hazard: comparison of three source models................. 8-77

Figure 8.2-2m Chattanooga 10 Hz shallow soil hazard: total and contribution by RLME 

and background ............................................................................................................... 8-78

Figure 8.2-2n Chattanooga 1 Hz shallow soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-79

Figure 8.2-2o Chattanooga PGA shallow soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-80

Figure 8.2-2p Chattanooga 10 Hz deep soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-81

Figure 8.2-2q Chattanooga 1 Hz deep soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-82

Figure 8.2-2r Chattanooga PGA deep soil hazard: total and contribution by RLME and 

background ...................................................................................................................... 8-83

Figure 8.2-2s Chattanooga 10 Hz hazard: comparison of three site conditions ...................... 8-84

Figure 8.2-2t Chattanooga 1 Hz hazard: comparison of three site conditions ......................... 8-85

Figure 8.2-2u Chattanooga PGA hazard: comparison of three site conditions........................ 8-86

Figure 8.2-2v Chattanooga 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones................................................................................................................................ 8-87
xlv 

Figure 8.2-2w Chattanooga 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones................................................................................................................................ 8-88

Figure 8.2-2x Chattanooga 10 Hz rock hazard: sensitivity to Mmax for source PEZ-N ........... 8-89

Figure 8.2-2y Chattanooga 1 Hz rock hazard: sensitivity to Mmax for source PEZ-N ............. 8-90

Figure 8.2-2z Chattanooga 10 Hz rock hazard: sensitivity to smoothing options .................... 8-91

Figure 8.2-2aa Chattanooga 1 Hz rock hazard: sensitivity to smoothing options .................... 8-92

Figure 8.2-2bb Chattanooga 10 Hz rock hazard: sensitivity to eight realizations for 

source PEZ-N, Case A..................................................................................................... 8-93

Figure 8.2-2cc Chattanooga 10 Hz rock hazard: sensitivity to eight realizations for 

source PEZ-N, Case B..................................................................................................... 8-94

Figure 8.2-2dd Chattanooga 10 Hz rock hazard: sensitivity to eight realizations for 

source PEZ-N, Case E..................................................................................................... 8-95

Figure 8.2-2ee Chattanooga 1 Hz rock hazard: sensitivity to eight realizations for source 

PEZ-N, Case A................................................................................................................. 8-96

Figure 8.2-2ff Chattanooga 1 Hz rock hazard: sensitivity to eight realizations for source 

PEZ-N, Case B................................................................................................................. 8-97

Figure 8.2-2gg Chattanooga 1 Hz rock hazard: sensitivity to eight realizations for source 

PEZ-N, Case E................................................................................................................. 8-98

Figure 8.2-3a Houston 10 Hz rock hazard: mean and fractile total hazard.............................. 8-99

Figure 8.2-3b Houston 1 Hz rock hazard: mean and fractile total hazard.............................. 8-100

Figure 8.2-3c Houston PGA rock hazard: mean and fractile total hazard.............................. 8-101

Figure 8.2-3d Houston 10 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-102

Figure 8.2-3e Houston 1 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-103

Figure 8.2-3f Houston PGA rock hazard: total and contribution by RLME and background.. 8-104

Figure 8.2-3g Houston 10 Hz rock hazard: contribution by background source .................... 8-105

Figure 8.2-3h Houston 1 Hz rock hazard: contribution by background source ...................... 8-106

Figure 8.2-3i Houston PGA rock hazard: contribution by background source ....................... 8-107

Figure 8.2-3j Houston 10 Hz rock hazard: comparison of three source models .................... 8-108

Figure 8.2-3k Houston is 1 Hz rock hazard: comparison of three source models.................. 8-109

Figure 8.2-3l Houston PGA rock hazard: comparison of three source models...................... 8-110

Figure 8.2-3m Houston 10 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-111

Figure 8.2-3n Houston 1 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-112

Figure 8.2-3o Houston PGA shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-113

Figure 8.2-3p Houston 10 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-114

Figure 8.2-3q Houston 1 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-115
xlvi 

Figure 8.2-3r Houston PGA deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-116

Figure 8.2-3s Houston 10 Hz hazard: comparison of three site conditions............................ 8-117

Figure 8.2-3t Houston 1 Hz hazard: comparison of three site conditions .............................. 8-118

Figure 8.2-3u Houston PGA hazard: comparison of three site conditions ............................. 8-119

Figure 8.2-3v Houston 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones .... 8-120

Figure 8.2-3w Houston 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones ..... 8-121 

Figure 8.2-3x Houston 10 Hz rock hazard: sensitivity to Mmax for source GHEX................. 8-122

Figure 8.2-3y Houston 1 Hz rock hazard: sensitivity to Mmax for source GHEX................... 8-123

Figure 8.2-3z Houston 10 Hz rock hazard: sensitivity to smoothing options.......................... 8-124

Figure 8.2-3aa Houston 1 Hz rock hazard: sensitivity to smoothing options ......................... 8-125

Figure 8.2-3bb Houston 10 Hz rock hazard: sensitivity to eight realizations for source 

GHEX, Case A ............................................................................................................... 8-126

Figure 8.2-3cc Houston 10 Hz rock hazard: sensitivity to eight realizations for source 

GHEX, Case B ............................................................................................................... 8-127

Figure 8.2-3dd Houston 10 Hz rock hazard: sensitivity to eight realizations for source 

GHEX, Case E ............................................................................................................... 8-128

Figure 8.2-3ee Houston 1 Hz rock hazard: sensitivity to eight realizations for source 

GHEX, Case A ............................................................................................................... 8-129

Figure 8.2-3ff Houston 1 Hz rock hazard: sensitivity to eight realizations for source 

GHEX, Case B ............................................................................................................... 8-130

Figure 8.2-3gg Houston 1 Hz rock hazard: sensitivity to eight realizations for source 

GHEX, Case E ............................................................................................................... 8-131

Figure 8.2-4a Jackson 10 Hz rock hazard: mean and fractile total hazard............................ 8-132

Figure 8.2-4b Jackson 1 Hz rock hazard: mean and fractile total hazard.............................. 8-133

Figure 8.2-4c Jackson PGA rock hazard: mean and fractile total hazard.............................. 8-134

Figure 8.2-4d Jackson 10 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-135

Figure 8.2-4e Jackson 1 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-136

Figure 8.2-4f Jackson PGA rock hazard: total and contribution by RLME and background .. 8-137

Figure 8.2-4g Jackson 10 Hz rock hazard: contribution by background source .................... 8-138

Figure 8.2-4h Jackson 1 Hz rock hazard: contribution by background source ...................... 8-139

Figure 8.2-4i Jackson PGA rock hazard: contribution by background source ....................... 8-140

Figure 8.2-4j Jackson 10 Hz rock hazard: comparison of three source models .................... 8-141

Figure 8.2-4k Jackson is 1 Hz rock hazard: comparison of three source models.................. 8-142

Figure 8.2-4l Jackson PGA rock hazard: comparison of three source models ...................... 8-143

Figure 8.2-4m Jackson 10 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-144

Figure 8.2-4n Jackson 1 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-145
xlvii 

Figure 8.2-4o Jackson PGA shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-146

Figure 8.2-4p Jackson 10 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-147

Figure 8.2-4q Jackson 1 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-148

Figure 8.2-4r Jackson PGA deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-149

Figure 8.2-4s Jackson 10 Hz hazard: comparison of three site conditions............................ 8-150

Figure 8.2-4t Jackson 1 Hz hazard: comparison of three site conditions .............................. 8-151

Figure 8.2-4u Jackson PGA hazard: comparison of three site conditions ............................. 8-152

Figure 8.2-4v Jackson 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones .... 8-153

Figure 8.2-4w Jackson 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones ..... 8-154

Figure 8.2-4x Jackson 10 Hz rock hazard: sensitivity to Mmax for source ECC-GC............. 8-155

Figure 8.2-4y Jackson 1 Hz rock hazard: sensitivity to Mmax for source ECC-GC............... 8-156

Figure 8.2-4z Jackson 10 Hz rock hazard: sensitivity to smoothing options.......................... 8-157

Figure 8.2-4aa Jackson 1 Hz rock hazard: sensitivity to smoothing options.......................... 8-158

Figure 8.2-4bb Jackson 10 Hz rock hazard: sensitivity to eight realizations for source 

ECC-GC, Case A ........................................................................................................... 8-159

Figure 8.2-4cc Jackson 10 Hz rock hazard: sensitivity to eight realizations for source 

ECC-GC, Case B ........................................................................................................... 8-160

Figure 8.2-4dd Jackson 10 Hz rock hazard: sensitivity to eight realizations for source 

ECC-GC, Case E ........................................................................................................... 8-161

Figure 8.2-4ee Jackson 1 Hz rock hazard: sensitivity to eight realizations for source 

ECC-GC, Case A ........................................................................................................... 8-162

Figure 8.2-4ff Jackson 1 Hz rock hazard: sensitivity to eight realizations for source ECCGC, Case B.................................................................................................................... 8-163

Figure 8.2-4gg Jackson 1 Hz rock hazard: sensitivity to eight realizations for source 

ECC-GC, Case E ........................................................................................................... 8-164

Figure 8.2-5a Manchester 10 Hz rock hazard: mean and fractile total hazard ...................... 8-165

Figure 8.2-5b Manchester 1 Hz rock hazard: mean and fractile total hazard ........................ 8-166

Figure 8.2-5c Manchester PGA rock hazard: mean and fractile total hazard ........................ 8-167

Figure 8.2-5d Manchester 10 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-168

Figure 8.2-5e Manchester 1 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-169

Figure 8.2-5f Manchester PGA rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-170

Figure 8.2-5g Manchester 10 Hz rock hazard: contribution by background source............... 8-171

Figure 8.2-5h Manchester 1 Hz rock hazard: contribution by background source................. 8-172

Figure 8.2-5i Manchester PGA rock hazard: contribution by background source.................. 8-173

Figure 8.2-5j Manchester 10 Hz rock hazard: comparison of three source models............... 8-174
xlviii 

Figure 8.2-5k Manchester is 1 Hz rock hazard: comparison of three source models ............ 8-175

Figure 8.2-5l Manchester PGA rock hazard: comparison of three source models................. 8-176

Figure 8.2-5m Manchester 10 Hz shallow soil hazard: total and contribution by RLME 

and background ............................................................................................................. 8-177

Figure 8.2-5n Manchester 1 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-178

Figure 8.2-5o Manchester PGA shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-179

Figure 8.2-5p Manchester 10 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-180

Figure 8.2-5q Manchester 1 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-181

Figure 8.2-5r Manchester PGA deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-182

Figure 8.2-5s Manchester 10 Hz hazard: comparison of three site conditions ...................... 8-183

Figure 8.2-5t Manchester 1 Hz hazard: comparison of three site conditions......................... 8-184

Figure 8.2-5u Manchester PGA hazard: comparison of three site conditions........................ 8-185

Figure 8.2-5v Manchester 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones.............................................................................................................................. 8-186

Figure 8.2-5w Manchester 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones.............................................................................................................................. 8-187

Figure 8.2-5x Manchester 10 Hz rock hazard: sensitivity to Mmax for source NAP .............. 8-188

Figure 8.2-5y Manchester 1 Hz rock hazard: sensitivity to Mmax for source NAP ................ 8-189

Figure 8.2-5z Manchester 10 Hz rock hazard: sensitivity to smoothing options .................... 8-190

Figure 8.2-5aa Manchester 1 Hz rock hazard: sensitivity to smoothing options.................... 8-191

Figure 8.2-5bb Manchester 10 Hz rock hazard: sensitivity to eight realizations for source 

NAP, Case A.................................................................................................................. 8-192

Figure 8.2-5cc Manchester 10 Hz rock hazard: sensitivity to eight realizations for source 

NAP, Case B.................................................................................................................. 8-193

Figure 8.2-5dd Manchester 10 Hz rock hazard: sensitivity to eight realizations for source 

NAP, Case E.................................................................................................................. 8-194

Figure 8.2-5ee Manchester 1 Hz rock hazard: sensitivity to eight realizations for source 

NAP, Case A.................................................................................................................. 8-195

Figure 8.2-5ff Manchester 1 Hz rock hazard: sensitivity to eight realizations for source 

NAP, Case B.................................................................................................................. 8-196

Figure 8.2-5gg Manchester 1 Hz rock hazard: sensitivity to eight realizations for source 

NAP, Case E.................................................................................................................. 8-197

Figure 8.2-6a Savannah 10 Hz rock hazard: mean and fractile total hazard......................... 8-198

Figure 8.2-6b Savannah 1 Hz rock hazard: mean and fractile total hazard........................... 8-199

Figure 8.2-6c Savannah PGA rock hazard: mean and fractile total hazard........................... 8-200

Figure 8.2-6d Savannah 10 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-201
xlix

Figure 8.2-6e Savannah 1 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-202

Figure 8.2-6f Savannah PGA rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-203

Figure 8.2-6g Savannah 10 Hz rock hazard: contribution by background source ................. 8-204

Figure 8.2-6h Savannah 1 Hz rock hazard: contribution by background source ................... 8-205

Figure 8.2-6i Savannah PGA rock hazard: contribution by background source .................... 8-206

Figure 8.2-6j Savannah 10 Hz rock hazard: comparison of three source models ................. 8-207

Figure 8.2-6k Savannah is 1 Hz rock hazard: comparison of three source models............... 8-208

Figure 8.2-6l Savannah PGA rock hazard: comparison of three source models ................... 8-209

Figure 8.2-6m Savannah 10 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-210

Figure 8.2-6n Savannah 1 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-211

Figure 8.2-6o Savannah PGA shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-212

Figure 8.2-6p Savannah 10 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-213

Figure 8.2-6q Savannah 1 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-214

Figure 8.2-6r Savannah PGA deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-215

Figure 8.2-6s Savannah 10 Hz hazard: comparison of three site conditions......................... 8-216

Figure 8.2-6t Savannah 1 Hz hazard: comparison of three site conditions............................ 8-217

Figure 8.2-6u Savannah PGA hazard: comparison of three site conditions .......................... 8-218

Figure 8.2-6v Savannah 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax 

zones.............................................................................................................................. 8-219

Figure 8.2-6w Savannah 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones .. 8-220

Figure 8.2-6x Savannah 10 Hz rock hazard: sensitivity to Mmax for source ECC-AM.......... 8-221

Figure 8.2-6y Savannah 1 Hz rock hazard: sensitivity to Mmax for source ECC-AM............ 8-222

Figure 8.2-6z Savannah 10 Hz rock hazard: sensitivity to smoothing options....................... 8-223

Figure 8.2-6aa Savannah 1 Hz rock hazard: sensitivity to smoothing options ...................... 8-224

Figure 8.2-6bb Savannah 10 Hz rock hazard: sensitivity to eight realizations for source 

ECC-AM, Case A ........................................................................................................... 8-225

Figure 8.2-6cc Savannah 10 Hz rock hazard: sensitivity to eight realizations for source 

ECC-AM, Case B ........................................................................................................... 8-226

Figure 8.2-6dd Savannah 10 Hz rock hazard: sensitivity to eight realizations for source 

ECC-AM, Case E ........................................................................................................... 8-227

Figure 8.2-6ee Savannah 1 Hz rock hazard: sensitivity to eight realizations for source 

ECC-AM, Case A ........................................................................................................... 8-228

Figure 8.2-6ff Savannah 1 Hz rock hazard: sensitivity to eight realizations for source 

ECC-AM, Case B ........................................................................................................... 8-229
l 

Figure 8.2-6gg Savannah 1 Hz rock hazard: sensitivity to eight realizations for source 

ECC-AM, Case E ........................................................................................................... 8-230

Figure 8.2-7a Topeka 10 Hz rock hazard: mean and fractile total hazard ............................. 8-231

Figure 8.2-7b Topeka 1 Hz rock hazard: mean and fractile total hazard ............................... 8-232

Figure 8.2-7c Topeka PGA rock hazard: mean and fractile total hazard ............................... 8-233

Figure 8.2-7d Topeka 10 Hz rock hazard: total and contribution by RLME and 

background .................................................................................................................... 8-234

Figure 8.2-7e Topeka 1 Hz rock hazard: total and contribution by RLME and background... 8-235

Figure 8.2-7f Topeka PGA rock hazard: total and contribution by RLME and background ... 8-236

Figure 8.2-7g Topeka 10 Hz rock hazard: contribution by background source...................... 8-237

Figure 8.2-7h Topeka 1 Hz rock hazard: contribution by background source........................ 8-238

Figure 8.2-7i Topeka PGA rock hazard: contribution by background source ........................ 8-239

Figure 8.2-7j Topeka 10 Hz rock hazard: comparison of three source models...................... 8-240

Figure 8.2-7k Topeka is 1 Hz rock hazard: comparison of three source models................... 8-241

Figure 8.2-7l Topeka PGA rock hazard: comparison of three source models ....................... 8-242

Figure 8.2-7m Topeka 10 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-243

Figure 8.2-7n Topeka 1 Hz shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-244

Figure 8.2-7o Topeka PGA shallow soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-245

Figure 8.2-7p Topeka 10 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-246

Figure 8.2-7q Topeka 1 Hz deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-247

Figure 8.2-7r Topeka PGA deep soil hazard: total and contribution by RLME and 

background .................................................................................................................... 8-248

Figure 8.2-7s Topeka 10 Hz hazard: comparison of three site conditions............................. 8-249

Figure 8.2-7t Topeka 1 Hz hazard: comparison of three site conditions................................ 8-250

Figure 8.2-7u Topeka PGA hazard: comparison of three site conditions .............................. 8-251

Figure 8.2-7v Topeka 10 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones ..... 8-252

Figure 8.2-7w Topeka 1 Hz rock hazard: sensitivity to seismotectonic vs. Mmax zones....... 8-253

Figure 8.2-7x Topeka 10 Hz rock hazard: sensitivity to Mmax for source MidC-A ................ 8-254

Figure 8.2-7y Topeka 1 Hz rock hazard: sensitivity to Mmax for source MidC-A .................. 8-255

Figure 8.2-7z Topeka 10 Hz rock hazard: sensitivity to smoothing options........................... 8-256

Figure 8.2-7aa Topeka 1 Hz rock hazard: sensitivity to smoothing options........................... 8-257

Figure 8.2-7bb Topeka 10 Hz rock hazard: sensitivity to eight realizations for source 

MidC-A, Case A ............................................................................................................. 8-258

Figure 8.2-7cc Topeka 10 Hz rock hazard: sensitivity to eight realizations for source 

MidC-A, Case B ............................................................................................................. 8-259
li

Figure 8.2-7dd Topeka 10 Hz rock hazard: sensitivity to eight realizations for source 

MidC-A, Case E ............................................................................................................. 8-260

Figure 8.2-7ee Topeka 1 Hz rock hazard: sensitivity to eight realizations for source 

MidC-A, Case A ............................................................................................................. 8-261

Figure 8.2-7ff Topeka 1 Hz rock hazard: sensitivity to eight realizations for source MidCA, Case B....................................................................................................................... 8-262

Figure 8.2-7gg Topeka 1 Hz rock hazard: sensitivity to eight realizations for source 

MidC-A, Case E ............................................................................................................. 8-263

Figure 9.3-1 1 Hz sensitivity to rupture orientation at Savannah for the Charleston 

regional source................................................................................................................. 9-24

Figure 9.3-2 10 Hz sensitivity to rupture orientation at Savannah for the Charleston 

regional source................................................................................................................. 9-25

Figure 9.3-3 1 Hz sensitivity to seismogenic thickness at Manchester for the Charlevoix 

area source ...................................................................................................................... 9-26

Figure 9.3-4 10 Hz sensitivity to seismogenic thickness at Manchester for the Charlevoix 

area source ...................................................................................................................... 9-27

Figure 9.3-5 1 Hz sensitivity to rupture orientation (dip) at Manchester for the Charlevoix 

area source ...................................................................................................................... 9-28

Figure 9.3-6 10 Hz sensitivity to rupture orientation (dip) at Manchester for the 

Charlevoix area source .................................................................................................... 9-29

Figure 9.3-7 1 Hz sensitivity to seismogenic thickness at Topeka for the Cheraw fault 

source .............................................................................................................................. 9-30

Figure 9.3-8 10 Hz sensitivity to seismogenic thickness at Topeka for the Cheraw fault 

source .............................................................................................................................. 9-31

Figure 9.3-9 1 Hz sensitivity to rupture orientation (dip) at Topeka for the Cheraw fault 

source .............................................................................................................................. 9-32

Figure 9.3-10 10 Hz sensitivity to rupture orientation at Topeka for the Cheraw fault 

source .............................................................................................................................. 9-33

Figure 9.3-11 1 Hz sensitivity to seismogenic thickness at Jackson for the Commerce 

area source ...................................................................................................................... 9-34

Figure 9.3-12 10 Hz sensitivity to seismogenic thickness at Jackson for the Commerce 

area source ...................................................................................................................... 9-35

Figure 9.3-13 1 Hz sensitivity to seismogenic thickness at Jackson for the ERM-N area 

source .............................................................................................................................. 9-36

Figure 9.3-14 10 Hz sensitivity to seismogenic thickness at Jackson for the ERM-N area 

source .............................................................................................................................. 9-37

Figure 9.3-15 1 Hz sensitivity to seismogenic thickness at Jackson for the ERM-S area 

source .............................................................................................................................. 9-38

Figure 9.3-16 10 Hz sensitivity to seismogenic thickness at Jackson for the ERM-S area 

source .............................................................................................................................. 9-39

Figure 9.3-17 1 Hz sensitivity to seismogenic thickness at Jackson for the Marianna area 

source .............................................................................................................................. 9-40

Figure 9.3-18 10 Hz sensitivity to seismogenic thickness at Jackson for the Marianna 

area source ...................................................................................................................... 9-41
lii

Figure 9.3-19 1 Hz sensitivity to seismogenic thickness at Topeka for the Meers fault 

and OKA area sources..................................................................................................... 9-42

Figure 9.3-20 1 Hz sensitivity to seismogenic thickness at Houston for the Meers fault 

and OKA area sources..................................................................................................... 9-43

Figure 9.3-21 10 Hz sensitivity to seismogenic thickness at Topeka for the Meers fault 

and OKA area sources..................................................................................................... 9-44

Figure 9.3-22 10 Hz sensitivity to seismogenic thickness at Houston for the Meers fault 

and OKA area sources..................................................................................................... 9-45

Figure 9.3-23 1 Hz sensitivity to rupture orientation at Houston for the OKA area source ...... 9-46

Figure 9.3-24 10 Hz sensitivity to rupture orientation at Houston for the OKA area source .... 9-47

Figure 9.3-25 1 Hz sensitivity to rupture orientation (dip) at Topeka for the OKA area 

source .............................................................................................................................. 9-48

Figure 9.3-26 1 Hz sensitivity to rupture orientation (dip) at Houston for the OKA area 

source .............................................................................................................................. 9-49

Figure 9.3-27 10 Hz sensitivity to rupture orientation (dip) at Topeka for the OKA area 

source .............................................................................................................................. 9-50

Figure 9.3-28 10 Hz sensitivity to rupture orientation (dip) at Houston for the OKA area 

source .............................................................................................................................. 9-51

Figure 9.3-29 1 Hz sensitivity to rupture orientation (dip) at Topeka for the Meers fault 

source .............................................................................................................................. 9-52

Figure 9.3-30 1 Hz sensitivity to rupture orientation (dip) at Houston for the Meers fault 

source .............................................................................................................................. 9-53

Figure 9.3-31 10 Hz sensitivity to rupture orientation (dip) at Topeka for the Meers fault 

source .............................................................................................................................. 9-54

Figure 9.3-32 10 Hz sensitivity to rupture orientation (dip) at Houston for the Meers fault 

source .............................................................................................................................. 9-55

Figure 9.3-33 1 Hz sensitivity to seismogenic thickness at Jackson for the NMFS fault 

sources............................................................................................................................. 9-56

Figure 9.3-34 10 Hz sensitivity to seismogenic thickness at Jackson for the NMFS fault 

sources............................................................................................................................. 9-57

Figure 9.3-35 1 Hz sensitivity to seismogenic thickness at Central Illinois for the Wabash 

Valley area source ........................................................................................................... 9-58

Figure 9.3-36 10 Hz sensitivity to seismogenic thickness at Central Illinois for the 

Wabash Valley area source ............................................................................................. 9-59

Figure 9.3-37 1 Hz sensitivity to rupture orientation (dip) at Central Illinois for the 

Wabash Valley area source ............................................................................................. 9-60

Figure 9.3-38 10 Hz sensitivity to rupture orientation (dip) at Central Illinois for the 

Wabash Valley area source ............................................................................................. 9-61

Figure 9.3-39 1 Hz sensitivity to fault ruptures vs. point source for the Central Illinois site 

from the Mid C–A background source.............................................................................. 9-62

Figure 9.3-40 10 Hz sensitivity to fault ruptures vs. point source for the Central Illinois 

site from the Mid C–A background source ....................................................................... 9-63

Figure 9.4-1 COVMH from EPRI (1989) team sources vs. ground motion amplitude for 

seven test sites: PGA (top), 10 Hz SA (middle), and 1 Hz SA (bottom)........................... 9-64
liii

Figure 9.4-2 COVMH from EPRI (1989) team sources vs. seismic hazard (i.e., annual 

frequency of exceedance) for seven test sites: PGA (top), 10 Hz SA (middle), and 1 

9-Hz SA (bottom) ............................................................................................................. 9-65

Figure 9.4-3 COVMH from seismic source experts (PEGASOS project) vs. amplitude (top) 

and annual frequency (bottom) ........................................................................................ 9-66

Figure 9.4-4 COVK and COVMH from Charleston alternatives for PGA, plotted vs. PGA 

amplitude (top) and hazard (bottom). COVMH is the total COV of mean hazard; see 

Table 9.4-2 for other labels for curves. ............................................................................ 9-67

Figure 9.4-5 COVK and COVMH from Charleston alternatives for 10 Hz, plotted vs. 10 Hz 

amplitude (top) and hazard (bottom). COVMH is the total COV of mean hazard; see 

Table 9.4-2 for other labels for curves. ............................................................................ 9-68

Figure 9.4-6 COVK and COVMH from Charleston alternatives for 1 Hz, plotted vs. 1 Hz 

amplitude (top) and hazard (bottom). COVMH is the total COV of mean hazard; see 

Table 9.4-2 for other labels for curves.. ........................................................................... 9-69

Figure 9.4-7 COVK and COVMH of total hazard from New Madrid for 1 Hz, plotted vs. 1 

Hz amplitude (top) and hazard (bottom). COVMH is the total COV; see the text for 

other labels for curves...................................................................................................... 9-70

Figure 9.4-8 PGA hazard curves for Manchester test site ....................................................... 9-71

Figure 9.4-9 COVMH of PGA hazard at Manchester site from ground motion equation vs. 

PGA.................................................................................................................................. 9-72

Figure 9.4-10 COV of PGA hazard at Manchester site from ground motion equation vs. 

hazard .............................................................................................................................. 9-73

Figure 9.4-11 COV of 10 Hz hazard at Manchester site from ground motion equations 

vs. hazard......................................................................................................................... 9-74

Figure 9.4-12 COV of 1 Hz hazard at Manchester site from ground motion equations vs. 

hazard .............................................................................................................................. 9-75

Figure 9.4-13 1 Hz spectral acceleration hazard curves for Manchester test site ................... 9-76

Figure 9.4-14 COVMH of PGA hazard at Chattanooga from ground motion equation vs. 

hazard .............................................................................................................................. 9-77

Figure 9.4-15 COVMH of 10 Hz hazard at Chattanooga from ground motion equation vs. 

hazard .............................................................................................................................. 9-78

Figure 9.4-16 COVMH of 1 Hz hazard at Chattanooga site from ground motion equation 

vs. hazard......................................................................................................................... 9-79

Figure 9.4-17 PGA hazard curves for Savannah test site........................................................ 9-80

Figure 9.4-18 COVMH of PGA hazard at Savannah site from ground motion equations vs. 

hazard .............................................................................................................................. 9-81

Figure 9.4-19 COVMH of 10 Hz hazard at Savannah site from ground motion equations 

vs. hazard......................................................................................................................... 9-82

Figure 9.4-20 COVMH of 1 Hz hazard at Savannah site from ground motion equations vs. 

hazard .............................................................................................................................. 9-83

Figure 9.4-21 PGA hazard curves for Columbia site ............................................................... 9-84

Figure 9.4-22 COVMH of PGA hazard at Columbia from ground motion equations vs. 

hazard .............................................................................................................................. 9-85
liv

Figure 9.4-23 COVMH of 10 Hz hazard at Columbia from ground motion equations vs. 

hazard .............................................................................................................................. 9-86

Figure 9.4-24 COVMH of 1 Hz hazard at Columbia from ground motion equations vs. 

hazard .............................................................................................................................. 9-87

Figure 9.4-25 COVMH of PGA hazard at Chattanooga (New Madrid only) vs. hazard ............. 9-88

Figure 9.4-26 COVMH of 10 Hz hazard at Chattanooga (New Madrid only) vs. hazard............ 9-89

Figure 9.4-27 COVMH of 1 Hz hazard at Chattanooga (New Madrid only) vs. hazard.............. 9-90

Figure 9.4-28 COVMH for PGA and 1 Hz SA vs. ground motion amplitude resulting from 

alternative ground motion experts, PEGASOS project..................................................... 9-91

Figure 9.4-29 COVMH for PGA and 1 Hz SA vs. mean hazard from alternative ground 

motion experts, PEGASOS project .................................................................................. 9-92

Figure 9.4-30 COVHAZ from ground motion equations vs. mean hazard for Chattanooga ....... 9-93

Figure 9.4-31 COVMH from ground motion equations vs. mean hazard for Central Illinois ...... 9-94

Figure 9.4-32 COVMH from soil experts vs. PGA and 1 Hz SA, PEGASOS project ................. 9-95

Figure 9.4-33 COVMH from soil experts vs. mean hazard for PGA and 1 Hz SA, 

PEGASOS project............................................................................................................ 9-96

Figure 9.4-34 COVMH resulting from site response models vs. mean hazard for four sites, 

1 Hz (top) and 10 Hz (bottom).......................................................................................... 9-97

Figure 11-1 Geologic time scale (Walker and Geissman, 2009) ...........................................11-10

Figure A-1 GEBCO elevation data for the CEUS study area (BODC, 2009). ........................ A-22

Figure A-2 CEUS SSC independent earthquake catalog ....................................................... A-24

Figure A-3 Bedrock geology and extended crust after Kanter (1994)..................................... A-26

Figure A-4 Crustal provinces after Rohs and Van Schmus (2007)......................................... A-28 

Figure A-5 Geologic map of North America ............................................................................ A-31 

Figure A-6 Locations of geologic cross sections in the CEUS................................................ A-33

Figure A-7 Precambrian crustal boundary after Van Schmus et al. (1996) ............................ A-35

Figure A-8a Precambrian geology and features after Reed (1993)........................................ A-37

Figure A-8b Explanation of Precambrian geology and features after Reed (1993) ................ A-38

Figure A-9 Precambrian provinces after Van Schmus et al. (2007)........................................ A-40

Figure A-10 Precambrian units after Whitmeyer and Karlstrom (2007) .................................. A-42

Figure A-11 Surficial materials in the conterminous United States after Soller et al. 

(2009).............................................................................................................................. A-44

Figure A-12 Basement and sediment thickness in the USGS Crustal Database for North 

America. Symbol size represents overlying sediment thickness (km); symbol color 

represents basement thickness (km). ............................................................................. A-46

Figure A-13 Top of basement P-wave seismic velocity in the USGS Crustal Database for 

North America ................................................................................................................. A-47

Figure A-14 Sediment thickness for North America and neighboring regions ........................ A-49

Figure A-15 Physiographic divisions of the conterminous United States after Fenneman 

and Johnson (1946) ........................................................................................................ A-51

Figure A-16 CEUS SSC free-air gravity anomaly grid. Shaded relief with 315-degree 

azimuth and 30-degree inclination applied...................................................................... A-54
lv

Figure A-17 CEUS SSC free-air gravity anomaly grid. Shaded relief with 180-degree 

azimuth and 30-degree inclination applied...................................................................... A-55

Figure A-18 CEUS SSC complete Bouguer gravity anomaly grid with free-air gravity 

anomaly in marine areas. Shaded relief with 315-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-56

Figure A-19 CEUS SSC complete Bouguer gravity anomaly grid with free-air gravity 

anomaly in marine areas. Shaded relief with 180-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-57

Figure A-20 CEUS SSC residual isostatic gravity anomaly grid. Shaded relief with 315-

degree azimuth and 30-degree inclination applied. ........................................................ A-58

Figure A-21 CEUS SSC residual isostatic gravity anomaly grid Shaded relief with 180-

degree azimuth and 30-degree inclination applied. ........................................................ A-59

Figure A-22 CEUS SSC regional isostatic gravity anomaly grid............................................. A-60

Figure A-23 CEUS SSC first vertical derivative of residual isostatic gravity anomaly grid...... A-61

Figure A-24 CEUS SSC first vertical derivative of Bouguer gravity anomaly grid with 

free-air anomaly in marine areas .................................................................................... A-62

Figure A-25 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

low pass filtered at 240 km.............................................................................................. A-63

Figure A-26 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

high pass filtered at 240 km. Shaded relief with 315-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-64

Figure A-27 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

high pass filtered at 240 km. Shaded relief with 180-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-65

Figure A-28 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

high pass filtered at 120 km. Shaded relief with 315-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-66

Figure A-29 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

high pass filtered at 120 km. Shaded relief with 180-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-67

Figure A-30 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

upward continued to 40 km ............................................................................................. A-68

Figure A-31 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

minus the complete Bouguer (with marine free-air) gravity anomaly upward 

continued to 40 km. Shaded relief with 315-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-69

Figure A-32 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

minus the complete Bouguer (with marine free-air) gravity anomaly upward 

continued to 40 km. Shaded relief with 180-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-70

Figure A-33 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

upward continued to 100 km ........................................................................................... A-71

Figure A-34 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

minus the complete Bouguer (with marine free-air) gravity anomaly anomaly 
lvi 

upward continued to 100 km. Shaded relief with 315-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-72

Figure A-35 CEUS SSC complete Bouguer (with marine free-air) gravity anomaly grid 

minus the complete Bouguer (with marine free-air) gravity anomaly upward 

continued to 100 km. Shaded relief with 180-degree azimuth and 30-degree 

inclination applied............................................................................................................ A-73

Figure A-36 CEUS SSC horizontal derivative of residual isostatic gravity anomaly grid ........ A-74

Figure A-37 CEUS SSC horizontal derivative of first vertical derivative of residual 

isostatic gravity anomaly grid .......................................................................................... A-75

Figure A-38 Corrected heat flow values from the SMU Geothermal Laboratory Regional 

Heat Flow Database (2008) ............................................................................................ A-77

Figure A-39 CEUS SSC total intensity magnetic anomaly grid (Ravat et al., 2009). 

Shaded relief with 315-degree azimuth and 30-degree inclination applied..................... A-80

Figure A-40 CEUS SSC total intensity magnetic anomaly grid (Ravat et al., 2009). 

Shaded relief with 180-degree azimuth and 30-degree inclination applied..................... A-81

Figure A-41 CEUS SSC differentially reduced to pole magnetic anomaly grid (Ravat, 

2009). Shaded relief with 315-degree azimuth and 30-degree inclination applied.......... A-82

Figure A-42 CEUS SSC differentially reduced to pole magnetic anomaly grid (Ravat, 

2009). Shaded relief with 180-degree azimuth and 30-degree inclination applied.......... A-83

Figure A-43 CEUS SSC tilt derivative of differentially reduced to pole magnetic anomaly 

grid (degrees) (Ravat, 2009)........................................................................................... A-84

Figure A-44 CEUS SSC horizontal derivative of tilt derivative of differentially reduced to 

pole magnetic anomaly grid (radians) (Ravat, 2009) ...................................................... A-85

Figure A-45 CEUS SSC tilt derivative of differentially reduced to pole magnetic anomaly 

grid (Ravat, 2009) ........................................................................................................... A-86

Figure A-46 CEUS SSC amplitude of analytic signal magnetic anomaly grid (Ravat, 

2009)............................................................................................................................... A-87

Figure A-47 CEUS SSC paleoliquefaction database .............................................................. A-89

Figure A-48 CEUS SSC compilation of seismic reflection and seismic refraction lines.......... A-91

Figure A-49 USGS National Seismic Hazard Maps (Petersen et al., 2008) ........................... A-93

Figure A-50 USGS NSHM ground motion hazard at spectral acceleration of 1 hz with 2% 

probability of exceedance in 50 years (Petersen et al., 2008) ........................................ A-94

Figure A-51 USGS NSHM ground motion hazard at spectral acceleration of 1 hz with 5% 

probability of exceedance in 50 years (Petersen et al., 2008) ........................................ A-95

Figure A-52 USGS NSHM ground motion hazard at spectral acceleration of 1 hz with 

10% probability of exceedance in 50 years (Petersen et al., 2008) ................................ A-96

Figure A-53 USGS NSHM ground motion hazard at spectral acceleration of 3 hz with 2% 

probability of exceedance in 50 years (Petersen et al., 2008) ........................................ A-97

Figure A-54 USGS NSHM ground motion hazard at spectral acceleration of 3 hz with 5% 

probability of exceedance in 50 years (Petersen et al., 2008) ........................................ A-98

Figure A-55 USGS NSHM ground motion hazard at spectral acceleration of 3 hz with 

10% probability of exceedance in 50 years (Petersen et al., 2008) ................................ A-99

Figure A-56 USGS NSHM ground motion hazard at spectral acceleration of 5 hz with 2% 

probability of exceedance in 50 years (Petersen et al., 2008) ...................................... A-100
lvii

Figure A-57 USGS NSHM ground motion hazard at spectral acceleration of 5 hz with 5% 

probability of exceedance in 50 years (Petersen et al., 2008) ...................................... A-101

Figure A-58 USGS NSHM ground motion hazard at spectral acceleration of 5 hz with 

10% probability of exceedance in 50 years (Petersen et al., 2008).............................. A-102

Figure A-59 USGS NSHM peak ground acceleration with 2% probability of exceedance 

in 50 years (Petersen et al., 2008)................................................................................ A-103

Figure A-60 USGS NSHM peak ground acceleration with 5% probability of exceedance 

in 50 years (Petersen et al., 2008)................................................................................ A-104

Figure A-61 USGS NSHM peak ground acceleration with 10% probability of exceedance 

in 50 years (Petersen et al., 2008)................................................................................ A-105

Figure A-62 Deformation of the North American Plate interior using GPS station data 

(Calais et al., 2006)....................................................................................................... A-107

Figure A-63 Stress measurement update for the CEUS (Hurd, 2010).................................. A-110

Figure A-64 CEUS SSC Project study area boundary.......................................................... A-112

Figure A-65 USGS Quaternary fault and fold database (USGS, 2006)................................ A-114

Figure A-66 Quaternary features compilation for the CEUS (Crone and Wheeler, 2000; 

Wheeler, 2005; USGS, 2010) ....................................................................................... A-116

Figure A-67 CEUS Mesozoic rift basins after Benson (1992)............................................... A-118

Figure A-68 CEUS Mesozoic rift basins after Dennis et al. (2004)....................................... A-120

Figure A-69 CEUS Mesozoic rift basins after Schlische (1993)............................................ A-122

Figure A-70 CEUS Mesozoic rift basins after Withjack et al. (1998)..................................... A-124

Figure A-71 RLME zones for the CEUS ............................................................................... A-126

Figure A-72 Mesozoic and non-Mesozoic zones for the CEUS, wide interpretation............. A-128

Figure A-73 Mesozoic and non-Mesozoic zones for the CEUS, narrow interpretation......... A-129

Figure A-74 CEUS seismotectonic zones model A............................................................... A-130

Figure A-75 CEUS seismotectonic zones model B............................................................... A-131

Figure A-76 CEUS seismotectonic zones model C .............................................................. A-132

Figure A-77 CEUS seismotectonic zones model D .............................................................. A-133

Figure E-1 Map of CEUS showing locations of regional data sets included in the CEUS 

SSC Project paleoliquefaction database, including New Madrid seismic zone and 

surrounding region; Marianna, Arkansas, area; St. Louis region; Wabash Valley 

seismic zone and surrounding region; Arkansas-Louisiana-Mississippi region; 

Charleston seismic zone; Atlantic Coastal region and the Central Virginia seismic 

zone; Newburyport, Massachusetts, and surrounding region; and Charlevoix 

seismic zone and surrounding region. ............................................................................ E-68 

Figure E-2 Diagram illustrating size parameters of liquefaction features, including sand 

blow thickness, width, and length; dike width; and sill thickness, as well as some of 

the diagnostic characteristics of these features. ............................................................. E-69

Figure E-3 Diagram illustrating sampling strategy for dating of liquefaction features as 

well as age data, such as 14C maximum and 14C minimum, used to calculate 

preferred age estimates and related uncertainties of liquefaction features..................... E-70

Figure E-4 GIS map of New Madrid seismic zone and surrounding region showing 

portions of rivers searched for earthquake-induced liquefaction features by M. 
lviii

Tuttle, R. Van Arsdale, and J. Vaughn and collaborators (see explanation); 

information contributed for this report. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................... E-71

Figure E-5 GIS map of New Madrid seismic zone and surrounding region showing 

locations of liquefaction features for which there are and are not radiocarbon data. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. ............................................................................................................................... E-72

Figure E-6 GIS map of New Madrid seismic zone and surrounding region showing 

locations of liquefaction features that are thought to be historical or prehistoric in 

age or whose ages are poorly constrained. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. .................................................. E-73

Figure E-7 GIS map of New Madrid seismic zone and surrounding region showing 

preferred age estimates of liquefaction features; features whose ages are poorly 

constrained are excluded. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. ................................................................................ E-74

Figure E-8 GIS map of New Madrid seismic zone and surrounding region showing 

measured thicknesses of sand blows. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................... E-75

Figure E-9 GIS map of New Madrid seismic zone and surrounding region showing 

preferred age estimates and measured thicknesses of sand blows. Map projection 

is USA Contiguous Albers Equal Area Conic, North America Datum 1983. ................... E-76

Figure E-10 GIS map of New Madrid seismic zone and surrounding region showing 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983......................................................................... E-77

Figure E-11 GIS map of New Madrid seismic zone and surrounding region showing 

preferred age estimates and measured widths of sand dikes. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................... E-78

Figure E-12 GIS map of New Madrid seismic zone and surrounding region illustrating 

preferred age estimates and measured thicknesses of sand blows as well as 

preferred age estimates and measured widths of sand dikes for sites where sand 

blows do not occur. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983............................................................................................. E-79

Figure E-13 GIS map of Marianna, Arkansas, area showing seismicity and locations of 

paleoliquefaction features relative to mapped traces of Eastern Reelfoot rift margin 

fault, White River fault zone, Big Creek fault zone, Marianna escarpment, and 

Daytona Beach lineament. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. ................................................................................ E-80

Figure E-14 (A) Trench log and (B) ground-penetrating radar profile, showing vertical 

sections of sand blows and sand dikes at Daytona Beach SE2 site along the 

Daytona Beach lineament southwest of Marianna, Arkansas. Vertical scale of GPR 

profile is exaggerated (modified from Al-Shukri et al., 2009). ......................................... E-81

Figure E-15 GIS map of Marianna, Arkansas, area showing locations of liquefaction 

features for which there are and are not radiocarbon data. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................... E-82

Figure E-16 GIS map of Marianna, Arkansas, area showing locations of liquefaction 

features that are thought to be historical or prehistoric in age or whose ages are 

poorly constrained. To date, no liquefaction features thought to have formed during 
lix

1811-1812 earthquakes have been found in area. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................... E-83

Figure E-17 GIS map of Marianna, Arkansas, area showing preferred age estimates of 

liquefaction features; features whose ages are poorly constrained are excluded. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. ............................................................................................................................... E-84

Figure E-18 GIS map of Marianna, Arkansas, area showing measured thicknesses of 

sand blows. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. ..................................................................................................... E-85 

Figure E-19 GIS map of Marianna, Arkansas, area showing preferred age estimates and 

measured thicknesses of sand blows. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................... E-86

Figure E-20 GIS map of Marianna, Arkansas, area showing measured widths of sand 

dikes. Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983..................................................................................................................... E-87 

Figure E-21 GIS map of Marianna, Arkansas, area showing preferred age estimates and 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983......................................................................... E-88

Figure E-22 GIS map of St. Louis, Missouri, region showing seismicity and portions of 

rivers searched for earthquake-induced liquefaction features by Tuttle and 

collaborators; information contributed for this report. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................... E-89

Figure E-23 GIS map of St. Louis, Missouri, region showing locations of liquefaction 

features, including several soft-sediment deformation structures, for which there are 

and are not radiocarbon data. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. ................................................................................ E-90

Figure E-24 GIS map of St. Louis, Missouri, region showing locations of liquefaction 

features that are thought to be historical or prehistoric in age or whose ages are 

poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983............................................................................................. E-91

Figure E-25 GIS map of St. Louis, Missouri, region showing preferred age estimates of 

liquefaction features; features whose ages are poorly constrained, including several 

that are prehistoric in age, are not shown. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................... E-92

Figure E-26 GIS map of St. Louis, Missouri, region showing measured thicknesses of 

sand blows at similar scale as used in Figure E-8 of sand blows in New Madrid 

seismic zone. Note that few sand blows have been found in St. Louis region. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. ............................................................................................................................... E-93

Figure E-27 GIS map of St. Louis, Missouri, region showing preferred age estimates and 

measured thicknesses of sand blows. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................... E-94

Figure E-28 GIS map of St. Louis, Missouri, region showing measured widths of sand 

dikes at similar scale as that used in Figure E-10 for sand dikes in New Madrid 

seismic zone. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. ..................................................................................................... E-95
lx

Figure E-29 GIS map of St. Louis, Missouri, region showing measured widths of sand 

dikes at similar scale as that used in Figures E-42 and E-48 for sand dikes in the 

Newburyport and Charlevoix regions, respectively. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................... E-96

Figure E-30 GIS map of St. Louis, Missouri, region showing preferred age estimates and 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983......................................................................... E-97

Figure E-31 GIS map of Wabash Valley seismic zone and surrounding region showing 

portions of rivers searched for earthquake-induced liquefaction features (digitized 

from McNulty and Obermeier, 1999). Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................... E-98

Figure E-32 GIS map of Wabash Valley seismic zone and surrounding region showing 

measured widths of sand dikes at similar scale as that used in Figures E-10 and E11 for sand dikes in New Madrid seismic zone. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. .................................................. E-99

Figure E-33 GIS map of Wabash Valley region of Indiana and Illinois showing preferred 

age estimates and paleoearthquake interpretation. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................. E-100

Figure E-34 GIS map of Arkansas-Louisiana-Mississippi (ALM) region showing 

paleoliquefaction study locations. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983....................................................................... E-101

Figure E-35 GIS map of Charleston, South Carolina, region showing locations of 

paleoliquefaction features for which there are and are not radiocarbon dates. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. ............................................................................................................................. E-102

Figure E-36 GIS map of Charleston, South Carolina, region showing locations of 

historical and prehistoric liquefaction features. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. ................................................ E-103

Figure E-37 Map of Atlantic coast region showing areas searched for paleoliquefaction 

features by Gelinas et al. (1998) and Amick, Gelinas, et al. (1990). Rectangles 

indicate 7.5-minute quadrangles in which sites were investigated for presence of 

paleoliquefaction features. The number of sites investigated is shown within that 

quadrangle, if known. Orange and yellow indicate quadrangles in which 

paleoliquefaction features were recognized.................................................................. E-104

Figure E-38 Map of Central Virginia seismic zone region showing portions of rivers 

searched for earthquake-induced liquefaction features by Obermeier and McNulty 

(1998)............................................................................................................................ E-105

Figure E-39 GIS map of Newburyport, Massachusetts, and surrounding region showing 

seismicity and portions of rivers searched for earthquake-induced liquefaction 

features (Gelinas et al., 1998; Tuttle, 2007, 2009). Solid black line crossing map 

represents Massachusetts–New Hampshire border. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................. E-106

Figure E-40 GIS map of Newburyport, Massachusetts, and surrounding region showing 

locations of liquefaction features for which there are and are not radiocarbon dates. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. ............................................................................................................................. E-107
lxi 

Figure E-41 GIS map of Newburyport, Massachusetts, and surrounding region showing 

locations of liquefaction features that are thought to be historical or prehistoric in 

age or whose ages are poorly constrained. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. ................................................ E-108

Figure E-42 GIS map of Newburyport, Massachusetts, and surrounding region showing 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983....................................................................... E-109

Figure E-43 GIS map of Newburyport, Massachusetts, and surrounding region showing 

preferred age estimates and measured widths of sand dikes. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................. E-110

Figure E-44 Map of Charlevoix seismic zone and adjacent St. Lawrence Lowlands 

showing mapped faults and portions of rivers along which reconnaissance and 

searches for earthquake-induced liquefaction features were performed. Charlevoix 

seismic zone is defined by concentration of earthquakes and locations of historical 

earthquakes northeast of Quebec City. Devonian impact structure in vicinity of 

Charlevoix seismic zone is outlined by black dashed line. Taconic thrust faults are 

indicated by solid black lines with sawteeth on upper plate; Iapetan rift faults are 

shown by solid black lines with hachure marks on downthrown side (modified from 

Tuttle and Atkinson, 2010). ........................................................................................... E-111

Figure E-45 GIS map of Charlevoix seismic zone and surrounding region showing 

locations of liquefaction features, including several soft-sediment deformation 

structures, for which there are and are not radiocarbon data. Note the location of 

1988 M 5.9 Saguenay earthquake northwest of the Charlevoix seismic zone. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. ............................................................................................................................. E-112

Figure E-46 GIS map of Charlevoix seismic zone and surrounding region showing 

locations of liquefaction features that are modern, historical, or prehistoric in age, or 

whose ages are poorly constrained. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983............................................................. E-113

Figure E-47 GIS map of Charlevoix seismic zone and surrounding region showing 

preferred age estimates of liquefaction features; features whose ages are poorly 

constrained are excluded. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. .............................................................................. E-114

Figure E-48 GIS map of Charlevoix seismic zone and surrounding region showing 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983....................................................................... E-115

Figure E-49 GIS map of Charlevoix seismic zone and surrounding region showing 

preferred age estimates and measured widths of sand dikes. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. ............................. E-116

Figure E-50 Photograph of moderate-sized sand blow (12 m long, 7 m wide, and 14 cm 

thick) that formed about 40 km from epicenter of 2001 M 7.7 Bhuj, India, 

earthquake (from Tuttle, Hengesh, et al., 2002), combined with schematic vertical 

section illustrating structural and stratigraphic relations of sand blow, sand dike, and 

source layer (modified from Sims and Garvin, 1995).................................................... E-117

Figure E-51 Tree trunks buried and killed by sand blows, vented during 1811-1812 New 

Madrid earthquakes (from Fuller, 1912)........................................................................ E-118
lxii

Figure E-52 Large sand-blow crater that formed during 2002 M 7.7 Bhuj, India, 

earthquake. Backpack for scale. Photograph: M. Tuttle (2001). ................................... E-119

Figure E-53 Sand-blow crater that formed during 1886 Charleston, South Carolina, 

earthquake. Photograph: J.K. Hillers (from USGS Photograph Library). ...................... E-120

Figure E-54 Photograph of sand blow and related sand dikes exposed in trench wall and 

floor in New Madrid seismic zone. Buried soil horizon is displaced downward 

approximately 1 m across two dikes. Clasts of soil horizon occur within dikes and 

overlying sand blow. Degree of soil development above and within sand blow 

suggests that it is at least several hundred years old and formed prior to 1811-1812 

New Madrid earthquakes. Organic sample (location marked by red flag) from crater 

fill will provide close minimum age constraint for formation of sand blow. For scale, 

each colored intervals on shovel handle represents 10 cm. Photograph: M. Tuttle...... E-121

Figure E-55 Sand dikes, ranging up to 35 cm wide, originate in pebbly sand layer and 

intrude overlying diamicton, These features were exposed in cutbank along 

Cahokia Creek about 25 km northeast of downtown St. Louis (from Tuttle, 2000)....... E-122

Figure E-56 Photograph of small diapirs of medium sand intruding base of overlying 

deposit of interbedded clayey silt and very fine sand, and clasts of clayey silt in 

underlying medium sand, observed along Ouelle River in Charlevoix seismic zone. 

Sand diapirs and clasts probably formed during basal erosion and foundering of 

clayey silt due to liquefaction of the underlying sandy deposit. Red portion of shovel 

handle represents 10 cm (modified from Tuttle and Atkinson, 2010)............................ E-123

Figures E-57 (A) Load cast formed in laminated sediments of Van Norman Lake during 

1952 Kern County, California, earthquake. Photograph: J. Sims (from Sims, 1975). 

(B) Load cast, pseudonodules, and related folds formed in laminated sediment 

exposed along Malbaie River in Charlevoix seismic zone. Sand dikes crosscutting 

these same laminated sediments occur at a nearby site. For scale, each painted 

interval of the shovel handle represents 10 cm (modified from Tuttle and Atkinson, 

2010). ............................................................................................................................ E-124

Figure E-58 Log of sand blow and uppermost portions of related sand dikes exposed in 

trench wall at Dodd site in New Madrid seismic zone. Sand dikes were also 

observed in opposite wall and trench floor. Sand blow buries pre-event A horizon, 

and a subsequent A horizon has developed in top of sand blow. Radiocarbon dating 

of samples collected above and below sand blow brackets its age between 490 and 

660 yr BP. Artifact assemblage indicates that sand blow formed during late 

Mississippian (300–550 yr BP or AD 1400–1670) (modified from Tuttle, Collier, et 

al., 1999). ...................................................................................................................... E-125

Figures E-59 (A) Photograph of earthquake-induced liquefaction features found in 

association with cultural horizon and pit exposed in trench wall near Blytheville, 

Arkansas, in New Madrid seismic zone. Photograph: M. Tuttle. (B) Trench log of 

features shown in (A). Sand dike formed in thick Native American occupation 

horizon containing artifacts of early Mississippian cultural period (950–1,150 yr BP). 

Cultural pit dug into top of sand dike contains artifacts and charcoal used to 

constrain minimum age of liquefaction features (modified from Tuttle and Schweig, 

1995). ............................................................................................................................ E-126

Figure E-60 In situ tree trunks such as this one buried and killed by sand blow in New 

Madrid seismic zone offer opportunity to date paleoearthquakes to the year and 

season of occurrence. Photograph: M. Tuttle. .............................................................. E-127
lxiii

Figure E-61 Portion of dendrocalibration curve illustrating conversion of radiocarbon age 

to calibrated date in calendar years. In example, 2-sigma radiocarbon age of 2,280–

2,520 BP is converted to calibrated date of 770–380 BC (from Tuttle, 1999)............... E-128

Figure E-62 Empirical relation developed between A horizon thickness of sand blows 

and years of soil development in New Madrid region. Horizontal bars reflect 

uncertainties in age estimates of liquefaction features; diamonds mark midpoints of 

possible age ranges (from Tuttle et al., 2000)............................................................... E-129

Figure E-63 Diagram illustrating earthquake chronology for New Madrid seismic zone for 

past 5,500 years based on dating and correlation of liquefaction features at sites 

(listed at top) across region from north to south. Vertical bars represent age 

estimates of individual sand blows, and horizontal bars represent event times of 

138 yr BP (AD 1811-1812); 500 yr BP ± 150 yr; 1,050 yr BP ± 100 yr; and 4,300 yr 

BP ± 200 yr (modified from Tuttle, Schweig, et al., 2002; Tuttle et al., 2005). .............. E-130

Figure E-64 Diagram illustrating earthquake chronology for New Madrid seismic zone for 

past 2,000 years, similar to upper portion of diagram shown in Figure E-63. As in 

Figure E-63, vertical bars represent age estimates of individual sand blows, and 

horizontal bars represent event times. Analysis performed during CEUS SSC 

Project derived two possible uncertainty ranges for timing of paleoearthquakes, 

illustrated by the darker and lighter portions of the colored horizontal bars, 

respectively: 503 yr BP ± 8 yr or 465 yr BP ± 65 yr, and 1,110 yr BP ± 40 yr or 1055 

± 95 yr (modified from Tuttle, Schweig, et al., 2002)..................................................... E-131

Figure E-65 Maps showing spatial distributions and sizes of sand blows and sand dikes 

attributed to 500 and 1,050 yr BP events. Locations and sizes of liquefaction 

features that formed during AD 1811-1812 (138 yr BP) New Madrid earthquake 

sequence shown for comparison (modified from Tuttle, Schweig, et al., 2002)............ E-132

Figure E-66 Liquefaction fields for 138 yr BP (AD 1811-1812); 500 yr BP (AD 1450); and 

1,050 yr BP (AD 900) events as interpreted from spatial distribution and 

stratigraphy of sand blows (modified from Tuttle, Schweig, et al., 2002). Ellipses 

define areas where similar-age sand blows have been mapped. Overlapping 

ellipses indicate areas where sand blows are composed of multiple units that 

formed during sequence of earthquakes. Dashed ellipse outlines area where 

historical sand blows are composed of four depositional units. Magnitudes of 

earthquakes in 500 yr BP and 1,050 yr BP are inferred from comparison with 1811-

1812 liquefaction fields. Magnitude estimates of December (D), January (J), and 

February (F) main shocks and large aftershocks taken from several sources; 

rupture scenario from Johnston and Schweig (1996; modified from Tuttle, Schweig, 

et al., 2002). .................................................................................................................. E-133

Figure E-67 Empirical relation between earthquake magnitude and epicentral distance to 

farthest known sand blows induced by instrumentally recorded earthquakes 

(modified from Castilla and Audemard, 2007)............................................................... E-134

Figure E-68 Distances to farthest known liquefaction features indicate that 500 and 

1,050 yr BP New Madrid events were at least of M 6.7 and 6.9, respectively, when 

plotted on Ambraseys (1988) relation between earthquake magnitude and 

epicentral distance to farthest surface expression of liquefaction. Similarity in size 

distribution of historical and prehistoric sand blows, however, suggests that 

paleoearthquakes were comparable in magnitude to 1811-1812 events or M ~7.6 

(modified from Tuttle, 2001). ......................................................................................... E-135

Figure H-1-1 Region covered by the CEUS SSC model......................................................... H-44
lxiv

Figure H-2-1 Master logic tree for the CEUS SSC model....................................................... H-45

Figure H-3-1 Logic tree for the Mmax zones branch of the master logic tree......................... H-46

Figure H-3-2 Mesozoic extended (MESE-W) and non-extended (NMESE-W) Mmax 

zones for the “wide” interpretation................................................................................... H-47

Figure H-3-3 Mesozoic extended (MESE-N) and non-extended (NMESE-N) Mmax zones 

for the “narrow” interpretation.......................................................................................... H-48

Figure H-4-1(a) Logic tree for the seismotectonic zones branch of the master logic tree....... H-49

Figure H-4-1(b) Logic tree for the seismotectonic zones branch of the master logic tree....... H-50

Figure H-4-2 Seismotectonic zones shown in the case where the Rough Creek Graben 

is not part of the Reelfoot Rift (RR) and the Paleozoic Extended zone is narrow 

(PEZ-N)........................................................................................................................... H-51

Figure H-4-3 Seismotectonic zones shown in the case where the Rough Creek Graben 

is part of the Reelfoot Rift (RR-RCG) and the Paleozoic Extended zone is narrow 

(PEZ-N)........................................................................................................................... H-52

Figure H-4-4 Seismotectonic zones shown in the case where the Rough Creek Graben 

is not part of the Reelfoot Rift (RR) and the Paleozoic Extended zone is wide (PEZW).................................................................................................................................... H-53

Figure H-4-5 Seismotectonic zones shown in the case where the Rough Creek Graben 

is part of the Reelfoot Rift (RR-RCG) and the Paleozoic Extended zone is wide 

(PEZ-W) .......................................................................................................................... H-54

Figure H-5-1 Logic tree for the RLME source branch of the master logic tree........................ H-55

Figure H-5-2 Location of RLME sources in the CEUS SSC model......................................... H-56

Figure H-5.1-1 Logic tree for Charlevoix RLME source .......................................................... H-57

Figure H-5.1-2 Charlevoix RLME source geometry ................................................................ H-58

Figure H-5.2-1(a) Logic tree for Charleston RLME source ..................................................... H-59

Figure H-5.2-1(b) Logic tree for Charleston RLME source ..................................................... H-60

Figure H-5.2-2 Charleston RLME alternative source geometries ........................................... H-61

Figure H-5.3-1 Logic tree for Cheraw RLME source............................................................... H-62

Figure H-5.3-2 Cheraw RLME source geometry..................................................................... H-63

Figure H-5.4-1 Logic tree for Meers RLME source ................................................................. H-64

Figure H-5.4-2 Meers RLME source geometries .................................................................... H-65

Figure H-5.5-1 Logic tree for NMFS RLME source................................................................. H-66

Figure H-5.5-2 New Madrid South (NMS) fault alternative RMLE source geometries: 

Blytheville Arch-Bootheel Lineament (BA-BL) and Blytheville Arch-Blytheville fault 

zone (BA-BFZ) ................................................................................................................ H-67

Figure H-5.5-3 New Madrid North (NMN) fault alternative RMLE source geometries: New 

Madrid North (NMN_S) and New Madrid North plus extension (NMN_L)....................... H-68

Figure H-5.5-4 Reelfoot Thrust (RFT) fault alternative RMLE source geometries: 

Reelfoot thrust (RFT_S) and Reelfoot thrust plus extensions (RFT_L)........................... H-69

Figure H-5.6-1 Logic tree for ERM-S RLME source ............................................................... H-70

Figure H-5.6-2 Logic tree for ERM-N RLME source ............................................................... H-71

Figure H-5.6-3 ERM-S RLME source geometries................................................................... H-72
lxv 

Figure H-5.6-4 ERM-N RLME source geometry ..................................................................... H-73

Figure H-5.7-1 Logic tree for Marianna RLME source ............................................................ H-74

Figure H-5.7-2 Marianna RLME source geometry .................................................................. H-75

Figure H-5.8-1 Logic tree for Commerce Fault Zone RLME source ....................................... H-76

Figure H-5.8-2 Commerce RLME source geometry ............................................................... H-77

Figure H-5.9-1 Logic tree for Wabash Valley RLME source ................................................... H-78

Figure H-5.9-2 Wabash Valley RLME source geometry ......................................................... H-79

Figure J-1 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 1 ........................................................................................................ J-2 

Figure J-2 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 2 ........................................................................................................ J-3 

Figure J-3 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 3 ........................................................................................................ J-4 

Figure J-4 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 4 ........................................................................................................ J-5 

Figure J-5 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 5 ........................................................................................................ J-6 

Figure J-6 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 6 ........................................................................................................ J-7 

Figure J-7 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 7 ........................................................................................................ J-8 

Figure J-8 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 8 ........................................................................................................ J-9 

Figure J-9 Map of the coefficient of variation of the rate and the standard deviation of the 

b-value for the study region under the Mmax zonation, with no separation of 

Mesozoic extended and non-extended; Case A magnitude weights................................ J-10

Figure J-10 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 1 ...................................................................................................... J-11

Figure J-11 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 2 ...................................................................................................... J-12

Figure J-12 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 3 ...................................................................................................... J-13
lxvi 

Figure J-13 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 4 ...................................................................................................... J-14

Figure J-14 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 5 ...................................................................................................... J-15

Figure J-15 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 6 ...................................................................................................... J-16

Figure J-16 Map of the rate and b-value for the study region under the Mmax zonation,

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 7 ...................................................................................................... J-17

Figure J-17 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 8 ...................................................................................................... J-18

Figure J-18 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with no separation of 

Mesozoic extended and non-extended; Case B magnitude weights................................ J-19

Figure J-19 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 1 ...................................................................................................... J-20

Figure J-20 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 2 ...................................................................................................... J-21

Figure J-21 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 3 ...................................................................................................... J-22

Figure J-22 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 4 ...................................................................................................... J-23

Figure J-23 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 5 ...................................................................................................... J-24

Figure J-24 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 6 ...................................................................................................... J-25

Figure J-25 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 7 ...................................................................................................... J-26

Figure J-26 Map of the rate and b-value for the study region under the Mmax zonation, 

with no separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 8 ...................................................................................................... J-27

Figure J-27 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with no separation of 

Mesozoic extended and non-extended; Case E magnitude weights................................ J-28
lxvii 

Figure J-28 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 1 ...................................................................................................... J-29

Figure J-29 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 2 ...................................................................................................... J-30

Figure J-30 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 3 ...................................................................................................... J-31

Figure J-31 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 4 ...................................................................................................... J-32

Figure J-32 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 5 ...................................................................................................... J-33

Figure J-33 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 6 ...................................................................................................... J-34

Figure J-34 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 7 ...................................................................................................... J-35

Figure J-35 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 8 ...................................................................................................... J-36

Figure J-36 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with separation of 

Mesozoic extended and non-extended; Case A magnitude weights................................ J-37

Figure J-37 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 1 ...................................................................................................... J-38

Figure J-38 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 2 ...................................................................................................... J-39

Figure J-39 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 3 ...................................................................................................... J-40

Figure J-40 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 4 ...................................................................................................... J-41

Figure J-41 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 5 ...................................................................................................... J-42

Figure J-42 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 6 ...................................................................................................... J-43
lxviii 

Figure J-43 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 7 ...................................................................................................... J-44

Figure J-44 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 8 ...................................................................................................... J-45

Figure J-45 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with separation of 

Mesozoic extended and non-extended; Case B magnitude weights................................ J-46

Figure J-46 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 1 ...................................................................................................... J-47

Figure J-47 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 2 ...................................................................................................... J-48

Figure J-48 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 3 ...................................................................................................... J-49

Figure J-49 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 4 ...................................................................................................... J-50

Figure J-50 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 5 ...................................................................................................... J-51

Figure J-51 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 6 ...................................................................................................... J-52

Figure J-52 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 7 ...................................................................................................... J-53

Figure J-53 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 8 ...................................................................................................... J-54

Figure J-54 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with separation of 

Mesozoic extended and non-extended; Case E magnitude weights................................ J-55

Figure J-55 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 1 ...................................................................................................... J-56

Figure J-56 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 2 ...................................................................................................... J-57

Figure J-57 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 3 ...................................................................................................... J-58
lxix

Figure J-58 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 4 ...................................................................................................... J-59

Figure J-59 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 5 ...................................................................................................... J-60

Figure J-60 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 6 ...................................................................................................... J-61

Figure J-61 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 7 ...................................................................................................... J-62

Figure J-62 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case A magnitude 

weights: Realization 8 ...................................................................................................... J-63

Figure J-63 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with separation of 

Mesozoic extended and non-extended; Case A magnitude weights................................ J-64

Figure J-64 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 1 ...................................................................................................... J-65

Figure J-65 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 2 ...................................................................................................... J-66

Figure J-66 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 3 ...................................................................................................... J-67

Figure J-67 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 4 ...................................................................................................... J-68

Figure J-68 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 5 ...................................................................................................... J-69

Figure J-69 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 6 ...................................................................................................... J-70

Figure J-70 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 7 ...................................................................................................... J-71

Figure J-71 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case B magnitude 

weights: Realization 8 ...................................................................................................... J-72

Figure J-72 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with separation of 

Mesozoic extended and non-extended; Case B magnitude weights................................ J-73
lxx 

Figure J-73 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 1 ...................................................................................................... J-74

Figure J-74 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 2 ...................................................................................................... J-75

Figure J-75 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 3 ...................................................................................................... J-76

Figure J-76 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 4 ...................................................................................................... J-77

Figure J-77 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 5 ...................................................................................................... J-78

Figure J-78 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 6 ...................................................................................................... J-79

Figure J-79 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 7 ...................................................................................................... J-80

Figure J-80 Map of the rate and b-value for the study region under the Mmax zonation, 

with separation of Mesozoic extended and non-extended; Case E magnitude 

weights: Realization 8 ...................................................................................................... J-81

Figure J-81 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the Mmax zonation, with separation of 

Mesozoic extended and non-extended; Case E magnitude weights................................ J-82

Figure J-82 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

1 ....................................................................................................................................... J-83

Figure J-83 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

2 ....................................................................................................................................... J-84

Figure J-84 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

3 ....................................................................................................................................... J-85

Figure J-85 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

4 ....................................................................................................................................... J-86

Figure J-86 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

5 ....................................................................................................................................... J-87

Figure J-87 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

6 ....................................................................................................................................... J-88
lxxi 

Figure J-88 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

7 ....................................................................................................................................... J-89

Figure J-89 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

8 ....................................................................................................................................... J-90

Figure J-90 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with narrow 

interpretation of PEZ; Case A magnitude weights ........................................................... J-91

Figure J-91 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

1 ....................................................................................................................................... J-92

Figure J-92 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

2 ....................................................................................................................................... J-93

Figure J-93 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

3 ....................................................................................................................................... J-94

Figure J-94 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

4 ....................................................................................................................................... J-95

Figure J-95 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

5 ....................................................................................................................................... J-96

Figure J-96 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

6 ....................................................................................................................................... J-97

Figure J-97 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

7 ....................................................................................................................................... J-98

Figure J-98 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

8 ....................................................................................................................................... J-99

Figure J-99 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with narrow 

interpretation of PEZ; Case B magnitude weights ......................................................... J-100

Figure J-100 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

1 ..................................................................................................................................... J-101

Figure J-101 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

2 ..................................................................................................................................... J-102

Figure J-102 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

3 ..................................................................................................................................... J-103
lxxii 

Figure J-103 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

4 ..................................................................................................................................... J-104

Figure J-104 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

5 ..................................................................................................................................... J-105

Figure J-105 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

6 ..................................................................................................................................... J-106

Figure J-106 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

7 ..................................................................................................................................... J-107

Figure J-107 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

8 ..................................................................................................................................... J-108

Figure J-108 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with narrow 

interpretation of PEZ; Case E magnitude weights ......................................................... J-109

Figure J-109 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

1 ..................................................................................................................................... J-110

Figure J-110 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

2 ..................................................................................................................................... J-111

Figure J-111 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

3 ..................................................................................................................................... J-112

Figure J-112 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

4 ..................................................................................................................................... J-113

Figure J-113 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

5 ..................................................................................................................................... J-114

Figure J-114 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

6 ..................................................................................................................................... J-115

Figure J-115 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

7 ..................................................................................................................................... J-116

Figure J-116 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case A magnitude weights: Realization 

8 ..................................................................................................................................... J-117

Figure J-117 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with narrow 

interpretation of PEZ; Case A magnitude weights ......................................................... J-118
lxxiii 

Figure J-118 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

1 ..................................................................................................................................... J-119

Figure J-119 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

2 ..................................................................................................................................... J-120

Figure J-120 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

3 ..................................................................................................................................... J-121

Figure J-121 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

4 ..................................................................................................................................... J-122

Figure J-122 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

5 ..................................................................................................................................... J-123

Figure J-123 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

6 ..................................................................................................................................... J-124

Figure J-124 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

7 ..................................................................................................................................... J-125

Figure J-125 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case B magnitude weights: Realization 

8 ..................................................................................................................................... J-126

Figure J-126 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with narrow 

interpretation of PEZ; Case B magnitude weights ......................................................... J-127

Figure J-127 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

1 ..................................................................................................................................... J-128

Figure J-128 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

2 ..................................................................................................................................... J-129

Figure J-129 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

3 ..................................................................................................................................... J-130

Figure J-130 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

4 ..................................................................................................................................... J-131

Figure J-131 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

5 ..................................................................................................................................... J-132

Figure J-132 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

6 ..................................................................................................................................... J-133
lxxiv 

Figure J-133 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

7 ..................................................................................................................................... J-134

Figure J-134 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with narrow interpretation of PEZ; Case E magnitude weights: Realization 

8 ..................................................................................................................................... J-135

Figure J-135 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with narrow 

interpretation of PEZ; Case E magnitude weights ......................................................... J-136

Figure J-136 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 1 ... J-137

Figure J-137 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 2 ... J-138

Figure J-138 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 3 ... J-139

Figure J-139 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 4 ... J-140

Figure J-140 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 5 ... J-141

Figure J-141 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 6 ... J-142

Figure J-142 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 7 ... J-143

Figure J-143 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 8 ... J-144

Figure J-144 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with wide

interpretation of PEZ; Case A magnitude weights ......................................................... J-145

Figure J-145 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 1 ... J-146

Figure J-146 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 2 ... J-147

Figure J-147 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 3 ... J-148

Figure J-148 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 4 ... J-149

Figure J-149 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 5 ... J-150

Figure J-150 Map of the rate and b-value for the study region under the seismotectonic

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 6 ... J-151

Figure J-151 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 7 ... J-152

Figure J-152 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 8 ... J-153
lxxv 

Figure J-153 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with wide 

interpretation of PEZ; Case B magnitude weights ......................................................... J-154

Figure J-154 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 1 ... J-155

Figure J-155 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 2 ... J-156

Figure J-156 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 3 ... J-157

Figure J-157 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 4 ... J-158

Figure J-158 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 5 ... J-159

Figure J-159 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 6 ... J-160

Figure J-160 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 7 ... J-161

Figure J-161 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 8 ... J-162

Figure J-162 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with wide 

interpretation of PEZ; Case E magnitude weights ......................................................... J-163

Figure J-163 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 1 ... J-164

Figure J-164 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 2 ... J-165

Figure J-165 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 3 ... J-166

Figure J-166 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 4 ... J-167

Figure J-167 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 5 ... J-168

Figure J-168 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 6 ... J-169

Figure J-169 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 7 ... J-170

Figure J-170 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case A magnitude weights: Realization 8 ... J-171

Figure J-171 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with wide 

interpretation of PEZ; Case A magnitude weights ......................................................... J-172

Figure J-172 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 1 ... J-173
lxxvi 

Figure J-173 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 2 ... J-174

Figure J-174 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 3 ... J-175

Figure J-175 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 4 ... J-176

Figure J-176 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 5 ... J-177

Figure J-177 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 6 ... J-178

Figure J-178 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 7 ... J-179

Figure J-179 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case B magnitude weights: Realization 8 ... J-180

Figure J-180 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with wide 

interpretation of PEZ; Case B magnitude weights ......................................................... J-181

Figure J-181 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 1 ... J-182

Figure J-182 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 2 ... J-183

Figure J-183 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 3 ... J-184

Figure J-184 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 4 ... J-185

Figure J-185 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 5 ... J-186

Figure J-186 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 6 ... J-187

Figure J-187 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 7 ... J-188

Figure J-188 Map of the rate and b-value for the study region under the seismotectonic 

zonation, with wide interpretation of PEZ; Case E magnitude weights: Realization 8 ... J-189

Figure J-189 Map of the coefficient of variation of the rate and the standard deviation of 

the b-value for the study region under the seismotectonic zonation, with wide 

interpretation of PEZ; Case E magnitude weights ......................................................... J-190

Figure K-1 Comparison of relationships between number of reporting stations and 

moment magnitude presented in Johnston et al. (1994) and Johnston (1996b)............. K-41

Figure K-2 Comparison of relationships between isoseismal areas and moment 

magnitude presented in Johnston et al. (1994) and Johnston (1996b)........................... K-42
lxxvii 

LIST OF TABLES

Table 2.2-1 Technical Meetings Conducted as Part of the CEUS SSC Project....................... 2-29

Table 2.2-2 Contributors to the CEUS SSC Project................................................................. 2-30

Table 3.2-1 Summary of Earthquakes Added–USGS Earthquake Catalog by Time 

Period ............................................................................................................................... 3-44

Table 3.2-2 Summary of Earthquakes Added–USGS Earthquake Catalog by Source............ 3-45

Table 3.3-1 Conversion Relationships Used–Develop Uniform Moment Magnitudes E[M]..... 3-46

Table 3.4-1 Comparison of CEUS SSC Catalog Declustering Results Obtained Using the 

EPRI (1988) Approach with the Gardner Knopoff (1974) Approach ................................ 3-47

Table 3.5-1 Probability of Detection and Equivalent Periods of Completeness for the 

CEUS for Magnitude Weighting Case A .......................................................................... 3-48

Table 3.5-2 Probability of Detection and Equivalent Periods of Completeness for the 

CEUS for Magnitude Weighting Case B .......................................................................... 3-51

Table 3.5-3 Probability of Detection and Equivalent Periods of Completeness for the 

CEUS for Magnitude Weighting Case E .......................................................................... 3-54

Table 4.1.2-1 Sample table indicating particular types of data that can be considered in 

the identification and characterization of seismic sources (Table 2, ANSI/ANS-2.27-

2008)................................................................................................................................ 4-26

Table 4.1.2-2 Sample table identifying the types of data that can be considered for 

characterizing different types of seismic sources, and an evaluation of the relative 

usefulness or credibility of the various data types (Budnitz et al., 1997).......................... 4-27

Table 4.1.2-3 Table showing the “generic” (not source-specific) evaluation of data to 

address indicators of a unique seismic source. The table indicates the TI Team’s 

assessment of the types of data that can be used to address the indicators and 

their relative usefulness. .................................................................................................. 4-28

Table 4.1.2-4 Example of Data Evaluation Table for the Illinois Basin–Extended 

Basement Zone (IBEB) .................................................................................................... 4-34

Table 4.1.2-5 Example of Data Summary Table for the Extended Continental Crust–

Atlantic Margin (ECC-AM) and Atlantic Highly Extended Crust (AHEX) Zones ............... 4-35

Table 4.1.3-1 Criteria Used to Define the Seismotectonic Zones and Mmax Zones ............... 4-37

Table 4.2.2-1 RLME Sources................................................................................................... 4-38

Table 4.2.4-1 Seismotectonic Zones ....................................................................................... 4-39

Table 5.2.1-1 Mesozoic-and-Younger Extended Superdomains (MESE)................................ 5-60

Table 5.2.1-2 Older Extended and Non-Extended Superdomains (NMESE) .......................... 5-61

Table 5.2.1-3 Composite SCR Superdomains (COMP)........................................................... 5-62

Table 5.2.1-4 Results of Analyses of Updated SCR Superdomains........................................ 5-63
lxxviii 

Table 5.2.1-5 Source Zones, P(mu > 81⁄4) Values, and Weights on Kijko (2004) K-S-B 

Estimates ......................................................................................................................... 5-64

Table 5.2.1-6 Mmax Distributions for the Two Example Seismic Sources............................... 5-65

Table 5.3.2-1 Alternative Cases Considered for the Magnitude-Dependent Weights.............. 5-65

Table 5.3.3-1 Miller and Rice (1983) Discrete 5-Point Approximation to a Continuous 

Probability Distribution and the Modified Form Used in This Study ................................. 5-65

Table 5.4-1 Assessment of Default Characteristics of Future Earthquakes in the CEUS........ 5-66

Table 5.4-2 Characteristics of Future Earthquakes for Individual Seismic Sources ................ 5-68

Table 5.4-3 Estimates of D90 for Individual Seismic Source Zones.......................................... 5-71

Table 6.1-1 Summary of Data Used to Assess RLME Recurrence Frequencies..................... 6-80

Table 6.1.1-1 Charlevoix RLME Recurrence Frequency ......................................................... 6-83

Table 6.1.2-1 Summary of Interpreted Charleston Earthquake Ages and Sizes from 

“Contemporary Ages Only” Scenario ............................................................................... 6-84

Table 6.1.2-2 Summary of Interpreted Charleston Earthquake Ages and Sizes from “All 

Ages” Scenario................................................................................................................. 6-84

Table 6.1.2-3 Charleston Liquefaction Feature Ages Used to Assess Ages of Prehistoric 

Earthquakes ..................................................................................................................... 6-85

Table 6.1.2-4 Charleston RLME Recurrence Frequency for Poisson Model ........................... 6-86

Table 6.1.2-5 Charleston RLME Recurrence Frequency for Renewal Model.......................... 6-87

Table 6.1.3-1 Range of Cheraw Fault Estimated Magnitudes (M)........................................... 6-88

Table 6.1.3-2 Cheraw RLME In-Cluster Recurrence Frequency ............................................. 6-89

Table 6.1.3-3 Cheraw RLME In-Cluster Slip Rates ................................................................. 6-89

Table 6.1.3-4 Cheraw RLME Out-of-Cluster Recurrence Frequency ...................................... 6-90

Table 6.1.3-5 Cheraw RLME Out-of-Cluster Slip Rates .......................................................... 6-90

Table 6.1.4-1 Range of Estimated Meers Fault Earthquake Magnitudes (M).......................... 6-91

Table 6.1.4-2 Meers RLME In-Cluster Recurrence Frequency................................................ 6-91

Table 6.1.4-3 Meers RLME Out-of-Cluster Recurrence Frequency......................................... 6-91

Table 6.1.5-1 Preferred Ages for Paleoearthquakes in the New Madrid Region1

................... 6-92

Table 6.1.5-2 Magnitude Comparisons for New Madrid 1811-1812 Earthquake 

Sequence ......................................................................................................................... 6-93

Table 6.1.5-3 Liquefaction Constraints on Age of AD 1450 NMFS RLME............................... 6-94

Table 6.1.5-4 Liquefaction Constraints on Age of AD 900 NMFS RLME................................. 6-95

Table 6.1.5-5 NMFS In-Cluster RLME Recurrence Frequency—Poisson Model .................... 6-96

Table 6.1.5-6 NMFS In-Cluster RLME Recurrence Frequency—Renewal Model ................... 6-96

Table 6.1.5-7 NMFS Out-of-Cluster RLME Recurrence Frequency—Poisson Model ............. 6-96

Table 6.1.6-1 Range of ERM-S Estimated Magnitudes (M)..................................................... 6-97

Table 6.1.6-2 Range of ERM-N Estimated Magnitudes (M) .................................................... 6-98

Table 6.1.6-3 ERM-S RLME Recurrence Frequency............................................................... 6-98

Table 6.1.6-4 ERM-N RLME Recurrence Frequency .............................................................. 6-99

Table 6.1.7-1 Marianna RLME Recurrence Frequency ........................................................... 6-99
lxxix 

Table 6.1.8-1 Range of Commerce Fault Zone RLME Estimated Magnitudes (M)................ 6-100

Table 6.1.8-2 Commerce Fault Zone RLME Recurrence Frequency..................................... 6-101

Table 6.1.9-1 Liquefaction Evidence for Prehistoric Earthquakes in the Southern Illinois 

Basin .............................................................................................................................. 6-102

Table 6.1.9-2 Wabash RLME Recurrence Frequency ........................................................... 6-109

Table 6.2-1 Alternative Mmax Zonation Models .................................................................... 6-109

Table 6.3.2-1 Maximum Magnitude Distributions for Mmax Distributed Seismicity 

Sources .......................................................................................................................... 6-110

Table 7.1-1 Data Summary and Data Evaluation Tables for Seismotectonic Zones in 

Appendices C and D ........................................................................................................ 7-81

Table 7.4.2-1 Maximum Magnitude Distributions for Seismotectonic Distributed 

Seismicity Sources ........................................................................................................... 7-82

Table 8.1-1 Description of Seven Test Sites............................................................................ 8-13

Table 8.2.1-1 Mean and Select Fractiles for Rock Hazard at Central Illinois: Digital Data

for Figures 8.2-1a through 8.2-1c..................................................................................... 8-14

Table 8.2.2-1 Mean and Select Fractiles for Rock Hazard at Chattanooga: Digital Data 

for Figures 8.2-2a through 8.2-2c..................................................................................... 8-16

Table 8.2.3-1 Mean and Select Fractiles for Rock Hazard at Houston: Digital Data for 

Figures 8.2-3a through 8.2-3c.......................................................................................... 8-18

Table 8.2.4-1 Mean and Select Fractiles for Rock Hazard at Jackson: Digital Data for 

Figures 8.2-4a through 8.2-4c.......................................................................................... 8-20

Table 8.2.5-1 Mean and Select Fractiles for Rock Hazard at Manchester: Digital Data for 

Figures 8.2-5a through 8.2-5c.......................................................................................... 8-22

Table 8.2.6-1 Mean and Select Fractiles for Rock Hazard at Savannah: Digital Data for 

Figures 8.2-6a through 8.2-6c.......................................................................................... 8-24

Table 8.2.7-1 Mean and Select Fractiles for Rock Hazard at Topeka: Digital Data for 

Figures 8.2-7a through 8.2-7c.......................................................................................... 8-26

Table 9.4-1 Available Information for Determining the Precision of Mean Hazard .................. 9-21

Table 9.4-2 Summary of an Example Logic Tree Representing Uncertainties for the 

Charleston Seismic Zone ................................................................................................. 9-21

Table 9.4-3 Basic Weights Given in EPRI (2004) for Ground Motion Equations ..................... 9-22

Table 9.4-4 Ground Motion Equations and Weights Used in USGS 2008 National Hazard 

Map for CEUS.................................................................................................................. 9-23

Table 9.4-5 Minimum COVMH Values Observed in Seismic Hazard ........................................ 9-23

Table A-1 CEUS SSC GIS Database ....................................................................................... A-7 

Table B-1 Earthquake Catalog.................................................................................................. B-6 

Table B-2 Moment Magnitude Data ...................................................................................... B-312

Table B-3 Approximate Moment Magnitude Data................................................................. B-324

Table C-5.4 Data Evaluation Future Earthquake Characteristics ............................................. C-3 

Table C-6.1.1 Data Evaluation Charlevoix RLME..................................................................... C-9 

Table C-6.1.2 Data Evaluation Charleston RLME .................................................................. C-14

Table C-6.1.3 Data Evaluation Cheraw Fault RLME .............................................................. C-30
lxxx 

Table C-6.1.4 Data Evaluation Oklahoma Aulacogen RLME ................................................. C-36 

Table C-6.1.5 Data Evaluation Reelfoot Rift–New Madrid Fault System RLMEs ................... C-42 

Table C-6.1.6 Data Evaluation Reelfoot Rift–Eastern Margin Fault(s) RLMEs ....................... C-51 

Table C-6.1.7 Data Evaluation Reelfoot Rift–Marianna RLME ............................................... C-62 

Table C-6.1.8 Data Evaluation Reelfoot Rift–Commerce Fault Zone RLME .......................... C-67 

Table C-6.1.9 Data Evaluation Wabash Valley RLME ............................................................ C-75 

Table C-7.3.1 Data Evaluation St. Lawrence Rift Zone ......................................................... C-83 

Table C-7.3.2 Data Evaluation Great Meteor Hotspot Zone ................................................... C-92 

Table C-7.3.3 Data Evaluation Northern Appalachian Zone ................................................... C-99 

Table C-7.3.4 Data Evaluation Paleozoic Extended Crust Zone .......................................... C-105 

Table C-7.3.5 Data Evaluation Illinois Basin-Extended Basement Zone .............................. C-112 

Table C-7.3.6 Data Evaluation Reelfoot Rift Zone ................................................................ C-124 

Tables C-7.3.7/7.3.8 Data Evaluation Extended Continental Crust—Atlantic ....................... C-131 

Tables C-7.3.9/7.3.10 Data Evaluation Extended Continental Crust–Gulf Coast ................ C-138 

Table C-7.3.12 Data Evaluation Midcontinent-Craton Zone ................................................ C-146 

Table D-5.4 Data Summary Future Earthquake Characteristics ............................................... D-3 

Table D-6.1.1 Data Summary Charlevoix RLME .................................................................... D-10 

Table D-6.1.2 Data Summary Charleston RLME .................................................................... D-17 

Table D-6.1.3 Data Summary Cheraw Fault RLME ................................................................ D-35 

Table D-6.1.4 Data Summary Oklahoma Aulacogen RLME ................................................... D-38 

Table D-6.1.5 Data Summary Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region ....... D-44 

Table D-6.1.9 Data Summary Wabash Valley RLME ............................................................. D-92 

Table D-7.3.1 Data Summary St. Lawrence Rift Zone (SLR) ............................................... D-121 

Table D-7.3.2 Data Summary Great Meteor Hotspot Zone (GMH) ....................................... D-141 

Table D-7.3.3 Data Summary Northern Appalachian Zone (NAP) ....................................... D-151 

Table D-7.3.4 Data Summary Paleozoic Extended Crust Zone ............................................ D-163 

Table D-7.3.7 Data Summary Extended Continental Crust Zone–Atlantic Margin (ECCAM) ................................................................................................................................ D-191 

Table D-7.3.9 Data Summary Extended Continental Crust Zone–Gulf Coast (ECC-GC) ..... D-225 

Table D-7.3.12 Data Summary Midcontinent-Craton Zone (MidC) ....................................... D-240 

Table E-1.2-1. Summary of Information on Liquefaction Features in Regional Data Sets........ E-5 

Table E-1.2-2 Summary of Type and Prevalence of Paleoliquefaction Features ..................... E-7 

Table E-2.1.3. Summary of Dating Techniques Used in Paleoliquefaction Studies................ E-30 

Table E-2.2. Uncertainties Related to Interpretation of Paleoearthquake Parameters ........... E-36 

Table 1: Key Questions and Topics That Workshop 2 Presenters Were Asked to 

Address ............................................................................................................................ F-35 

Table H-3-1 Weighted Alternative Seismogenic Crustal Thickness Values for Mmax 

Zones .............................................................................................................................. H-20 

Table H-3-2 Aleatory Distributions for Characterization of Future Earthquake Ruptures 

for Mmax Zones .............................................................................................................. H-20 
lxxxi 

Table H-3-3 Maximum Magnitude Distributions for Mmax Distributed Seismicity Sources .... H-20

Table H-4-1 Seismotectonic Source Zones ............................................................................ H-21

Table H-4-2 Weighted Alternative Seismogenic Crustal Thickness Values for 

Seismotectonic Zones..................................................................................................... H-21

Table H-4-3 Aleatory Distributions for Characterization of Future Earthquake Ruptures 

for Seismotectonic Zones................................................................................................ H-22

Table H-4-4 Maximum Magnitude Distributions for Seismotectonic Distributed Seismicity 

Sources ........................................................................................................................... H-24

Table H-5.1-1 Charlevoix RLME Magnitude Distribution ........................................................ H-25

Table H-5.1-2 Annual Frequencies for Charlevoix RLME Events Data Set 1: 1870 and 

1663 ................................................................................................................................ H-25 

Table H-5.1-3 Annual Frequencies for Charlevoix RLME Events Data Set 2: 3 

Earthquakes in 6–7 kyr BP.............................................................................................. H-25

Table H-5.1-4 Annual Frequencies for Charlevoix RLME Events Data Set 3: 4 

Earthquakes in 9.5–10.2 kyr BP...................................................................................... H-26

Table H-5.2-1 Charleston RLME Magnitude Distribution........................................................ H-26

Table H-5.2-2 Annual Frequencies for Charleston RLME Events Poisson Model, 2,000-

Year Time Period Earthquakes 1886, A, B, and C.......................................................... H-26

Table H-5.2-3 Annual Frequencies for Charleston RLME Events Poisson Model, 5,500-

Year Time Period Earthquakes 1886, A, B, and C.......................................................... H-27

Table H-5.2-4 Annual Frequencies for Charleston RLME Events Poisson Model, 5,500-

Year Time Period Earthquakes 1886, A, B, C, and D ..................................................... H-27

Table H-5.2-5 Annual Frequencies for Charleston RLME Events Poisson Model, 5,500-

Year Time Period Earthquakes 1886, A, B, C, and E ..................................................... H-27

Table H-5.2-6 Annual Frequencies for Charleston RLME Events Poisson Model, 5,500-

Year Time Period Earthquakes 1886, A, B, C, D, and E................................................. H-28

Table H-5.2-7 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.3, 2,000-Year Time Period Earthquakes 1886, A, B, and C ..................................... H-28

Table H-5.2-8 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.5, 2,000-Year Time Period Earthquakes 1886, A, B, and C ..................................... H-28

Table H-5.2-9 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.7, 2,000-Year Time Period Earthquakes 1886, A, B, and C ..................................... H-29

Table H-5.2-10 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.3, 5,500-Year Time Period Earthquakes 1886, A, B, and C ..................................... H-29

Table H-5.2-11 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.5, 5,500-Year Time Period Earthquakes 1886, A, B, and C ..................................... H-29

Table H-5.2-12 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.7, 5,500-Year Time Period Earthquakes 1886, A, B, and C ..................................... H-30

Table H-5.2-13 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.3, 5,500-Year Time Period Earthquakes 1886, A, B, C, and D................................. H-30

Table H-5.2-14 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.5, 5,500-Year Time Period Earthquakes 1886, A, B, C, and D................................. H-30
lxxxii 

Table H-5.2-15 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.7, 5,500-Year Time Period Earthquakes 1886, A, B, C, and D................................. H-31

Table H-5.2-16 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.3, 5,500-Year Time Period Earthquakes 1886, A, B, C, and E................................. H-31

Table H-5.2-17 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.5, 5,500-Year Time Period Earthquakes 1886, A, B, C, and E................................. H-31

Table H-5.2-18 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.7, 5,500-Year Time Period Earthquakes 1886, A, B, C, and E................................. H-32

Table H-5.2-19 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.3, 5,500-Year Time Period Earthquakes 1886, A, B, C, D, and E ............................ H-32

Table H-5.2-20 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.5, 5,500-Year Time Period Earthquakes 1886, A, B, C, D, and E ............................ H-32

Table H-5.2-21 Annual Frequencies for Charleston RLME Events BPT Renewal Model, α

= 0.7, 5,500-Year Time Period Earthquakes 1886, A, B, C, D, and E ............................ H-33

Table H-5.3-1 Cheraw RLME Magnitude Distribution............................................................. H-33

Table H-5.3-2 Annual Frequencies for Cheraw RLME Events In-Cluster Case, Data Set: 

2 Earthquakes in 20–25 kyr ............................................................................................ H-33

Table H-5.3-3 Annual Frequencies for Cheraw RLME Events In-Cluster Case, Data Set: 

3 Earthquakes in 20–25 kyr ............................................................................................ H-34

Table H-5.3-4 Slip Rates for Cheraw Fault In-Cluster Case, Data Set: 3.2–4.1 m in 20–

25 kyr .............................................................................................................................. H-34

Table H-5.3-5 Annual Frequencies for Cheraw RLME Events Out-of-Cluster Case, Time 

Between Clusters ............................................................................................................ H-34

Table H-5.3-6 Slip Rates for Cheraw Fault Out-of-Cluster Case, Data Set: 7–8 m in 0.4–

2.0 myr ............................................................................................................................ H-35

Table H-5.4-1 Meers RLME Magnitude Distribution ............................................................... H-35

Table H-5.4-2 Annual Frequencies for Meers RLME Events In-Cluster Case........................ H-35

Table H-5.4-3 Annual Frequencies for Meers RLME Events Out-of-Cluster Case................. H-36

Table H-5.5-1 NMFS RLME Magnitude Distribution ............................................................... H-36

Table H-5.5-2 Annual Frequencies for NMFS RLME Events In-Cluster Case, Poisson 

Model .............................................................................................................................. H-36

Table H-5.5-3 Annual Frequencies for NMFS RLME Events In-Cluster Case, BPT Model, 

α = 0.3 ............................................................................................................................. H-37

Table H-5.5-4 Annual Frequencies for NMFS RLME Events In-Cluster Case, BPT Model, 

α = 0.5 ............................................................................................................................. H-37

Table H-5.5-5 Annual Frequencies for NMFS RLME Events In-Cluster Case, BPT Model, 

α = 0.7 ............................................................................................................................. H-37

Table H-5.5-6 Annual Frequencies for NMFS RLME Events Out-of-Cluster Case, 

Poisson Model................................................................................................................. H-38

Table H-5.6-1 ERM-S RLME Magnitude Distribution.............................................................. H-38

Table H-5.6-2 ERM-N RLME Magnitude Distribution ............................................................. H-38

Table H-5.6-3 Annual Frequencies for ERM-S RLME Events Data Set: 2 Earthquakes in 

17.7–21.7 kyr .................................................................................................................. H-39
lxxxiii 

Table H-5.6-4 Annual Frequencies for ERM-S RLME Events Data Set: 3 Earthquakes in 

17.7–21.7 kyr .................................................................................................................. H-39

Table H-5.6-5 Annual Frequencies for ERM-S RLME Events Data Set: 4 Earthquakes in 

17.7–21.7 kyr .................................................................................................................. H-39

Table H-5.6-6 Annual Frequencies for ERM-N RLME Events Data Set: 1 Earthquake in 

12–35 kyr ........................................................................................................................ H-40

Table H-5.6-7 Annual Frequencies for ERM-N RLME Events Data Set: 2 Earthquakes in 

12–35 kyr ........................................................................................................................ H-40

Table H-5.7-1 Marianna RLME Magnitude Distribution .......................................................... H-40

Table H-5.7-2 Annual Frequencies for Marianna RLME Events Data Set: 3 Earthquakes 

in 9.6–10.2 kyr................................................................................................................. H-41

Table H-5.7-3 Annual Frequencies for Marianna RLME Events Data Set: 4 Earthquakes 

in 9.6–10.2 kyr................................................................................................................. H-41

Table H-5.8-1 Commerce RLME Magnitude Distribution........................................................ H-41

Table H-5.8-2 Annual Frequencies for Commerce RLME Events Data Set: 2 

Earthquakes in 18.9–23.6 kyr ......................................................................................... H-42

Table H-5.8-3 Annual Frequencies for Commerce RLME Events Data Set: 3 

Earthquakes in 18.9–23.6 kyr ......................................................................................... H-42

Table H-5.9-1 Wabash RLME Magnitude Distribution ............................................................ H-42

Table H-5.9-2 Annual Frequencies for Wabash RLME Events Data Set: 2 Earthquakes 

in 11–13 kyr..................................................................................................................... H-43

PPRP Comment Response Table ...............................................................................(Appendix I)

Table K-1 SCR Earthquake Catalog ......................................................................................... K-5 

Table K-2 SCR Domains Updated from Johnston et al. (1994).............................................. K-34

EXECUTIVE SUMMARY 

The Central and Eastern United States Seismic Source Characterization for Nuclear Facilities 

(CEUS SSC) Project was conducted over the period from April 2008 to December 2011 to 

provide a regional seismic source model for use in probabilistic seismic hazard analyses 

(PSHAs) for nuclear facilities. The study replaces previous regional seismic source models 

conducted for this purpose, including the Electric Power Research Institute–Seismicity Owners 

Group (EPRI-SOG) model (EPRI, 1988, 1989) and the Lawrence Livermore National 

Laboratory model (Bernreuter et al., 1989). Unlike the previous studies, the CEUS SSC Project 

was sponsored by multiple stakeholders—namely, the EPRI Advanced Nuclear Technology 

Program, the Office of Nuclear Energy and the Office of the Chief of Nuclear Safety of the U.S. 

Department of Energy (DOE), and the Office of Nuclear Regulatory Research of the Nuclear 

Regulatory Commission (NRC). The study was conducted using Senior Seismic Hazard Analysis 

Committee (SSHAC) Study Level 3 methodology to provide high levels of confidence that the 

data, models, and methods of the larger technical community have been considered and the 

center, body, and range of technically defensible interpretations have been included. 

The regional seismic source characterization (SSC) model defined by this study can be used for 

site-specific PSHAs, provided that appropriate site-specific assessments are conducted as 

required by current regulations and regulatory guidance for the nuclear facility of interest. This 

model has been designed to be compatible with current and anticipated ground-motion 

characterization (GMC) models. The current recommended ground-motion models for use at 

nuclear facilities are those developed by EPRI (2004, 2006a, 2006b). The ongoing Next 

Generation Attenuation–East (NGA-East) project being supported by the NRC, DOE, and EPRI 

will provide ground-motion models that are appropriate for use with the CEUS SSC model. The 

methodology for a SSHAC Level 3 project as applied to the CEUS SSC Project is explained in 

the SSHAC report (Budnitz et al., 1997), which was written to discuss the evolution of expert 

assessment methodologies conducted during the previous three decades for purposes of 

probabilistic risk analyses. The methodological guidance provided in the SSHAC report was 

intended to build on the lessons learned from those previous studies and, specifically, to arrive at 

processes that would make it possible to avoid the issues encountered by the previous studies 

(NRC, 2011).

The SSHAC assessment process, which differs only slightly for Level 3 and 4 studies, is a 

technical process accepted in the NRC’s seismic regulatory guidance (Regulatory Guide 1.208) 

for ensuring that uncertainties in data and scientific knowledge have been properly represented in 

seismic design ground motions consistent with the requirements of the seismic regulation 

10 CFR Part 100.23 (―Geologic and Seismic Siting Criteria‖). Therefore, the goal of the SSHAC 

assessment process is the proper and complete representation of knowledge and uncertainties in 

the SSC and GMC inputs to the PSHA (or similar hazard analysis). As discussed extensively in 

lxxxv
Executive Summary 

the SSHAC report (Budnitz et al., 1997) and affirmed in NRC (2011), a SSHAC assessment 

process consists of two important sequential activities, evaluation and integration. For a Level 3 

assessment, these activities are conducted by the Technical Integration (TI) Team under the 

leadership of the TI Lead. As described in NRC (2011), 

The fundamental goal of a SSHAC process is to carry out properly and document completely the 

activities of evaluation and integration, defined as: 

Evaluation: The consideration of the complete set of data, models, and methods proposed by 

the larger technical community that are relevant to the hazard analysis. 

Integration: Representing the center, body, and range of technically defensible interpretations 

in light of the evaluation process (i.e., informed by the assessment of existing data, models, 

and methods). 

Each of the assessment and model-building activities of the CEUS SSC Project is associated with 

the evaluation and integration steps in a SSHAC Level 3 process. Consistent with the 

requirements of a SSHAC process, the specific roles and responsibilities of all project 

participants were defined in the Project Plan, and adherence to those roles was the responsibility 

of the TI Lead and the Project Manager. The technical assessments are made by the TI Team, 

who carry the principal responsibility of evaluation and integration, under the technical 

leadership of the TI Lead. The Database Manager and other technical support individuals assist 

in the development of work products. Resource and proponent experts participate by presenting 

their data, models, and interpretations at workshops and through technical interchange with the 

TI Team throughout the project. The Participatory Peer Review Panel (PPRP) is responsible for a 

continuous review of both the SSHAC process being followed and the technical assessments 

being made. The project management structure is headed by the Project Manager, who serves as 

the liason with the sponsors and the PPRP and manages the activities of all participants. The 

SSHAC Level 3 assessment process and implementation is discussed in depth in Chapter 2 of 

this report. 

Each of the methodology steps in the SSHAC guidelines (Budnitz, 1997) was addressed 

adequately during the CEUS SSC Project. Furthermore, the project developed a number of 

enhancements to the process steps for conducting a SSHAC Study Level 3 project. For example, 

the SSHAC guidelines call for process steps that include developing a preliminary assessment 

model, calculating hazard using that model in order to identify the key issues, and finalizing the 

model in light of the feedback provided from the hazard calculations and sensitivity analyses. 

Because of the regional nature of the project and the multitude of assessments required, four 

rounds of model-building and three rounds of feedback were conducted. These activities ensured 

that all significant issues and uncertainties were identified and that the appropriate effort was 

devoted to the issues of most significance to the hazard results. A comparison of the activities 

conducted during the CEUS SSC Project with those recommended in the SSHAC guidelines 

themselves (Section 2.6) led to the conclusion that the current standards of practice have been 

met for a SSHAC Study Level 3 process—both those that are documented in the SSHAC report 

and those that resulted from precedents set by projects conducted since the SSHAC report was 

issued. 

lxxxvi
Executive Summary 

The catalog of past earthquakes that have occurred in a region is an important source of 

information for the quantification of future seismic hazards. This is particularly true in stable 

continental regions (SCRs) such as the CEUS where the causative mechanisms and structures for 

the occurrence of damaging earthquakes are generally poorly understood, and the rates of crustal 

deformation are low such that surface and near-surface indications of stresses in the crust and the 

buildup and release of crustal strains are difficult to quantify. Because the earthquake catalog is 

used in the characterization of the occurrence of future earthquakes in the CEUS, developing an 

updated earthquake catalog for the study region was an important focus of the CEUS SSC 

Project. The specific goals for earthquake catalog development and methods used to attain those 

goals are given in Chapter 3. 

The earthquake catalog development consists of four main steps: catalog compilation, 

assessment of a uniform size measure to apply to each earthquake, identification of dependent 

earthquakes (catalog declustering), and assessment of the completeness of the catalog as a 

function of location, time, and earthquake size. An important part of the catalog development 

process was review by seismologists with extensive knowledge and experience in catalog 

compilation. The result is an earthquake catalog covering the entire study region for the period 

from 1568 through the end of 2008. Earthquake size is defined in terms of the moment 

magnitude scale (Hanks and Kanamori, 1979), consistent with the magnitude scale used in 

modern ground-motion prediction equations (GMPEs) for CEUS earthquakes. A significant 

contribution of the CEUS SSC Project is the work conducted to develop an updated and 

consistent set of conversion relationships between various earthquake size measures 

(instrumental magnitudes and intensity) and moment magnitude. 

The conceptual SSC framework described in Chapter 4 was developed early in the CEUS SSC 

Project in order to provide a consistent approach and philosophy to SSC by the TI Team. This 

framework provides the basic underpinnings of the SSC model developed for the project, and it

led to the basic structure and elements of the master logic tree developed for the SSC model. In 

considering the purpose of the CEUS SSC Project, the TI Team identified three attributes that are 

needed for a conceptual SSC framework: 

1. A systematic, documented approach to treating alternatives using logic trees, including 

alternative conceptual models for future spatial distributions of seismicity (e.g., stationarity); 

alternative methods for expressing the future temporal distribution of seismicity (e.g., 

renewal models, Poisson models); and alternative data sets for characterizing seismic sources 

(e.g., paleoseismic data, historical seismicity data). 

2. A systematic approach to identifying applicable data for the source characterization, 

evaluating the usefulness of the data, and documenting the consideration given to the data by 

the TI Team. 

3. A methodology for identifying seismic sources based on defensible criteria for defining a 

seismic source, incorporating the lessons learned in SSC over the past two decades, and 

identifying the range of approaches and models that can be shown to be significant to hazard. 

Each of these needs was addressed by the methodology used in the project. For example, the 

need for a systematic approach to identifying and evaluating the data and information that 

underlie the source characterization assessments was met by the development of Data Summary 

lxxxvii
Executive Summary 

and Data Evaluation tables. These tables were developed for each seismic source to document 

the information available at the time of the CEUS SSC assessments (the Data Summary tables) 

and the way those data were used in the characterization process (the Data Evaluation tables). 

Given the evolution of approaches to identifying seismic sources, it is appropriate to provide a 

set of criteria and the logic for their application in the CEUS SSC Project. In the project, unique 

seismic sources are defined to account for distinct differences in the following criteria: 

Earthquake recurrence rate 

Maximum earthquake magnitude (Mmax) 

Expected future earthquake characteristics (e.g., style of faulting, rupture orientation, depth 

distribution) 

Probability of activity of tectonic feature(s) 

Rather than treat these criteria as operating simultaneously or without priority, the CEUS SSC 

methodology works through them sequentially. Further, because each criterion adds complexity 

to the seismic source model, it is applied only if its application would lead to hazard-significant 

changes in the model. In this way, the model becomes only as complex as required by the 

available data and information. 

The CEUS SSC master logic tree is tied to the conceptual SSC framework that establishes the 

context for the entire seismic source model. The master logic tree depicts the alternative 

interpretations and conceptual models that represent the range of defensible interpretations, and 

the relative weights assessed for the alternatives. By laying out the alternatives initially, the 

subsequent detailed source evaluations were conducted within a framework that ensures 

consistency across the sources. Important elements of the master logic tree are as follows: 

Representation of the sources defined based on paleoseismic evidence for the occurrence of 

repeated large-magnitude earthquakes (RLMEs, defined as two or more earthquakes with 

M ≥ 6.5). 

Alternatives to the spatial distribution of earthquakes based on differences in maximum 

magnitudes (Mmax zones approach). 

Representation of uncertainty in spatial stationarity of observed seismicity based on 

smoothing of recurrence parameters. 

Representation of possible differences in future earthquake characteristics (e.g., style, 

seismogenic thickness, and orientation of ruptures), which lead to definition of 

seismotectonic zones in the logic tree (seismotectonic zones approach). 

The methodologies used by the project to make the SSC assessments are discussed in Chapter 5. 

The heart of any SSC model for PSHA is a description of the future spatial and temporal 

distribution of earthquakes. Continued analysis of the historical seismicity record and network 

monitoring by regional and local seismic networks has led to acceptance within the community 

that the general spatial patterns of observed small- to moderate-magnitude earthquakes provide 

predictive information about the spatial distribution of future large-magnitude earthquakes. The 

analyses leading to this conclusion have focused on whether the observed patterns of earthquakes 

lxxxviii
Executive Summary 

have varied through time; therefore, in effect, this is an assessment of uncertainty in whether 

small- to moderate-magnitude earthquakes have been relatively stationary through time.

However, the available data on larger-magnitude earthquakes and their relationship to the spatial 

distribution of smaller earthquakes based on the observed record are quite limited. These data are 

not sufficient to allow confidence in the predictions generated by empirical spatial models. For 

this reason, geologic and geophysical data are needed to specify the locations of future 

earthquakes in addition to the observed patterns of seismicity. 

Detailed studies in the vicinity of large historical and instrumental earthquakes, and liquefaction 

phenomena associated with them, coupled with field and laboratory studies of geotechnical 

properties, are leading to a stronger technical basis for (1) placing limits on the locations of 

paleoearthquakes interpreted by the distribution of liquefaction phenomena and (2) defining their 

magnitudes. In some cases, the paleoseismic evidence for RLMEs is compelling, and the TI 

Team has included the RLME source in the SSC model. The locations of RLME sources 

notwithstanding, the spatial distribution of distributed seismicity sources has advanced in PSHA 

largely because of the assumption of spatial stationarity, and the SSC and hazard community 

uses approaches to ―smooth‖ observed seismicity to provide a map that expresses the future 

spatial pattern of recurrence rates. The CEUS SSC model is based largely on the assumption, 

typical in PSHA studies, that spatial stationarity of seismicity is expected to persist for a period 

of approximately 50 years. 

Estimating Mmax in SCRs such as the CEUS is highly uncertain despite considerable interest 

and effort by the scientific community over the past few decades. Mmax is defined as the upper 

truncation point of the earthquake recurrence curve for individual seismic sources, and the 

typically broad distribution of Mmax for any given source reflects considerable epistemic 

uncertainty. Because the maximum magnitude for any given seismic source in the CEUS occurs 

rarely relative to the period of observation, the use of the historical seismicity record provides 

important but limited constraints on the magnitude of the maximum event. Because of the 

independent constraints on earthquake size, those limited constraints are used to estimate the 

magnitudes of RLME. For distributed seismicity source zones, two approaches are used to assess 

Mmax: the Bayesian approach and the Kijko approach. In the Bayesian procedure (Johnston et 

al., 1994), the prior distribution is based on the magnitudes of earthquakes that occurred 

worldwide within tectonically analogous regions. As part of the CEUS SSC Project, the TI Team 

pursued the refinement and application of the Bayesian Mmax approach becauses it provides a 

quantitative and repeatable process for assessing Mmax. 

The TI Team also explored alternative approaches for the assessment of Mmax that provide 

quantitative and repeatable results, and the team identified the approach developed by Kijko 

(2004) as a viable alternative. While the Kijko approach requires fewer assumptions than the 

Bayesian approach in that it uses only the observed earthquake statistics for the source, this is 

offset by the need for a relatively larger data sample in order to get meaningful results. Both 

approaches have the positive attribute that they are repeatable given the same data and they can 

be readily updated given new information. The relative weighting of the two approaches for 

inclusion in the logic tree is source-specific, a function of the numbers of earthquakes that are 

present within the source upon which to base the Mmax assessment: sources with fewer 

earthquakes are assessed to have little or no weight for the Kijko approach, while those with 

lxxxix
Executive Summary 

larger numbers of events are assessed higher weight for the Kijko approach. In all cases, because 

of the stability of the Bayesian approach and the preference for ―analogue‖ approaches within the 

larger technical community, the Bayesian approach is assessed higher weight than the Kijko 

approach for all sources. 

A major effort was devoted to updating the global set of SCR earthquakes and to assessing 

statistically significant attributes of those earthquakes following the approach given in Johnston 

et al. (1994). In doing so, it was found that the only significant attribute defining the prior 

distribution is the presence or absence of Mesozoic-or-younger extension. The uncertainty in this 

assessment is reflected in the use of two alternative priors: one that takes into account the 

presence or absence of crustal domains having this attribute, and another that combines the entire 

CEUS region as a single SCR crustal domain with a single prior distribution. The use of the 

Bayesian—and Kijko—approach requires a definition of the largest observed magnitude within 

each source, and this assessment, along with the associated uncertainty, was incorporated into the 

Mmax distributions for each seismic source. Consideration of global analogues led to the 

assessment of an upper truncation to all Mmax distributions at 81⁄4 and a lower truncation at 51⁄2. 

The broad distributions of Mmax for the various seismic source zones reflect the current 

epistemic uncertainty in the largest earthquake magnitude within each seismic source. 

The CEUS SSC model is based to a large extent on an assessment that spatial stationarity of 

seismicity will persist for time periods of interest for PSHA (approximately the next 50 years). 

Stationarity in this sense does not mean that future locations and magnitudes of earthquakes will 

occur exactly where they have occurred in the historical and instrumental record. Rather, the 

degree of spatial stationarity varies as a function of the type of data available to define the 

seismic source. RLME sources are based largely on paleoseismic evidence for repeated largemagnitude (M ≥ 6.5) earthquakes that occur in approximately the same location over periods of a 

few thousand years. On the other hand, patterns of seismicity away from the RLME sources 

within the Mmax and seismotectonic zones are defined from generally small- to moderatemagnitude earthquakes that have occurred during a relatively short (i.e., relative to the repeat 

times of large events) historical and instrumental record. Thus, the locations of future events are 

not as tightly constrained by the locations of past events as for RLME sources. The spatial 

smoothing operation is based on calculations of earthquake recurrence within one-quarter-degree 

or half-degree cells, with allowance for ―communication‖ between the cells. Both a- and bvalues are allowed to vary, but the degree of variation has been optimized such that b-values 

vary little across the study region. 

The approach used to smooth recurrence parameters is a refinement of the penalized-likelihood 

approach used in EPRI-SOG (EPRI, 1988), but it is designed to include a number of elements 

that make the formulation more robust, realistic, and flexible. These elements include the 

reformulation in terms of magnitude bins, the introduction of magnitude-dependent weights, 

catalog incompleteness, the effect of Mmax, spatial variation of parameters within the source 

zone, and the prior distributions of b. A key assessment made by the TI Team was the weight 

assigned to various magnitude bins in the assessment of smoothing parameters (Cases A, B, 

and E). This assessment represents the uncertainty in the interpretation that smaller magnitudes 

define the future locations and variation in recurrence parameters. Appropriately, the penalizedlikelihood approach results in higher spatial variation (less smoothing) when the low-magnitude 

xc
Executive Summary 

bins are included with high weight, and much less variation (higher smoothing) in the case where 

the lower-magnitude bins are given low or zero weight. The variation resulting from the final set 

of weights reflects the TI Team’s assessment of the epistemic uncertainty in the spatial variation 

of recurrence parameters throughout the SSC model. 

The earthquake recurrence models for the RLME sources are somewhat simpler than those for 

distributed seismicity sources because the magnitude range for individual RLMEs is relatively 

narrow and their spatial distribution is limited geographically such that spatial variability is not a 

concern. This limits the problem to one of estimating the occurrence rate in time of a point 

process. The data that are used to assess the occurrence rates are derived primarily from 

paleoseismic studies and consist of two types: data that provide estimated ages of the 

paleoearthquakes such that the times between earthquakes can be estimated, and data that 

provide an estimate of the number of earthquakes that have occurred after the age of a particular 

stratigraphic horizon. These data are used to derive estimates of the RLME occurrence rates and 

their uncertainty. 

The estimation of the RLME occurrence rates is dependent on the probability model assumed for 

the temporal occurrence of these earthquakes. The standard model applied for most RLME 

sources in this study is the Poisson model, in which the probability of occurrence of an RLME in 

a specified time period is completely characterized by a single parameter, λ, the rate of RLME 

occurrence. The Poisson process is ―memoryless‖—that is, the probability of occurrence in the 

next time interval is independent of when the most recent earthquake occurred, and the time 

between earthquakes is exponentially distributed with a standard deviation equal to the mean 

time between earthquakes. For two RLME sources (Reelfoot Rift–New Madrid fault system and 

the Charleston source), the data are sufficient to suggest that the occurrence of RLMEs is more 

periodic in nature (the standard deviation is less than the mean time between earthquakes). For 

these RLME sources a simple renewal model can also be used to assess the probability of 

earthquake occurrence. In making an estimate of the probability of occurrence in the future, this 

model takes into account the time that has elapsed since the most recent RLME occurrence. 

The CEUS SSC model has been developed for use in future PSHAs. To make this future use 

possible, the SSC model must be combined with a GMC model. At present, the GMPEs in use 

for SCRs such as the CEUS include limited information regarding the characteristics of future 

earthquakes. In anticipation of the possible future development of GMPEs for the CEUS that will 

make it possible to incorporate similar types of information, a number of characteristics of future 

earthquakes in the CEUS are assessed. In addition to characteristics that might be important for 

ground motion assessments, there are also assessed characteristics that are potentially important 

to the modeling conducted for hazard analysis. Future earthquake characteristics assessed include 

the tectonic stress regime, sense of slip/style of faulting, strike and dip of ruptures, seismogenic 

crustal thickness, fault rupture area versus magnitude relationship, rupture length-to-width aspect 

ratio, and relationship of ruptures to source boundaries. 

Chapters 6 and 7 include discussions of the seismic sources that are defined by the Mmax zones 

and the seismotectonic zones branches of the master logic tree. Because of convincing evidence 

for their existence, both approaches include RLME sources. The rarity of repeated earthquakes 

relative to the period of historical observation means that evidence for repeated events comes 

xci
Executive Summary 

largely from the paleoseismic record. By identifying the RLMEs and including them in the SSC 

model, there is no implication that the set of RLMEs included is in fact the total set of RLMEs 

that might exist throughout the study region. This is because the presently available studies that 

locate and characterize the RLMEs have been concentrated in certain locations and are not 

systematic across the entire study region. Therefore, the evidence for the existence of the RLMEs 

is included in the model where it exists, but the remaining parts of the study region are also 

assessed to have significant earthquake potential, which is evidenced by the inclusion of 

moderate-to-large magnitudes in the Mmax distributions for every Mmax zone or seismotectonic 

zone. 

In Chapter 6, each RLME source is described in detail by the following factors: (1) evidence for 

temporal clustering, (2) geometry and style of faulting, (3) RLME magnitude, and (4) RLME 

recurrence. The descriptions document how the data have been evaluated and assessed to arrive 

at the various elements of the final SSC model, including all expressions of uncertainty. The 

Data Summary and Data Evaluation tables (Appendices C and D) complement the discussions in 

the text, documenting all the data that were considered in the course of data evaluation and 

integration process for each particular seismic source. 

Alternative models for the distributed seismicity zones that serve as background zones to the 

RLME sources are either Mmax zones or seismotectonic zones. The Mmax zones are described 

in Chapter 6 and are defined according to constraints on the prior distributions for the Bayesian 

approach to estimating Mmax. The seismotectonic zones are described in Chapter 7 and are 

identified based on potential differences in Mmax as well as future earthquake characteristics. 

Each seismotectonic zone in the CEUS SSC model is described according to the following 

attributes: (1) background information from various data sets; (2) bases for defining the 

seismotectonic zone; (3) basis for the source geometry; (4) basis for the zone Mmax (e.g., largest 

observed earthquake); and (5) future earthquake characteristics. Uncertainties in the 

seismotectonic zone characteristics are described and are represented in the logic trees developed 

for each source. 

For purposes of demonstrating the CEUS SSC model, seismic hazard calculations were 

conducted at seven demonstration sites throughout the study region, as described in Chapter 8. 

The site locations were selected to span a range of seismic source types and levels of seismicity. 

The results from the seismic hazard calculations are intended for scientific use to demonstrate the 

model, and they should not be used for engineering design. Mean hazard results are given for a 

range of spectral frequencies (PGA, 10 Hz, and 1 Hz) and for a range of site conditions. All 

calculations were made using the EPRI (2004, 2006) ground-motion models such that results 

could be compared to understand the SSC effects alone. Sensitivity analyses were conducted to 

provide insight into the dominant seismic sources and the important characteristics of the 

dominant seismic source at each site. The calculated mean hazard results are compared with the 

results using the SSC model from the 2008 U.S. Geological Survey national seismic hazard maps 

and the SSC model from the Combined Operating License applications for new nuclear power 

reactors. The hazard results using the CEUS SSC model given in Chapter 8 are reasonable and 

readily understood relative to the results from other studies, and sensitivities of the calculated 

hazard results can be readily explained by different aspects of the new model. The TI Team 

concludes that the SSC model provides reasonable and explainable calculated seismic hazard 

xcii
Executive Summary 

results, and the most important aspects of the SSC model to the calculated hazard (e.g., 

recurrence rates of RLME sources, recurrence parameters for distributed seismicity sources, 

Mmax) and their uncertainties have all been appropriately addressed. 

Presumably, the GMC model input to the PSHA calculations will be replaced in the future by the 

results of the ongoing NGA-East project. The calculated hazard at the demonstration sites in 

Chapter 8 comes from the regional CEUS SSC model and does not include any local refinements 

that might be necessary to account for local seismic sources. Depending on the regulatory 

guidance that is applicable for the facility of interest, additional site-specific studies may be 

required to provide local refinements to the model. 

To assist future users of the CEUS SSC model, Chapter 9 presents a discussion on the use of the 

model for PSHA. The basic elements of the model necessary for hazard calculations are given in 

the Hazard Input Document (HID). This document provides all necessary parameter values and 

probability distributions for use in a modern PSHA computer code. The HID does not, however, 

provide any justification for the values, since that information is given in the text of this report. 

Chapter 9 also describes several simplifications to seismic sources that can be made to increase 

efficiency in seismic hazard calculations. These simplifications are recommended on the basis of 

sensitivity studies of alternative hazard curves that represent a range of assumptions on a 

parameter’s value. Sensitivities are presented using the test sites in this study. For applications of 

the seismic sources from this study, similar sensitivity studies should be conducted for the 

particular site of interest to confirm these results and to identify additional simplifications that 

might be appropriate. For the seismic sources presented, only those parameters that can be 

simplified are discussed and presented graphically. The sensitivity studies consisted of 

determining the sensitivity of hazard to logic tree branches for each node of the logic tree 

describing that source. The purpose was to determine which nodes of the logic tree could be 

collapsed to a single branch in order to achieve more efficient hazard calculations without 

compromising the accuracy of overall hazard results. 

Finally, this report provides a discussion of the level of precision that is associated with seismic 

hazard estimates in the CEUS. This discussion addresses how seismic hazard estimates might 

change if the analysis were repeated by independent experts having access to the same basic 

information (geology, tectonics, seismicity, ground-motion equations, site characterization). It 

also addresses how to determine whether the difference in hazard would be significant if this 

basic information were to change and that change resulted in a difference in the assessed seismic 

hazard. This analysis was performed knowing that future data and models will continue to be 

developed and that a mechanism for evaluating the significance of that information is needed. 

Based on the precision model evaluated, if an alternative assumption or parameter is used in a 

seismic hazard study, and it potentially changes the calculated hazard (annual frequency of 

exceedence) by less than 25 percent for ground motions with hazards in the range 10–4

to 10–6, 

that potential change is within the level of precision at which one can calculate seismic hazard. It 

should be noted, however, that a certain level of precision does not relieve users from performing 

site-specific studies to identify potential capable seismic sources within the site region and 

vicinity as well as to identify newer models and data. Also, this level of precision does not 

relieve users from fixing any errors that are discovered in the CEUS SSC model as it is 

xciii
Executive Summary 

implemented for siting critical facilities. In addition, NRC has not defined a set value for 

requiring or not requiring siting applicants to revise or update PSHAs. 

Included in the report are appendices that summarize key data sets and analyses: the earthquake 

catalog, the Data Summary and Data Evaluation tables, the paleoliquefaction database, the HID, 

and documentation important to the SSHAC process. These data and analyses will assist future 

users of the CEUS SSC model in the implementation of the model for purposes of PSHA. The 

entire report and database will be provided on a website after the Final Project Report is issued. 

The TI Team, Project Manager, and Sponsors determined the approach for quality assurance on 

the CEUS SSC Project in 2008, taking into account the SSHAC assessment process and national 

standards. The approach was documented in the CEUS SSC Project Plan dated June 2008 and 

discussed in more detail in the CEUS SSC Report (Appendix L). Beyond the assurance of quality 

arising from the external scientific review process, it is the collective, informed judgment of the 

TI Team (via the process of evaluation and integration) and the concurrence of the PPRP (via the 

participatory peer review process), as well as adherence to the national standard referred to in 

Appendix L, that ultimately lead to the assurance of quality in the process followed and in the 

products that resulted from the SSHAC hazard assessment framework. 

xciv
October 24, 2011 

Cliff Munson 

Senior Technical Advisor 

Office of New Reactors 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555 

Robert Roche 

Project Manager 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555 

 

Richard H. Lagdon, Jr. 

Chief of Nuclear Safety 

Office of the Under Secretary for Nuclear 

Security, S-5 

U.S. Department of Energy 

1000 Independence Avenue SW 

Washington, DC 20585 

Thomas P. Miller 

Senior Technical Advisor 

Office of Nuclear Energy, NE-72/GTN 

U.S. Department of Energy 

1000 Independence Avenue SW 

Washington, DC 20585 

 

Jeffrey F. Hamel 

Advanced Nuclear Technology Program 

Manager 

Electric Power Research Institute 

3420 Hillview Avenue 

Palo Alto, CA 94304 

Gentlemen: 

Reference: Central and Eastern United States Seismic Source Characterization for Nuclear 

Facilities Project: Participatory Peer Review Panel Final Report

Introduction 

This letter constitutes the final report of the PPRP1

 (“the Panel”) for the Central and Eastern 

United States Seismic Source Characterization for Nuclear Facilities Project (the “CEUS SSC 

Project” or “the Project”). The eight Panel members (Jon P. Ake, Walter J. Arabasz, William J. 

Hinze, Annie M. Kammerer, Jeffrey K. Kimball, Donald P. Moore, Mark D. Petersen, J. Carl 

Stepp) participated in the Project in a manner fully consistent with the SSHAC Guidance.2

 The 

Panel was actively engaged in all phases and activities of the Project’s implementation, including 

final development of the Project Plan and planning of the evaluation and integration activities, 

which are the core of the SSHAC assessment process. 

                                                       

1

 Participatory Peer Review Panel 

2

 Budnitz, R. J., G. Apostolakis, D. M. Boore, L. S. Cluff, K. L. Coppersmith, C. A. Cornell, and P. A. 

Morris, 1997. Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty

and the Use of Experts (known as the “Senior Seismic Hazard Analysis Committee Report,” or the

“SSHAC Guidance”). NUREG/CR-6372, U. S. Nuclear Regulatory Commission. TIC; 235076. 

Washington, DC. 

xix 

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PPRP Final Report, CEUS SSC PROJECT October 24, 2011 

xx

The Panel’s involvement, described more fully later in this letter, also included review of 

analyses performed by the Project to support the evaluation and integration processes, review of 

interim evaluation and integration products, and review of the interim draft project report and the 

final project report. Additionally, panel members participated in specific analyses as resource 

experts, and panel members were observers in or participated as resource experts in eight of the 

eleven Technical Integrator Team (TI Team) working meetings held to implement the integration 

phase of the assessment process. We want to express our appreciation for the opportunity to 

participate in the CEUS SSC Project in this way. 

In the remainder of this letter we provide our observations and conclusions on key elements of 

the project implementation process, and we summarize our reviews of the draft and final project 

reports. As we explain in our comments, assurance that the center, body, and range of the 

technically-defensible interpretations (“CBR of the TDI”)3 have been properly represented in the 

CEUS SSC Model fundamentally comes from implementing the structure and rigor of the 

SSHAC Guidance itself. We are aware that the SSHAC Guidance is accepted by the Nuclear 

Regulatory Commission and the Department of Energy for developing seismic hazard models 

that provide reasonable assurance, consistent with the seismic safety decision-making practices 

of these agencies, of compliance with their seismic safety policies and regulatory requirements. 

For these reasons, we describe aspects of the SSHAC Guidance to provide context for our 

observations and conclusions. 

Project Plan: Conformity to the SSHAC Assessment Process 

The SSHAC Guidance recognizes that observed data, available methods, models, and 

interpretations all contain uncertainties. These uncertainties lead to alternative scientific 

analyses and interpretations. In other words, experts in the broad technical community do not 

hold a single interpretation. Accepting this scientific situation, the SSHAC assessment process is 

designed to engage the scientific community in an orderly assessment of relevant data, methods, 

models, and interpretations that constitute current scientific knowledge as the basis for 

development of a seismic hazard model that represents the CBR of the TDI. 

The assessment process is carried out by means of two main activities: evaluation and

integration.

4

 In implementation, the evaluation activities are structured to inform the integration 

activities. The evaluations are carried out by means of workshops in which the TI Team engages 

proponents of alternative interpretations that represent the range of relevant current community 

knowledge. Resource experts in the various relevant data sets are also engaged. The workshops 

have the dual purposes of, first, evaluating the degree to which alternative interpretations are 

supported by observed data and, second, defining uncertainties in the degree to which the 

interpretations are defensible, given the observed data. Integration is carried out by individual 

evaluator experts or evaluator expert teams (Level 4 process) or by a Technical Integrator (TI) 

Team (Level 3 process) who, informed by the evaluation activities, characterize the range of 

                                                       

3 See Section 2.1 in the CEUS SSC Final Report for discussion of concepts relating to the center, body, 

and range of the “technically-defensible interpretations” vs. the center, body, and range of the “informed 

technical community.” 

4 For an excellent discussion of this two-stage process, see Practical Implementation Guidelines for 

SSHAC Level 3 and 4 Hazard Studies, USNRC NUREG-XXXX, Draft for Review, Office of Nuclear 

Regulatory Research, May 2011. 

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PPRP Final Report, CEUS SSC PROJECT October 24, 2011 

 xxi 

defensible alternative interpretations in an integrated hazard model and assess the scientific 

uncertainty distribution. Based on our review of the Project Plan and our subsequent discussions 

with the Project Team, we concurred that the Plan conformed with the SSHAC Guidance,

incorporating lessons learned from fourteen years experience using the Guidance, and that the 

planned implementation was structured to properly carry out the SSHAC assessment process for 

development of the CEUS SSC Model. 

SSHAC Level 3 Assessment Process 

The SSHAC Guidance describes implementation processes for four levels of assessment 

depending on the scientific complexity of the assessment and the intended use of the assessed 

hazard model. For an assessment such as the regional SSC model for the Central and Eastern 

United States, which will be used at many sites for making safety and licensing decisions for 

nuclear facilities, the SSHAC Guidance recommends using an assessment Level 3 or Level 4. 

There are process differences between a Level 3 and Level 4 implementation, but the objective is 

the same: to obtain from multiple proponent experts information that supports an informed 

assessment of the range of existent relevant interpretations and associated uncertainties that 

together represent current community knowledge and to perform an informed assessment of the 

CBR of the TDI. We understand that within the SSHAC assessment process “technically 

defensible” means that observed data are sufficient to support evaluation of the interpretation and 

the corresponding uncertainty. 

In a Level 4 assessment process a TI Team facilitates the assessment, identifying and engaging 

proponent and resource experts, performing supporting analyses, and conducting knowledge 

evaluation workshops and assessment integration working meetings. Multiple experts or teams 

of experts perform as evaluators of the range of existent interpretations and as integrators of the 

hazard model. The individual evaluator experts or evaluator expert teams take ownership of 

their individual or team assessments. In a Level 3 assessment all of these activities are 

consolidated under a single TI Team consisting of a TI Lead, multiple evaluator experts 

representing the scope of required scientific expertise, and experienced data and hazard analysts. 

As we noted earlier in this report, assurance that the CBR of the TDI is properly represented in a 

hazard model comes from rigorously implementing the SSHAC assessment process itself. We 

note that an important lesson learned from multiple implementations of the SSHAC Guidance

over the past fourteen years is that the Level 3 and Level 4 assessment processes provide 

comparably high assurance that the relevant scientific knowledge and the community uncertainty 

distribution are properly assessed and represented in the hazard model. The Level 3 assessment 

is significantly more integrated and cohesive and is more efficient to implement. These 

considerations led us to endorse use of the Level 3 assessment for implementation of the CEUS 

SSC Project in our Workshop No. 1 review letter. During the course of the Project we observed

that the higher level of cohesiveness inherent in the Level 3 assessment process leads to 

significantly improved communication, facilitating the experts’ performance of their technical 

work. 

xcvii
PPRP Final Report, CEUS SSC PROJECT October 24, 2011 

xxii

Overall Project Organization 

A complex project with multiple sponsors such as the CEUS SSC Project cannot be successful 

unless it is well organized and energetically managed so that the various participants understand 

the interconnectedness of their activities and perform their technical work as a cohesive group. 

In this regard the adopted project management structure allowed the Project Manager to provide 

integrated overall project leadership, manage the database development activities, and effectively 

maintain communication with the PPRP and project sponsors while allowing TI Team lead to 

concentrate on the structural and technical activities of the assessment as the Project unfolded. 

We conclude that the project organization was effective overall and particularly so with regard to 

facilitating the TI Team’s implementation of the assessment process. 

Implementing the SSHAC Level 3 Assessment Process 

Irrespective of the level of implementation, evaluation and integration are the main activities of a 

SSHAC assessment. The evaluation activities aim to identify and evaluate all relevant available 

data, models, methods, and scientific interpretations as well as uncertainties associated with each 

of them. The integration activities, informed by the evaluations, aim to represent the CBR of the 

TDI in a fully integrated SSC model. 

Evaluation 

Consistent with the SSHAC Guidance the evaluation phase of the CEUS SSC project 

accomplished a comprehensive evaluation of the data, models, methods, and scientific 

interpretations existent in the larger technical community that are relevant to the SSC model. In 

significant part the process was carried out in three structured workshops, each focusing on 

accomplishing a specific step in the evaluation process. 

The first workshop (WS-1) focused on evaluations of relevant geological, geophysical, and 

seismological datasets (including data quality and uncertainties) and on identification of hazardsignificant data and hazard-significant SSC assessment issues. It became clear that a number of 

issues relating to the earthquake catalog, the paleoliquefaction data set, the potential-field 

geophysical data, updating procedures for assessing maximum earthquake magnitude, and 

development of procedures for assessing earthquake recurrence would require focused analyses. 

These analyses were appropriately carried out within the TI Team working interactively with 

appropriate resource experts recognized by the larger scientific and technical community. 

WS-2 focused on evaluations of the range of alternative scientific interpretations, methods, and 

models within the larger scientific community and on corresponding uncertainties. WS-3 

focused on evaluations of hazard feedback derived at seven representative test locations using a 

preliminary CEUS SSC model. Specifically, the workshop focused on the identification of the 

key issues of most significance to completing the SSC model assessment. 

Experience has shown that evaluations to gain understanding of the quality of various data sets 

and uncertainties associated with them are essential for fully informing an SSC assessment. We 

observed that in WS-1 resource experts for the various data sets did a high-quality job of 

describing the data sets and giving their perspective about the data quality and associated 

uncertainties. We conclude that the understanding of data quality and uncertainties gained in 

WS-1 together with continued interactions between the TI Team and data resource experts 

xcviii
PPRP Final Report, CEUS SSC PROJECT October 24, 2011 

 

significantly informed the TI Team’s evaluations. The TI Team’s evaluations of the data quality 

and uncertainties are well documented in the innovative “Data Summary Tables” and “Data 

Evaluation Tables” included in the Project Report. Importantly, the TI Team continued to 

effectively engage data resource experts in productive analyses of potential-field geophysical 

data, the earthquake catalog, development of the paleoearthquake data set (including an 

integrated assessment of the paleoliquefaction data in order to extend the earthquake catalog), the 

development of methods for assessing maximum earthquakes, and the development of 

earthquake recurrence analyses. All of these focused analyses strongly informed the assessment 

process. Moreover, documentation of the analyses resulted in stand-alone products of the Project 

that will serve future users of the CEUS SSC Model.

The compilation and evaluation of potentially relevant methods, models, and alternative 

scientific interpretations representing the community knowledge and corresponding uncertainties 

must be considered the core process activity of any SSHAC assessment. This step was largely 

carried out in WS-2. Success in defining the community knowledge depends on fully engaging 

proponent experts representing the range of methods, models, and interpretations existent at the 

time. Full engagement means that the proponent experts completely and clearly describe their 

interpretations and the data that support them and provide their individual evaluations of 

corresponding uncertainties. We observed that the actions taken by the Project and TI Team to 

explain the workshop goals and to guide participants toward meeting those goals was very 

productive. We conclude that the workshop was highly successful in meeting the stated goals 

and that it fully met the expectation of the SSHAC Guidance with respect to evaluating the range 

of alternative scientific interpretations. The discussions during the workshop and between the TI 

Team and Panel following the workshop evolved the “SSC Framework” concept, which 

provided transparent criteria that framed the TI Team’s systematic identification and assessment 

of seismic sources throughout the CEUS. 

Feedback from hazard calculations and sensitivity analyses is an important step in a SSHAC 

assessment to understand the importance of elements of the model and inform the final 

assessments. For development of a regional SSC model to be used for site-specific probabilistic 

seismic hazard analyses (PSHAs) at many geographically distributed sites, feedback based on the 

preliminary model is particularly important. Following WS-2 a preliminary SSC model termed 

“the SSC sensitivity model,” was developed and used for hazard sensitivity calculations that 

were evaluated in WS-3. While the SSC sensitivity model was clearly preliminary, the 

evaluation of sensitivity results that took place in WS-3 provided important feedback for 

completing analyses and for supporting the TI Team’s development of the preliminary CEUS 

SSC model. The Panel was able to review the preliminary model and provide feedback in a 

subsequent project briefing meeting on March 24, 2010. 

Together the three workshops provided the TI Team interactions with the appropriate range of 

resource and proponent experts. These experts were carefully identified to present, discuss, and 

debate the data, models, and methods that together form the basis for assuring that the CBR of 

the TDI have been properly represented in the hazard model. Experts representing academia, 

government, and private industry participated. The TI Team also reached out to a wide range of 

experts as they developed the database and performed the integration activities to develop the 

SSC model. The Panel participated throughout this process, and is satisfied that the TI Team 

fully engaged appropriate experts to accomplish the goals of a SSHAC Guidance. 

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PPRP Final Report, CEUS SSC PROJECT October 24, 2011 

xxiv

Integration 

Consistent with the SSHAC Guidance, integration is the process of assessing the CBR of the TDI 

and representing the assessment in the SSC model. Informed by the evaluation process, the 

integration process includes representation of the range of defensible methods, models, and 

interpretations of the larger technical community together with new models and methods 

developed by analyses during the evaluation and integration process. 

For the CEUS SSC Project, development of the earthquake catalog, methods for assessing and 

representing maximum earthquake magnitudes, and methods for earthquake recurrence 

assessment continued during the integration process. The Panel reviewed all the analyses at 

various stages of development and provided comments and recommendations. The TI Team 

performed the integration process by means of eleven working meetings. Members of the Panel 

participated in most of these working meetings as observers or resource experts. The full Panel 

participated in the discussions during both feedback meetings and provided formal comments 

and recommendations following the meetings. We observed that the integration process was

thorough and that it acceptably complied with the SSHAC Guidance. Based on our participation 

and observations we conclude that the integrated CEUS SSC Model appropriately represents the 

center, body, and range of current methods, models and technically defensible interpretations. 

PPRP Engagement 

Consistent with the SSHAC Guidance, the Panel was fully engaged in peer-review interactions 

with the TI Team and the Project Manager of the CEUS SSC Project throughout the entire 

project period—from development of the Project Plan in early to mid 2008 through production of 

the Final Project Report in mid to late 2011.5 The Panel provided both written and oral peerreview comments on both technical and process aspects at many stages of the Project’s 

evolution. Key PPRP activities, leading up to this final report, have included: 

• Review of the Project Plan. 

• Formulation of a PPRP implementation plan, specifically for the CEUS SSC Project, to 

ensure adherence to the general guidance provided by SSHAC and NUREG-1563 for the 

scope and goals of a PPRP review. 

• Involvement in each of the three Project workshops, including advising in the planning 

stage; participating collectively as a review panel during the workshop (and individually 

as resource experts when requested by the TI Team), providing timely comments on 

technical and process issues; and submitting a written report of the Panel’s observations 

and recommendations following each workshop. 

• Development and implementation of a process, together with the TI Team, to document 

the resolution of recommendations made in PPRP formal communications. 

• Participation as observers (and occasionally as resource experts when requested by the TI 

Team) in eight of the TI Team’s 11 working meetings. 

• Peer-review and written comments, including several informal reports, on the TI Team’s 

intermediate work products, particularly early versions of the CEUS SSC Model. 

                                                       

5

 See CEUS SSC Final Report: Section 2.5, Table 2.2-1, and Appendix I 

c
PPRP Final Report, CEUS SSC PROJECT October 24, 2011 

 

• Direct interaction with the TI Team and Project Manager in more than 20 teleconferences 

and four face-to-face briefings—in addition to the three workshops and eight working 

meetings of the TI Team noted above. 

• Extensive, critical peer-review of the Project’s 2010 Draft Report and 2011 Final Report. 

The Panel, collectively and individually, fully understood the SSHAC Guidance for a structured 

participatory peer review and the requirements for a Level 3 assessment process; had full and 

frequent access to information and interacted extensively with the TI Team and Project Manager 

throughout the entire project; provided peer-review comments at numerous stages; and, as 

documented within the Final Project Report, was fully engaged to meet its peer-review 

obligations in an effective way. 

Project Report 

The SSHAC Guidance makes clear that adequate documentation of process and results is crucial 

for their understanding and use by others in the technical community, by later analysis teams, 

and by the project sponsors. The Panel understood what was needed to conform to the SSHAC 

requirements, and it was committed to ensuring that the documentation of technical details 

associated with the CEUS SSC Model in the Project Report was clear and complete. The Panel 

was equally committed to ensuring the transparency of process aspects of the project, both in 

implementation and in description in the Project Report. 

The Panel provided lengthy compilations of review comments (see Appendix I of the Project 

Report) for both the 2010 Draft Report and the 2011 Final Report. These included hundreds of 

comments, categorized as general, specific, relating to clarity and completeness, or editorial. 

The massive amount of detail provided by the TI Team in the Project Report and the 

intensiveness of the Panel’s review comments both reflect great diligence and a mutual 

understanding by the TI Team and the PPRP of the thoroughness and high quality of 

documentation expected in the Project Report. 

The Project Manager and the TI Lead provided review criteria to the Panel for both the draft and 

final versions of the Project Report. The criteria for reviewing the Draft Report6

 covered the 

range of technical and process issues consistent with requirements of the SSHAC Guidance, 

including draft implementation guidance (see footnote #4). Key criteria, among others, include 

sufficiency of explanatory detail; adequate consideration of the full range of data, models, and 

methods—and the views of the larger technical community; adequate justification of the data 

evaluation process, logic-tree weights, and other technical decisions; proper treatment of 

uncertainties; and conformance to a SSHAC Level 3 assessment process. To be clear, the PPRP 

is charged with judging the adequacy of the documented justification for the CEUS SSC Model 

and its associated logic-tree weights. The TI Team “owns” the Model and logic-tree weights. 

Criteria for reviewing the Final Report focused on reaching closure to comments made on the 

Draft Report and ensuring that no substantive issues remained unresolved. To that end, among 

its many review comments on the Final Report the Panel identified “mandatory” comments, 

which the TI Team was required to address in the final version of the Project Report. 

                                                       

6

 See PPRP report dated October 4, 2010, in Appendix I of CEUS SSC Final Report 

ci
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cii
PROJECT ACKNOWLEDGMENTS 

This study was sponsored by the Electric Power Research Institute (EPRI) Advanced Nuclear 

Technology Action Plan Committee, the U.S. Department of Energy (DOE) Office of Nuclear 

Energy and Office of the Chief of Nuclear Safety, and the U.S. Nuclear Regulatory Commission 

(NRC) Office of Nuclear Regulatory Research. Technical experts from the DOE, NRC, U.S. 

Geological Survey, Defense Nuclear Facility Safety Board, industry, and academia participated 

in the study as part of the Technical Integration (TI) Team or as members of the Participatory 

Peer Review Panel (PPRP). Any statements, opinions, findings, conclusions, or 

recommendations expressed in this material are those of the authors and do not necessarily 

reflect those of the participating or sponsoring agencies. 

Jeffrey F. Hamel was the EPRI Advanced Nuclear Technology Program Manager. Lawrence A. 

Salomone of Savannah River Nuclear Solutions, LLC, served as the Project Manager for the 

study. Kevin J. Coppersmith of Coppersmith Consulting Inc., served as the lead for the TI Team. 

J. Carl Stepp of Earthquake Hazards Solutions, and Walter J. Arabasz, Research Professor 

Emeritus of Geology and Geophysics at the University of Utah, served as Co-chairmen for the 

PPRP. The entire Central and Eastern United States Seismic Source Characterization Project 

Team and their roles are discussed in Section 2 and are shown on the project oganization chart 

(Figure 2.3-1) of the report. 

The authors of the report wish to acknowledge the contributions of the following people: the 

resource experts who participated in Workshop 1, the proponent experts who participated in 

Workshop 2, and the technical experts who provided valuable insights, perspective, and 

references throughout the study. The names of all these contributors are listed in Table 2.2-2. 

In addition, the authors of the report appreciate the support of Geraldine Moore-Butler as 

administrative assistant and Nancy L. Sutherland as technical editor for the project. This report 

was assembled at AMEC. 

ciii
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SPONSORS’ PERSPECTIVE 

This report describes a new seismic source characterization model for the Central and Eastern 

United States (CEUS) for use in probabilistic seismic hazard analysis (PSHA) for nuclear 

facilities. PSHA has become a generally accepted procedure for supporting seismic design, 

seismic safety and decision making for both industry and government. Input to a PSHA consists 

of seismic source characterization (SSC) and ground motion characterization (GMC); these two 

components are necessary to calculate probabilistic hazard results (or seismic hazard curves) at a 

particular geographic location. 

The 1986 Electric Power Research Institute and Seismicity Owners Group (EPRI-SOG) study 

included both an SSC and GMC component. Recent applications for new commercial reactors 

have followed U.S. Nuclear Regulatory Commission (NRC) regulatory guidance (RG 1.208) by 

using the EPRI-SOG source model as a starting point and updating it as appropriate on a sitespecific basis. This CEUS SSC Project has developed a new SSC model for the CEUS to replace 

the SSC component of the EPRI-SOG study. 

The CEUS SSC Project was conducted using a Senior Seismic Hazard Analysis Committee 

(SSHAC) Level 3 process, as described in the NRC publication, Recommendations for 

Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and Use of Experts 

(NUREG/CR-6372). The goal of the SSHAC process is to represent the center, body, and range 

of technically defensible interpretations of the available data, models, and methods. The CEUS 

SSC model is applicable to any site within the CEUS and can be used with the EPRI 2004/2006 

GMC model to calculate seismic hazard at any site of interest. Long-term efforts to replace the 

EPRI 2004/2006 GMC model with the Next Generation Attenuation Relationships for Central 

and Eastern North America obtained from the NGA-East Project is scheduled for completion in 

2014. 

The updated CEUS SSC model provides industry and government with the following: a new 

model for the commercial nuclear industry to perform PSHAs for future reactor license 

applications; the NRC to support its review of early site permit (ESP) and construction and 

operating license (COL) applications; and the U.S. Department of Energy (DOE) to support 

modern PSHAs to meet design and periodic review requirements for its current and future 

nuclear facilities. Specific benefits of the model are as follows: 

Consistency: For many sites, seismic sources at distances up to 300 km (186 mi.) or more 

significantly contribute to hazard at some spectral frequencies. Consequently, seismic hazard 

models for many sites have significant geologic overlap. If done separately, there is a 

likelihood of conflicting assessments for the same regions. A regional source model allows 

for consistent input into a PSHA. An updated conceptual SSC framework that provides a 

cv
Sponsors’ Perspective

consistent basis for identifying and characterizing seismic sources in the CEUS has been 

developed. The NRC will no longer need to review each time each applicant’s regional SSC

model when the accepted CEUS SSC model is used. This will avoid lengthy review of the 

regional SSC model in ESP and COL applications for sites within the CEUS that use the 

accepted regional CEUS SSC model to develop its site-specific SSC model. 

Stability: This CEUS SSC model was developed using the accepted state-of-practice 

SSHAC methodology that involved the following tasks: 

o Development of a comprehensive database and new tools for documenting the data 

consideration process. 

o Multiple workshops to identify applicable data, debate alternative hypotheses, and 

discuss feedback. 

o Multiple working meetings by the Technical Integration (TI) Team to develop the SSC 

model and fully incorporate uncertainties. 

o Technical advancements in a number of areas, such as developing a uniform earthquake 

catalog, developing an updated approach for assessing maximum magnitude, compiling 

data evaluation tables, incorporating paleoseismic data, and using spatial smoothing 

tools. 

o Participatory peer review, including four panel briefings, multiple interactions, and 

periodic formal feedback. 

o Proper documentation of all process and technical aspects of the project. 

Experience has shown that stability is best achieved through proper and thorough 

characterization of our knowledge and uncertainties, coupled with the involvement of the 

technical community, regulators, and oversight groups. 

Greater Longevity: An explicit goal of the SSHAC methodology is to represent the center, 

body, and range of the technically defensible interpretations of the available data, models,

and methods. Using the SSHAC process provides reasonable assurance that this goal has 

been achieved. Representing the center, body, and range of interpretations at the time of the 

study means that as new information is acquired and various interpretations evolve as a 

result, the current thinking at any point is more likely to be addressed in the study. As new 

information becomes available, an existing SSC will require periodic reviews to evaluate the 

implications of the new findings. The need for updates to a particular study is now better 

understood as a result of findings of the CEUS SSC Project sensitivity studies to determine 

the significance of source characteristics. 

Cost and Schedule Savings: The CEUS SSC model can be used to perform a PSHA at any 

geographic location within the CEUS. It is applicable at any point within the CEUS, subject 

to site-specific refinements required by facility-specific regulations or regulatory guidance. 

Having stable, consistent input into a regional PSHA will reduce the time and cost required 

to complete a commercial nuclear site’s ESP or COL licensing application, prepare a DOE 

site’s PSHA, and develop design input for new commercial and DOE mission-critical nuclear 

facilities.

cvi
Sponsors’ Perspective 

cvii 

 Advancement of Science: The CEUS SSC Project provides new data, models, and methods. 

This information was shared at three workshops with international observers as a means to 

provide technology transfer for application in other regions. The CEUS SSC earthquake 

catalog, which merges and reconciles several catalogs and provides a uniform moment 

magnitude for all events, and the CEUS SSC paleoliquefaction database provide a new 

baseline for future research and updates. New approaches used in this project for spatial 

smoothing of recurrence parameters, assessment of maximum magnitude, and systematical 

documentation of all data considered and evaluated also benefit future research and PSHA 

updates. 

The sponsors of the CEUS SSC Project are utilities and vendors on the EPRI Advanced Nuclear 

Technology Action Plan Committee, the DOE Office of Nuclear Energy, the DOE Office of the 

Chief of Nuclear Safety, and the NRC Office of Nuclear Regulatory Research. Technical experts 

from the DOE, NRC, U.S. Geological Survey (USGS), and Defense Nuclear Facility Safety 

Board (DNFSB) participated in the study as part of the TI Team or as members of the 

Participatory Peer Review Panel (PPRP). 

The product of the CEUS SSC Project is a robust peer-reviewed regional CEUS SSC model for 

use in PSHAs. This model will be applicable to the entire CEUS, providing an important 

baseline for future research and updates. The CEUS SSC Project demonstrates that a SSHAC 

Level 3 approach can achieve the goals of considering the knowledge and uncertainties of the 

larger technical community within a robust and transparent framework. The value of the new 

CEUS SSC model has been enhanced by the participation of key stakeholders from industry, 

government, and academia who were part of the CEUS SSC Project Team. 

Looking forward, the NRC will publish NUREG-2117 (2012), Practical Implementation 

Guidelines for SSHAC Level 3 and 4 Hazard Studies that provides SSHAC guidance on the need 

to update a regional model. The guidance covers updating both regional and site-specific 

assessments. It addresses the “refinement” process of starting with a regional model and refining 

it for site-specific applications. 
Page intentionally left blank 
ABBREVIATIONS 

AD anno domini (in the year of the Lord) 

AFE annual frequency of exceedance 

AIC Akaike information criterion 

ALM Alabama-Louisiana-Mississippi (zone of possible paleoseismic features) 

AM Atlantic Margin (seismotectonic zone) 

AHEX Atlantic Highly Extended Crust (seismotectonic zone) 

ANSS U.S. Advanced National Seismic System 

ANT Advanced Nuclear Technology 

APC Action Plan Comittee 

BA Blytheville arch 

BC before Christ 

BCFZ Big Creek fault zone 

BFZ Blytheville fault zone 

BL Bootheel lineament 

BMA Brunswick magnetic anomaly 

BP before present 

BPT Brownian passage time 

BTP Branch Technical Position 

CAD computer-aided design

cix
Abbreviations 

CBR center, body, and range 

CCFZ Crittenden County fault zone 

CDZ Commerce deformation zone 

CENA Central and Eastern North America

CERI Center for Earthquake Research and Information 

CEUS Central and Eastern United States 

CFZ Commerce fault zone 

CFR Code of Federal Regulations 

CGL Commerce geophysical lineament 

CGRGC Cottonwood Grove–Rough Creek graben 

CI confidence interval 

CNWRA Center for Nuclear Waste Regulatory Analysis 

COCORP Consortium for Continental Reflection Profiling 

COCRUST Consortium for Crustal Reconnaissance Using Seismic Techniques 

COL combined construction and operating license 

COLA combined operating license application 

COMP composite prior, composite superdomain 

CON contemporary (with earthquake occurrence) 

COV coefficient of variation 

CPT cone penetration test 

CVSZ Central Virginia seismic zone 

D&G Dewey and Gordon (1984 catalog) 

DEM digital elevation model 

cx
Abbreviations 

DNFSB Defense Nuclear Facilities Safety Board 

DOE U.S. Department of Energy 

DWM Division of Waste Management 

ECC Extended Continental Crust 

ECC-AM Extended Continental Crust–Atlantic Margin (seismotectonic zone) 

ECC-GC Extended Continental Crust–Gulf Coast (seismotectonic zone) 

ECFS East Coast fault system 

ECFS-C East Coast fault system—central segment 

ECFS-N East Coast fault system—northern segment 

ECFS-S East Coast fault system—southern segment 

EC-SFS East Coast–Stafford fault system 

ECMA East Coast magnetic anomaly 

ECRB East Continent rift basin 

ECTM Eastern Canada Telemetered Network 

E[M] expected moment magnitude listed in the CEUS SSC catalog for an earthquake 

ENA eastern North America 

EP Eau Plain shear zone 

EPRI Electric Power Research Institute 

EPRI-SOG Electric Power Research Institute–Seismicity Owners Group 

ERM Eastern rift margin 

ERM-N Eastern rift margin—north

ERM-RP Eastern rift margin—river (fault) picks 

ERM-S Eastern rift margin—south

cxi
Abbreviations 

ERM-SCC Eastern rift margin—south/Crittenden County 

ERM-SRP Eastern rift margin—south/river (fault) picks 

ERRM Eastern Reelfoot Rift Margin 

ESP early site permit 

ESRI Environmental Systems Research Institute 

ETSZ Eastern Tennessee seismic zone 

EUS Eastern United States 

FAFC Fluorspar Area fault complex 

FGDC Federal Geographic Data Committee 

ft foot or feet 

FTP file transfer protocol 

ft/s feet per second 

ft/yr feet per year 

FWLA Fugro William Lettis & Associates 

FWR Fort Wayne rift 

Ga billion years ago 

GC Gulf Coast 

GCVSZ Giles County, Virginia, seismic zone 

GHEX Gulf Coast Highly Extended Crust (seismotectonic zone) 

GIS geographic information system 

GLTZ Great Lakes tectonic zone 

GMC ground-motion characterization (model) 

GMH Great Meteor Hotspot (seismotectonic zone) 

cxii
Abbreviations 

GMPE ground-motion prediction equation 

GMRS ground-motion response spectra 

GPR ground-penetrating radar 

GPS global positioning system 

GSC Geological Survey of Canada 

Gyr gigayears (109 years) 

HF Humboldt fault 

HID hazard input document 

I0 maximum intensity 

IAEA International Atomic Energy Agency

IBEB Illinois Basin Extended Basement (seismotectonic zone) 

IPEEE Individual Plant Examination for External Events 

IRM Iapetan rifted margin 

ISC International Seismological Centre 

ITC informed technical community 

ka thousand years ago 

K-Ar potassium-argon 

km kilometer(s) 

km2 square kilometer(s) 

km/sec kilometers per second 

K-S Kijko-Sellevoll 

K-S-B Kijko-Sellevoll-Bayes 

kyr thousand years 

cxiii
Abbreviations 

LDO Lamont-Doherty Earth Observatory (catalog) 

LHS Latin hypercube sampling 

LLNL Lawrence Livermore National Laboratory 

ln(FA) logarithm of felt area (with felt area measured in km2) 

LS least squares 

LSA La Salle anticlinal belt 

LWLS locally weighted least squares 

m meter(s) 

M magnitude 

M, MW moment magnitudes 

Ma million years ago 

MAR Marianna (RLME source) 

mb body-wave magnitude (short period) 

mbLg body-wave magnitude determined from higher-mode (Lg) surface waves

MC coda magnitude 

MCMC Markov Chain Monte Carlo 

MD duration magnitude 

MESE Mesozoic and younger extended crust 

MESE-N Mesozoic-and-younger extended crust or Mmax zone that is ―narrow‖

MESE-W Mesozoic-and-younger extended crust or Mmax zone that is ―wide‖

mi. mile(s)

mi.2 square mile(s) 

MIDC midcontinent 

cxiv
Abbreviations 

MidC Midcontinent-Craton (seismotectonic zone) 

Mfa felt-area magnitude 

ML local magnitude 

Mmax, Mmax maximum magnitude 

MMI modified Mercalli intensity 

mm/yr millimeters per year 

MN Nuttli magnitude 

Mo Scalar seismic moment 

MRS Midcontinent rift system 

m/s meters per second 

MS surface-wave magnitude 

MSF Meeman-Shelby fault 

Mw 

Myr million years 

NAD83 North American Datum of 1983 

NAP Northern Appalachian (seismotectonic zone) 

Nd neodymium 

NEDB National Earthquake Database 

NEI Nuclear Energy Institute 

NEIC National Earthquake Information Center 

NF Niagara fault zone 

NMESE Non-Mesozoic and younger extended crust

NMESE-N Mesozoic-and-younger extended crust or Mmax zone that is ―narrow‖

cxv
Abbreviations 

NMESE-W Mesozoic-and-younger extended crust or Mmax zone that is ―wide‖

NMFS New Madrid fault system 

NMN New Madrid North fault 

NMS New Madrid South fault 

NMSZ New Madrid seismic zone 

NN New Madrid north (fault segment as designated by Johnston and Schweig, 1996) 

NOAA National Oceanic and Atmospheric Administration 

NPP nuclear power plant(s) 

NR Nemaha Ridge 

NRC U.S. Nuclear Regulatory Commission 

NRHF Nemaha Ridge–Humboldt fault

NSHMP National Seismic Hazard Mapping Project 

NW New Madrid west (fault segment as designated by Johnston and Schweig, 1996) 

OKA Oklahoma aulacogen (seismotectonic zone) 

OKO Oklahoma Geological Survey Leonard Geophysical Observatory (catalog) 

OSL optically stimulated luminescence 

Pa probability of activity (of being seismogenic) 

PEZ Paleozoic Extended Crust (seismotectonic zone) 

PGA peak ground acceleration 

PM Project Manager 

PPRP Participatory Peer Review Panel 

PSHA probabilistic seismic hazard analysis 

PVHA probabilistic volcanic hazard analysis 

cxvi
Abbreviations 

RCG Rough Creek graben 

RF Reelfoot fault 

RFT Reelfoot thrust (fault) 

RLME repeated large-magnitude earthquake (source) 

RR Reelfoot rift zone 

RS Reelfoot South (fault segment) 

SA spectral acceleration 

SCL St. Charles lineament 

SCML south-central magnetic lineament 

SCR stable continental region 

SCSN South Carolina Seismic Network 

SEUS Southeastern United States (catalog) 

SEUSSN Southeastern United States Seismic Network 

SGFZ Ste. Genevieve fault zone 

SHmax maximum horizontal stress, compression, or principal stress 

SLR St. Lawrence rift (seismotectonic zone) 

SLTZ Spirit Lake tectonic zone 

SLU Saint Louis University (catalog) 

SNM Sanford et al. (2002 catalog) 

SOG Seismicity Owners Group 

SPT standard penetration test 

SRA Stover, Reagor, and Algermissen (1984 catalog) 

SRTM Shuttle Radar Topography Mission 

cxvii
Abbreviations 

SSC seismic source characterization 

SSE safe shutdown earthquake 

SSHAC Senior Seismic Hazard Analysis Committee 

Str&Tur Street and Turcotte (1977 catalog) 

SUSN Southeastern United States Network 

TC technical community 

TFI technical facilitator/integrator 

TI technical integration 

USGS U.S. Geological Survey 

USNSN U.S. National Seismograph Network 

UTC Coordinated Universal Time 

VP/VS ratio of P-wave velocity to S-wave velocity 

WES Weston Observatory (catalog) 

WIPP Waste Isolation Pilot Project 

WQSZ Western Quebec seismic zone 

WRFZ White River fault zone 

WUS Western United States 

WVFS Wabash Valley fault system 

WVSZ Wabash Valley seismic zone 

WWSSN World-Wide Standardized Seismograph Network 

cxviii
NUREG-2115 DOE/NE-0140 EPRI 1021097

APPENDIX C 

Data Evaluation Tables 

C-1

C 

APPENDIX 

DATA EVALUATION TABLES

Default Source Characteristics for CEUS SSC Project Study Region 

Table C-5.4 Future Earthquake Characteristics 

RLME Sources 

Table C-6.1.1 Charlevoix RLME 

Table C-6.1.2 Charleston RLME 

Table C-6.1.3 Cheraw Fault RLME 

Table C-6.1.4 Oklahoma Aulacogen RLME 

Table C-6.1.5 Reelfoot Rift–New Madrid Fault System RLMEs 

Table C-6.1.6 Reelfoot Rift–Eastern Margin Fault RLME 

Table C-6.1.7 Reelfoot Rift–Marianna RLME 

Table C-6.1.8 Reelfoot Rift–Commerce Fault Zone RLME 

Table C-6.1.9 Wabash Valley RLME 

Seismotectonic Zones 

Table C-7.3.1 St. Lawrence Rift Zone (SLR) 

Table C-7.3.2 Great Meteor Hotspot Zone (GMH) 

Table C-7.3.3 Northern Appalachian Zone (NAP) 

Table C-7.3.4 Paleozoic Extended Crust Zone (PEZ; narrow [N] and wide [W]) 

Table C-7.3.5 Illinois Basin-Extended Basement Zone (IBEB) 

Table C-7.3.6 Reelfoot Rift Zone (RR; including Rough Creek Graben 

[RR-RCG]) 

Tables C-7.3.7/7.3.8 Extended Continental Crust Zone–Atlantic Margin (ECC-AM) and 

Atlantic Highly Extended Crust (AHEX) 

Tables C-7.3.9/7.3.10 Extended Continental Crust Zone–Gulf Coast 

(ECC-GC) and Gulf Coast Highly Extended Crust (GHEX) 

[No Table C-7.3.11] [Oklahoma Aulacogen (OKA); see Table C-6.1.4] 

Table C-7.3.12 Midcontinent-Craton Zone (MidC) 

Mmax Zones 

Criteria for defining the MESE/NMESE boundary for the two-zone alternative are discussed in 

Section 6.2.2. MESE-N includes ECC-AM, ECC-GC, AHEX, GHEX, RR, SLR, NAP, GMH, 
Appendix C 

C-2

and PEZ-N. MESE-W differs from MESE-N in that it adopts the wide alternative geometries 

(i.e., PEZ-W, RR-RCG, and IBEB). See tables listed above for data pertinent to the definition of 

the boundaries of the zones and evidence for Mesozoic and younger tectonism. Default future 

earthquakes rupture parameters (Table 4.1.3-1) are assigned to both the one-zone and two-zone 

Mmax sources.

Introduction 

The Data Evaluation tables were developed to identify the data used, to evaluate the quality of 

the data, and to specify the degree of reliance on each data set in characterizing seismic sources. 

Labeling of Data Evaluation tables is keyed to the specific chapter and section where the 

corresponding source is described. Full citations of references listed in the tables are provided in 

Chapter 10. 

The Data Evaluation tables include the following attributes: 

The first column is a listing of the data, by data type, used in the evaluation for a particular 

RLME or seismotectonic source. See Appendix A for information regarding the sources for 

data sets specific to the CEUS SSC Project. 

The second column is an assessment of the quality of the data by the TI Team. This 

assessment is qualitative and takes into account the resolution, completeness, and distribution 

of the data relative to the best data of that type currently available. In some cases the 

assessment of the quality of a particular data set differs somewhat for different seismic 

sources. This is a reflection of the perceived value of the particular data set toward 

addressing the SSC characteristics of each seismic source. 

The third column is used for notes about the data quality. This usually includes comments 

about whether the data have been published in abstract form or full papers and other issues 

regarding the defensibility of the data. 

The fourth column identifies the particular seismic source to which the data have been 

applied in the evaluation. 

The fifth and sixth columns provide an assessment of the degree of reliance on the data set 

for purposes of SSC, and a short description of how the data were relied on. The intent is to 

assist the reader in understanding how the data set was used and what the evaluation of the 

degree of reliance was based on. 

The seventh column indicates whether the data exists in GIS format within the project 

database. If the data are not in GIS format, they will be found in the database in other formats 

such as a PDF file.

Although many different types of data were considered for the characterization of each seismic 

source, not all data types were used (e.g., some types of geophysical data or seismological data 

[such as focal mechanisms] are either not available or have limited usefulness for defining or 

characterizing a particular seismic source). Therefore, not all of the data types that were 

considered are listed in the tables. All data that were considered are included in the Data 

Summary tables (see Appendix D). Additional information on the Data Evaluation tables is 

provided in Section 4.1.2.2. Finally, please note that magnitudes are reported in the magnitude 

scale designated in the cited publication. 
Table C-5.4 Data Evaluation 

Future Earthquake Characteristics 

Identified Source 

Default for entire CEUS SSC 

C-3

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

Atkinson (2004) 4 Compilation of digital 

seismograms from 186 

earthquakes in 

southeastern Canada 

and northeastern United 

States from 1990 to 

2003.

All sources 3 Used for focal depth distribution, 

but range of magnitudes is only 

2.5–5.6, so little constraint on 

larger magnitudes.

N

CEUS SSC earthquake catalog 5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty 

assessments.

All sources 2 Provides information on focal 

depth, but quality varies across 

region.

Y

Chapman et al. (1997) 5 Eastern Tennessee wellconstrained focal 

mechanism solutions 

derived using a new 

velocity model and 

relocated hypocenters.

All sources 4 Used for assessing sense of slip 

and focal depths.

N

Dineva et al. (2004) 4 Relocated earthquakes 

in the 1990–2001 period 

in the southern Great 

Lakes and three focal 

mechanisms.

All sources 2 Used for sense of slip but very few 

events.

N
Table C-5.4 Data Evaluation 

Future Earthquake Characteristics 

Identified Source 

Default for entire CEUS SSC 

C-4

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Horton et al 2005) 4 Compilation of better 

focal mechanisms in 

Reelfoot, Rough Creek, 

and Wabash Valley 

All sources 3 Used for assessing sense of slip. N

Kim (2003) 4 Assessment of the June 

18, 2002, Caborn, 

Indiana, earthquake 

(MW 4.6) using regional 

and teleseismic 

waveform data.

All sources 1 Provides information on focal depth 

and sense of slip in Wabash Valley 

area; very localized.

N

Kim and Chapman (2005) 4 Detailed study of 2003 

event in central Virginia 

using regional 

waveforms.

All sources 2 Provides information on depth and 

sense of slip, but very few events.

N

Mai (2005) 3 Compilation of data 

related to hypocenter 

depths in relation to the 

normalized downdip 

width of fault rupture for 

crustal faults.

All sources 3 Used to assess the expected depth 

distribution of earthquakes as a 

function of earthquake magnitude.

N

S. Mazzotti (CEUS SSC WS2 

presentation)

3 Compilation of focal 

mechanisms in the St. 

Lawrence in the 

Charlevoix area.

All sources 3 Includes events having range of 

data quality.

N
Table C-5.4 Data Evaluation 

Future Earthquake Characteristics 

Identified Source 

Default for entire CEUS SSC 

C-5

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Seeber et al. (1998) 3 Local study of Cacoosing 

Valley earthquakes near 

Reading, Pennsylvania.

All sources 1 Local study with information on 

focal depth and sense of slip.

N

Shumway (2008) 5 Special study in New 

Madrid area with new 

velocity profile.

All sources 4 High quality focal mechanisms, 

locations, and focal depths for 

sense of slip.

N

Sibson (1984) 2 Compilation and physical 

analysis of earthquake 

focal depths for larger 

crustal earthquakes.

All sources 3 Provides a basis for assessing the 

width of the seismogenic zone 

using earthquake hypocenters; 

roughly the 95th percentile cutoff of 

seismicity.

N

Sibson and Xie (1998) 3 Compilation of fault dips

moderate to large (M > 

5.5) reverse-slip 

intracontinental 

earthquakes with the 

slip-vector raking 90 ± 

30° in the fault plane.

All sources 3 Global compilation used to 

constrain the dips of reverse faults.

N

Somerville et al. (2001) 3 Compilation of modelingderived rupture areas 

and seismic moment for 

eastern North America 

earthquakes.

All sources 5 Provides preferred rupture area vs 

magnitude relationship.

N
Table C-5.4 Data Evaluation 

Future Earthquake Characteristics 

Identified Source 

Default for entire CEUS SSC 

C-6

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Sykes et al. (2008) 4 High-quality earthquake 

locations and focal 

depths in the New York 

region.

All sources 3 Good quality focal depths for a 

local region, limited magnitude 

range.

N

Talwani (CEUS SSC WS2) 3 Compilation of focal 

mechanisms and focal 

depths in the Charleston, 

South Carolina, area.

All sources 3 Variable data quality but good 

compilation of data for this region.

N

Tanaka (2004) 5 High quality and large 

numbers of welldetermined focal depths 

for Japanese 

earthquakes, as well as 

extensive compilation of 

thermal measurements.

All sources 5 Provides strong technical basis for 

the correlation between the 

maximum crustal thickness and 

D90, which is the depth above 

which 90% of the seismicity lies.

N

van Lanen and Mooney (2007) 3 Compilation of 

earthquake focal depth 

in eastern North America 

as a function of moment 

magnitude.

All sources 3 Good compilation but variable data 

quality; used for depth as function 

of magnitude.

N

Regional Stress

CEUS SSC stress data set 5 Includes additional data 

points not shown on 

World Stress Map.

All sources 3 Provides indications of the 

expected tectonic stress regime 

and the sense of slip.

Y
Table C-5.4 Data Evaluation 

Future Earthquake Characteristics 

Identified Source 

Default for entire CEUS SSC 

C-7

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Zoback (1992) 3 Based on focal 

mechanisms available in 

late 1980s.

All sources 2 Used to assess the amount of 

strike-slip versus thrust faulting in 

the CEUS; also provides 

indications of orientations of 

ruptures.

N

Tectonic Strain–Paleoseismicity

Wesnousky (2008) 4 Compilation of empirical 

data regarding the 

seismologic and geologic 

characteristics of 

earthquake ruptures.

All sources 3 Used for relationship between fault 

length-to-width aspect ratio versus 

magnitude for future ruptures.

N

Geologic Mapping

Marshak and Paulsen (1997) 3 Maps based on regionalscale extrapolations of 

local data sets.

All sources 2 Used to confirm the presence of 

potential northwest-trending future 

earthquake rupture orientations.

N

Other

NAGRA (2004) 3 Assessments from 

expert panel of rupture 

width as function of 

magnitude.

All sources 4 Used for characterizing the depth 

distribution of future earthquake 

ruptures using the focal depth 

distribution of observed 

hypocenters.

N
Table C-5.4 Data Evaluation 

Future Earthquake Characteristics 

Identified Source 

Default for entire CEUS SSC 

C-8

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Sibson (2007) 3 Assessment of base of 

seismogenic zone based 

on physical constraints.

All sources 2 Provides physical basis for 

estimating depth of seismogenic 

zone from seismicity; confirms 

magnitude dependence of focal 

depths.

N
Table C-6.1.1 Data Evaluation 

Charlevoix RLME 

Identified Source 

Charlevoix RLME within the St. Lawrence Rift Zone 

C-9

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude 

conversions and 

uncertainty 

assessments.

Charlevoix 5 Used to evaluate recurrence 

parameters.

Y

Lamontagne and Ranalli 

(1997)

5 Relocated hypocentral 

depth.

Charlevoix 5 Used to evaluate thickness of 

seismogenic crust and style of 

faulting.

Y

Historical Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude 

conversions and 

uncertainty 

assessments.

Charlevoix 5 Largest historical earthquake in the 

CEUS SSC earthquake catalog is the 

1663 Charlevoix earthquake 

Y

Ebel (1996) 3 Determined magnitude 

from felt effects.

Charlevoix 5 Used to evaluate maximum 

magnitude.

Y

Ebel (2006b) 3 Determined magnitude 

from felt effects.

Charlevoix 5 Used to evaluate maximum 

magnitude.

N
Table C-6.1.1 Data Evaluation 

Charlevoix RLME 

Identified Source 

Charlevoix RLME within the St. Lawrence Rift Zone

C-10

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Ebel (2009) 3 Determined magnitude 

from felt effects and 

attenuation 

relationships.

Charlevoix 5 Used to evaluate maximum 

magnitude.

N

Lamontagne et al. (2008) 4 Earthquake 

parameters and felt 

effects for major 

Canadian 

earthquakes.

Charlevoix 4 Magnitudes derived from special 

studies are cited directly in CEUS 

SSC earthquake catalog.

Y

Magnetic Anomaly

CEUS SSC magnetic data

set

5 High-quality regional 

data

Charlevoix 1 The Charlevoix zone is not 

subdivided based on different 

basement terranes or tectonic 

features imaged in the magnetic 

anomaly map. 

Y

Gravity Anomaly

CEUS SSC gravity data set 5 High-quality regional 

data

Charlevoix 1 The Charlevoix zone is not 

subdivided based on different 

basement terranes or tectonic 

features imaged in the gravity 

anomaly map.

Y
Table C-6.1.1 Data Evaluation 

Charlevoix RLME 

Identified Source 

Charlevoix RLME within the St. Lawrence Rift Zone 

C-11 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Seismic Reflection

Tremblay et al. (2003) 3 Relocates offshore 

SQUIP data

Charlevoix 2 Images a transition from a half 

graben to a graben of the St. 

Lawrence fault within the St. 

Lawrence estuary.

N

Local Geologic and Tectonic Maps

Lemieux et al. (2003) 4 Delineates spatial 

relationship between 

rift faults and impact 

crater. 

Charlevoix 5 Used for source geometry. N

Tremblay et al. (2003) 4 Delineates relationship 

between rift faults and 

impact crater.

Charlevoix 5 Used for source geometry. N

Geodetic Strain

Mazzotti and Adams (2005) 3 Seismic moment rate 

of 0.1–5.0 1017 Nm/yr 

for Charlevoix.

Charlevoix 3 Provides a model for localizing 

earthquakes at Charlevoix

N

Regional Stress

Baird et al., (2009) 4 Performs 2-D stress 

modeling of the impact 

crater and rift faults.

Charlevoix 5 Modeling results confirm source 

geometry.

N
Table C-6.1.1 Data Evaluation 

Charlevoix RLME 

Identified Source 

Charlevoix RLME within the St. Lawrence Rift Zone

C-12

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

CEUS SSC stress data set 4 Provides additional 

new measurements to 

World Stress Map.

Charlevoix 1 Data includes thrust mechanisms 

with minor strike-slip. Orientations 

vary from E-W to NE-SW.

Y

Heidbach et al. (2008)

(World Stress Map)

3 Compilation of 

worldwide stress data.

Charlevoix 2 Entries for SLR are predominantly 

thrust mechanisms with some strikeslip. Orientations of maximum 

horizontal stress vary from E-W to 

NE-SW.

Y

Focal Mechanisms

Bent (1992) 3 Analyzed historical 

waveforms for 1925 

earthquake.

Charlevoix 4 Used to characterize future ruptures. N

Lamontagne (1999) 4 Determined focal 

mechanisms for 

Charlevoix 

earthquakes. 

Charlevoix 4 Used to characterize future ruptures. N

Lamontagne and Ranalli 

(1997)

4 Well-constrained focal 

mechanisms within the 

Charlevoix seismic 

zone.

Charlevoix 2 Thrust focal mechanisms correspond 

to larger-magnitude events, whereas 

smaller-magnitude events display 

greater variation in nodal planes 

corresponding to reactivation of 

fractures.

N

Li et al. (1995) 4 Determined focal 

mechanisms for two M 

4 earthquakes.

Charlevoix 4 Used to characterize future ruptures. N
Table C-6.1.1 Data Evaluation 

Charlevoix RLME 

Identified Source 

Charlevoix RLME within the St. Lawrence Rift Zone 

C-13 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Paleoseismicity

Tuttle and Atkinson (2010) 4 Results of regional 

paleoliquefaction study 

in Charlevoix.

Charlevoix 4 Mmax assessment—Evidence for 

prehistoric earthquakes in Charlevoix 

area. Suggests stationarity of largemagnitude earthquakes in 

Charlevoix.

Y

CEUS SSC 

paleoliquefaction database

5 Compilation (with 

attributions) of 

paleoliquefaction 

observations

Charlevoix 4 Contains data presented in Tuttle

and Atkinson (2010).

Y

Dionne (2001) 4 Detailed mapping and 

dating of Holocene 

deposits.

Charlevoix 5 Evidence of mid-Holocene sea-level 

lowstand may result in 

incompleteness interval.

N

Doig (1990) 3 Documents silt layers 

in cores attributed to 

earthquake-induced 

landslides.

Charlevoix 2 Uncertain magnitude estimates 

difficult to relate specifically to 

recurrence.

N

Filion et al. (1991) 3 Provides ages for 

prehistoric landslides 

attributed to 

earthquakes.

Charlevoix 2 Uncertain magnitude estimates 

difficult to relate specifically to 

recurrence.

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-14

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty 

assessments.

L, R, N 5 Highest concentration of seismicity 

located in local Charleston area. 

Possible association of seismicity with 

offshore Helena Banks fault. Locations 

of Middleton Place–Summerville and 

Bowman seismic zones. Magnitudes of 

the earthquakes in the Adams Run 

seismic zone (coda magnitudes [MC] < 

2.3) are too small to appear in the 

CEUS SSC earthquake catalog.

Y

Madabhushi and Talwani 

(1993)

3 Total of 58 

instrumentally recorded 

earthquakes between 

1980 and 1991 with MD

0.8–3.3 in Charleston 

area. 

L 4 Mapped location of Middleton Place–

Summerville seismic zone. 

Y

Smith and Talwani (1985) 2 Abstract describing 

location of Bowman 

seismic zone and gravity 

surveys conducted in 

vicinity of Bowman 

seismic zone.

N 1 Abstract provides brief description of 

location of Bowman seismic zone.

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-15 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

South Carolina Seismic 

Network (2005)

4 Tabulation of 

microseismicity in 

Charleston area, 

recorded between 1974 

and 2002. 

L, N 4 Includes local Charleston earthquakes 

with magnitudes smaller than those 

listed in the CEUS SSC earthquake 

catalog. Spatially concentrated in 1886 

epicentral area.

Y

Tarr et al. (1981) 2 Instrumentally recorded 

microseismicity in the 

Charleston area 

between 1973 and 1979. 

L 2 Mapped locations of the Middleton 

Place–Summerville, Bowman, and 

Adams Run seismic zones. 

N

Tarr and Rhea (1983) 2 Instrumentally recorded 

microseismicity in the 

Charleston area 

between 1973 and 1979. 

L 2 Mapped locations of the Middleton 

Place–Summerville, Bowman, and 

Adams Run seismic zones. 

N

Historical Seismicity

Bakun and Hopper (2004b) 5 Preferred 1886 

magnitude estimate 

based on assumed 

location at Middleton 

Place–Summerville 

seismic zone.

L, R, N 5 Magnitude of 1886 Charleston 

earthquake is estimated between Mw

6.4 and 7.2 (at 95% confidence level), 

with preferred estimate of Mw 6.9. 

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-16

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Bollinger (1977) 5 Isoseismal 

determinations for 1886 

earthquake, based on 

reinterpretation of 

Dutton’s (1889) basic 

intensity data.

L 5 Maximum epicentral intensity MMI X, 

with MMI IX in city of Charleston. 

Isoseismals define roughly coastparallel elongation. Magnitude of 1886 

earthquake estimated at mb 6.8 to 7.1. 

Y

Bollinger (1983) 3 Poorly constrained 

estimate of seismogenic 

crustal thickness at 

Charleston.

L, R, N 3 Estimates 1886 earthquake at mb 6.7, 

with rupture length approximately 25 

km, width approximately 12 km, 

average slip 1 m, based on empirical 

relations. Notes ongoing 

microseismicity concentrated in 1886 

meizoseismal area.

Y

Bollinger (1992) 4 Estimate of seismogenic 

crustal thickness at 

Charleston.

L, R, N 4 Seismic source characterization for the 

Savannah River Site describes input 

parameters for PSHA, including 

seismogenic crustal thickness 

estimates of 14 and 25 km, 

respectively, for ―Local Charleston‖ and 

―SC Piedmont and Coastal Plain‖ 

seismic sources.

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-17 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Chapman and Talwani 

(2002)

4 Estimate of seismogenic 

crustal thickness at 

Charleston.

L, R, N 4 Seismic source characterization for 

South Carolina Department of 

Transportation describes input 

parameters for PSHA, including 

seismogenic crustal thickness estimate 

of 25 km.

N

Dutton (1889) 4 Intensity data and 

mapping of liquefaction 

―craterlets‖ for the 1886 

earthquake. 

L 2 Intensity data not explicitly used in 

source characterization, but these data 

later reinterpreted by Bollinger (1977), 

Bakun and Hopper (2004b), and 

others. Descriptions of largest and 

most spatially concentrated liquefaction 

―craterlets‖ near Charleston used, in 

part, to define epicentral region of 1886 

earthquake. 

N

Johnston (1996b) 4 Johnston (1996b) 

magnitude estimate for 

1886 earthquake is 

significantly lower than 

Johnston et al. (1994) 

estimate of 7.56 ± 0.35.

L, R, N 5 Magnitude estimate for 1886 

Charleston earthquake of Mw

7.3 ± 0.26 based on isoseismal area 

regression accounting for eastern 

North America anelastic attenuation. 

N

Martin and Clough (1994) 4 Magnitude estimate 

based on critical 

reassessment of 

available data. 

L, R, N 4 Magnitude estimate for 1886 

Charleston earthquake of Mw 7.0 to 7.5 

based on geotechnical assessment of 

1886 liquefaction data. 

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-18

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Silva et al. (2003) 4 Estimate of seismogenic 

crustal thickness at 

Charleston.

L, R, N 4 Estimates of seismogenic crustal 

thickness at Charleston of 16 and 20 

km, inferred from contemporary 

seismicity.

N

Talwani (1982) 3 Early depiction of 

Woodstock fault, refined 

and superseded by 

subsequent publications.

N 2 Relocated seismicity in the 1886 

meizoseismal area suggests (1) rightlateral strike-slip events on the NEstriking Woodstock fault; and (2) SWside-up thrust events on the NWstriking Ashley River fault.

N

Magnetic Anomaly

CEUS SSC magnetic data

set

5 High-quality regional 

data

R 2 Reviewed in defining the regional 

source configuration.

Y

Gravity Anomaly

CEUS SSC gravity data set 5 High-quality regional 

data

R 2 Reviewed in defining the regional 

source configuration.

Y

Seismic Reflection
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-19 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Behrendt et al. (1981) 4 Data suggest onshore 

faulting but do not 

provide unambiguous 

constraints on fault 

geometry and upward 

terminations within 

Coastal Plain sediments.

L, R 4 Subsurface fault mapping in 1886 

epicentral area, including the proposed 

Cooke fault. 

N

Behrendt et al. (1983) 4 High-resolution, 

multichannel seismicreflection data clearly 

image the Helena Banks 

fault. Surveys limited to 

~50 km SW and NE 

offshore of Charleston. 

R 4 Mapping and age estimate of offshore 

Helena Banks fault. 

N

Behrendt and Yuan (1987) 4 High-resolution, 

multichannel seismicreflection data clearly 

image the Helena Banks 

fault. Surveys limited to 

~50 km SW and NE 

offshore of Charleston. 

R 4 Mapping and age estimate of offshore 

Helena Banks fault. 

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-20

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Chapman and Beale (2008) 5 ―Fault C‖ clearly imaged 

in reprocessed seismic 

reflection line. 

Orientation, length, and 

upward termination of 

fault currently 

unresolved. Strike and 

length of ―fault C‖

inferred from alignment 

of possible faults in 

adjacent seismic lines. 

Fault at least as young 

as Miocene or possibly 

Pliocene. 

L, N 5 ―Fault C‖ postulated to be fault that 

ruptured in 1886 Charleston 

earthquake. Location used in defining 

Local source configuration.

Y

Chapman and Beale (2010) 5 Reprocessed seismic 

reflection data suggest 

the 1886 epicentral area 

lies within a zone of 

extensive upper crustal 

faulting, but does not 

constrain 

geometry/extent of 

possible faults.

L, N 5 ―Fault C‖ postulated to be fault that 

ruptured in 1886 Charleston 

earthquake. Location used in defining 

Local source configuration.

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-21 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Hamilton et al. (1983) 4 Data suggest onshore 

faulting but do not 

provide unambiguous 

constraints on fault 

geometry and upward 

terminations within 

Coastal Plain sediments.

L, R 4 Postulated Cooke, Gants, and Drayton 

faults in Charleston 1886 epicentral 

area. Strikes, lengths, and ages not 

well constrained. 

N

Marple and Miller (2006) 2 Data suggesting the 

existence of the 

proposed Berkeley fault 

are equivocal. Paper 

includes useful summary 

of data used by others to 

constrain previously 

proposed faults near 

Charleston. 

L, N 2 Marple and Miller (2006) call into 

question the existence of the Adams 

Run fault of Weems and Lewis (2002). 

N

Regional Geologic and Tectonic Maps

Nystrom (1996) 4 Simplified seismic 

hazard map of South 

Carolina Coastal plain 

with minimal 

documentation. 

L, R, N 1 Map roughly outlines those areas of 

coastal South Carolina most 

susceptible to liquefaction. 

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-22

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Local Geologic and Tectonic Maps

Bartholomew and Rich 

(2007)

2 Authors postulate 

Dorchester fault in 1886 

epicentral area based on 

indirect evidence. 

L 2 Subsurface fault mapping in 1886 

epicentral area.

Y

Colquhoun et al. (1983) 3 Data suggesting the 

existence of proposed 

Charleston and GarnerEdisto faults are 

equivocal. 

L 3 Early mapping of the proposed 

Charleston and Garner-Edisto faults 

based on subsurface stratigraphy and 

borehole control. 

N

Dura-Gomez and Talwani 

(2009)

4 Article presents minor 

modifications to 

previously mapped 

subsurface faults near 

Charleston. 

L, N 3 Slightly revised mapping of faults in the 

subsurface near Middleton Place–

Summerville seismic zone. 

N

Marple and Miller (2006) 4 Data suggesting 

existence of the 

proposed Berkeley fault 

are equivocal. Paper 

includes useful summary 

of data used by others to 

constrain previously 

proposed faults near 

Charleston.

L, N 3 Marple and Miller (2006) call into 

question the existence of the Adams 

Run fault of Weems and Lewis (2002). 

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-23 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Marple and Talwani (1993) 4 Early depiction of Zone 

of River Anomalies and 

Woodstock fault, refined 

and superseded by 

subsequent publications. 

L, N 1 Early mapping of Zone of River 

Anomalies and proposed Woodstock 

fault. Superseded by subsequent 

publications. 

N

Marple and Talwani (2000) 4 Zone of River Anomalies 

proposed as tectonic 

feature, based on 

equivocal 

geomorphologic, 

seismic, and geophysical 

data. Data suggesting 

existence of southern 

segment are more 

robust than those for 

central and northern 

segments. 

N 3 Identification of Zone of River 

Anomalies expands on earlier work 

(e.g., Marple and Talwani 1993).

Y

McCartan et al. (1984) 4 No faults mapped. L, R, N 1 Geologic mapping at 1:250,000 scale 

of greater Charleston area. 

N

Talwani and Dura-Gomez 

(2009)

4 Minor modifications to 

previously mapped 

subsurface faults near 

Charleston. 

L, N 3 Subsurface fault mapping in 1886 

epicentral area.

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-24

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Talwani and Katuna (2004) 4 Viable alternate 

explanations (groundshaking-related) exist for 

postulated primary 

surface rupture. 

L, N 3 Subsurface fault mapping in 1886 

epicentral area. Postulated 1886 

coseismic effects and potential surface 

rupture. 

Y

Weems and Lewis (2002) 3 Viable alternate 

(nontectonic) 

explanations exist for 

mapped features, 

including Adams Run 

and Charleston faults. 

L 4 Subsurface fault mapping in 1886 

epicentral area.

Y

Geodetic Strain

Trenkamp and Talwani 

(n.d.)

2 Study suffers from 

admitted monument 

instability, small number 

of surveys (three), and 

short period of GPS 

measurements (six

years). 

L, R, N 2 This as-yet-unpublished study presents 

campaign GPS data from a 20-station 

grid near Charleston that suggest 

average shear strain rate (~109to 107

rad/yr) that is one to two orders of 

magnitude higher than the surrounding 

region. Largest interpreted strains 

located in Middleton Place–

Summerville seismic zone and 

attributed to local fault intersections.

Y
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-25 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Paleoseismicity

Amick and Gelinas (1991) 3 Short paper published in 

Science magazine; 

presents summary of 

data and interpretations 

described in more detail 

in other publications 

(e.g., Amick, Gelinas, et 

al., 1990; and Amick, 

Maurath, and Gelinas, 

1990). 

L, R, N 5 Largest paleoliquefaction features are 

at sites near Charleston, suggesting 

repeated large earthquakes near 

Charleston. Majority of 

paleoliquefaction features can be 

explained by a source near Charleston, 

but suggest the possibility of a 

separate (moderate?) source located 

~100 km northeast. 

N

Amick, Gelinas, et al. 

(1990)

4 Areas searched in which 

no features found are 

identified by 7.5-minute 

quadrangle only. 

Detailed reconnaissance 

maps not available. 

L, R, N 5 Paleoliquefaction features found only in 

coastal Carolinas. Largest 

paleoliquefaction features are at sites 

near Charleston, suggesting repeated 

large earthquakes near Charleston. 

Return period for large (M ~ 7+) 

earthquakes near Charleston 

estimated at 500–600 years. 

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-26

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Amick, Maurath, and 

Gelinas (1990)

4 Areas searched in which 

no features found are 

identified by 7.5-minute 

quadrangle only. 

Detailed reconnaissance 

maps not available. 

L, R, N 5 Paleoliquefaction features found only in 

coastal Carolinas. Largest 

paleoliquefaction features are at sites 

near Charleston, suggesting repeated

large earthquakes near Charleston. 

Return period for large (M ~ 7+) 

earthquakes near Charleston 

estimated at 500–600 years. 

N

Dutton (1889) 4 Basic intensity data and 

mapping of liquefaction 

―craterlets‖ for the 1886 

earthquake. 

L, R, N 5 Observed greatest concentration of 

1886 liquefaction ―craterlets‖ at and 

north of Charleston. 

N

Hu et al. (2002a) 3 Geotechnical data that 

form basis of Hu et al.’s 

(2002b) assessment of 

paleoearthquake 

magnitudes.

L, R, N 1 Background geotechnical data used by 

Hu et al. (2002b) to estimate 

geotechnical estimates of 

paleoearthquake magnitudes

N

Hu et al. (2002b) 3 Superseded by Leon et 

al. (2005) study, which

includes two of the same 

three coauthors. 

L, R, N 3 Geotechnical estimates of 

paleoearthquake magnitudes, based 

on Talwani and Schaeffer’s (2001) 

earthquake scenarios.

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-27 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Leon (2003) 3 Dissertation, relevant 

portions of which later 

published as and 

superseded by Leon et 

al. (2005).

L, R, N 3 Geotechnical estimates of 

paleoearthquake magnitudes.

Assumes Talwani and Schaeffer’s 

(2001) earthquake scenarios. 

N

Leon et al. (2005) 4 Geotechnical magnitude 

estimates for Charleston 

paleoearthquakes 

generally lower than 

previously identified (see 

Hu et al. 2002b). 

L, R, N 4 Geotechnical estimates of 

paleoearthquake magnitudes. 

Assumes Talwani and Schaeffer’s 

(2001) earthquake scenarios.

N

Noller and Forman (1998) 3 Interpreted two or three

paleoliquefaction events 

at Gapway Ditch site, 

where Amick, Gelinas, et 

al. (1990); Amick, 

Maurath, and Gelinas 

(1990); and Talwani and 

Schaeffer (2001) 

interpreted one

paleoliquefaction event. 

No scale provided with 

exposure log. 

L, R, N 3 Timing of paleoliquefaction events 

used to help constrain return period for 

large earthquakes at Charleston. 

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-28

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Obermeier (1996b) 3 General overview of 

Charleston liquefaction 

and paleoliquefaction. 

L, R, N 4 Large diameters (3+ m) of some 

prehistoric craters suggest these likely 

were caused by earthquakes ―much 

stronger than M5 to 5.5.‖ (p. 350). 

Sandblow craters that formed roughly 

600 and 1,250 yr BP extend along 

coast at least as far as 1886 features, 

suggesting that some prehistoric 

earthquakes likely may have been at 

least as large as 1886.

Y

Obermeier et al. (1989) 3 Description of 

liquefaction and 

paleoliquefaction feature 

size and spatial 

concentration are 

qualitative and not well 

documented, but taken 

as evidence for repeated 

large earthquakes 

located at or near 

Charleston. 

L, R, N 4 Size and spatial concentration of both 

1886 liquefaction and paleoliquefaction 

features are greatest near Charleston, 

and decrease with distance up and 

down the coast, despite similarities in 

liquefaction susceptibility throughout 

region. This indicates repeated large 

earthquakes located at or near 

Charleston. 

N

Olson et al. (2005b) 5 Magnitude-bound 

relations calibrated for 

CEUS. 

L, R, N 3 Magnitude-bound relations calibrated 

for CEUS. Used to help constrain 

source geometries.

N
Table C-6.1.2 Data Evaluation 

Charleston RLME 

Identified Sources 

Charleston RLME with alternatives: L: Local; R: Regional; N: Narrow 

C-29 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Talwani and Schaeffer 

(2001)

4 Paleoearthquake 

scenarios based on 

1-sigma radiocarbon age 

constraints.

L, R, N 5 Tabulation of available 

paleoliquefaction data for Charleston 

region. Talwani and Schaeffer’s (2001) 

1-sigma radiocarbon age data were 

recalibrated to 2-sigma for use in 

CEUS SSC Project. Return period for 

large (M ~ 7+) earthquakes near 

Charleston estimated at 500–600 

years. 

N

Talwani et al. (2008) 2 Single undated 

paleoliquefaction feature 

does not provide any 

reliable constraints on 

timing, magnitude, or 

location of 

paleoearthquakes. 

L, R, N 2 Paleoearthquake magnitude estimated 

at ~6.9 (scale unspecified) based on

unspecified geotechnical analyses. 

N

Weems and Obermeier 

(1990)

3 Early assessment of 

paleoliquefaction-based 

earthquake recurrence 

at Charleston, refined 

and superseded by more 

recent publications.

L, R, N 2 Describe evidence for three, and 

possibly four, middle to late Holocene 

earthquakes preserved in the geologic 

record as paleoliquefaction features, as 

well as evidence for events as old as 

30,000 years.

N
Table C-6.1.3 Data Evaluation 

Cheraw Fault RLME 

Identified Source 

Cheraw fault 

C-30

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

Cheraw 

fault

0 No association of instrumental 

seismicity with the Cheraw fault.

Y

Historical Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

Cheraw 

fault

0 No association of historical seismicity 

with the Cheraw fault.

Y

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional 

data 

Cheraw 

fault

0 Cheraw fault not expressed as a 

distinct lineament in the magnetic 

anomaly map. General NE trend of 

the fault is subparallel to regional 

trends to the N and NW of the fault.

Y

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional 

data 

Cheraw 

fault

0 Cheraw fault not imaged or apparent 

in the gravity data.

Y
Table C-6.1.3 Data Evaluation 

Cheraw Fault RLME 

Identified Source 

Cheraw fault 

C-31 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Regional Geologic and Tectonic Maps

Scott et al. (1978) 4 Scale 1:250,000 Cheraw 

fault

0 Map source cited by Crone (1997) for 

bedrock fault. Not used directly for 

location of Cheraw RLME source 

geometry.

N

Sharps (1976) 4 Scale 1:250,000

Cited by Crone, 

Machette, Bradley, et 

al. (1997) as original 

map that identified the 

Sharps (1976) Cheraw 

fault.

Cheraw 

fault

0 Original map source cited by Crone 

(1997) for bedrock fault. Not used 

directly for location of Cheraw RLME 

source geometry.

N

Local Geologic and Tectonic Maps

Petersen et al. (2008) 4 Source 

characterization 

parameters went 

through USGS 

community review 

process.

Cheraw 

fault

4 All parameters for Cheraw fault 

retained from 2002; fault modeled 

using a slip rate of 0.15 mm/yr based 

on data from last two events and a 

maximum magnitude of 7.0 ± 0.2 

determined from the Wells and 

Coppersmith (1994) fault length 

relationship based on all slip types

together. Fixed recurrence time of 

17,400 years is used with truncated 

Gutenberg-Richter model from M 6.5 

to 7.0. This yields a mean recurrence 

N
Table C-6.1.3 Data Evaluation 

Cheraw Fault RLME 

Identified Source 

Cheraw fault 

C-32

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

time of 5,000 years for earthquakes 

with minimum magnitude of 6.5.

Fault source parameters (2008 

hazard maps) 

http://gldims.cr.usgs.gov

/webapps/cfusion/Sites/c2002_search

/search_fault_2002.cfm—

Length: 44 km (27.3 mi.)

Dip: 60°N

Slip rate: 0.15 mm/yr

Width: 17 km (10.6 mi.)

Characteristic magnitude: 7 (based on 

Ellsworth (2003) relation.

Characteristic rate: 1.15E-04.

USGS National Hazard 

Mapping Project

5 Detailed summary of 

previous mapping and 

paleoseismic 

investigations on the 

Cheraw fault. 

Cheraw 

fault

4 Trace is from 1:24,000-scale mapping 

(and interpretation of aerial 

photographs), transferred to a 

1:250,000 topographic base (Crone, 

Machette, Bradley, et al., 1997).

Fault source location (total length): 

46.24 km (28.73 mi.; measured from 

Quaternary fault map database).

Y

USGS 10 m DEM 4 Resolution of 10 m 

data is sufficient to 

image the Quaternary 

active trace of the 

Cheraw 

fault

4 Interpretation of 10 m DEM suggests 

that Cheraw fault may have surface 

expression beyond the length of fault 

source as defined in USGS Fault and 

Fold Database (source length used in 

Y
Table C-6.1.3 Data Evaluation 

Cheraw Fault RLME 

Identified Source 

Cheraw fault 

C-33 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Cheraw fault. the 2008 National Seismic Hazard 

Mapping Program). A possible 

lineament (north-facing scarp) 

extends approximately 16–20 km 

(10–12.4 mi.) to NE of mapped end of 

Cheraw fault. A railroad lies adjacent 

to and just north of the scarp where it 

is best expressed, suggesting it may 

be modified or nontectonic in origin.

Assuming lineament is tectonic, total 

length of fault source inferred from 

DEM is 62–66 km (38.5–41 mi.).

Regional Stress

CEUS SSC stress data

set

5 Includes additional 

data points not shown 

on World Stress Map.

Cheraw 

fault

0 No new data points in SE Colorado 

near Cheraw fault. 

Y

Heidbach et al. (2008)

(World Stress Map)

3 Worldwide compilation 

of stress data (updated 

by CEUS SSC data 

set).

Cheraw 

fault

1 No nearby measurements to Cheraw 

fault. Normal sense of displacement 

on E-NE-trending fault is consistent 

with regional stress field.

Y

Zoback and Zoback 

(1991)

4 Comprehensive 

regional study that 

discusses stress data 

and identifies stress 

domains for the United 

Cheraw 

fault

3 Regional stress data indicate that 

Cheraw fault is within the transition 

region between Cordilleran extension 

(Basin and Range and Rio Grande 

rift) and CEUS midplate stress (E-NEdirected maximum horizontal 

N
Table C-6.1.3 Data Evaluation 

Cheraw Fault RLME 

Identified Source 

Cheraw fault 

C-34

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

States. compressive stress). Normal faulting 

would be consistent with Cordilleran 

extension. 

Tectonic Strain—Paleoseismicity

Crone (1997)

Crone, Machette, Bradley, 

et al. (1997)

5 Detailed paleoseismic 

trenching and mapping 

investigation.

Cheraw 

fault

5 Provides detailed source 

characterization information:

Style of faulting—inferred normal 

based on trench exposures.

Length of fault—approximately 44 km 

(27.3 mi.) based on mapping and 

interpretation of aerial photograph.

Timing of recent events—~8 ka, 12 

ka, and 20–25 ka. Older events must 

have occurred before about 100 ka.

Interpretation of amounts of vertical 

offset on the Cheraw fault—

Most recent event: ~0.5–1.1 m

(~1.6–3.6 ft.).

Penultimate event: ~1.1–1.6 m

(~1.6–5.2 ft.).

Oldest event: ~1.5 m (4.9 ft.).

Fault behavior—temporal clustering 

(relatively short time intervals of 

activity [e.g., 15–20 kyr) separated by 

long intervals of quiescence [e.g., 100 

kyr])

N
Table C-6.1.3 Data Evaluation 

Cheraw Fault RLME 

Identified Source 

Cheraw fault 

C-35 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Avg. recurrence in active period—8 

kyr

Slip rate—long-term: ≤0.007 mm/yr (8 

m [26.2 ft.]/1.2 Ma)

Late Pleistocene-Holocene rate—

0.14–0.18 mm/yr (determined by 

dividing the amount of offset [3.6 m, 

or 11.8 ft.] on oldest faulted deposits 

in trench by age of the deposits [20–

25 ka])

Dr. A. Crone, USGS, 

electronic comm., April 21, 

2010

4 Reconsideration of 

trenching data to better 

constrain uncertainties 

in number of 

paleoearthquakes.

Cheraw 

fault

4 Recurrence—Evaluation of number of 

paleoearthquakes recorded by 

stratigraphic and structural features in 

trench. Evidence for the penultimate 

event as presented by Crone, 

Machette, et al. (1997) not as 

definitive as evidence for earliest and 

latest events.

N
Table C-6.1.4 Data Evaluation 

Oklahoma Aulacogen RLME 

Identified Sources 

Meers fault RLME with alternatives—localized and random distribution; Oklahoma Aulacogen Zone (OKA) 

C-36

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

Luza and Lawson (1993) 4 Data appear robust, but 

report does not contain 

comments on how many 

and which of the reported 

earthquakes are induced 

by or related to 

hydrocarbon exploration. 

OKA and

Meers fault

3 Reported earthquake depths are 

used to constrain seismogenic 

depth and fault depth.

N

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

4 High-quality regional data OKA 4 Reviewed in defining geometry of 

aulacogen source zone. Extent of 

aulacogen was partially constrained 

by extent of associated magnetic 

anomaly.

N

Gravity Anomaly

CEUS SSC gravity anomaly 

data set

4 High-quality regional data OKA 4 Reviewed in defining geometry of 

aulacogen source zone. Extent of 

aulacogen was partially constrained 

by extent of associated gravity 

anomaly.

N
Table C-6.1.4 Data Evaluation 

Oklahoma Aulacogen RLME 

Identified Sources 

Meers fault RLME with alternatives—localized and random distribution; Oklahoma Aulacogen Zone (OKA) 

C-37 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Seismic Reflection

Brewer (1982) 3 Presents only two raw 

reflection lines, which are 

poorly reproduced. Maps 

and interpreted cross

section are more useful 

and considered of 

moderate quality.

OKA 3 Used to help define geometry of 

aulacogen source zone based on 

extent of faults within the ArbuckleWichita-Amarillo Uplift.

N

Brewer et al. (1983) 3 Presents only one raw 

reflection line, which is 

poorly reproduced. Maps 

and interpreted cross

section are more useful 

and considered of 

moderate quality.

OKA 3 Used to help defining geometry of 

aulacogen source zone based on 

extent of faults associated with the 

Arbuckle-Wichita-Amarillo Uplift.

N

Good et al. (1983) 4 Presents interpreted 

COCORP seismic 

reflection line across the 

Meers fault and Oklahoma 

Aulacogen.

OKA and 

Meers fault

3 Used to help define N-S extent of 

the aulacogen and to help constrain 

dip of Meers fault at depth.

N

McConnell (1989) 3 Data considered of 

moderate quality for 

defining the dip of the 

Meers fault at depth.

Meers fault 4 Used to help constrain dip of fault at 

depth.

N
Table C-6.1.4 Data Evaluation 

Oklahoma Aulacogen RLME 

Identified Sources 

Meers fault RLME with alternatives—localized and random distribution; Oklahoma Aulacogen Zone (OKA) 

C-38

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Miller et al. (1990) 4 Presents shallow (<200 m) 

interpretations of seismic 

reflection data across the 

Meers fault.

Meers fault 4 Used to help constrain shallow dip 

of fault.

N

Regional Geologic and Tectonic Maps

Ham et al. (1964) 3 Data considered of 

moderate quality with 

respect to accuracy and 

completeness of 

identifying faults 

associated with ArbuckleWichita-Amarillo Uplift.

OKA 5 Used to help define geometry of 

aulacogen source zone based on 

extent of faults associated with the 

Arbuckle-Wichita-Amarillo Uplift.

N

Keller and Stephenson 

(2007)

3 Data considered of 

moderate quality with 

respect to outlining extent 

of the aulacogen based on 

gravity anomaly data.

OKA 3 Used in defining geometry of 

aulacogen source zone based on 

the interpreted extent of aulacogen 

from gravity data.

N

McConnell (1989) 2 Data considered of 

moderate to poor quality 

because no details are 

given with respect to what 

data constrains the Meers 

fault dip.

Meers fault 4 Used to help constrain dip of fault. N
Table C-6.1.4 Data Evaluation 

Oklahoma Aulacogen RLME 

Identified Sources 

Meers fault RLME with alternatives—localized and random distribution; Oklahoma Aulacogen Zone (OKA) 

C-39 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Texas Bureau of Economic 

Geology (1997)

3 Data considered of 

moderate quality with 

respect to accuracy and 

completeness of 

identifying faults 

associated with ArbuckleWichita-Amarillo Uplift.

OKA 5 Used to help define geometry of 

aulacogen source zone based on 

extent of faults associated with the 

Arbuckle-Wichita-Amarillo Uplift.

N

Local Geologic and Tectonic Maps

Cetin (2003) 2 Proposes a NW extension 

of Meers fault beyond that 

previously recognized. 

Data considered of poor 

quality because of lack of 

supporting evidence.

Meers fault 5 Used to define potential NW 

extension of Meers fault.

N

Ramelli and Slemmons 

(1986)

5 Data considered of good 

quality for describing the 

geomorphic expression of 

fault trace.

Meers fault 3 Considered in defining extent of the 

fault and the Quaternary history of 

the fault.

N

Ramelli and Slemmons 

(1990)

5 Data considered of good 

quality with respect to

defining extent of fault.

Meers fault 3 Considered in defining extent of 

fault.

N
Table C-6.1.4 Data Evaluation 

Oklahoma Aulacogen RLME 

Identified Sources 

Meers fault RLME with alternatives—localized and random distribution; Oklahoma Aulacogen Zone (OKA) 

C-40

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Ramelli et al. (1987) 5 Fault trace is digitized in 

USGS Quaternary Fault 

and Fold Database; and 

this USGS version is used 

to define fault trace. Data 

considered of good 

quality.

Meers fault 5 Used to define trace of Holocene 

active fault.

N

Paleoseismicity

Crone and Luza (1990) 4 Data considered of 

moderate quality with 

respect to defining 

characteristics of fault 

rupture (e.g., surface 

offset, fault dip, horizontalto-vertical slip ratio).

Meers fault 2 Considered in defining 

characteristics of fault rupture.

N

Swan et al. (1993) 4 Data considered of good 

quality with respect to 

identifying rupture events 

on the fault and dates 

constraining timing of 

those ruptures. Data 

considered of moderate 

quality in defining 

characteristics of those 

ruptures (e.g., surface 

offsets).

Meers fault 5 Used to define recurrence rates and 

earthquake magnitudes from fault 

slip estimates.

N
Table C-6.1.4 Data Evaluation 

Oklahoma Aulacogen RLME 

Identified Sources 

Meers fault RLME with alternatives—localized and random distribution; Oklahoma Aulacogen Zone (OKA) 

C-41 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Other

Crone (1994) 5 Data considered of good 

quality with respect to 

summarizing and 

evaluating available data 

on Meers fault.

Meers fault 3 Considered in evaluating 

robustness and quality of available 

data on Meers fault.

N

Wheeler and Crone (2001) 5 Data considered of good 

quality with respect to 

analyzing available data 

concerning Meers fault.

Meers fault 3 Considered in evaluating 

robustness and quality of available 

data on Meers fault.

Y
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-42

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty 

assessments.

NMN, NMS, 

and RFT

3 Provides constraints on fault 

location and geometry.

Y

Chiu et al. (1992) 4 Publication discussing 

results of Portable Array 

for Numerical Data 

Acquisition (PANDA) 

survey. Provides 

detailed discussion of 

seismicity in New 

Madrid seismic zone 

(NMSZ).

NMN, NMS, 

RFT

5 Focal depth—Seismic activity in 

central NMSZ occurs continuously 

between ~5 and 14 km (3.1 and 

8.7 mi.) depth.

Seismicity illuminates fault zones.

RFT geometry—Two NE-trending 

vertical segments are

concentrated about a plane that 

dips at ~31°SW; a separate zone 

to the SE of axial zone defines a 

plane that dips at ~48°SW; 

projects to surface near Reelfoot 

Lake and Lake County uplift.

N

Historical Seismicity

Dr. William Bakun (USGS, 

electronic comm., 

February 3, 2010)

4 Electronic comm. 

confirming 2004 

magnitude estimates 

based on intensity for 

1811-1812 earthquakes.

NMN, NMS, 

RFT

5 Magnitude of 1811-1812 

earthquakes used to constrain 

Mmax for NMFS RLMEs (see 

Table 6.1.5-2).

N
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-43 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Exelon ESP (2004)

(includes estimates based 

on Johnston, 1996b; 

Hough et al. 2000; Bakun 

and Hopper, 2004a; pers.

comm. from Drs.

Johnston, Hough, and 

Bakun)

3 Compilation and update 

(2003–2004 time frame) 

of best estimates of size 

of 1811-1812 

earthquake sequence. 

NRC reviewed 

assessment for Early 

Site Permit Application.

NMN, NMS, 

and RFT

5 Evaluation of intensity data for the 

1811-1812 sequences provides

basis for assessing magnitude of 

these events, which are 

considered typical of prehistoric 

events based on similar sizes and 

distribution of paleoliquefaction 

features (Tuttle, Schweig, et al., 

2002; see Table 6.1.5-2).

N

Hough and Page (2011) 3 Presents magnitude 

estimates based on 

assessments by multiple 

experts.

NMN, NMS, 

RFT

5 Magnitude of 1811-1812 

earthquakes used to constrain 

Mmax for NMFS RLMEs—

Revisions to previous estimates 

(See Table 6.1.5-2).

N

Dr. Arch Johnston (CERI, 

pers. comm., February 16, 

2010)

2 Telephone 

conversation—New 

studies to evaluate size 

of 1811-1812 

earthquakes are being 

considered but have not 

yet started.

NMN, NMS, 

and RFT

4 Estimated sizes of 1811-1812 

earthquakes as reported in EGC 

ESP (2004) study have not been 

revised.

N

Seismic Reflection

Interpretation of seismic-reflection data has been integrated with other geologic, geophysical, and seismological data as reported in publications 

to define the structures within the Reelfoot rift. Specific lines not used directly in this study.
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-44

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Regional Geologic and Tectonic Maps

Csontos et al. (2008) 3 Structure-contour map 

of the top of basement 

showing subbasins and 

bounding NE- and SEstriking faults. Due to 

projection of the map 

showing interpretations 

of basement faults, the 

locations are considered

approximate.

NMS and 

RFT

5 Geometry and style of faulting—

Interpretation of basement 

structures and reactivation of 

faults (e.g., RFT as inverted 

basement normal fault).

N

Local Geologic and Tectonic Maps

Cramer (2001) 4 Publication scale map 

(Figure 3) with 

registration for 

digitization.

NMN, NMS, 

and RFT

2 Used to help constrain locations of 

alternative segments of the 

NMFS.

N

Guccione (2005) and 

Guccione et al. (2005) 

4 Includes detailed maps 

showing offset 

geomorphic features.

NMS 4 Used to constrain location of 

Bootheel fault (previously referred 

to as the Bootheel lineament).

N

Johnston and Schweig 

(1996)

3 Small-scale line 

drawings of faults 

interpreted to be 

sources of 1811-1812 

events.

NMN, NMS, 

and RFT

4 Interpretation formed the initial 

starting basis for the delineation of 

geometries for the New Madrid 

fault system sources.

Y
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-45 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Mueller and Pujol (2001) 4 Detailed structurecontour map of fault 

plane (Figure 3).

RFT 4 Downdip geometry and depth of 

seismogenic crust—Structurecontour map of Reelfoot blind 

thrust.

N

Van Arsdale et al. (1999) 4 Publication scale 

maps—good registration 

for digitization (Figures 

1 and 2).

RFT 5 Used to define the SE segment of 

the Reelfoot thrust fault.

N

Wheeler et al. (1994) 4 Detailed compilation 

map, USGS 

Miscellaneous 

Investigations Map.

NMS 3 Locations of subsurface faults—

Cottonwood Grove fault, Ridgely 

fault, unnamed fault west of 

Cottonwood Grove fault.

N

Geodetic Strain

Calais et al. (2006) 4 Two independent 

geodetic solutions from 

close to 300 continuous 

GPS stations.

NMN, NMS, 

and RFT

4 Based on observation that there is 

no detectable residual motion in 

the NMSZ at the 95% confidence 

level, some weight is assigned to 

the model that the NMFS is ―out of 

the cluster.‖

N
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-46

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Calais and Stein (2009) 5 Presents current results 

(through 2008) of GPS 

measurements.

NMN, NMS, 

and RFT 

4 Temporal clustering—Conclusion 

of paper suggests that the 

recurrence rate estimated from 

seismicity in NMSZ is consistent 

with rates suggested by geodetic 

measurements. This supports 

―out-of-cluster’‖ model.

N

Smalley et al. (2005) 4 Provides discussion of 

possible mechanisms to 

explain local but not 

regional geodetic signal.

NMN, NMS,

and RFT

3

Temporal clustering issue—

Evidence for ongoing strain across 

RFT and strike-slip fault zone; no 

apparent far-field signature. Notes 

that regardless of geodetic results, 

the challenge remains to reconcile 

geodetic observations with the 

detailed geological evidence 

available for repeated large 

earthquakes within Central United 

States, and that the cause of such 

earthquakes is not well 

understood.

N

Regional Stress

Forte et al. (2007) 3 Regional analysis NMN, NMS, 

and RFT

1 Provides rationale for 

concentrating seismic stress in the 

vicinity of the Reelfoot rift–NMSZ.

N
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-47 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Grana and Richardson 

(1996)

4 Regional analysis, 

models the rift pillow in 

New Madrid region.

NMN, NMS, 

and RFT) 

3 Temporal clustering—Modeling 

indicates that stresses from the 

load of the rift pillow may still be 

present in the upper crust and 

may still play a role in present-day 

deformation. This supports ―incluster’‖ model.

N

Li et al. (2009) 3 3-D viscoelasto-plastic 

finite-element model

addresses generic 

issues of spatiotemporal 

variations in seismicity 

in intraplate regions. 

NMN, NMS, 

and RFT 

2 Temporal clustering—Supports 

migration of seismicity within 

NMSZ (out of cluster model). 

Model replicates some of the 

spatiotemporal complexity of 

clustered, episodic, and migrating 

intraplate earthquakes.

Time-scale-dependent 

spatiotemporal patterns of 

intraplate seismicity support the 

suggestions that seismicity 

patterns observed from short-term 

seismic records may not reflect 

the long-term patterns of intraplate 

seismicity.

N

Tectonic Strain
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-48

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Hildenbrand and 

Hendricks (1995)

4 Detailed discussion of 

interpretations of 

geopotential data sets.

NMS 2 Temporal clustering—Limit of 

long-term cumulative 

deformation—NW-trending 

features related to South-Central 

magnetic lineament (SCML) and 

Paducah gravity lineament (PGL)

cross Reelfoot graben with no 

substantial lateral offsets, thus 

limiting the amount of lateral 

movement along axial faults of 

Reelfoot graben since formation of 

these features. 

N

Van Arsdale (2000) 4 Provides evidence for 

varying slip rate over 

time.

RFT 2 Temporal clustering—Geologic 

observations from interpretation of 

seismic profiles indicate that 

cumulative post-Late Eocene slip 

on structures in the NMSZ is low.

N

Focal Mechanisms

Herrmann and Ammon 

(1997)

4 Well-constrained focal 

mechanisms.

NMFS 3 Seismogenic depth—focal 

mechanisms show depths of up to 

16 km (10 mi.) for earthquakes in 

Reelfoot rift.

N
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-49 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Shumway (2008) 4 Earthquakes in the NE

NMSZ were relocated 

using a velocity model 

of Mississippi 

embayment with 

appropriate depths to 

bedrock beneath 

seismic stations.

NMN 4 NMN long geometry—This shows 

that this part of the NE NMSZ is 

influenced by the same fault 

pattern and stress regime as NMN 

fault, may be an extension of 

NMSZ, and therefore may 

represent alternate locations of 

January 23, 1812, rupture.

N

Zoback (1992) 4 Well-constrained focal 

mechanisms.

NMFS 3 Style of faulting in Reelfoot rift—

Four focal mechanisms show 

predominantly strike-slip motion.

N

Paleoseismicity

CEUS SSC 

paleoliquefaction 

database (includes 

information from Tuttle, 

2001; Tuttle, Schweig, et 

al., 2002, 2006)

5 Comprehensive 

database, peerreviewed, includes 

uncertainties in timing of 

paleoliquefaction 

events).

NMN, NMS, 

and RFT

5 Recurrence—Provides information 

on ―in cluster‖ recurrence interval 

for RFT.

Y

Exelon (2004) (includes

information from Tuttle, 

2001; Tuttle, Schweig, et 

al., 2002)

4 Comprehensive 

database; includes 

published and 

unpublished data. 

NMN, NMS, 

and RFT

1 Recurrence—Superseded by 

CEUS SSC paleoliquefaction 

database.

Y
Table C-6.1.5 Data Evaluation 

Reelfoot Rift–New Madrid Fault System RLMEs 

Identified Sources 

New Madrid North (NMN); New Madrid South (NMS); Reelfoot Thrust fault (RFT) 

C-50

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of

Data Use

In GIS 

Database

Holbrook et al. (2006) 4 Detailed analysis of 

geomorphic indicators of 

Holocene deformation in 

NMSZ. 

RFT 4 Recurrence—Provides information 

on ―out of cluster‖ recurrence 

interval for RFT.

N

Kelson et al. (1996) 5 Detailed and welldocumented 

paleoseismic 

investigation of surface 

deformation related to 

paleoearthquakes on 

RFT.

RFT 3 Recurrence—Basis for estimating 

timing and recurrence intervals for 

RFT. Dates of earthquakes in 

general agreement with 

paleoliquefaction data. 

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift–Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault south–

river (fault) picks (ERM-RP); and Eastern Rift Margin south–Crittenden County fault zone (ERM-SCC) 

C-51 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

ERM-S 1 Reviewed for alignment of 

microseismicity.

Y

Chiu et al. (1997) 4 Detailed analysis of 

seismicity along SE 

margin of Reelfoot rift.

ERM-S 3 Analysis of seismicity suggests 

there is an active fault source 

along the SE flank of the Reelfoot 

rift.

N

Historical Seismicity

Hough and Martin (2002) 4 Analysis of sparse 

intensity data for a large 

aftershock of the 1811 

earthquake.

ERM-S 2 Evidence for active fault along 

ERM—Aftershock of December 

1811 NMSZ earthquake (NM1-

B)—M 6.1 ± 0.2, location of event 

not well constrained, but probably 

beyond the southern end of the 

NMSZ, near Memphis, Tennessee 

(within the SW one-third to onehalf of the band of seismicity 

identified by Chiu et al. [1997]).

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift—Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault 

south—river (fault) picks (ERM-RP); and Eastern rift margin south—Crittenden County fault zone (ERM-SCC) 

C-52

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional 

data.

ERM zones 2 Geometry—The fault zones 

coincide with the eastern margin of 

the rift, which is marked by a 

change from low values (within the 

graben) to higher magnetic values. 

Geopotential anomalies, however, 

provided less resolution than 

surface data (i.e., surface 

expression of faulting, topographic 

lineament, trench exposures) for 

locating the zone of recent 

faulting.

Y

Hildenbrand (1982) 4 Analysis based on 

closely spaced truckmounted magnetometer 

survey.

ERM zones 4 Geometry—Width of zone of 

faulting associated with the rift 

margin.

Eastern Reelfoot rift margin is 

interpreted to be a 5.5 km (3.4 mi.) 

wide zone in which magnetic 

basement has an average dip of 

20°NW into the graben.

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift–Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault south–

river (fault) picks (ERM-RP); and Eastern Rift Margin south–Crittenden County fault zone (ERM-SCC) 

C-53 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional 

data.

ERM RLMEs 0 Gravity anomaly data did not 

provide good resolution for 

delimiting the boundaries of the 

fault zone.

Y

Seismic Reflection

Cox et al. (2006) 4 Published 

interpretations of highresolution S-wave 

seismic profile (selected 

portions of 

uninterpreted profiles 

provided).

ERM-N and 

ERM-S

5 Geometry—Seismic profiles 

(shallow S-wave, electrical 

profiles) collected at paleoseismic 

sites are used to identify faults.

N

Luzietti et al. (1992) 4 Interpretation of goodquality high-resolution 

(Mini-Sosie) seismic 

data that show 

stratigraphy down to 1.2 

km (0.7 mi.); (selected 

portions of 

uninterpreted profiles 

provided).

ERM-SCC 5 Geometry and activity of fault 

source—Evidence for reactivation 

of the Crittenden County fault zone 

in Pleistocene to possibly 

Holocene time.

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift—Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault 

south—river (fault) picks (ERM-RP); and Eastern rift margin south—Crittenden County fault zone (ERM-SCC) 

C-54

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Beatrice Magnani (CERI) 

unpublished data

Magnani et al. (2009)

3 Preliminary results of 

location of fault picks 

provided as PDF.

ERM-RP 4 Geometry and activity—This data 

provided the basis for the location 

of the alternative segment defined 

by seismic data (ERM-RP).

Connection of the three localities 

along the river seismic survey 

where recent faulting was 

observed suggest that there may 

be an alternative, more northerly

trending fault along SE margin of 

rift zone.

N

Odum et al. (2010) 4 Reinterpretation of a 

seismic-reflection 

profile across the scarp 

at Meeman-Shelby 

Forest State Park 25 

km north of Memphis, 

Tennessee.

ERM-S 2 Figures 1 and 7 show revised 

orientation of Meeman-Shelby 

fault (MSF) and relationship to 

Joiner Ridge. This alternative 

geometry for the MSF is not 

modeled directly as part of the 

RLME due to lack of information 

regarding timing and recent 

activity on the MSF.

Geometry—Figure 3 is used to 

define the limits of the zones 

associated with the eastern 

Reelfoot rift margin.

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift–Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault south–

river (fault) picks (ERM-RP); and Eastern Rift Margin south–Crittenden County fault zone (ERM-SCC) 

C-55 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Parrish and Van Arsdale 

(2004)

4 Published 

interpretations of 

seismic profile (selected 

portions of 

uninterpreted profiles 

provided).

ERM-S 3 Geometry—Interpretation of major 

basement faults and Tertiary faults 

along southeastern margin of 

Reelfoot rift—used in conjunction 

with paleoseismic investigations to 

identify location of fault source.

N

Williams et al. (2001) 4 Published 

interpretations of a 

seismic-reflection 

profile across the scarp 

at the Meeman-Shelby 

Forest State Park 25 

km north of Memphis, 

Tennessee. Revised 

interpretation provided 

in Odum et al. (2010).

ERM-S 2 Geometry—Meeman-Shelby fault 

(MSF) pick lies ~5 km (3 mi.) east 

of the magnetically defined 

southeastern margin of the 

Reelfoot rift. Is similar to the 

Crittenden County fault zone 

(CCFZ) in seismic profiles (up to 

the west). Seismic data suggest 

that the ERM-S may subparallel 

the CCFZ. Possible continuation of 

fault on a N33°E trend based on 

similar structure observed in a 

proprietary industry seismic line 33 

km (20.5 mi.) to the northeast. 

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift—Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault 

south—river (fault) picks (ERM-RP); and Eastern rift margin south—Crittenden County fault zone (ERM-SCC) 

C-56

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Local Geologic and Tectonic Maps

Cox et al. (2006) 4 Provides detailed maps 

of paleoseismic 

localities.

ERM-S and 

ERM-N

5 Geometry—Figures 1, 4, and 8 

show locations of seismic lines 

and trenches used to constrain 

location of fault source.

Used to locate detailed 

paleoseismic investigation sites 

and ERM-S and ERM-N fault 

source.

N

Crone (1992) 4 Peer-reviewed 

publication.

CCFZ 4 Geometry—Figure 2 used to 

locate the CCFZ.

N

Regional Stress

CEUS SSC stress data 

set

5 Most comprehensive 

data set available for 

CEUS.

ERM-S and 

ERM-N

2 Style of faulting—Right-lateral slip 

on eastern margin fault sources is 

consistent with stress indicators 

that show general E-W trend to the 

maximum horizontal compression 

axis.

Y
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift–Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault south–

river (fault) picks (ERM-RP); and Eastern Rift Margin south–Crittenden County fault zone (ERM-SCC) 

C-57 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Tectonic Strain

Cox et al. (2001a) 3 Summary of 

paleoseismic 

investigations and 

overall structural model 

for active faults along 

the SE margin of the 

Reelfoot rift. Trench log 

details not sufficient to 

evaluate postulated 

offset channel.

ERM-S and 

ERM-N

4 Geometry—Total length of Eastern 

Rift Margin faults: 150 km (93.2 

mi.).

Activity—Topographic 

expression—Linear topographic 

scarp.

N

Focal Mechanisms

Chiu et al. (1997) 4 Provides detailed 

analysis of focal 

mechanisms.

ERM-S 4 Style of faulting—The style of 

faulting along the southeast 

margin of the Reelfoot rift inferred 

from analysis of is complex with 

the dominant pattern being rightlateral strike-slip with reverse 

movement.

Seismogenic crustal thickness—

Nine out of 10 well-constrained 

focal depths are ≤17.3 km. One 

deeper earthquake is at 22.8 km.

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift—Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault 

south—river (fault) picks (ERM-RP); and Eastern rift margin south—Crittenden County fault zone (ERM-SCC) 

C-58

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Paleoseismicity

CEUS SSC 

paleoliquefaction 

database

5 Most comprehensive 

database of paleoliquefaction for CEUS.

ERM-S and 

ERM-N

4 Constraints on estimated size of 

prehistoric earthquake—

Evaluation of potential 80 km

(50 mi.) rupture at ~2,500 yr BP. 

There are no known 

paleoliquefaction features of this 

age observed in rivers in western 

Tennessee.

Location and age of 

paleoliquefaction in western 

Kentucky that could possibly be 

associated with a rupture on the 

ERM-N: 11,300 yr BP ± 200 yr.

Y
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift–Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault south–

river (fault) picks (ERM-RP); and Eastern Rift Margin south–Crittenden County fault zone (ERM-SCC) 

C-59 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Cox, Van Arsdale, and 

Larsen (2002)

3 NEHRP report—

Interpretation of 

trenching and boring 

data with some 

constraints on timing 

from radiocarbon dates.

Trench log details not 

sufficient to evaluate 

postulated offset 

channel.

ERM-S and 

ERM-N

4 Recurrence and style of faulting—

Used to evaluate timing of events, 

recurrence intervals, slip rate, and 

components of slip (H and V). 

Confirms that the SE Reelfoot rift 

margin is a fault zone with multiple 

high-angle faults and associated 

folding based on shallow seismic 

profiles and paleoseismological 

investigations.

Stratigraphic and structural 

relationships in trench exposure at 

a site near Porter Gap are 

interpreted to show 8–15 m (26.2–

49.2 ft.) of right-lateral offset of a 

late Wisconsinan paleo-channel 

(~20 ka)., suggesting average slip 

rate of between 0.85 and 0.37 

mm/year. 

Evidence for an earthquake ca.

2,500–2,000 yr BP on SE Reelfoot 

rift margin that ruptured ≥ 80 km 

from Shelby County (15–25 km 

[9.3–15.5 mi.] north of Memphis 

metropolitan area) to Porter Gap 

(just south of intersection with the 

RF).

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift—Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault 

south—river (fault) picks (ERM-RP); and Eastern rift margin south—Crittenden County fault zone (ERM-SCC) 

C-60

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Cox et al. (2006) 3 Interpretation of 

trenching and boring 

data with some 

constraints on timing 

from radiocarbon dates. 

Trench log details not 

sufficient to evaluate 

postulated offset 

channel.

ERM-S and 

ERM-N

5 Recurrence and style of faulting—

Used to evaluate timing of events, 

recurrence intervals, slip rate, and 

components of slip (H and V). 

Age constraints from paleoseismic 

investigations at Shelby County 

and at Porter Gap site are 

consistent with an earthquake ca.

2,500–2,000 years ago (most 

recent event) that ruptured ≥80 km

(50 mi.).

Late Wisconsinan and Holocene 

faulting along the SE rift margin 

fault system observed adjacent to 

hanging wall of Reelfoot thrust, but

only Wisconsinan faulting is noted 

adjacent to footwall of the thrust. It 

is hypothesized that the NE

segment of the SE rift margin 

turned off in Holocene when 

Reelfoot stepover thrust turned on.

N
Table C-6.1.6 Data Evaluation 

Reelfoot Rift–Eastern Margin Fault(s) RLMEs 

Identified Sources 

Reelfoot Rift–Eastern Rift Margin (ERM) RLMEs 

Eastern Reelfoot Rift Margin fault north (ERM-N)*; Eastern Reelfoot Rift Margin fault south (ERM-S)*; Eastern Rift Margin fault south–

river (fault) picks (ERM-RP); and Eastern Rift Margin south–Crittenden County fault zone (ERM-SCC) 

C-61 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Tuttle et al. (2006) 4 Detailed discussion of

paleoliquefaction 

features near Marianna, 

Arkansas.

ERM-S 2 Timing and recurrence of largemagnitude earthquakes—Based 

on radiocarbon dating liquefaction 

features at the Daytona Beach and 

St. Francis sites near Marianna, 

Arkansas, formed about 3500 BC 

and 4800 BC (5,000 and 7,000 

years ago), respectively. Marianna 

sand blows are similar in size to 

NMSZ. 

Several faults in Marianna area 

(including eastern Reelfoot rift 

margin [ERRM], White River fault 

zone [WRFZ], and Big Creek fault 

zone [BCFZ]) are thought to be 

active based on apparent 

influence on local topography and 

hydrography. ERRM appears to be 

most likely source of very large 

earthquakes during the middle 

Holocene. (See also Section 6.1.7,

Marianna [MAR] RLME.)

Y

* ERM-N and ERM-S are included in the Big Creek fault as defined by Fisk (1944). 
Table C-6.1.7 Data Evaluation 

Reelfoot Rift–Marianna RLME 

Identified Source 

Marianna zone (MAR) 

C-62

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake

catalog

5 Comprehensive 

catalog; includes 

magnitude 

conversions and 

uncertainty 

assessments.

MAR 1 Reviewed for alignment of 

microseismicity, seismicity scattered.

Y

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional 

data.

MAR 0 Location of RLME source is not 

based on magnetic anomaly map.

Y

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional 

data.

MAR 0 Location of RLME source is not 

based on gravity anomaly map.

Y

Local Geologic and Tectonic Maps

Csontos et al. (2008) 3 Due to projection of 

the map showing 

interpretations of 

basement faults, the 

locations are 

considered

approximate.

MAR 2 Potential fault sources for Marianna 

paleoliquefaction features.

Considered in evaluation of the 

orientation and style of faulting.

N
Table C-6.1.7 Data Evaluation 

Reelfoot Rift–Marianna RLME 

Identified Source 

Marianna zone (MAR) 

C-63 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Fisk (1944) 3 Due to the small 

scale and 

methodology used in 

mapping, the fault 

locations are 

considered 

approximate.

MAR 3 Location of faults with possible 

geomorphic expression of Quaternary 

faulting—Potential fault sources for 

Marianna paleoliquefaction features

(e.g., White River fault zone, Big 

Creek fault zone) considered in 

evaluation of the orientation and style 

of faulting.

N

Schumm and Spitz (1996) 4 Detailed analysis and 

discussion of 

geomorphic evidence 

(anomalies in 

channel morphology) 

for neotectonic 

deformation on 

regional and faultspecific basis.

MAR 3 Location and activity of potential fault 

sources—White River fault zone, Big 

Creek fault zone.

Considered in evaluation of the 

orientation and style of faulting.

N

Spitz and Schumm (1997) 4 Detailed analysis and 

discussion of 

geomorphic evidence 

(anomalies in 

channel morphology) 

for neotectonic 

deformation on 

regional and faultspecific basis.

MAR 3 Location and activity of potential fault 

sources—White River fault zone, Big 

Creek fault zone, eastern Reelfoot rift 

margin.

Activity—Geomorphic evidence for 

Quaternary tectonic deformation in 

vicinity of Marianna. 

Style of faulting—White River fault 

zone is left-lateral strike-slip fault.

N
Table C-6.1.7 Data Evaluation 

Reelfoot Rift–Marianna RLME 

Identified Source 

Marianna zone (MAR) 

C-64

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Regional Stress

CEUS SSC stress data set 5 Most comprehensive 

data set available for 

CEUS.

MAR 2 Right-lateral slip on NE-trending fault 

and left-lateral slip on NW-trending 

sources is consistent with stress 

indicators that show general E-W 

trend to the maximum horizontal 

compression axis.

Y

Tectonic Strain

Al-Qadhi (2010) 2 Unpublished Ph.D.

dissertation.

MAR 3 Local source of large-magnitude 

earthquakes—Provides additional 

information on total length of the 

Marianna lineament based on 

geophysical (GPR) survey data.

Y

Al-Shukri et al. (2009) 4 NEHRP report—

Provides good 

illustrations and 

discussion of results 

of high-resolution 

ground-penetrating 

radar (GPR) and 

resistivity profiles and 

three-dimensional 

surveys that were 

conducted to define 

the morphology and 

assist in the 

MAR 4 Local source of large-magnitude 

earthquakes—Marianna lineament 

identified from geophysical surveys, 

possible fault in trench exhibits 

similar orientation.

Recurrence—Provides constraints on 

the timing of paleoliquefaction 

features.

Y 
Table C-6.1.7 Data Evaluation 

Reelfoot Rift–Marianna RLME 

Identified Source 

Marianna zone (MAR) 

C-65 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

interpretation of the 

origin of large 

earthquake-induced 

liquefaction features.

Paleoseismicity

CEUS SSC 

paleoliquefaction database

(includes results from Al 

Shukri et al., 2005; Tuttle et 

al., 2006; Al Shukri et al.,

2009) 

5 Most comprehensive 

database of 

paleoliquefaction for 

CEUS.

MAR 4 Used to identify locations and ages of 

paleoliquefaction features in the 

Marianna region.

4.8 ka, 5.5 ka, 6.8 ka, 9.9 ka, 

something older (9.9–38 ka?).

Y

Al-Qadhi (2010) 2 Unpublished 

dissertation.

MAR 3 Local source of large-magnitude 

earthquakes—Used to constrain total 

length of the Daytona Beach 

lineament.

GPR surveys used to identify 

additional paleoliquefaction features 

along the trend of the lineament.

Y
Table C-6.1.7 Data Evaluation 

Reelfoot Rift–Marianna RLME 

Identified Source 

Marianna zone (MAR) 

C-66

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Tuttle et al. (2006) 4 Provides detailed 

discussion of studies 

to evaluate 

paleoliquefaction 

features near 

Marianna, Arkansas.

ERM-S 

MAR

3 Timing and recurrence of largemagnitude earthquakes—

Based on radiocarbon dating 

liquefaction features at the Daytona 

Beach and St. Francis sites near 

Marianna, Arkansas, formed about 

3500 BC and 4800 BC (5,000 and 

7,000 years ago), respectively. 

Marianna sand blows are similar in 

size to NMSZ. 

Several faults in Marianna area 

(including the eastern Reelfoot rift 

margin [ERRM], the White River fault 

zone [WRFZ], and Big Creek fault 

zone [BCFZ]) are thought to be active 

based on apparent influence on local 

topography and hydrography. ERRM 

appears to be most likely source of 

very large earthquakes during the 

middle Holocene.

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-67 

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC 

earthquake catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty assessments.

CFZ 1 Spatial association of seismicity—Some 

association of seismicity along 

Commerce geophysical lineament.

Recurrence—Not used to estimate 

recurrence. Recurrence is based on 

paleoseismic evidence.

Y

Harrison and 

Schultz (1994)

2 Publication discussing 

association of seismicity; 

includes summary of other 

publications.

CFZ 1 Support for localized source—Shows 12 

earthquakes near proposed trace of 

Commerce geophysical lineament 

(CGL) and suggests these earthquakes 

can be attributed to movement along 

structures associated with CGL.

N

Langenheim and 

Hildenbrand (1997)

4 Good maps and tabulated 

data on mb > 3 

earthquakes along or near 

CGL.

CFZ 2 Evidence for localized source of 

seismicity—Postulates an association of 

seismicity with Commerce geophysical 

lineament (CGL). The diversity of 

associated focal mechanisms and the 

variety of surface structural features 

along length of CGL, however, 

obscures its relation to release of 

present-day strain. 

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-68

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Magnetic Anomaly

CEUS SSC 

magnetic anomaly

data set

5 High-quality regional data. CFZ 2 Commerce fault zone source generally 

coincident with magnetic anomaly. 

Anomaly extends beyond region where 

paleoseismic studies document 

repeated late Pleistocene surface 

faulting. 

Y

Langenheim and 

Hildenbrand (1997) 

4 Detailed evaluation of 

geopotential anomalies.

CFZ 3 Quaternary active faulting appears to be 

localized along Commerce geophysical 

lineament, a magnetic and gravity 

anomaly. Modeling indicates that 

source of magnetic and gravity

anomalies is probably a mafic dike 

swarm. However, paleoseismic studies

and high-resolution seismic profiles are 

used to define the location of CFZ.

N

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional data. CFZ 1 Commerce geophysical lineament is 

defined in part by gravity anomaly as 

described in literature. CFZ RLME 

zone, however, is not well defined by 

the regional gravity data.

Y
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-69 

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Langenheim and 

Hildenbrand (1997) 

4 Detailed evaluation of 

geopotential anomalies.

CFZ 2 Quaternary active faulting appears to be 

localized along Commerce geophysical 

lineament, a gravity and magnetic 

anomaly. However, paleoseismic 

studies and high-resolution seismic 

profiles are used to define location of 

active traces of the CFZ.

N

Seismic Reflection

Palmer, Hoffman, et 

al. (1997)

Palmer, Shoemaker, 

et al. (1997)

4 Published interpretations 

of shallow high-resolution 

seismic-reflection profiles 

(selected portions of 

uninterpreted profiles 

provided).

CFZ 4 Location and style of faulting—The CFZ

striking N50°E overlies a major regional 

basement geophysical lineament and is 

present on two shallow seismicreflection lines at southern margin of the 

escarpment. Fault is favorably oriented 

to be reactivated as right-lateral strikeslip fault.

N

Stephenson et al. 

(1999)

4 Published interpretations 

of high-resolution seismicreflection profiles (selected 

portions of uninterpreted 

profiles provided).

CFZ 4 Location and style of faulting (Quilin 

site, Idalia Hills, and Benton Hills 

sites)—Interpretation of postCretaceous faulting extending into the 

Quaternary. Used in conjunction with 

paleoseismic investigations to identify 

location of fault source and to evaluate 

style of faulting and amount of reverse 

displacement.

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-70

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Regional Stress

CEUS SSC stress 

database

4 Provides additional new 

measurements to World 

Stress Map.

CFZ 2 A and B quality directions of maximum 

horizontal stress based on focal 

mechanisms show E-W to WNW trends 

in vicinity of Commerce fault. 

Y

Focal Mechanisms

Herrmann and 

Ammon (1997)

4

Presents results based on 

combination of traditional 

regional seismic network 

observations with direct 

seismogram modeling to 

improve estimates of small 

earthquake faulting 

geometry, depth, and size.

CFZ 3 Style of faulting—Focal mechanism 

analysis of a M 3.85 earthquake 

(February 5, 1994) along the northwardprojected trend of CFZ shows motion 

was primarily right-lateral strike-slip 

along a N-NE azimuth.

N

Langenheim and 

Hildenbrand (1997)

4 Tabulation of data for mb >

3 earthquakes along CGL.

CFZ 3 Focal mechanism and location of the 

earthquake near Thebes Gap are

consistent with movement along nearly 

vertical NE-trending Commerce fault in 

the present regional stress field. 

However, focal mechanisms of other 

earthquakes shown by Harrison and 

Schultz (1994) near CGL are mixed, 

ranging from thrust to normal fault 

solutions. Focal mechanisms of two 

events that predate establishment of a 

comprehensive seismic network in the 

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-71 

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Midcontinent may be suspect.

Shumway (2008) 4 Detailed analysis of 

seismicity data using 

recent velocity model.

CFZ 4 Depth of seismogenic crust—welllocated earthquakes to depths between 

13 and 15 km (8 and 9 mi.).

Focal mechanisms—Half of the wellconstrained earthquakes have a NEtrending nodal plane with strike-slip 

component (comparable to previous 

studies by Chiu et al., 1992).

N

Paleoseismicity

Baldwin et al. (2006) 4 Detailed discussion of 

paleoseismic 

investigations.

CFZ 5 Character of deformation zone—

Seismic-reflection data image a 0.5 km 

(0.3 mi.) wide zone of NE-striking, nearvertical faults that offset Tertiary and 

Quaternary reflectors and coincide with 

near-surface deformation. The regional 

NE strike of fault zone, as well as

presence of near-vertical faults and 

complex flower-like structures, and 

preferential alignment with 

contemporary central U.S. stress 

regime, indicates that the fault zone 

likely accommodates right-lateral 

transpressive deformation.

Recurrence—Stratigraphic and 

structural relationships in trenches 

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-72

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

provide evidence for at least two late 

Quaternary faulting events on Idalia Hill 

fault zone overlying Commerce section 

of Commerce geophysical lineament. 

The penultimate event occurred in late 

Pleistocene (before 23.6–18.9 ka). The 

most recent event occurred in late 

Pleistocene to early Holocene (18.5–7.6 

ka). Events overlap in age, with two 

prehistoric events interpreted by 

Vaughn (1994) that occurred 23–17 ka 

and 13.4–9 ka, and one event 

recognized by Harrison et al. (1995) 

that occurred 35–25 ka. 

Length of documented Quaternary 

faulting along CGL: 75 km (45 mi.).

Baldwin et al. (2008) 4 Well-illustrated NEHRP 

report; comprehensive 

discussion of evidence for 

timing of recent 

deformation.

CFZ 4 Location and geometry of Penitentiary 

fault—Evidence for linking observed 

Pleistocene-Holocene deformation with 

previously mapped faults overlying the 

Commerce geophysical lineament. The 

fault is accommodating dextral 

transpression.

Timing and amount of displacement—

Faults project upsection into the latest 

Pleistocene Henry Formation (older 

than ~25 ka) and possibly Holocene 

Cahokia Formation. Vertical offset of 

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-73 

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

reflectors 2–6 m (6.5–20 ft.).

CEUS SSC 

paleoliquefaction 

database

5 Comprehensive database; 

peer-reviewed; includes 

uncertainties in timing of 

paleo-liquefaction events).

CFZ 5 Recurrence—Provides preferred ages 

for paleoliquefaction features in vicinity 

of CFZ.

Y

Harrison et al.

(1999)

4 Interpretation of highresolution seismic profile 

data and paleoseismic 

trenching investigations 

(on secondary structures).

CFZ- 5 Style of faulting—The overall style of 

neotectonic deformation is interpreted 

as right-lateral strike-slip faulting.

Recurrence—Documents evidence for 

four episodes of Quaternary faulting on 

secondary structures in hills west of 

assumed primary fault along range 

front: one in late- to post-Sangamon, 

pre- to early Roxana time (~60–50 ka); 

one in syn- or post-Roxana, pre-Peoria 

time (~35–25 ka); and two in Holocene 

time (middle to late Holocene, and 

possibly during 1811-1812 earthquake 

sequence). 

N

Harrison et al. 

(2002)

4 USGS Miscellaneous 

Investigations publication; 

mapping supplemented by 

dates.

CFZ 4 Timing of recent earthquakes—At least 

two events may have occurred in the 

latest Holocene (just after 2-sigma

calibrated calendar ages of 3747–3369 

BC and AD 968–639).

N
Table C-6.1.8 Data Evaluation 

Reelfoot Rift–Commerce Fault Zone RLME 

Identified Source 

Commerce fault zone (CFZ) 

C-74

Data/References

Quality 

(1=low, 

5=high) Notes on Quality of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Palmer, Hoffman, et 

al. (1997)

Palmer, Shoemaker, 

et al. (1997)

4 Publications with highresolution seismic data 

images; numerous postCretaceous faults and 

folds; discusses 

neotectonic significance.

CFZ 4 Style of faulting—English Hills. 

Evidence for deep-seated tectonic fault. 

Style of faulting—Faults are interpreted 

as flower structures with N-NE-striking, 

vertically dipping, right-lateral obliqueslip faults.

Amount of displacement—Near-vertical 

displacements with maximum offsets on 

the order of 15 m (50 ft.).

N

Vaughn (1994) 2 NEHRP report—Relatively 

few liquefaction features 

studied and dated in area; 

often significant 

uncertainties in age 

estimates.

CFZ 5 Paleoliquefaction results to evaluate 

timing of events. Preferred ages in 

CEUS SSC database based on 

communications between author and 

Dr. M. Tuttle.

Y
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-75 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC 

earthquake catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty assessments.

WV 0 Not used to evaluate recurrence 

parameters for RLME.

Magnitudes smaller than the 

RLME are included in Illinois 

Basin Extended Basement or 

Mmax zone.

Y

Hamburger et al. 

(2008)

3 Abstract WV 4 Evidence for reactivation of 

structures in present stress 

regime—04:30 CDT, April 18, 

2008, M 5.4 earthquake.

Y

Withers et al. (2009) 3 Abstract; preliminary 

analysis.

WV 4 Evidence for reactivation of 

structures in the present stress 

regime—April 18, 2008, Mw 5.2 

(Mw 5.4 GCMT

[http://www.global cmt.org])

Mt. Carmel, Illinois, 

earthquake—Largest event in 20 

years in Wabash Valley seismic 

zone (WVSZ).

Y
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-76

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Yang et al. (2009) 3 Abstract; preliminary 

analysis.

WV 5 Analysis of aftershocks using 

sliding-window cross-correlation 

technique and double-difference 

relocation algorithm give a bestfit plane having a nearly E-W 

trend with orientation of 248 and 

dip angle of 81. Fault is nearly 

vertical down to ~20 km (12.5 

mi.). 

Provides constraints on 

seismogenic width.

N

Historical Seismicity

McBride et al. (2007) 5 Integrated assessment 

based on seismicity, 

borehole, geophysical, and 

industry seismic profile 

data analysis.

WV 5 Discusses possible association 

of recent earthquakes (April 3, 

1974, mb = 4.7; June 10, 1987, 

mb = 5.2; and November 9, 

1968, mb = 5.5 events) with 

three distinct upper-crust 

sources. Provides detailed 

discussion of parameters 

(magnitude, depth, focal 

mechanism) for each event.

Y
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-77 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Magnetic Anomaly

CEUS SSC magnetic

anomaly data set

5 High-quality regional data. WV 1 Boundaries of WV RLME not 

uniquely defined by magnetic 

anomaly map.

Y

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional data. WV 1 Boundaries of WV RLME not 

uniquely defined by gravity 

anomaly map.

Y

Seismic Reflection

McBride, 

Hildenbrand, et al. 

(2002)

5 Provides simplified line 

drawings and 

interpretations of four 

reprocessed migrated 

seismic profiles. Also 

provides excerpts of 

reprocessed seismicreflection profiles. Includes 

detailed geologic 

discussion based on 

integrated review of 

seismic, and geopotential 

data.

WV 3 Used to define style of faulting 

and possible source structures 

within the source zone.

N
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-78

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

McBride et al. (2007) 4 Builds on McBride, 

Hildenbrand, et al. (2002) 

and provides additional 

interpretations of seismicreflection data. Presents 

both raw (selected 

excerpts) and interpreted 

sections.

WV 3 Used to define style of faulting 

and possible source structures 

within the source zone.

N

Regional Geologic and Tectonic Maps

Nelson (1995) 5 Digital file of Illinois 

structural trends map.

WV 3 Constraint on boundary of 

source zone—Used to identify 

major structural trends (Wabash 

Valley fault system [WVFS], La 

Salle anticlinal belt).

Y

Local Geologic and Tectonic Maps

Sexton et al. (1986) 3 Small-scale publication 

figure.

WV 3 Used to define style of faulting 

and possible source structures 

within the source zone—Map of 

individual faults within the WVFS 

that extend to basement.

Y

Wheeler et al. (1997) 3 Compilation map (scale 

1:250,000).

WV 2 Constraint on boundary of 

source zone—Identifies areas of 

possible neotectonic 

deformation.

N
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-79 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Geodetic Strain

Hamburger et al. 

(2002)

1 Only one year of data. WV 1 Generally consistent with focal 

mechanism data from historical 

events.

N

Hamburger et al. 

(2009)

3 Abstract WV 1 GPS data for WVSZ indicate 

systematic northwestward 

motion of about 0.5–0.7 mm/yr 

with respect to Stable North 

American Reference Frame. 

Results suggest that elevated 

seismicity and strain in WVSZ

could result from aseismic slip 

triggered by viscous relaxation in 

the lower crust long after New 

Madrid earthquake.

N

Regional Stress

CEUS SSC stress 

data set

5 Includes two additional 

new stress measurements 

based on focal 

mechanisms. 

WV 2 East trend consistent with 

previous measurements shown 

on World Stress Map. 

Y

Heidbach et al. 

(2008)

(World Stress Map)

3 Worldwide compilation of 

stress data.

WV 2 Three events used by World 

Stress Map, while tectonically 

and spatially distinct, represent 

N
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-80

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

contemporary maximum 

horizontal compressive stress 

that trends just north of east in 

southern Illinois and Indiana 

(McBride et al., 2007).

Tectonic Strain

Fraser et al. (1997) 2 Geomorphic analysis. 

Indirect evidence for 

neotectonic deformation. 

Apparent deformation 

could result from other 

nontectonic fluvial channel 

processes.

WV 3 Constraints on boundary of 

zone—Used as one potential 

indicator of a more localized 

region of deformation in vicinity 

of Vincennes. 

Y

Wheeler and Cramer 

(2002)

4 Systematic evaluation of 

potential source zone for 

two largest 

paleoearthquakes in 

WVSZ.

WV 4 Constraints on boundary of 

zone—The Tri-State source 

zone defined by Wheeler and 

Cramer and used by USGS to 

define an Mmax source region 

for WVSZ is captured by using a 

leaky boundary for ruptures 

originating in the WV RLME.

Y

Counts et al. (2008, 

2009a, 2009b)

Van Arsdale et al. 

4 Paleoseismic studies 

(trenching, 

paleoliquefaction, and 

geomorphic analyses) 

provide good indication of 

WV 4 Constraints on boundary of 

zone—Quaternary activity on 

faults within WVFS used as an 

indicator of a more localized 

region of deformation in vicinity 

Y
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-81 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

(2009)

Woolery (2005)

Quaternary deformation on 

faults within the WVFS.

of Vincennes.

Focal Mechanisms

Hamburger et al. 

(2002, 2008)

Larson (2002)

Larson et al. (2009)

McBride, 

Hildenbrand, et al.

(2002)

McBride et al. (2007)

Withers et al. (2009)

Yang et al. (2009)

4 Well-constrained focal 

mechanisms for several 

recent moderate-sized 

(M 4–5.4) earthquakes in 

Wabash Valley region of 

southern Illinois and 

Indiana.

WV 5 Style of deformation—Focal 

mechanisms indicate ongoing 

deformation along reactivated 

Precambrian and Paleozoic 

basement structures. Analyses 

indicate three seismotectonic 

environments in upper crust: 

strike-slip (E-NE and NE trends) 

and reverse fault.

N

Paleoseismicity

CEUS SSC 

paleoliquefaction 

database

5 Comprehensive database; 

peer-reviewed; includes 

uncertainties in timing of 

paleo-liquefaction events).

WV 4 Recurrence—Provides 

constraints on timing of 

Vincennes and Skelton 

paleoearthquakes

Y
Table C-6.1.9 Data Evaluation 

Wabash Valley RLME 

Identified Source 

Wabash Valley (WV) RLME 

C-82

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

[various studies by 

numerous 

researchers; see 

Table 6.1.9-1]

4–5 One of the best 

paleoliquefaction data sets 

available for a region in the 

CEUS. Back-calculations 

using site-specific field 

observations and 

seismological observations 

have been put into a 

probabilistic framework.

WV 5 Recurrence and magnitude—

Paleoliquefaction data provide a 

basis for identifying as many as 

eight prehistoric earthquakes in 

the region. The proximities of the 

two largest prehistoric events—

the Vincennes (~6,100 yr BP) 

and the Skelton earthquakes

(~12,000 yr BP)—are used to 

characterize recurrence of 

RLMEs.

Detailed analyses of Vincennes 

earthquake (~6,100 BP) provide 

a reasonable constraint on size 

and location of this event. 

Y
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-83 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

SLR 5 Used to evaluate recurrence 

parameters.

Y

Lamontagne and Ranalli 

(1997)

5 Relocated hypocentral 

depth.

SLR 5 Used to evaluate thickness of 

seismogenic crust and style of 

faulting.

Y

Historical Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

SLR 5 The prior distribution for Mmax is 

modified by the largest observed 

historical earthquake taken from 

the CEUS SSC earthquake 

catalog.

Y

Lamontagne et al. (2008) 4 Earthquake 

parameters and felt 

effects for major 

Canadian earthquakes.

SLR 4 Magnitudes derived from special 

studies are cited directly in CEUS 

SSC earthquake catalog.

Y
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-84

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional 

data.

SLR 2 St. Lawrence rift zone is not 

subdivided based on different 

basement terranes or tectonic 

features imaged in the magnetic 

anomaly map. 

Magnetic anomalies to the west 

reflect Grenville basement as 

opposed to rift faulting. Data does 

not assist in delineating eastern 

boundary.

Y

Gravity Anomaly

CEUS SSC gravity data set 5 High-quality regional 

data.

SLR 0 The St. Lawrence rift zone 

generally encompasses a region 

of low-amplitude gravity 

anomalies. The boundaries were 

not drawn based on this data set.

Y

Seismic Reflection

Tremblay et al. (2003) 3 Relocates offshore 

SQUIP data.

SLR 2 Images a transition from a half 

graben to a graben of the St. 

Lawrence fault within the St. 

Lawrence estuary. 

N
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-85 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Geophysical Anomalies

Li et al. (2003) 3 Determined velocity 

structure from 

inversion of Rayleigh 

waves.

SLR 3 Deep crustal velocity anomalies 

beneath the Adirondacks are 

attributed to the Cretaceous Great 

Meteor hotspot. 

N

Local Geologic and Tectonic Maps

Garrity and Soller (2009)

(Database of the Geologic 

Map of North America)

5 1:5,000,000-scale 

geologic map in GIS 

format compiled from 

various national maps.

SLR 4 Boundary drawn to capture 

mapped normal faults in the 

Adirondacks.

N

Higgins and van Breemen 

(1998)

3 Presents age dates 

and mapping for the 

Sept Iles layered mafic 

intrusion.

SLR 4 Used to define source geometry 

for Saguenay graben.

N

Hodych and Cox (2007) 3 Presents maps and 

age dates for the Lac 

Matapedia and Mt. St.-

Anselme basalt flows 

of Quebec.

SLR 4 Used to define source geometry 

for eastern boundary.

N

Kamo et al. (1995) 3 Compilation of Iapetan 

faults, dikes, and other 

intrusive volcanic 

rocks.

SLR 5 Defines Ottawa graben and 

southern limit of rift system.

N
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-86

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Kanter (1994) 3 Data is considered of 

good quality for 

defining location of 

major crustal divisions.

SLR 5 Used to define source geometry. Y

McCausland and Hodych 

(1998)

3 Reviews interpretations 

of the Skinner Cove 

volcanic of 

Newfoundland.

SLR 4 Used to define source geometry 

for Ottawa graben and New York 

promontory.

N

Wheeler (1995) 3 Compilation of late 

Neoproterozoic to early 

Cambrian faults.

SLR 4 Used to define source geometry. N

Whitmeyer and Karlstrom 

(2007)

3 Presents regional 

geologic map of North 

America documenting 

the assembly of the 

continent by 

successive tectonic 

events.

SLR 5 Used to define source geometry. Y

Geodetic Strain

Mazzotti and Adams (2005) 3 Modeled seismic 

moment rates from 

earthquake statistics.

SLR 3 Seismic moment rate varies from 

(0.1 to 0.5) × 1017 Nm/yr for entire 

zone rift system if Charlevoix is 

confined to its own zone or (0.1–

5.0) × 1017 Nm/yr if Charlevoix is 

combined with the entire rift 

N
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-87 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

system.

Regional Stress

CEUS SSC stress data set 4 Provides additional 

new measurements to 

World Stress Map.

SLR 1 Data includes thrust mechanisms 

with minor strike-slip. Orientations 

vary from E-W to NE-SW.

Y

Heidbach et al. (2008)

(World Stress Map)

3 Compiled worldwide 

stress indicators from 

focal mechanisms, 

borehole breakouts, 

etc.

SLR 2 Entries for SLR are predominantly 

thrust mechanisms with some 

strike-slip. Orientations of 

maximum horizontal stress vary 

from E-W to NE-SW.

Y

Focal Mechanisms

Bent (1992) 3 Analyzed historical 

waveforms for 1925 

Charlevoix earthquake.

SLR 4 Used to characterize future 

ruptures.

N

Bent (1996a) 3 Analyzed historical 

waveforms for 1935 

Timiskaming 

earthquake.

SLR 4 Used to characterize future 

ruptures.

N

Bent (1996b) 3 Analyzed historical 

waveforms for 1944 

Cornwall-Massena 

earthquake.

SLR 4 Used to characterize future 

ruptures.

N
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-88

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Bent and Perry (2002) 4 Determined focal 

depths for ENA 

earthquakes.

SLR 4 Used to characterize future 

ruptures.

N

Bent et al. (2002) 4 Determined 

earthquake parameters 

for 2000 Kipawa 

earthquake.

SLR 4 Used to characterize future 

ruptures.

N

Bent et al. (2003) 4 Determined focal 

mechanisms for 

Western Quebec 

seismic zone.

SLR 4 Used to characterize future 

ruptures.

N

Du et al. (2003) 4 Determined focal 

mechanisms for 

moderate earthquakes 

in NE United States 

and SE Canada.

SLR 4 Used to characterize future 

ruptures.

N

Lamontagne (1999) 4 Determined focal 

mechanisms for 

Charlevoix 

earthquakes. 

SLR 4 Used to characterize future 

ruptures.

N

Lamontagne and Ranalli 

(1997)

4 Determined focal 

mechanisms. 

SLR 4 Used to characterize future 

ruptures.

N
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-89 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Lamontagne et al. (2004) 4 Determined focal 

mechanism for 1999 

Côte-Nord earthquake.

SLR 4 Used to characterize future 

ruptures.

N

Li et al. (1995) 4 Determined focal 

mechanisms for two M 

4 earthquakes.

SLR 4 Used to characterize future 

ruptures.

N

Nábĕlek and Suárez (1989) 3 Determined 

earthquake parameters 

for 1983 Goodnow, 

New York, earthquake. 

SLR 4 Used to characterize future 

ruptures.

N

Seeber et al. (2002) 4 Determined 

earthquake parameters 

for 2002 Au Sable 

Forks, New York, 

earthquake.

SLR 4 Used to characterize future 

ruptures.

N

Paleoseismicity

Aylsworth et al. (2000) 3 Documents disturbed 

sediment and 

paleolandslides along 

Ottawa River.

SLR 4 Provides evidence for persistent 

prehistoric earthquake activity 

along the eastern OttawaBonnechere graben.

N

CEUS SSC 

paleoliquefaction database

5 Compilation (with 

attributions) of 

paleoliquefaction 

SLR 4 Localization of liquefaction 

features in Charlevoix support 

characterization of a RLME 

N
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-90

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

observations. source.

Doig (1990) 3 Documents silt layers 

in cores attributed to 

earthquake-induced 

landslides near 

Charlevoix.

SLR 4 Provides evidence for persistent 

prehistoric earthquake activity near 

Charlevoix. 

N

Doig (1991) 3 Documents silt layers 

in cores attributed to 

earthquake-induced 

landslides near 

Saguenay.

SLR 4 Provides evidence for persistent 

prehistoric earthquake activity near 

Saguenay. 

N

Doig (1998) 3 Documents silt layers 

in cores attributed to 

earthquake-induced 

landslides near 

Timiskaming.

SLR 4 Provides evidence for persistent 

prehistoric earthquake activity near 

Timiskaming. 

N

Filion et al. (1991) 3 Provides ages for 

prehistoric landslides 

attributed to 

earthquakes.

SLR 4 Provides evidence for persistent 

prehistoric earthquake activity near 

Charlevoix.

N

Tuttle et al. (1990) 4 Documents liquefaction 

features associated 

with the 1988 

Saguenay earthquake.

SLR 4 Provides evidence for at least one 

older earthquake near Saguenay.

Y
Table C-7.3.1 Data Evaluation 

St. Lawrence Rift Zone 

Identified Source 

St. Lawrence Rift (SLR)

C-91 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Tuttle et al. (1992) 4 Documents liquefaction 

features associated 

pre-1988 Saguenay 

earthquake.

SLR 4 Provides evidence for at least one 

older earthquake near Saguenay.

Y
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH)

C-92

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC 

earthquake catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty assessments.

GMH 5 Used to evaluate recurrence 

parameters.

Y

Ma and Atkinson 

(2006)

5 Relocated hypocentral 

depth.

GMH 5 Focal depths cluster at 5, 8, 12, 15, and 

22 km and may reflect layering in 

seismogenic properties within the crust.

N

Ma and Eaton (2007) 5 Relocated hypocentral 

depth.

GMH 5 Deep earthquakes (greater than 17 km 

in depth) are localized as clusters at 

Maniwaki and Mont-Laurier.

N

Ma et al. (2008) 5 Relocated hypocentral 

depth in Northern 

Ontario.

GMH 5 Spatial distribution of earthquakes 

indicates an aseismic area northwest of 

the GMH seismotectonic zone along 

the hotspot track.

N

Historical Seismicity

Adams and Basham 

(1991)

3 Provides description of 

earthquakes in 

northeastern Canada.

GMH 4 Description of Western Quebec seismic 

zone considered in geometry for GMH 

seismotectonic zone. NW-trending 

band of seismicity north of Ottawa 

River attributed to GMH track.

N
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH) 

C-93 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

CEUS SSC 

earthquake catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty assessments.

GMH 5 Prior distribution for Mmax is modified 

by the largest observed historical 

earthquake taken from CEUS SSC 

earthquake catalog.

Y

Magnetic Anomaly

CEUS SSC magnetic 

data set

5 High-quality regional 

data.

GMH 1 GMH zone is not subdivided based on 

different basement terranes or tectonic 

features imaged on magnetic anomaly 

map. 

Y

Gravity Anomaly

CEUS SSC gravity 

data set

5 High-quality regional

data.

GMH 1 GMH zone is not subdivided based on 

different basement terranes or tectonic 

features imaged on magnetic anomaly 

map.

Y

Seismic Reflection

Ma and Eaton (2007) 4 Compares location of 

seismicity to published 

interpretations of 

Lithoprobe Lines 52 and 

53. 

GMH 4 Seismicity does not generally correlate 

with structure in Western Quebec 

seismic zone (WQSZ); shear zones of 

Grenville province cut across NW-SE 

trend of WQSZ at high angle. The 

Maniwaki cluster exhibits repeating 

events with deep seismicity localized 

within footwall of Baskatong crustal 

ramp, and intermediate and shallow 

N
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH)

C-94

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

seismicity localized within hanging wall. 

Geophysical Anomalies

Eaton et al. (2006) 4 Determined crustal 

thickness from 

teleseismic results that 

agree with previous 

published refraction 

surveys.

GMH 5 Minima on crustal thickness maps 

coincides with GMH source zone.

N

Li et al. (2003) 3 Determined velocity 

structure from inversion 

of Rayleigh waves.

GMH 3 Southwestern portion of zone includes 

deep negative crustal velocity 

anomaly. 

N

Rondenay et al. (2000) 3 Modeled velocity of crust 

from travel time inversion 

of teleseismic data.

GMH 3 Images a low-velocity corridor oblique 

to GMH zone.

N

Local Geologic and Tectonic Maps

Duncan (1984) 4 Determined Ar ages for 

offshore seamounts.

GMH 2 Source geometry for GMH was not 

drawn to encompass Cretaceous 

volcanism in region.

N

Faure et al. (1996b) 5 Paleostress analysis of 

Cretaceous rocks.

GMH 5 Monteregian plutons intruded along 

reactivated structures along OttawaBonnechere graben. 

N
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH) 

C-95 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Faure et al. (2006) 5 Jurassic paleostress 

orientations associated 

with opening of Atlantic.

GMH 5 Opening of Atlantic resulted in 

widespread extension hundreds of 

kilometers into craton. Paleostress 

orientations from Jurassic rocks differ

from those in Cretaceous rocks.

N

Heaman and 

Kjarsgaard (2000)

5 Determined U-Pb 

perovskite ages for 

kimberlite dikes.

GMH 3 Source geometry for GMH was not 

drawn to encompass Cretaceous 

volcanism in the region.

N

Matton and Jebrak 

(2009)

4 Proposes that 

Cretaceous alkaline 

magmas result from 

periodic reactivation of 

preexisting zones of 

weakness combined with 

coeval asthenospheric 

upwelling during major 

stages of Atlantic tectonic 

evolution.

GMH 5 Provides mechanisms for widespread 

Cretaceous volcanisms and rational 

for not drawing a source zone along 

proposed hotspot tracks.

N

Poole (1970) 3 Provides descriptions 

and ages for Cretaceous 

Monteregian plutons. 

GMH 3 Source geometry for GMH 

incorporates thin crust and deep 

earthquakes and was not drawn to

encompass Cretaceous volcanism in 

the region.

N
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH)

C-96

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Zartman (1977) 2 Compiled ages for 

plutonic rocks in White 

Mountains.

GMH 2 Source geometry for GMH 

incorporates thin crust and deep 

earthquakes and was not drawn to 

encompass Cretaceous volcanism in 

the region.

N

Geodetic Strain

Mazzotti and Adams 

(2005)

3 Modeled seismic moment 

rates from earthquake 

statistics.

GMH 3 Seismic moment rate of (0.1–5.0) ×

1017 N m/yr (Newton-meter per year) 

for entire zone, which corresponds to a 

Mw 7 earthquake every 150 years. 

N

Regional Stress

CEUS SSC stress 

data set

4 Provides additional new 

measurements to World 

Stress Map.

GMH 1 Data includes thrust mechanisms in a 

variety of orientations.

Y

Heidbach et al. (2008)

(World Stress Map)

3 Compiled worldwide 

stress indicators from 

focal mechanisms, 

borehole breakouts, etc.

GMH 2 Limited entries for the GMH—

dominantly thrust mechanisms with 

some strike-slip. Orientations of 

maximum horizontal stress vary from 

E-W to NW-SE, N-S, and NNE-SSW.

Y
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH) 

C-97 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Focal Mechanisms

Bent (1996b) 3 Compiles existing focal 

mechanisms with data for 

the 1944 CornwallMassena earthquake.

GMH 3 Mechanisms of GMH are 

predominantly thrust mechanisms, 

although interpreting which nodal 

plane corresponds to the fault plane is 

ambiguous. 

N

Bent et al. (2003) 4 Determines focal 

mechanisms from 

earthquakes occurring 

from 1994 through 2000.

GMH 4 Thrust or oblique-thrust in response to 

NE compression. 

N

Du et al. (2003) 4 Reanalyzes earthquake 

source parameters from 

additional stations.

GMH 5 Focal mechanisms have strikes of one 

of their nodal planes parallel to the 

general trend of seismicity.

N

Lamontagne et al. 

(1994)

4 Determines earthquake 

parameters from several 

stations in network.

GMH 5 The October 19, 1990, Mont-Laurier 

earthquake has a reverse mechanism 

with steeply N-dipping, E-W-oriented 

nodal plane.

N

Ma and Eaton (2007) 4 Determined focal 

mechanism for February 

25, 2006, Mw 3.7 

earthquake and compiled 

existing focal 

mechanisms.

GMH 5 Reverse mechanisms have SWtrending P-axes that change to E-Wtrending P-axes in southern portion of 

the zone.

N
Table C-7.3.2 Data Evaluation 

Great Meteor Hotspot Zone 

Identified Source 

Great Meteor Hotspot (GMH)

C-98

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Paleoseismicity

Aylsworth et al. (2000) 3 Poor constraints on 

magnitude or location of 

paleoearthquakes 

causing observed 

deformation.

GMH 1 Study area located outside of GMH 

within St. Lawrence rift (SLR)

seismotectonic zone. Location of 

paleoearthquakes may lie within SLR 

or GMH, but no geotechnical analysis 

of materials has been performed to 

constrain location and magnitude.

N

CEUS SSC 

paleoliquefaction 

database

5 Compilation (with 

attributions) of 

paleoliquefaction 

observations.

GMH n/a No data located within zone. Y
Table C-7.3.3 Data Evaluation 

Northern Appalachian Zone 

Identified Source 

Northern Appalachian (NAP)

C-99 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC 

earthquake catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

NAP 5 Used to evaluate recurrence 

parameters.

Y

Historical Seismicity

Burke (2004) 4 Identifies historical 

earthquakes from 

newspapers.

NAP 4 Defines clusters of seismicity at 

Moncton, Passamaquoddy Bay, and 

Central Highlands (Miramichi). Eastern 

boundary drawn to exclude 

Passamaquoddy Bay seismicity from 

NAP to ECC.

N

Burke (2009) 5 Identifies historical 

earthquakes from 

newspapers and 

provides isoseismal 

maps where available.

NAP 5 Provides estimate of magnitude for 

historical earthquakes based on felt 

area.

N

CEUS SSC 

earthquake catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

NAP 5

The prior distribution for Mmax is 

modified by the largest observed 

historical earthquake taken from the 

CEUS SSC earthquake catalog. 

Y
Table C-7.3.3 Data Evaluation 

Northern Appalachian Zone 

Identified Source 

Northern Appalachian (NAP)

C-100

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Ebel (1996) 3 Estimates magnitude 

and location of 1638 

earthquake.

NAP 5 Considered for maximum observed 

earthquake.

N

Leblanc and Burke 

(1985)

4 Estimates magnitude 

and location of four 

earthquakes in Maine 

and New Brunswick.

NAP 3 Provides magnitude estimates for 

historical earthquakes.

N

Magnetic Anomaly

CEUS SSC magnetic

anomaly data set

5 High-quality regional 

data.

NAP 2 The NAP is not subdivided based on 

different basement terranes or tectonic 

features imaged in the magnetic 

anomaly map. 

The eastern boundary follows magnetic 

highs west of the Fundy basin. Sparse 

magnetic highs parallel the western 

boundary.

Y

Gravity Anomaly

CEUS SSC gravity 

data set

5 High-quality regional 

data.

NAP 1 The NAP generally encompasses a 

region of intermediate gravity 

anomalies with lower values to the 

west in the SLR and higher values 

to the east in ECC.

Y
Table C-7.3.3 Data Evaluation 

Northern Appalachian Zone 

Identified Source 

Northern Appalachian (NAP)

C-101 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Seismic Reflection

Hughes and Luetgert 

(1991)

3 Seismic-refraction 

results from 

Adirondacks to Maine.

NAP 4 Delineates crustal thickness within 

seismotectonic zone.

N

Spencer et al. (1989) 3 Presents results of 

Quebec-Maine seismicreflection and seismicrefraction profiles.

NAP 5 Images Iapetan growth faults below 

detachment.

N

Stewart et al. (1993) 3 Integrates results of 

Quebec-Maine seismicreflection profiles in 

tectonostratigraphic 

units.

NAP 4 Delineates Appalachian terranes. N

Geophysical Anomalies

Li et al. (2003) 3 Determined velocity 

structure from inversion 

of Rayleigh waves.

NAP 3 SW portion of zone includes deep 

negative crustal velocity anomaly. 

N
Table C-7.3.3 Data Evaluation 

Northern Appalachian Zone 

Identified Source 

Northern Appalachian (NAP)

C-102

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Local Geologic and Tectonic Maps

CEUS SSC basins 

compilation

4 Data is considered of 

generally good quality; 

however, quality is likely 

variable as it represents 

a compilation from 

various published maps 

and various 

scales/detail.

NAP 5 SW boundary extends to Connecticut 

River valley in western Massachusetts

and Connecticut; eastern boundary 

extends to Fundy basin.

Y

Klitgord et al. (1988) 3 Review of Mesozoic 

basins along Atlantic 

continental margin.

NAP 5 Eastern boundary of NAP drawn to the 

west of the Bay of Fundy shown on 

Plate 2C.

N

Moench and Aleinikoff 

(2003)

3 Presentation of updated 

tectonic map for 

northern New England.

NAP 4 Appalachian terrane boundaries from 

Figure 1 considered in NW boundary.

N

Murphy and Keppie 

(2005)

3 Compilation of major 

Paleozoic strike-slip 

faults.

NAP 4 Eastern boundary in Nova Scotia 

drawn along strike-slip faults.

N

Geodetic Strain

Mazzotti and Adams 

(2005)

3 Modeled seismic 

moment rates from 

earthquake statistics.

NAP 3 Seismic moment rate of (0.1–5.0) ×

1017 Nm/yr for entire zone. 

N
Table C-7.3.3 Data Evaluation 

Northern Appalachian Zone 

Identified Source 

Northern Appalachian (NAP)

C-103 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Regional Stress

CEUS SSC stress 

data set

4 Provides additional new 

measurements to World 

Stress Map.

NAP 1 Data includes thrust mechanisms in a 

variety of orientations.

Y

Heidbach et al. (2008)

(World Stress Map)

3 Compiled worldwide 

stress indicators from 

focal mechanisms, 

borehole breakouts, etc.

NAP 2 Limited entries for the NAP—

dominantly thrust mechanisms with 

some strike-slip. Orientations of 

maximum horizontal stress vary from 

E-W to NW-SE, N-S and NNE-SSW.

Y

Focal Mechanisms

Bent et al. (2003) 4 Focal mechanisms for 

two New Brunswick 

earthquakes.

NAP 4 Considered in future earthquake 

characteristics.

N

Brown and Ebel 

(1985)

3 Source parameters for 

aftershocks of 1982 

Gaza, New Hampshire, 

earthquake.

NAP 3 Considered in future earthquake 

characteristics.

N

Ebel and Bouck 

(1988)

3 Source parameters for 

earthquakes occurring

in NE from 1981 to 

1987.

NAP 3 Considered in future earthquake 

characteristics.

N
Table C-7.3.3 Data Evaluation 

Northern Appalachian Zone 

Identified Source 

Northern Appalachian (NAP)

C-104

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Ebel et al. (1986) 3 Source parameters for 

1940 Ossipee, New 

Hampshire, 

earthquakes.

NAP 3 Considered in future earthquake 

characteristics.

N

Paleoseismicity

CEUS SSC 

paleoliquefaction 

database

4 Compilation (with 

attributions) of 

paleoliquefaction 

observations.

NAP N Mmax determined from the largest 

observed historical earthquake.

Y
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-105 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

PEZ-W, 

PEZ-N

5 Used to evaluate recurrence 

parameters.

Y

Dineva et al. (2004) 5 Relocated hypocenters 

near the Great Lakes.

PEZ-W 4 Used to evaluate the spatial 

relationships of seismicity with 

structure.

N

Historical Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude conversions 

and uncertainty 

assessments.

PEZ-W, 

PEZ-N

5

The prior distribution for Mmax is 

modified by the largest observed 

historical earthquake taken from 

the CEUS SSC earthquake

catalog. 

Y

Seeber and Armbruster 

(1993)

3 Reviewed historical 

seismicity in the vicinity 

of Lakes Ontario and 

Erie.

PEZ-W 4 Added and removed historical 

earthquakes from CEUS SSC 

earthquake catalog.

N
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-106

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional 

data.

PEZ-W, 

PEZ-N

2 The PEZ zone is not subdivided 

based on different basement 

terranes or tectonic features 

imaged in the magnetic anomaly 

map. 

New York–Alabama lineament not 

used to delineate source zone.

Y

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional 

data.

PEZ-W, 

PEZ-N

4 Eastern boundary defined by 

gravity gradient.

Y

Seismic Reflection

Cook and Oliver (1981) 3 Regional synthesis of 

gravity data and 

seismic-reflection 

profiles.

PEZ-W, 

PEZ-N

4 Gravity gradient used to define the 

eastern boundary. Provides 

seismic evidence that gravity 

gradient is interpreted as an edge 

effect corresponding to the 

boundary between continental crust 

and former oceanic crust.

N

Fakundiny and Pomeroy 

(2002)

4 Reprocessed seismic 

data for the ClarendonLinden fault system.

PEZ-W, 

PEZ-N

1 Shows evidence of reactivation of 

Clarendon-Linden fault system in 

lower Paleozoic units.

N
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-107 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Forsyth, Milkereit, 

Davidson, et al. (1994)

4 Reprocessed marine 

seismic lines from 

Lakes Erie and Ontario.

PEZ-W Shows evidence of reactivation in 

lower Paleozoic units in eastern 

Lake Erie.

N

O’Dowd et al. (2004) 5 Interprets seismic data 

from Southern Ontario 

Seismic Project line 4 

with magnetic data.

PEZ-W 5 Defines western boundary along 

the Central Metasedimentary Belt 

boundary zone.

N

Ouassaa and Forsyth 

(2002)

4 Reprocessed seismic 

data for the ClarendonLinden fault system.

PEZ-W, 

PEZ-N

1 Shows evidence of reactivation of 

the Clarendon-Linden fault system

in lower Paleozoic units.

N

Geophysical Anomalies

Steltenpohl et al. (2010) 5 Reprocesses new 

magnetic data for 

Alabama.

PEZ-N 5 Defines the western boundary of 

PEZ-N.

N
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-108

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Local Geologic and Tectonic Maps

CEUS SSC basins 

compilation

4 Data is considered of 

generally good quality; 

however, quality is

likely variable as it 

represents a

compilation from 

various published maps 

and various 

scales/detail.

PEZ-W, 

PEZ-N

5 Western limit of Mesozoic rift 

basins used to define eastern 

boundary 

Y

Garrity and Soller (2009) 5 Database with 

1:5,000,000-scale 

geologic map in GIS 

format compiled from 

various national maps.

SLR 4 Boundary drawn to capture 

mapped normal faults in the 

Adirondacks.

N

Kamo et al. (1995) 3 Compilation of Iapetan 

faults, dikes, and other 

intrusive volcanic rocks.

PEZ-N 4 Western Boundary includes 

Grenville dike swarm, which is 

coeval with Iapetan rifting.

N

Kanter (1994) 4 Data is considered 

good quality for defining 

location of major crustal 

divisions.

PEZ-W, 

PEZ-N

4 Used to define source geometry. Y

McKenna et al. (2007) 2 Presents a heat flow 

map in Figure 2.

PEZ-W, 

PEZ-N

1 Data not used to define source 

geometry.

N
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-109 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Thomas (1991) 2 Locations of transforms 

and rift faults are 

approximate—based on 

palinspastic 

restorations.

PEZ-W, 

PEZ-N

3 Provides a conceptual basis for 

drawing zones; however, location 

of boundaries is refined by other 

data sets.

N

Wheeler (1995) 3 Compilation of late 

Neoproterozoic to early 

Cambrian faults.

PEZ-W, 

PEZ-N

4 Used to define source geometry. N

Whitmeyer and Karlstrom 

(2007)

4 Presents regional 

geologic map of North 

America documenting 

assembly of the 

continent by successive 

tectonic events.

PEZ-W, 

PEZ-N

3 Used to define source geometry. Y

Regional Stress

CEUS SSC stress data

set

4 Provides additional new 

measurements to World 

Stress Map.

PEZ-W, 

PEZ-N

1 Data includes strike-slip 

mechanisms with minor thrust 

mechanisms. Orientations 

generally trend NE-SW. Minor 

normal mechanisms.

Y
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-110

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Heidbach et al. (2008)

(World Stress Map)

3 Compiled worldwide 

stress indicators from 

focal mechanisms, 

borehole breakouts, 

etc.

PEZ-W, 

PEZ-N

2 Data includes strike-slip 

mechanisms with minor thrust 

mechanisms. Orientations 

generally trend NE-SW. Minor 

normal mechanisms.

Y

Focal Mechanisms

Herrmann (1978) 3 Earthquake 

parameters.

PEZ-W 4 Considers focal mechanisms and 

hypocentral depth for 1966 and 

1967 Attica earthquakes.

N

Kim et al. (2006) 4 Parameters for an 

earthquake in Lake 

Ontario.

PEZ-W 4 Focal mechanism considered in 

characterization.

N

Paleoseismicity

CEUS SSC 

paleoliquefaction 

database

5 Compilation (with 

attributions) of 

paleoliquefaction 

observations.

PEZ-W; 

PEZ-N

1 Considered in discussion along 

with references below; however,

largest observed earthquake 

determined from historical 

seismicity.

Y

Law et al. (1994) 4 Paleoseismic 

investigations in New 

River Valley of 

Pembroke, Virginia.

PEZ-N; PEZW

3 Describes fault and graben 

structures in alluvial deposits.

N
Table C-7.3.4 Data Evaluation 

Paleozoic Extended Crust Zone

Identified Source 

Paleozoic Extended Crust Zone (PEZ) with alternatives: W: Wide; N: Narrow

C-111 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Law et al. (2000) 4 Paleoseismic 

investigations in New 

River Valley of 

Pembroke, Virginia.

PEZ-N; PEZW

3 Describes extensional and reverse 

faults cutting alluvial surfaces.

N

Tuttle et al. (2002) 5 Paleoliquefaction 

investigation 

surrounding the 

Clarendon-Linden fault 

system.

PEZ-W 4 Identifies a lack of paleoliquefaction 

features. Historical seismicity used 

to evaluate maximum magnitude.

N
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-112

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC 

earthquake catalog

5 Comprehensive 

catalog; includes 

magnitude 

conversions and 

uncertainty 

assessments.

IBEB 5 Used to evaluate recurrence parameters. Y

Hamburger et al. 

(2008)

3 Abstract IBEB 4 Style of faulting and future earthquake 

characteristics—Reactivation of 

structures in contemporary stress regime 

in Illinois basin region—04:30 CDT, April 

18, 2008, M 5.4 earthquake, located near 

New Harmony fault at depth of ~14 km

(~9 mi.).

Y

Withers et al. (2009) 3 Abstract—citing 

preliminary analysis.

IBEB 4 Style of faulting and future earthquake 

characteristics—Reactivation of 

structures in contemporary stress regime 

in Illinois basin region—April 18, 2008, 

Mw 5.2 (Mw 5.4 GCMT [http://www.global 

cmt.org]) Mt. Carmel, Illinois, earthquake. 

Largest event in 20 years in Wabash 

Valley seismic zone.

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-113 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Yang et al. (2009) 3 Abstract—citing 

preliminary analysis.

IBEB 4 Style of faulting and future earthquake 

characteristics—Reactivation of 

structures in contemporary stress regime 

in Illinois basin region. Analysis of 

aftershocks from 2008 M 5.4 Mt. Carmel 

earthquake using sliding-window crosscorrelation technique and doubledifference relocation algorithm gives a 

best-fit plane having a nearly E-W trend 

with an orientation of 248 degrees and a 

dip angle of 81 degrees. Fault is nearly 

vertical down to ~20 km (~12.5 mi.). 

Provides constraints on seismogenic 

width.

N

Historical Seismicity

Bakun and Hopper 

(2004a)

5 Analysis of specific 

historical 

earthquakes.

IBEB 4 Earthquake catalog and recurrence—

Incorporated into earthquake catalog 

used to evaluate recurrence.

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-114

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

McBride et al. (2007) 5 Integrated 

assessment based 

on seismicity, 

borehole, 

geophysical, and 

industry seismic 

profile data analysis.

IBEB 5 Style of faulting and future rupture 

characteristics—Discusses possible 

association of recent earthquakes (April 

3, 1974, mb 4.7; June 10, 1987, mb 5.2; 

and November 9, 1968, mb 5.5 events) 

with three distinct upper-crust sources in 

Illinois basin region. Provides detailed 

discussion of parameters (magnitude, 

depth, focal mechanism) for each event.

Y

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional 

data.

IBEB 2 Boundaries of proto-Illinois basin 

(Precambrian rift basin and extended 

basement terrane) as outlined in 

publications (based on seismic data, 

deep boreholes, and geopotential data) 

are not uniquely defined by magnetic 

anomaly map.

Geopotential field data used by 

researchers to define published 

boundaries of basins.

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-115 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

McBride et al. (2001) 2 Extended abstract 

summarizing 

observations on

geopotential field 

derivative maps.

IBEB 2 Constraints on boundaries to the IBEB—

First vertical derivative of the reduced-topole magnetic intensity map shows a 

subdued magnetic intensity character 

associated with Proterozoic rifting and/or 

volcanic sequences in the basement as 

inferred from deep seismic-reflection 

profiles; pattern continues to the north 

and east beyond limits of deep-reflection 

profile data.

Outer margins of sequences, especially 

to the south and west, marked by 

prominent coincident closed-contour 

magnetic and gravity anomalies, which 

indicate mafic igneous source intrusions.

N

Gravity Anomaly

CEUS SSC gravity

anomaly data set

5 High-quality regional 

data.

IBEB 2 Boundaries of proto-Illinois basin 

(Precambrian rift basin and extended 

basement terrane) as outlined in 

publications (based on seismic data, 

deep boreholes, and geopotential data) 

are not uniquely defined by gravity 

anomaly map.

Geopotential field data used by 

researchers to define published 

boundaries of basins.

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-116

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Seismic Reflection

McBride, Hildenbrand,

et al. (2002)

5 Simplified line 

drawings and 

interpretations of four 

reprocessed 

migrated seismic 

profiles. Excerpts of 

reprocessed seismicreflection profiles. 

Detailed geologic 

discussion based on 

integrated review of 

seismic and 

geopotential data. 

IBEB 4 Used to define style of faulting and 

possible basement source structures 

within source zone.

N
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-117 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

McBride et al. (2007) 5 Builds on McBride, 

Hildenbrand, et al. 

(2002) and provides 

additional 

interpretations of 

seismic-reflection 

data. Presents both 

raw (selected 

excerpts) and 

interpreted sections.

IBEB 4 Concepts and ideas in paper help inform 

drawing the zone boundaries.

Style of faulting and future earthquake 

characteristics—Used to define style of 

faulting and possible reactivated 

basement structures within source zone. 

Notes that limitations of available data 

preclude a precise interpretation of 

―correspondence‖ between specific 

earthquakes and subsurface structures.

Notes that geopotential field data display 

trends that mimic the structural trends 

interpreted from reflection profiles and 

earthquake information. This suggests 

that mapped fault zones correspond in a 

general way to gross lateral lithologic 

changes. 

N
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-118

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Pratt et al. (1992) 4 Integrated analysis 

of seismic profile, 

geopotential 

anomaly maps, and 

drilling data to 

characterize 

Precambrian 

basement rocks. 

IBEB 2 Describes layered Precambrian rock 

sequences and internal features (half 

graben and sequence boundaries that 

indicate depositional basin) beneath 

Illinois basin. Shows examples of 

COCORP lines.

Limited constraints on boundary of 

zone—discusses extent of Centralia 

sequence (Precambrian layered igneous 

sequence) and notes presence of half 

graben and faults within sequence.

N

Regional Geologic and Tectonic Maps

Baranoski et al. (2009) 3 Interpretation of 

seismic, boring, and 

geophysical data 

sets.

IBEB 4 Concepts and ideas in paper help inform 

drawing the zone boundaries—Map of 

the East Continent rift basin used to 

define limits of IBEB zone.

Y

Drahovzal (2009) 3 Interpretation of 

seismic, boring, and 

geophysical data 

sets.

IBEB 4 Concepts and ideas in paper help inform 

drawing the zone boundaries—Map of 

the East Continent rift basin used to 

define limits of IBEB zone.

Y

McBride, Pugin, et al. 

(2003)

3 Interpretation of 

seismic, boring, and 

geophysical data 

sets.

IBEB 4 Concepts and ideas in paper help inform 

drawing the zone boundaries—Map of 

proto-Illinois basin used to define limits of 

IBEB zone.

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-119 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Nelson (1995) 5 Comprehensive 

compilation of 

structural mapping 

for entire state of 

Illinois and adjoining 

regions. (Digital 

format)

IBEB 2 Identifies major structural trends 

(Wabash Valley fault system, La Salle 

anticlinal belt). Although some historical 

earthquakes, such as the 1987 mb 5.2 

earthquake, may be associated with a 

fault-propagation fold (possible 

reactivation of a basement fault during

Laramide orogeny, McBride et al. (2007) 

suggest that a clear association of 

seismicity with mapped structural trends 

is not well documented throughout 

southern Illinois basin.

Y

Geodetic Strain

Hamburger et al. 

(2002)

1 Only one year of 

data.

IBEB 1 Generally consistent with focal 

mechanism data from historical events.

N
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-120

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Hamburger et al. 

(2008)

3 Abstract IBEB 3 Style of faulting—analysis of GPS data 

suggests systematic NW motion of about 

0.5–0.7 mm/yr with respect to Stable 

North American Reference Frame.

Block models, which assume boundaries 

along Cottonwood Grove–Rough Creek 

Graben (CGRCG) and Wabash Valley 

fault system (WVFS), indicate marginal 

block velocities, with possible strike-slip 

motion along the WVFS and E-W

motions along the CGRCG.

N

Hamburger et al. 

(2009)

3 Abstract IBEB 2 Localization and stationarity of more 

concentrated seismicity—data from a 56-

site-campaign GPS geodetic network in 

southern Illinois basin indicate systematic 

NW motion of about 0.5–0.7 mm/yr with 

respect to Stable North American 

Reference Frame.

Average strains for entire network show 

marginally significant strains, with an 

orientation rotated 45 degrees from 

overall direction of intraplate stress in 

U.S. midcontinent.

Significant changes in strain and 

seismicity rates in southern Illinois basin 

can persist for several hundred years 

following New Madrid earthquakes. The 

N
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-121 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

seismicity rate can increase by as much 

as a factor of seven over background 

rate in the near field, but by a much 

smaller amount in the far field.

Regional Stress

CEUS SSC stress 

data set

4 No additional stress 

measurements from 

World Stress map 

except for two events 

in Wabash Valley 

RLME.

IBEB 0 Same as World Stress Map—No 

additional new data.

Y

Heidbach et al. (2008)

(World Stress Map)

3 Worldwide 

compilation of stress 

data.

IBEB 3 Three events used by the World Stress 

Map, while tectonically and spatially 

distinct, represent contemporary 

maximum horizontal compressive stress 

that trends just north of east in southern 

Illinois and Indiana (McBride et al., 

2007).

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-122

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Tectonic Strain Focal Mechanisms

Hamburger et al. 

(2008)

Larson (2002)

Larson et al. (2009)

McBride, Hildenbrand, 

et al. (2002)

McBride et al. (2007)

Withers et al. (2009)

Yang et al. (2009)

4 Well-constrained 

focal mechanisms for 

several recent 

moderate-sized (M 

4–5.4) earthquakes 

in Wabash Valley 

region of southern 

Illinois and Indiana.

IBEB 4 Focal mechanisms indicate ongoing 

deformation along reactivated 

Precambrian and Paleozoic basement 

structures. Analyses indicate three 

seismotectonic environments in upper 

crust: strike-slip (E-NE and NE trends) 

and reverse fault.

N

Larson et al. (2009) 3 Abstract—citing 

preliminary analysis

IBEB 4 04:30 CDT, April 18, 2008, M 5.4 

earthquake, E-W focal mechanism. 

Y
Table C-7.3.5 Data Evaluation 

Illinois Basin-Extended Basement Zone 

Identified Source 

Illinois Basin-Extended Basement (IBEB) 

C-123 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Paleoseismicity

Paleoliquefaction 

studies by numerous 

researchers (see 

Table 6.1.9-1 and 

Appendix E—CEUS 

SSC paleoliquefaction 

database)

4–5 One of best 

paleoliquefaction 

data sets available 

for a region in CEUS.

IBEB 5 Constraint on zone boundary—Evidence 

for several moderate- to large-magnitude 

prehistoric earthquakes suggest possible 

different recurrence rate in southern 

Illinois/Indiana relative to surrounding 

regions

Mmax—paleoearthquakes are used to

modify likelihood function for Mmax 

distribution.

Y
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-124

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and uncertainty 

assessments.

RR and RRRCG

5 Used to develop recurrence 

parameters.

Y

Chiu et al. (1992) 4 Publication discussing results 

of PANDA survey.

RR 5 Focal depth—Seismic activity in 

central NMSZ occurs 

continuously between ~5 and 14 

km (~3 and 9 mi.) depth.

N

Chiu et al. (1997) 4 Peer-reviewed publication.

Results from three seismic 

networks (1974–1994).

RR

(SE margin)

4 Focal depth—Nine earthquakes 

with focal mechanisms; 6.3–22.8 

km (4–14.2 mi.); five 

earthquakes between 13.9 and 

17.3 km (8.6–10.7 mi.).

N

Magnetic Anomaly

CEUS SSC magnetic 

anomaly data set

5 High-quality regional data. RR and RRRCG4 Used to evaluate alternate 

geometries of RR.

Y

Hildenbrand and 

Hendricks (1995)

5 Detailed discussion of 

interpretations of 

geopotential data sets.

RR and RRRCG

5 Source boundaries—Used to 

evaluate locations of plutons of 

possible Mesozoic or younger 

age (limits of significant 

Mesozoic extension).

N
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-125 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional data. RR and RRRCG1 Source boundaries—Used to 

evaluate alternate geometries of 

RR.

Y

Seismic Reflection

(See Table D-6.1.5 Data 

Summary—Reelfoot 

Rift–New Madrid 

Seismic Zone)

n/a n/a RR 1 Seismic-reflection data 

integrated into publications that 

define structures within RR. 

Specific lines not used directly in 

this study.

N

Odum et al. (2010) 3 Provides interpreted highresolution seismic profile 

data to support alternative 

structural model. Discusses 

evidence for recency. 

RR 2 Style of faulting and future 

rupture characteristics—

Potential fault source within RR

that is not modeled as an RLME.

N

Pratt (2009) 3 Abstract and poster 

presentation (pers. comm.,

October 29, 2010, USGS 

Memphis meeting).

RR 3 Broad zone of faulting is present 

in the rift.

N
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-126

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Regional Geologic and Tectonic Maps

Csontos et al. (2008) 3 Integrated structure-contour 

map of top of basement 

showing subbasins and 

bounding NE- and SEstriking faults.

RR 5 Source boundaries—Used to 

constrain boundaries of RR.

Geometry and style of faulting—

Used to evaluate future rupture 

characteristics.

N

Bear et al. (1997)

Hildenbrand and 

Hendricks (1995)

Hildenbrand and Ravat 

(1997)

Kolata and Hildenbrand 

(1997)

Wheeler (1997)

3 Published articles that 

provide good documentation 

of data that can be used to 

evaluate northern limit of RR.

RR 4 Various publications that provide 

evidence for northern terminus of 

RR and lack of continuity with 

Rough Creek graben (RCG) and 

structures in Wabash Valley 

seismic zone region.

N

Hildenbrand et al. 

(2001)

3 Detailed discussion of 

structures in the New Madrid 

seismic zone region of the 

RR. Good-quality figures 

showing interpretations.

RR 5 Source boundaries—Used to 

constrain boundaries of RR.

N
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-127 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Soderberg and Keller 

(1981)

Kolata and Nelson 

(1991)

Potter and Drahovzal 

(1994)

Nelson (1995)

5 Published articles that 

provide good documentation 

of data that can be used to 

evaluate continuity of RR and 

RCG.

RR-RCG 4 Possible structural continuity of 

RR and RCG—The RCG in 

western Kentucky is structurally 

connected to northern portion of 

RR that includes Fluorspar area 

of southern Illinois.

Y

Local Geologic and Tectonic Maps

Nelson and Lumm

(1987)

Kolata and Nelson

(1991)

4 Published articles based on 

integration of subsurface 

geologic, seismologic, and 

geophysical data. Published 

figures are of a quality that 

can be used to define 

structures.

RR-RCG 5 Boundaries of RCG—Bounded 

on north by south-dipping, listric 

Rough Creek fault, and on NW

by Shawneetown fault.

Southern boundary 

approximately follows Pennyrile 

fault system, which forms 

southern margin to the Paleozoic 

syn-rift deposits.

N

Regional Stress

Forte et al. (2007) 3 Regional analysis of 

properties of upper mantle 

and lower crust.

RR and RRRCG

1 Provides rationale for 

concentrating seismic stress in 

the vicinity of RR, but is not 

specific enough to use to draw 

source zone boundaries.

N
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-128

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Grana and Richardson 

(1996)

3 Detailed discussion of stress 

data in NMSZ.

RR 1 Modeling indicates that stresses 

from the load of rift pillow may 

still be present in upper crust 

and may still play a role in 

present-day deformation. 

Justification for RR.

N

Li et al. (2009) 3 Process-oriented paper 

based on 3-D viscoelastoplastic finite-element model.

RR and RRRCG (out-ofcluster 

model)

2 Supports migration of seismicity 

within RR. Model replicates 

some of the spatiotemporal 

complexity of clustered, episodic, 

and migrating intraplate 

earthquakes.

Time-scale-dependent spatiotemporal patterns of intraplate 

seismicity support suggestions 

that seismicity patterns observed 

from short-term seismic records 

may not reflect long-term 

patterns of intraplate seismicity.

N
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-129 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Focal Mechanisms

Shumway (2008) 4 Detailed analysis of 

seismicity data using recent 

velocity model and 

appropriate depths to 

bedrock beneath seismic 

stations.

RR 4 Style of faulting and depth of 

seismogenic crust based on 

well-constrained focal 

mechanism date. 

N

Zoback (1992) 4 Well-constrained focal 

mechanisms.

RR and RRRCG

3 Style of faulting in RR—Four 

focal mechanisms show 

predominantly strike-slip motion.

N

Paleoseismicity

Database of published 

and unpublished data 

provided by Dr. M. Tuttle 

(included in CEUS SSC 

paleoliquefaction 

database)

5 Well-documented database. RR and RRRCG5 No evidence to date for repeated 

Holocene earthquakes in RCG.

Y

Harrison and Schultz 

(2002)

Wheeler (2005)

3 Published descriptions of 

Quaternary deformation in 

Slinkard Quarry, Missouri.

RR 3 Activity and style of faulting—

Evidence for possible prehistoric 

earthquakes in Cape Girardeau, 

Missouri, area.

N
Table C-7.3.6 Data Evaluation 

Reelfoot Rift Zone 

Identified Sources 

Reelfoot Rift Zone (RR); Reelfoot Rift–Rough Creek Graben (RR-RCG) 

C-130

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

McBride, Nelson, and 

Stephenson (2002)

4 Integrated analysis of 

evidence; good-quality maps 

and figures.

RR 4 Discussion of evidence for timing 

of earthquakes on Fluorspar 

Area fault complex; hypothesis 

of temporal changes and 

migration of seismicity within rift.

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-131 

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude 

conversions and 

uncertainty 

assessments.

ECC-AM, 

AHEX

5 Used to define recurrence parameters. Y

Historical Seismicity

Bakun et al. (2003) 4 Detailed assessment 

of Cape Ann

earthquake and two 

other historical events 

using new MMI model 

and site corrections 

for eastern North

America.

ECC-AM 4 Location of western ECC-AM boundary 

offshore Massachusetts drawn to include 

the preferred location of Cape Ann 

earthquake. The 95% confidence level for 

location was used in weighting possibility 

that Cape Ann earthquake should be 

used to modify Mmax prior distribution for 

both ECC-AM and NAP.

N

Bollinger et al. (1991) 3 Spatial distribution 

(including depth) of 

earthquakes in the 

CEUS through 1986. 

Data largely 

superseded by the 

CEUS SSC 

earthquake catalog.

ECC-AM 2 Hypocenters of Coastal Plain shocks are 

distributed throughout upper 13 km of 

crust, where focal mechanisms indicate a 

N-NE maximum compressive stress.

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-132

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Ebel (2006) 4 Detailed reexamination of 1755 

Cape Ann earthquake 

from firsthand 

historical accounts.

ECC-AM 4 Location of western ECC-AM boundary 

offshore Massachusetts drawn to include 

location of Cape Ann earthquake.

N

Magnetic Anomaly

CEUS SSC magnetic 

anomaly database

5 High-quality regional 

data set

ECC-AM, 

AHEX

3 Considered for defining boundaries of 

zone along eastern and southern 

margins. ECC zone is not subdivided 

based on different basement terranes or 

tectonic features imaged in the magnetic 

anomaly map.

N

Holbrook (1994a, 1994b) 4 Multichannel seismicreflection and wideangle ocean-bottom 

seismic profiles 

provide seismic 

velocity model of U.S.

Atlantic continental 

margin

ECC-AM, 

AHEX

4 Concludes that transitional igneous crust 

was created by rift-related intrusives, 

marking eastern boundary of extended 

continental crust. These studies confirm 

that the western margin of East Coast 

magnetic anomaly (ECMA) marks 

boundary between extended continental 

crust and transitional crust, and eastern 

margin of ECMA corresponds 

approximately to western margin of 

oceanic crust.

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-133 

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Klitgord et al. (1988) 4 Regional synthesis of

structural and 

geophysical data to 

develop tectonic 

framework of U.S.

Atlantic continental 

margin.

ECC-AM, 

AHEX

4 Eastern boundary follows ECMA

presented on Plate 2A. 

N

McBride and Nelson 

(1988)

4 Integration of 

magnetic anomaly 

analysis with 

COCORP deepreflection data.

ECC-AM 4 Uses seismic data to investigate source 

of Brunswick magnetic anomaly and

concludes that it is a deep structure 

marking Alleghanian collision. This was 

used to define southern border of 

ECC-AM.

N

Gravity Anomaly

CEUS SSC gravity 

anomaly database

5 High-quality regional 

data set

ECC-AM, 

AHEX

2 The ECC zone is not subdivided based 

on different basement terranes or 

tectonic features imaged in the gravity 

anomaly map.

Y

Klitgord et al. (1988) 4 Regional synthesis of 

structural and

geophysical data to 

develop tectonic 

framework of U.S.

Atlantic continental 

margin.

ECC-AM, 

AHEX

5 Eastern boundary follows landward edge 

of oceanic crust shown on Plate 2B. 

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-134

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Pratt (1988) 4 Regional seismic 

reflection line across 

Virginia Piedmont.

ECC-AM 4 Concludes that Appalachian gravity 

anomaly gradient marks a fundamental 

zone of weakness coincident with 

western extent of thinned continental 

crust.

N

Seismic Reflection

[various studies] 3-5 Interpretations from 

various publications 

such as Cook and 

Vasudevan (2006);

Glover et al. (1995);

Hatcher et al. (1994);

and Sheridan et al. 

(1993). (See ECC 

Data Summary 

Table.)

ECC-AM, 

AHEX

1 Interpretations of deep crustal seismic 

profiles (COCORP) provide good 

information for identifying and 

characterizing structures and major 

terrane boundaries in basement. No 

basement structures, however, are 

identified as specific seismic sources in 

this study. 

N

Geophysical Anomaly

Li et al. (2003) 4 Determined velocity 

structure from 

inversion of Rayleigh 

waves.

ECC-AM 4 NW-trending prong of ECC in eastern 

New York, western Massachusetts, and 

SW Vermont captures the negative 

crustal velocity anomaly attributed to the 

Great Meteor hotspot.

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-135 

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Regional Geologic and Tectonic Maps

CEUS SSC basins 

compilation

4 Data is considered of 

generally good 

quality; however,

quality is likely 

variable as it 

represents a 

compilation from 

various published 

maps and various 

scales/detail.

ECC-AM 5 Data set includes digital GIS compilation 

of Mesozoic basins from a variety of 

published sources. Used to delineate 

western margin of ECC zone.

Y

Kanter (1994) 4 Data is considered of 

good quality for 

defining location of 

major crustal divisions 

(e.g., oceanic crust, 

extended crust, 

transitional crust) in 

the Gulf of Mexico 

region.

ECC-AM 5 Data on the location of extended crust 

were used for defining the source 

geometry.

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-136

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Klitgord et al. (1988) 4 Regional synthesis of 

structural and 

geophysical data to 

develop tectonic 

framework of U.S.

Atlantic continental 

margin.

ECC-AM 4 Eastern boundary includes Carolina 

trough, Baltimore canyon trough, Georgia 

Banks basin, and Scotia basin inboard of 

the East Coast magnetic anomaly 

illustrated on Plate 2C. Western 

boundary of ECC in New England drawn 

to the west of Bay of Fundy shown on 

Plate 2C.

N

Murphy and Keppie (2005) 3 Regional compilation 

of major Paleozoic 

strike-slip faults.

ECC-AM 4 Western boundary in Nova Scotia drawn 

along strike-slip faults separating 

Avalonia and Meguma terranes.

N

Pe-Piper and Piper (2004) 4 Regional-scale fault 

mapping in Grand 

Banks region of 

Atlantic Canada.

ECC-AM 4 Western boundary in Nova Scotia drawn 

along strike-slip fault system separating 

Avalonia and Meguma terranes.

N

Regional Stress

CEUS SSC stress data set 4 Provides additional 

new measurements to 

World Stress Map

ECC-AM 1 Update of World Stress Map data for 

CEUS shows consistent orientation of 

maximum horizontal stress in ECC.

Y

Zoback and Zoback (1989) 4 Good-quality data 

regional set that is 

outdated but still 

consistent with 

updated stress 

measurements.

ECC-AM 1 Maximum horizontal stress in eastern 

U.S. roughly NE to ENE.

N
Tables C-7.3.7/7.3.8 Data Evaluation 

Extended Continental Crust—Atlantic 

Identified Sources 

Extended Continental Crust—Atlantic Margin (ECC-AM); Atlantic Highly Extended Crust (AHEX) 

C-137 

Data

Reference

Quality 

(1=low, 

5=high)

Notes on Quality

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Paleoseismicity

CEUS SSC 

paleoliquefaction database

5 High-quality data set ECC-AM 2 With the exception of the Charleston 

RLME, paleoliquefaction data is 

insufficient for constraining source 

parameters within ECC-AM.

Y

Obermeier and McNulty 

(1998)

2 Abstract ECC-AM 0 The search for paleoliquefaction along 

300 km of rivers in Central Virginia 

seismic zone (CVSZ) documented only 

two to three features and does not 

provide evidence for RLME, which, in 

part, is why CVSZ is not broken out as a 

separate seismic source in this study. 

Increased rate of seismicity can be 

modeled with spatial smoothing.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-138

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive 

catalog; includes 

magnitude 

conversions and 

uncertainty 

assessments.

ECC-GC, 

GHEX

5 Used to define recurrence parameters. Y

Magnetic Anomaly

CEUS SSC magnetic 

anomaly database

5 High-quality regional 

data.

ECC-GC, 

GHEX

0 Considered for defining boundaries of 

zone.

Y

Gravity Anomaly

CEUS SSC gravity anomaly 

database

5 High-quality regional 

data.

ECC-GC, 

GHEX

0 Considered for defining boundaries of 

zone.

Y

Regional Geologic and Tectonic Maps

Baksi (1997) 3 Data considered of 

moderate quality for 

defining northern 

extent of Mesozoic 

extension.

ECC-GC 1 Concepts and ideas in paper helped

inform drawing zone boundaries.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-139 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Bird et al. (2005) 4 Data considered of 

good quality for 

defining extent of 

oceanic crust in Gulf 

of Mexico.

GHEX 5 Northern boundary of oceanic crust 

used in defining southern boundary of 

the zone.

N

Buffler and Sawyer (1985) 3 Data considered of 

moderate quality for 

defining extent of 

transitional and 

oceanic crust in Gulf 

of Mexico.

ECC-GC, 

GHEX

1 Concepts and ideas in paper helped

inform drawing the zone boundaries.

N

Byerly (1991) 3 Data considered of 

moderate quality for 

defining northern 

extent of Mesozoic 

extension.

ECC-GC 1 Concepts and ideas in paper helped

inform drawing the zone boundaries.

N

Cook et al. (1979) 3 Data considered of 

moderate quality for 

defining extent of Rio 

Grande rift–related 

extension.

ECC-GC 2 Used to inform western extent of 

boundary.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-140

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Daniels et al. (1983) 4 Data considered of 

good quality for 

defining eastern 

extent of Mesozoic 

extension.

ECC-GC 4 Eastern extent of Mesozoic extension 

considered in defining eastern boundary 

of the zone.

N

Dellinger, Dewey, et al. 

(2007)

Dellinger, Ehlers, and Clarke

(2007)

3 Data considered of 

moderate quality for 

discussing 

characteristics of 

Green Canyon 

earthquake.

GHEX 3 Used to help inform maximum observed 

earthquake in the zone.

N

Dewey and Dellinger (2008) 3 Data considered of 

moderate quality for 

discussing 

characteristics of 

Green Canyon 

earthquake.

GHEX 3 Used to help inform maximum observed 

earthquake in the zone.

N

Dickerson and Muehlberger 

(1994)

3 Data considered of 

moderate quality for 

defining extent of Rio 

Grande rift–related 

extension.

ECC-GC 2 Used to inform western extent of 

boundary.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-141 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Gray et al. (2001) 2 Data considered of 

moderate quality for 

defining extent of Rio 

Grande rift–related 

extension.

ECC-GC 1 Used to inform western extent of 

boundary.

N

Hall and Najmuddin (1994) 3 Data considered of 

moderate quality for 

defining extent of 

oceanic crust.

GHEX 1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N

Harry and Londono (2004) 3 Data considered of 

moderate quality for 

defining extent of 

Mesozoic extension.

ECC-GC 1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N

Hatcher et al. (2007) 3 Data considered of 

moderate quality for 

defining northern 

extent of Mesozoic 

extension.

ECC-GC 1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N

Hendricks (1988) 3 Data considered of 

moderate quality for 

defining northern 

extent of Mesozoic 

extension.

ECC-GC 1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-142

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Hildenbrand and Hendricks 

(1995)

4 Data considered of 

good quality for 

presenting location of 

Cretaceous igneous 

intrusions in southern 

Arkansas.

ECC-GC 4 Used in defining northern extent of the 

zone in region of southern Arkansas 

and eastern Texas.

N

Kanter (1994) 4 Data considered of 

good quality for 

defining location of 

major crustal divisions 

(e.g., oceanic crust, 

extended crust, 

transitional crust) in 

Gulf of Mexico region.

ECC-GC, 

GHEX

5 Data on the location of oceanic crust 

and extent of transitional crust were 

used in defining source geometries.

Y

Klitgord et al. (1984) 4 Data considered of 

good quality for 

defining eastern 

extent of Mesozoic 

extension.

ECC-GC 4 Eastern extent of Mesozoic extension 

considered in defining eastern boundary 

of the zone.

N

Marton and Buffler (1994) 3 Data considered of 

moderate quality for 

defining extent of 

transitional and 

oceanic crust in Gulf 

of Mexico.

ECC-GC, 

GHEX

1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-143 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

McBride and Nelson (1988) 3 Data considered of 

moderate quality for 

defining northern 

extent of Mesozoic 

extension.

ECC-GC 1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N

McBride et al. (2005) 3 Data considered of 

moderate quality for 

defining northern 

extent of Mesozoic 

extension.

ECC-GC 1 Concepts and ideas in paper help 

inform drawing the zone boundaries.

N

Murray (1961) 2 Data considered of 

moderate quality for 

defining extent of Rio 

Grande rift–related 

extension.

ECC-GC 1 Used to inform the western extent of 

boundary.

N

Nagihara and Jones (2005) 4 Data considered of 

good quality for 

defining extent of 

oceanic crust in Gulf 

of Mexico.

GHEX 4 Northern boundary of oceanic crust was 

used in defining southern boundary of 

the zone.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-144

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Nettles (2007) 3 Data considered of 

moderate quality for 

discussing 

characteristics of the 

Green Canyon 

earthquake.

GHEX 3 Used to help inform the maximum 

observed earthquake in the zone.

N

Petersen et al. (2008) 4 Data considered of 

good quality for 

defining landward limit 

of Precambrian 

Iapetan rifting.

ECC-GC 5 Limit of Precambrian rifting was used in 

defining NE boundary of the zone.

N

Pindell and Kennan (2001) 4 Data considered of 

good quality for 

defining extent of 

oceanic crust and 

transitional crust in 

Gulf of Mexico.

GHEX 2 Concepts and ideas in paper help 

inform drawing zone boundaries.

N

Pindell et al. (2000) 4 Data considered of 

good quality for 

defining extent of 

oceanic crust and 

transitional crust in 

Gulf of Mexico.

GHEX 4 Northern boundary of the oceanic crust 

was used in defining southern boundary 

of the zone.

N
Tables C-7.3.9/7.3.10 Data Evaluation 

Extended Continental Crust–Gulf Coast 

Identified Sources 

Extended Continental Crust–Gulf Coast (ECC-GC); Gulf Coast Highly Extended Crust (GHEX) 

C-145 

Data/References

Quality 

(1=low, 

5=high)

Notes on Quality 

of Data

Source 

Considered

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Discussion of 

Data Use

In GIS 

Database

Salvador (1991a) 3 Data considered of 

moderate quality for 

defining extent of 

Mesozoic extension.

ECC-GC 2 Concepts and ideas in paper help 

inform drawing zone boundaries.

N

Sawyer et al. (1991) 4 Data considered of 

good quality for 

defining extent of 

oceanic crust in Gulf 

of Mexico.

ECC-GC, 

GHEX

3 Northern boundary of the oceanic crust 

was used in defining southern boundary 

of the zone, and the boundary between 

the thick and thin transitional crust was 

used in defining boundaries between 

the GHEX and ECC-GC zones.

N

Thomas (1988)

Thomas (2006)

3 Data considered of 

moderate quality for 

defining extent of 

Mesozoic extension.

ECC-GC 2 Concepts and ideas in paper help 

inform drawing zone boundaries.

N

N

Wheeler and Frankel (2000) 4 Data considered of 

good quality for 

defining location of the 

Iapetan margin of the 

ancestral North 

American continent.

ECC-GC 4 Used in defining northern extent of the 

zone in regions where (1) the Mesozoic 

rifting is thought to be coincident with 

Paleozoic rifting, or (2) there is 

considerable uncertainty in the limit of 

Mesozoic rifting and the various 

interpretations of rifting encompass the 

Iapetan margin boundary.

N
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (MidC) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-146

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

Instrumental Seismicity

CEUS SSC earthquake 

catalog

5 Comprehensive catalog; 

includes magnitude 

conversions and 

uncertainty assessments.

MIDC-A, 

MIDC-B, 

MIDC-C, 

MIDC-D

5 Used to evaluate recurrence 

parameters.

Y

Historical Seismicity

Bakun and Hopper 

(2004a)

4 Reanalysis of intensity 

data.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

4 Estimated magnitude for 

historical earthquake used in 

recurrence and Mmax 

assessments—Associates an 

April 9, 1952, M 4.9 (4.5–5.2) 

earthquake with the Nemaha 

fault in Oklahoma.

N

CEUS SSC earthquake 

catalog

5 Comprehensive catalog 

includes magnitude 

conversions and 

uncertainty assessments.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

5 The prior distribution for Mmax 

is modified by the largest 

observed historical earthquake 

taken from the CEUS SSC 

earthquake catalog. 

Y
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (Mid-C) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-147 

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

Niemi et al. (2004) 1 This paper, which relies on 

a previous assessment of 

size of historical 

earthquake (Seeber and 

Armbruster, 1991), does 

not provide any 

independent analysis of 

the earthquake catalog. 

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

2 Considered in evaluating 

association of a historical 

earthquake (1867 M 5.2 

Wamego earthquake) with 

basement Nemaha Ridge–

Humboldt fault structures.

N

Magnetic Anomaly

Atekwana (1996)

Hinze et al. (1975)

Klasner et al. (1982)

Bickford et al. (1986)

Van Schmus (1992)

NICE Working Group

(2007)

3 Publications that describe 

basement terranes that 

have been mapped and 

identified in part from 

interpretation of patterns 

and characteristics of the

magnetic anomalies

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

2 Style of faulting and future 

ruptures—Provides indication of 

structural trends in basement.

N
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (MidC) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-148

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

CEUS SSC magnetic 

anomaly data set

5 High-quality regional data. MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

2

(except for 

border with 

Reelfoot rift 

where the 

reliance 

was 4)

The Mid-C zone is not 

subdivided based on different 

basement terranes or tectonic 

features imaged in the magnetic 

anomaly map. 

The border between Reelfoot 

Rift and Mid-C seismotectonic 

zones is defined in part by the 

limit of magnetic anomalies that 

are interpreted to be Mesozoic 

plutons associated with 

Mesozoic rifting in the RR.

Y

Gravity Anomaly

CEUS SSC gravity 

anomaly data set

5 High-quality regional data. MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

1 The Mid-C zone is not 

subdivided based on different 

basement terranes or tectonic 

features imaged in the gravity 

anomaly map.

Y
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (Mid-C) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-149 

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

Keller (2010) 2 Unpublished report: 

Provides limited 

interpretation of area in 

Oklahoma.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

1 Evaluation of zone of structures 

associated with a region of 

elevated seismicity—

Midcontinent rift system 

(MRS)—concludes that MRS 

may extend south to Wichita 

uplift and seismicity may be 

associated with this feature and 

Nemaha fault zone/ridge. This 

is accounted for in the variable 

smoothing of seismicity within 

the zone. 

Y

Seismic Reflection

(See Table D-7.3.12 

Data Summary—

Midcontinent-Craton 

Zone)

3-5 Interpretations from 

various publications.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

1 Interpretations of deep crustal 

seismic profiles (COCORP, 

GLIMPCE) provide best 

information for identifying and 

characterizing structures and 

major terrane boundaries in the 

basement. No basement 

structures, however, are 

identified in this study as 

specific seismic sources. 

N
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (MidC) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-150

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

Geodetic Strain

Calais et al. (2006) 3 Provides a combination of 

two independent geodetic 

solutions using data from 

close to 300 continuous 

GPS stations covering 

CEUS.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

3 Surface deformation in North 

American Plate interior is best 

fit by a model that includes rigid 

rotation of North America with 

respect to global reference 

point and a component of strain 

related to glacial isostatic 

adjustment (GIA). 

No significant deviation from 

rigidity resolvable at the 0.7

mm/yr level.

EW strain < 1.5 × 10–10 yr–1.

No areas of localized strain 

found.

N

Regional Stress

CEUS SSC stress data

set

4 Provides additional new 

measurements to World 

Stress Map.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

1 An additional measurement in 

NE Oklahoma is consistent with 

previous measurements.

Y
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (Mid-C) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-151 

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

Heidbach et al. (2008)

(World Stress Map)

3 Most current published 

version of map.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

2 Limited entries for the Mid-C—

Maximum horizontal 

compressional stress 

orientations vary from E-W (NE

Kansas) to E-NE (Wisconsin 

and Ohio) to N-NE (W

Minnesota, SW Kansas). 

Y

Focal Mechanisms

Zoback (1992) 4 Well-constrained focal 

mechanisms.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

3 Limited focal mechanisms for 

the craton (e.g., W Minnesota; 

Illinois platform; Sharpsburg, 

Kentucky) Perry, Ohio; 

generally indicate strike-slip

motion.

N

Paleoseismicity

CEUS SSC 

paleoliquefaction 

database

5 Compilation (with 

attributions) of 

paleoliquefaction 

observations.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

3 Mmax assessment—Evidence 

for possible prehistoric 

earthquakes in St. Louis area.

Y
Table C-7.3.12 Data Evaluation 

Midcontinent-Craton Zone 

Identified Sources 

Alternative Midcontinent-Craton (MidC) source zone configurations (MIDC-A, MIDC-B, MIDC-C, and MIDC-D) are based on different 

combinations of alternative zone boundaries for the Paleozoic Extended Zone (Table C-7.3.4) and Reelfoot Rift Zone (Table C-7.3.6) 

C-152

Data Type/References

Quality 

(1=low, 

5=high)

Notes on Quality 

or Data

Source 

Considered 

Used in 

SSC and 

Reliance 

Level 

(0=no, 

5=high)

Description of 

Data Use

In GIS 

Database

Niemi et al. (2004) 3 Detailed evaluation of 

historical seismicity and 

neotectonic field 

investigations (including 

paleoliquefaction studies) 

in E Kansas.

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

3 Nemaha Ridge/Humboldt fault 

(Kansas)—Initial results 

suggest that liquefaction 

features (e.g., clastic dikes), 

which may be attributed to 

seismically induced liquefaction, 

are present, but may not be 

pervasive in this region. These 

data suggest that the 1867 M 

5.2 Wamego earthquake may

characterize the seismic source 

in this region.

N

Tuttle, Chester, et al. 

(1999)

Tuttle (2005a)

Tuttle (2005b)

4 Results of regional 

paleoliquefaction study in 

SE Missouri; provides 

detailed description of 

features and postulated 

locations of causative 

faults (possibly in IBEB).

MIDC-A,

MIDC-B, 

MIDC-C, 

MIDC-D

3 Mmax assessment—Evidence 

for possible prehistoric 

earthquakes in St. Louis area.

Location and magnitude of 

paleoearthquakes is not well 

constrained by data. There is 

not sufficient data to support 

characterization of an RLME 

source in St. Louis.

N
NUREG-2115 DOE/NE-0140 EPRI 1021097

APPENDIX D 

Data Summary Tables 

D-1 

D 

APPENDIX 

DATA SUMMARY TABLES 

Default Source Characteristics for CEUS SSC Project Study Region 

Table D-5.4 Future Earthquake Characteristics 

RLME Sources 

Table D-6.1.1 Charlevoix RLME 

Table D-6.1.2 Charleston RLME 

Table D-6.1.3 Cheraw Fault RLME 

Table D-6.1.4 Oklahoma Aulacogen RLME 

Table D-6.1.5 Reelfoot Rift–New Madrid Seismic Zone RLMEs 

[No Table D-6.1.6] [Reelfoot Rift–Eastern Rift Margin RLME; see Table D-6.1.5] 

[No Table D-6.1.7] [Reelfoot Rift–Marianna RLME; see Table D-6.1.5] 

[No Table D-6.1.8] [Reelfoot Rift–Commerce Fault Zone RLME; see Table D-6.1.5] 

Table D-6.1.9 Wabash Valley RLME 

Seismotectonic Zones 

Table D-7.3.1 St. Lawrence Rift Zone (SLR) 

Table D-7.3.2 Great Meteor Hotspot Zone (GMH) 

Table D-7.3.3 Northern Appalachian Zone (NAP) 

Table D-7.3.4 Paleozoic Extended Crust Zone (PEZ; narrow [N] and wide [W]) 

[No Table D-7.3.5] [Illinois Basin-Extended Basement Zone (IBEB); 

see Table D-6.1.9] 

[No Table D-7.3.6] [Reelfoot Rift Zone (RR) including Rough Creek Graben 

(RR-RCG); see Table D-6.1.5] 

Table D-7.3.7 Extended Continental Crust Zone–Atlantic Margin (ECC-AM) 

[No Table D-7.3.8] [Atlantic Highly Extended Crust Zone (AHEX); 

see Table D-7.3.7] 

Table D-7.3.9 Extended Continental Crust Zone–Gulf Coast (ECC-GC) 

[No Table D-7.3.10] [Gulf Coast Highly Extended Crust Zone (GHEX); 

see Table D-7.3.9] 

[No Table D-7.3.11] [Oklahoma Aulacogen (OKA); see Table D-6.1.4] 

Table D-7.3.12 Midcontinent-Craton Zone (MidC) 
D-2 

Mmax Zones 

Criteria for defining the MESE/NMESE boundary for the two-zone alternative are discussed in 

Section 6.2.2. MESE-N includes ECC-AM, ECC-GC, AHEX, GHEX, RR, SLR, NAP, GMH, 

and PEZ-N. MESE-W differs from MESE-N in that it adopts the wide alternative geometries 

(i.e., PEZ-W, RR-RCG, and IBEB). See the tables listed above for data pertinent to the definition 

of the boundaries of the zones and evidence for Mesozoic and younger tectonism. Default future 

earthquakes rupture parameters (Table 4.1.3-1) are assigned to both the one-zone and two-zone 

Mmax sources. 

Introduction 

The Data Summary tables were developed to provide information on the various data that were 

considered during the course of the characterization of seismic sources. The table designation is 

linked to the chapter and section where the table is first cited. In some cases, information related 

to multiple seismic sources is included in a single table. The tables provide the citations to the 

data and a description of the key conclusions and their potential relevance to SSC. Full citations 

of references listed in the tables are provided in Chapter 10. All data sets included in the tables 

were reviewed, although not all were ultimately used to characterize a particular seismic source. 

Additional information on the Data Summary tables is provided in Section 4.1.2.2. 

Please note that magnitudes are reported in the magnitude scale designated in the cited 

publication.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-3 

Citation Title Description and Relevance to SSC

Atkinson (2004) Empirical Attenuation of 

Ground-Motion Spectral 

Amplitudes in Southeastern 

Canada and the Northeastern 

United States

Presents a database of 1,700 digital seismograms from 186 earthquakes of magnitude 

MN 2.5–5.6 that occurred in SE Canada and the NE United States from 1990 to 2003.

The focus of the paper is the development of ground motion attenuation relationships, 

but the database represents high-quality instrumental recordings; source parameters 

are given for all events. This information can be used to examine various future 

earthquake characteristics such as focal depth.

Chapman et al. 

(1997)

A Statistical Analysis of 

Earthquake Focal Mechanisms 

and Epicenter Locations in the 

Eastern Tennessee Seismic 

Zone

This paper reports that 26 well-constrained focal mechanism solutions are derived 

using a new velocity model and relocated hypocenters. The results suggest that strikeslip motion on steeply dipping planes is the dominant mode of faulting throughout the 

300 km (186 mi.) long Eastern Tennessee seismic zone. Most of the mechanisms can 

be grouped into two populations. The larger population is characterized by steeply 

dipping N-S- and E-W-striking nodal planes with right-lateral and left-lateral slip, 

respectively. The second population differs from the first by an approximate 45°

eastward rotation about the B-axis. The results suggest a series of NE-trending en

echelon basement faults, intersected by several east-trending faults. Most of the largermagnitude instrumentally located earthquakes in the seismic zone occurred close to 

the statistically identified potential faults.

Dineva et al. (2004) Seismicity of the Southern 

Great Lakes: Revised 

Earthquake Hypocenters and 

Possible Tectonic Controls

Using data from 27 seismograph stations for the period 1990–2001, 106 hypocenters 

with magnitudes of 0.9–5.4 were relocated in the region of the southern Great Lakes.

Both the seismicity and magnetic anomalies exhibit statistically significant preferred 

orientations at N40°E–N45°E, but the correlation of the earthquake clusters with 

specific magnetic lineaments remains uncertain. Three preliminary focal mechanisms 

of earthquakes with magnitudes MN 3.1–3.8 show unusual normal faulting, with nodal 

planes in almost the same direction as the magnetic trends, N42°E–N52°E.

Heidbach et al.

(2008)

(World Stress Map)

The World Stress Map Project 

Database Release 2008

Compilation of stress indicators for the CEUS shows consistent tectonic stress 

directions in the NE quadrant. No strong evidence for stress subprovinces.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-4 

Citation Title Description and Relevance to SSC

Horton et al. (2005) The 6 June 2003 Bardwell, 

Kentucky, earthquake 

sequence: Evidence for a 

Locally Perturbed Stress Field 

in the Mississippi Embayment

Includes a compilation of earthquake focal mechanisms of the earthquakes that 

occurred in the central U.S. since 1960s, including Reelfoot rift, Rough Creek graben in 

western Kentucky, and Wabash Valley fault system along SE Illinois/SW Indiana 

border. Special study of the June 6, 2003, Bardwell, Kentucky, earthquake, including a 

number of aftershocks, has been done to provide high-quality locations and focal 

mechanisms. Mechanisms are primarily strike-slip, with a component of reverse 

faulting. Focal mechanisms of earthquakes in the New Madrid seismic zone with E-Wtrending nodal planes have different trending P axes, suggesting a strong perturbation

in the stress field over a distance of about 60 km (37 mi.).

Kim (2003) The 18 June 2002 Caborn, 

Indiana, Earthquake: 

Reactivation of Ancient Rift in 

the Wabash Valley Seismic 

Zone?

Presents an assessment of the June 18, 2002, Caborn, Indiana, earthquake (Mw 4.6) 

using regional and teleseismic waveform data, and concludes that the event occurred 

on a steeply dipping fault at a depth of about 18 km (11 mi.). The source mechanism 

determined from regional waveform analysis is predominantly strike-slip along nearvertical nodal planes. The June 2002 event at 18 km (11 mi.) depth and the southcentral Illinois earthquake on November 9, 1968 (Mw 5.3), which occurred at 25 km 

(15.5 mi.) depth, suggest that seismogenic depth in the Wabash Valley seismic zone 

extends to at least 18 km (11 mi.). 

Kim and Chapman 

(2005)

The 9 December 2003 Central 

Virginia Earthquake Sequence: 

A Compound Earthquake in the 

Central Virginia Seismic Zone

The December 9, 2003, central Virginia earthquake sequence was a compound 

earthquake consisting of two nearly identical events occurring about 12 sec apart. The 

source mechanism determined from regional waveform inversion indicates

predominantly thrust faulting at a depth of approximately 10 ± 2 km (6 ± 1 mi.). A 

regional stress model for the Central Virginia seismic zone derived from the December 

9, 2003, events and 11 previous earthquakes indicates a thrust-faulting stress regime.

The December 9, 2003, earthquake sequence occurred among the systems of 

Paleozoic and Mesozoic faults above the southern Appalachian décollement, which is 

at 12–19 km (7–12 mi.) depth in the Piedmont geologic province of central Virginia.

Mai et al. (2005) Hypocenter Locations in FiniteSource Rupture ModelsThe paper compiles data related to hypocenter depths in relation to the normalized 

downdip width of fault rupture for crustal faults and subduction zones. The relationships 

can be used to assess expected depth distribution of earthquakes as a function of 

earthquake magnitude.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-5 

Citation Title Description and Relevance to SSC

Marshak and Paulsen 

(1997)

Structural Style, Regional 

Distribution, and Seismic 

Implications of Midcontinent 

Fault-and-Fold Zones, United 

States

Summarizes steeply dipping faults and associated monoclinal forced folds, which were 

active in pulses during the Phanerozoic, although it is suggested that they initiated 

during episodes of Proterozoic extensional tectonism. Based on fault-trace orientation, 

Midcontinent fault-and-fold zones are divided into two sets—one trending N-NE and 

the other trending W-NW. Many W-NW-trending fault-and-fold zones link along strike to 

define semicontinuous NW-trending deformation corridors. One of these, the 200 km

(124 mi.) wide Transamerican tectonic zone (TTZ), traces over 2,500 km (1,553 mi.) 

from Idaho to South Carolina. Seismicity most frequently occurs where N-NE-trending

fault-and-fold zones cross the TTZ, suggesting that intracratonic strain in the U.S.

currently concentrates at or near intersecting fault zones within this corridor.

Mazzotti (2009 CEUS 

SSC Workshop 2 

presentation)

Strain (and Stress) Constraints 

on Seismicity in the St. 

Lawrence Valley

Map showing ~50 focal mechanisms indicates primarily reverse faulting, with a 

component of strike-slip. Plots of interpreted maximum compressive stress directions 

show that both α1 and α2 are horizontal. Also shown are differences in the orientation 

of α1 for events to the north of the axis of the St. Lawrence (in the NE quadrant) versus 

south (approximately E-W).

NAGRA (2004) Probabilistic Seismic Hazard 

Analysis for Swiss Nuclear 

Power Plant Sites (PEGASOS 

Project)

This large PSHA was conducted for four nuclear power plant sites in Switzerland, 

which is characterized by a seismotectonic setting very similar to the CEUS. Presents 

an approach to characterize the depth distribution of future earthquake ruptures using 

the focal depth distribution of observed hypocenters. The approach takes advantage of 

observed seismicity as well as studies of the magnitude dependence of focal depths.

Seeber et al. (1998) The 1994 Cacoosing Valley 

Earthquakes near Reading, 

Pennsylvania: A Shallow 

Rupture Triggered by Quarry 

Unloading

The paper discusses the mbLg 4.6 main shock on January 16, 1994, in the Cacoosing 

Valley, 10 km (6 mi.) west of Reading, SE Pennsylvania. This zone matches the nodal 

plane with reverse and left-lateral slip (strike 135°, dip 54°SW, and rake 55°) of a focal 

mechanism obtained from aftershock first motions and from main-shock waveforms. 

Shumway (2008) Focal Mechanisms in the 

Northeast New Madrid Seismic 

Zone

Earthquakes in the NE New Madrid seismic zone from June 1995 to June 2006 were 

relocated using a velocity model of the Mississippi embayment with appropriate depths 

to bedrock beneath seismic stations. Focal mechanisms were generated for events on 

the NE-trending alignments. The results show that most of the earthquakes are strikeslip and approximately half the focal mechanisms have a N-NE-striking nodal plane 

and a right-lateral, strike-slip component consistent with earlier studies of the NMNF to 

the southwest.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-6 

Citation Title Description and Relevance to SSC

Sibson (1982) Fault Zone Models, Heat Flow, 

and the Depth Distribution of 

Earthquakes in the Continental 

Crust of the United States

Models of fault zones in continental crust, based on analysis of rock deformation 

textures, suggest that depth of seismic activity is controlled by the passage from a 

pressure-sensitive, dominantly frictional regime to strongly temperature-dependent, 

quasi-plastic mylonitization at greenschist and higher grades of metamorphism. Based 

on models of the frictional and rheological properties of quartz-bearing rocks, crude 

strength-depth curves for different geotherms are developed. In such models, shear 

resistance peaks sharply at the inferred seismic-aseismic transition. Depth at which 

90% of microseismic activity occurs is plotted on the modeled strength-depth curves for 

various heat flow provinces of the conterminous U.S.

Sibson (1984) Roughness at the Base of the 

Seismogenic Zone: 

Contributing Factors

Observational data such as earthquake focal depths and considerations of the strength 

profile of continental crust are both used to draw conclusions regarding the controls of 

the thickness of the seismogenic zone. Implications are drawn regarding the likely 

depths of large earthquakes and their magnitude dependence.

Sibson (2007) Au-Quartz Mineralization near 

the Base of the Continental 

Seismogenic Zone

The base of the continental seismogenic zone is defined within individual fault zones 

by the transition with depth from pressure-sensitive factional (FR) faulting to 

temperature-sensitive quasi-plastic (QP) ductile shearing. The depth of this FR-QP 

transition fluctuates principally as a consequence of variations in geothermal gradient 

and crustal lithology but other factors (e.g., fluid pressure level, strain rate) also play a 

role. Topographic irregularities in the seismic-aseismic transition determine rupture 

nucleation sites and probably play a critical role in focusing the discharge of 

overpressured metamorphic fluids into the seismogenic layer. This information has 

implications to the depth of larger earthquakes and their nucleation near the base of 

the seismogenic zone.

Sibson and Xie 

(1998)

Dip Range for Intracontinental 

Reverse Fault Ruptures: Truth 

Not Stranger than Friction?

Histograms of fault dips have been compiled for moderate to large (M > 5.5) reverseslip intracontinental earthquakes with the slip-vector raking 90° ± 30° in the fault plane. 

The principal data set is restricted to earthquakes where the fault plane in the focal 

mechanism can be unambiguously distinguished from the auxilliary plane; the reverse 

fault dips are bracketed within the range of 12°–60° with a prominent peak in the 25°–

35° interval and a subsidiary peak in the 45°–55° interval.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-7 

Citation Title Description and Relevance to SSC

Somerville et al. 

(2001)

Ground Motion Attenuation 

Relations for the Central and 

Eastern United States

As part of developing ground-motion attenuation relations, the authors first developed 

earthquake source scaling relations for use in generating ground motions. The source 

models have spatially varying slip distributions on the fault plane, and are described by 

self-similar scaling relations between seismic moment and source parameters such as 

fault dimensions and rise time derived from the slip models of three recent earthquakes 

in eastern Canada. Scaling relationships of earthquake rupture models are presented 

relating fault rupture area and seismic moment that are deemed to be appropriate for 

eastern North America.

Sykes et al. (2008) Observations and Tectonic 

Setting of Historic and 

Instrumentally Located 

Earthquakes in the Greater 

New York City–Philadelphia 

Area

As part of discussions of seismicity in the New York region, high-quality earthquake 

locations and focal depths are given. The focal depth distribution provides information 

on seismogenic crustal thickness for the region.

Talwani (2009 CEUS 

SSC Workshop 2 

presentation)

The Source and Magnitude of 

the Charleston Earthquake

The presentation summarized the latest instrumental seismicity data for the Charleston 

region. Included in the talk was a plot of focal depth distribution for instrumental events 

in the region.

Tanaka (2004) Geothermal Gradient and Heat 

Flow Data in and Around Japan 

(II): Crustal Thermal Structure 

and Its Relationship to 

Seismogenic Layer

The high-quality database of seismicity of Japan (Japan Meteorological Agency, or 

JMA) and an extensive compilation of thermal measurements (Tanaka et al., 2004) are 

used to quantify the concept of temperature as a fundamental parameter for 

determining thickness of the seismogenic zone. Qualitative comparisons between each 

data of heat flow and geothermal gradient, and the lower limit of crustal earthquake 

hypocentral distributions beneath the Japanese Islands show that, as expected, the 

lower limit of seismicity is inversely related to heat flow and geothermal gradient. 

Gridded heat flow or geothermal gradient and D90, the depth above which 90% of 

earthquakes occur, correlated well with each other. The evaluated temperatures for D90

range between 250°C and 450°C except for higher heat flow data. The consistency of 

temperature for D90 over a large depth interval almost all over the Japanese islands 

support the concept that the temperature is the dominant factor governing the focal 

depth in the crust.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-8 

Citation Title Description and Relevance to SSC

Tanaka and Ishikawa 

(2002)

Temperature Distribution and 

Focal Depth in the Crust of the 

Northeastern Japan

Comparisons are made between heat flow, thermal gradient and earthquake 

databases for NE Japan. Temperatures in the crust were calculated using a steadystate one-dimensional heat-conductive transport model with heat generation as a 

function of heat flow and thermal gradient. The evaluated temperatures for D90, the 

depth above which 90% of earthquakes occur, range between 200°C and 500°C 

except for high heat flow and thermal gradient data. The consistency of temperature for 

D90 over a large depth interval supports the theory that temperature is the dominant 

factor governing the focal depth in the crust.

van Lanen and 

Mooney (2007)

Integrated Geologic and 

Geophysical Studies of North 

American Continental Intraplate 

Seismicity

The paper provides a histogram of earthquake focal depth in eastern North America 

(ENA) as a function of moment magnitude. The compilation for ENA is compared to 

other stable continental regions. The paper concludes that seismicity is correlated with 

the NE-SW structural grain of the crust of ENA, which in turn reflects the opening and 

closing of the proto- and modern Atlantic Ocean. This structural grain can be discerned 

as clear NE-SW lineaments in the Bouguer gravity and aeromagnetic anomaly maps. 

Stable continental region seismicity either (1) follows the NE-SW lineaments, (2) is 

aligned at right angles to these lineaments, or (3) forms clusters at what have been 

termed stress concentrators.

Wesnousky (2008) Displacement and Geometrical 

Characteristics of Earthquake 

Surface Ruptures: Issues and 

Implications for Seismic-Hazard 

Analysis and the Process of 

Earthquake Rupture

This paper includes a compilation of empirical data regarding the seismologic and 

geologic characteristics of earthquake ruptures. The data set is aimed at establishing 

rupture characteristics and their uncertainties for use in seismic hazard and fault 

displacement hazard analyses. A relationship between fault length-to-width aspect ratio

versus magnitude is presented.

Zoback (1992) Stress Field Constraints on 

Intraplate Seismicity in Eastern 

North America

Focal mechanisms of 32 North American CEUS earthquakes are evaluated to 

determine if slip is compatible with a broad-scale regional stress field derived from 

plate-driving forces and, if so, under what conditions. Independent information on in 

situ stress orientations from well bore breakout and hydraulic fracturing data is used to 

assess relative stress magnitudes. The evaluation of the data confirmed a roughly 

north-to-south contrast in stress regime between the CEUS and SE Canada: most 

CEUS earthquakes occur in response to a strike-slip stress regime, whereas SE

Canada events require a thrust-faulting stress regime.
Table D-5.4 Data Summary 

Future Earthquake Characteristics 

D-9 

Citation Title Description and Relevance to SSC

Zoback (2010) CEUS SSC stress data set Database updates the compilation for the CEUS developed originally for the World 

Stress Map. Uses a variety of indicators (e.g., earthquake focal mechanisms, in situ 

stress measurements) of the orientation of the maximum compressive stresses. Stress 

data based on earthquake focal mechanisms and other in situ stress indicators were 

compiled for the past 10 years and added to the existing world stress map.

Orientations of maximum compressive stress directions are consistent with those 

compiled earlier. There is no longer compelling evidence for a northwesterly directed 

stress province along the Atlantic margin, as postulated in the 1980s. There is some 

suggestion of stress rotation within the New Madrid seismic zone, which would suggest 

a weak zone, but the evidence is not strong.
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-10 

Citation Title Description and Relevance to SSC

Geologic Structures Interpreted from Geologic, Gravity, Magnetic, and Seismic Profile Data

Lemieux et al. 

(2003)

Structural Analysis of Supracrustal 

Faults in the Charlevoix Area, 

Quebec: Relation to Impact Cratering 

and the St-Laurent Fault System

Two major sets of fault orientations (N290°–N320° and N020°–N040°) are found 

outside the impact zone, with minor fault sets trending N270–N280 and N000–

N020. Within the impact crater, fault orientations are more scattered but are 

similar to the NW- and NE-trending systems of the external domain. The spread 

of orientations within the central portion of the crater is attributed to the impactrelated polygonal pattern of normal faults, whereas the NW and NE fault sets 

represent the youngest reactivation. 

Coarse-grained cataclastic breccias up to 50 m thick are exposed along brittle 

faults striking NE and NW outside the impact crater. Similar cataclastic breccias 

are also found within the impact crater but are usually less than a few meters 

thick. Polymictic clastic matrix breccia is found exclusively within the impact 

crater. Fragments of cataclastic breccia are present, suggesting recurrent 

brecciation during incremental faulting events. Pseudotachylyte and foliated 

gouge are locally related to the cataclastic breccia, indicating that these rocks 

originate from a post-impact single and progressive tectonic event along the St. 

Lawrence rift system.

The St-Laurent fault influenced the deposition of Ordovician deposits during late 

stages of the Taconian orogeny by syndepositional faulting preserved as major 

lateral thickness variations within the section, presence of slump deformation in 

almost all stratigraphic units, preservation of pseudotachylyte within 

synsedimentary breccias, and occurrence of fault breccia clasts. However, the 

geometry and structural characteristics of faulting are consistent with Mesozoic 

fault reactivation due to rifting of the North Atlantic region. 
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-11 

Citation Title Description and Relevance to SSC

Tremblay and 

Lemieux (2001)

Supracrustal Faults of the St. 

Lawrence Rift System Between CapTourmente and Baie-Saint-Paul, 

Quebec

The Cap-Tourmente and St. Lawrence faults are late Proterozoic–early Paleozoic 

normal faults attributed to rifting during the opening of the Iapetus Ocean. The St. 

Lawrence rift system is a NE-trending half graben that links the NW-trending

grabens of the Ottawa-Bonnechere and Saguenay aulacogens. The St. Lawrence 

fault trends N020°–N050° and dips 60°–70° to the southeast. Fault rocks consist 

of fault breccia, cataclastite, foliated gouge, and pseudotachylyte with a minimum 

thickness of 20 m near Sault-au-Cochon. Fault rocks exposed at Cap-Tourmente 

consist of 10–15 m thick zones of protocataclasite, cataclasite, and fault breccia. 

Within the Charlevoix area, the St. Lawrence fault is characterized by a welldeveloped and extensive series of cataclastic rock, gouge, and associated 

pseudotachylyte. The Cap-Tourmente fault trends E-W and dips approximately 

80° to the south. Fault rocks consist mostly of fault breccia more than 10 m thick, 

as well as cataclastic rocks and dark pseudotachylyte veins. The St. Lawrence 

fault is crosscut by the Cap-Tourmente fault at Cap-Tourmente.

West of Cap-Tourmente, the Montmorency Falls fault occupies the same 

structural position as the St. Lawrence fault, suggesting that they formed from en

echelon faults trending parallel to the axis of the St. Lawrence rift. The CapTourmente fault possibly represents a transfer fault, producing an oblique relay 

between two longitudinal normal faults. The St. Lawrence fault crosses the 

Charlevoix impact crater without major trend deflection or fault offsets within or at 

the boundaries of the Devonian impact structure. This observation suggests that 

impact-related faults did not significantly alter the orientation of preexisting 

structures and that reactivation is younger than the impact structure, most 

probably concurrent with the opening of the Atlantic Ocean in the Mesozoic. 
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-12 

Citation Title Description and Relevance to SSC

Tremblay et al. 

(2003)

Supracrustal Faults of the St. 

Lawrence Rift System, Quebec: 

Kinematics and Geometry as 

Revealed by Field Mapping and 

Marine Seismic Reflection Data

Presents strike orientations, dip angles, and pitch angles for faults with evidence 

for frictional sliding in the St. Lawrence rift system. NE-trending longitudinal faults 

show three trends (N025, N040, and N070) and generally dip to the SE, although 

a minor number dip to the NW. Transverse faults show two trends (N290 and 

N310) and dip to the NE or SW, which is consistent with the horst-and-graben 

geometry. Both sets of faults are high-angle faults with dip angles averaging 75°–

80°. The pitch value of fault lineations is greater than 70°, indicating that most 

structures are dip-slip faults. Longitudinal and transverse faults show mutual 

crosscutting relationships, suggesting that they represent conjugate structures 

related to the same tectonic event. 

The St-Laurent fault has experienced at least 800 m of vertical throw at Sault-auCochon. The Cap-Tourmente fault has a minimum vertical fault throw of 700 m. 

The Montmorency fault has an 80 m fault scarp near Quebec City, and 

stratigraphic analysis suggests that fault throw should be less than 150 m, which 

is considerably less than the other faults. Several offshore faults subparallel to 

that fault may have vertical downthrow displacements up to 1 km (0.6 mi.). 

Longitudinal faults likely result from the development of en echelon faults trending 

parallel to the rift axis, and transfer faults represent transfer faults or 

accommodation zones. Variations in fault throw are likely a result of propagation 

of extension along transfer faults. 

The presence of cataclastic rocks, pseudotachylytes, and fault gouge is 

consistent with changes of deformation mechanics during progressive and 

incremental deformation in the upper crust.

High-resolution seismic profiles in the St. Lawrence estuary indicate that the 

Laurentian Channel trough transitions from a half graben to a graben structure 

from SW to NE. 

The authors speculate that reactivation of the St. Lawrence rift system is postOrdovician, younger than the Devonian impact cratering event, and that it 

experienced additional fault throw and shoulder uplift during the Mesozoic 

opening of the North Atlantic. 
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-13 

Citation Title Description and Relevance to SSC

Magnitude Estimates

Bent (1992) A Re-examination of the 1925 

Charlevoix, Québec Earthquake

Analysis of additional waveforms resulted in magnitude estimates of Mw 6.2, Ms

6.2 ± 0.3, and mb 6.5 ± 0.4. Due to insufficient 1-sec period data, mbLg was not 

determined. 

Ebel (1996) The Seventeenth Century Seismicity 

of Northeastern North America

Ebel (1996) assigned a M ≥ 7.0 ± 0.5 to the 1663 Charlevoix earthquake. This 

interpretation is based on accounts of landsliding and liquefaction along the St. 

Lawrence River and several of its tributaries, and on felt effects in Quebec, 

Acadia (Maine), and eastern Massachusetts. Based on this distribution of felt 

effects, the magnitude of the 1663 event is somewhat larger than the 1925 

Charlevoix earthquake.

Ebel (2006b) Thoughts Concerning Earthquake 

Sources in the Northeastern U.S.

Postulated that if the total length of the Charlevoix seismic zone (70 km) produced 

a single rupture, the 1663 event would be M 7.5, and all modern seismicity can be 

thought of as aftershocks of this event.

Ebel (2009) On the Magnitude of the 1663 

Charlevoix, Quebec Earthquake

A rupture length of 70 km (43.5 mi.; the length of the seismic zone) could produce 

a main-shock magnitude of M 7.1–7.5. Interpreted MMI VI reports at Roxbury, 

Massachusetts, with an intensity-attenuation relationship as an MLg 7.5 (M 7.8), 

and with recent ground-motion attenuation relationships as an M 7.5. These lines 

of evidence suggest a magnitude of M 7.5 ± 0.3 for the 1663 Charlevoix event.

Lamontagne et al. 

(2008)

Significant Canadian Earthquakes of 

the Period 1600-2006

Repeated large-magnitude historical earthquakes have occurred in Charlevoix: 

February 5, 1663, M 7; December 6, 1791, M 5.8; October 17, 1860, M 6; 

October 20, 1870, M 6.5; and March 1, 1925, M 6.2.

Recurrence

Doig (1990) 2300 Yr History of Seismicity from 

Silting Events in Lake Tadoussac, 

Charlevoix, Quebec

Inferred a variable recurrence rate for the Charlevoix seismic zone from silt layers 

in lakes due to earthquake-induced landslides. Some silt layers in the section 

were correlated with historic earthquakes from 1638, 1663, 1791, 1870, and 

1925. From 320 BC to AD 800, determined a 120-year recurrence interval, 270 

years between AD 800 and 1500, and 75 years from AD 1500 to the present.
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-14 

Citation Title Description and Relevance to SSC

Filion et al. (1991) A Chronology of Landslide Activity in 

the Valley of Rivière du Gouffre, 

Charlevoix, Quebec

Sampled tree trunks buried in landslide flow materials from four sectors along the 

Gouffre River between Saint-Urban and Baie-Saint-Paul. The age distribution of 

tree trunks indicates that landslides have occurred at 5,670, 3,170, 2,500, and 

1,870 yr BP, with most ages <600 yr BP. Comparison of tree-ring widths 

throughout the study area suggests that trees died during the latent period 

between the 1662 and 1663 growing seasons, possibly due to synchronous 

landslides. The authors interpret these two landslides as having been caused by 

the February 1663 Charlevoix earthquake. These results provide no evidence for 

the 1925 earthquake. The authors emphasize the importance of tree-ring 

techniques to delineate the areal extent of landslides caused by the 1663 

earthquake and to caution against exaggerating the geomorphic consequences of 

earthquakes.

Tuttle and Atkinson 

(2010)

Localization of Large Earthquakes in 

the Charlevoix Seismic Zone, 

Quebec, Canada, During the Past 

10,000 Years

Provides evidence for three Holocene paleoearthquakes in Charlevoix with M ≥ 

6.2, including at least two prehistoric episodes at 5 and 10 ka.

Seismicity—Focal Mechanisms and Fault Geometry

Baird et al. (2009) Stress Channeling and Partitioning of 

Seismicity in the Charlevoix Seismic 

Zone, Quebec, Canada

Seismicity is localized along two elongate bands of seismicity bounded by rift 

faults extending NE of the Charlevoix impact crater. In a 2-D stress model, faults 

are represented as frictional discontinuities, and the impact crater as an elastic 

continuum of reduced modulus. Stress trajectories flow around the weak impact 

crater, concentrating stress along weak faults into the impact crater, resulting in 

seismicity in linear bands. The asymmetric placement of the rift faults through the 

crater results in increased seismicity potential along the rift, north of the crater. 

Observed seismicity, is therefore interpreted as a result of stress concentration 

due to the interaction of the crater (local zone of weakness) and rift faults (largescale weak zone). Small to moderate seismicity occurs within the crater and 

larger earthquakes are localized along the rift faults. 

Three-dimensional modeling would be able to accurately model the bowl shape of 

the crater and may be able to examine why seismicity extends below the crater 

into Grenville basement. Current observations of reverse reactivation of rift faults 

associated with glacial rebound could not be assessed with the 2-D model 

presented in this paper and would require examination with a 3-D model. 
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-15 

Citation Title Description and Relevance to SSC

Bent (1992) A Re-examination of the 1925 

Charlevoix, Québec Earthquake

Analysis of additional waveforms resulted in source parameters of strike 42° ± 7°, 

dip 53° ± 7°, rake 105° ± 10°, depth 10 km (6.2 mi.), seismic moment 3.1 ± 2.5 ×

1025 dyne cm (Mw 6.2), Ms 6.2 ± 0.3, mb 6.5 ± 0.4, source duration 5 sec, and 

stress drop 35 bars. The dip is shallower than would be expected from observed 

surface faults but consistent with recent seismicity. The focal mechanism is 

consistent with horizontal compression in the NW-SE direction, which is 

orthogonal to the regional stress field, indicating an anomalous stress field in 

Charlevoix that may be depth dependent. 

Lamontagne and 

Ranalli (1996)

Thermal and Rheological Constraints 

on the Earthquake Depth Distribution 

in the Charlevoix, Canada, Intraplate 

Seismic Zone

Compares the depth distribution of Charlevoix earthquakes to rheological models 

of the region. The maximum depth of earthquakes can be controlled by either the 

brittle-ductile transition or the velocity-weakening to velocity-strengthening fault 

behavior. The rheological change at the brittle-ductile transition was modeled by 

calculating geotherms assuming a variety of rock compositions in the upper and 

middle crust. The depth distribution of earthquakes in Charlevoix requires 

geotherms very close to the upper limit for felsic rocks and a wet lower crust. The 

temperature-controlled sliding stability transition can occur at 300°C and 450°C 

for quartz or feldspar plasticity. Hydrolytic weakening of feldspars at 350°C occurs 

at 25 km (15.5 mi.) for the upper geotherms. The maximum crustal stress 

difference has an upper limit of about 100–200 MPa, requiring high pore fluid 

pressure or low coefficient of friction in mid- to lower crust. Thrust reactivation of 

steeply dipping faults requires a low coefficient of friction. The authors attribute 

the presence of earthquakes in the Charlevoix region to brittle-ductile transition 

deeper than 25 km (15.5 mi.), corresponding to higher than average geotherms;

onset of ductility for hydrated feldspar at about 350°C; high pore-fluid pressure;

and a low friction coefficient, possibly related to unhealed zones of intense 

fracturing.
Table D-6.1.1 Data Summary 

Charlevoix RLME 

D-16 

Citation Title Description and Relevance to SSC

Lamontagne and 

Ranalli (1997)

Faults and Spatial Clustering of 

Earthquakes near La Malbaie, 

Charlevoix Seismic Zone, Canada

Focal mechanisms for earthquakes larger than M 3 show reverse faulting, 

whereas smaller-magnitude earthquakes indicate both normal and strike-slip 

mechanisms, suggesting that local stress and/or strength conditions control their 

occurrence. However, focal mechanisms for larger events of the Charlevoix 

seismic zone suggest reactivation of paleo-rift faults in response to regional 

stresses. The distribution of spatially clustered events (doublets and triplets) 

within the Charlevoix seismic zone indicates that very few events have occurred 

on the same fractures with similar focal mechanisms, implying that these fault 

zones occur in highly fractured rocks. These observations, indicate that the 

Charlevoix seismic zone is characterized by highly fractured zones responding to 

regional stresses and local perturbations in stress or strength, possibly enhanced 

by pore fluid pressures.

Geodetic and Modeling Studies—Hypotheses for Causes of Intraplate Seismicity

Mazzotti and 

Adams (2005)

Rates and Uncertainties on Seismic 

Moment and Deformation Rates in 

Eastern Canada

Modeled seismic moment rates from earthquake statistics from the Charlevoix 

seismic zone can reach up to 2–10 × 1017 N m yr–1, equivalent to a magnitude Mw

= 7 earthquake every 35–150 years. Relative motion and strain rates derived from 

earthquake statistics may reach up to 1–2 mm yr–1for the Charlevoix seismic 

zone. The lack of deformation suggests that the high strain rate might represent a 

short-term process such as postglacial rebound.

Seismic Source Characterization Models

Adams and 

Halchuk (2003)

Fourth Generation Seismic Hazard 

Maps of Canada: Values for Over 

650 Canadian Localities Intended for 

the 2005 National Building Code of 

Canada

Charlevoix is separated as a zone in the H model and combined with other St. 

Lawrence seismicity in the R model. The authors modeled recurrence rates with a 

beta value of 1.74 ± 0.11 with a maximum magnitude of 7.5. 

Tuttle and Atkinson 

(2010)

Localization of Large Earthquakes in 

the Charlevoix Seismic Zone, 

Quebec, Canada, During the Past 

10,000 Years

The absence of liquefaction features to the south in the Trois-Rivières seismic 

zone of the GSC H model (TRR on Figure 3-3) suggests that large-magnitude 

events in Charlevoix are spatially stationary.
Table D-6.1.2 Data Summary 

Charleston RLME 

D-17 

Citation Title Description and Relevance to SSC

Geologic Structures Interpreted from Geologic, Geomorphic, Geophysical and Seismic-Profile Data

Bartholomew and 

Rich (2007)

The Walls of Colonial Fort Dorchester: A 

Record of Structures Caused by the 

August 31, 1886 Charleston, South 

Carolina, Earthquake and Its Subsequent 

Earthquake History

The Dorchester fault is proposed as a near-vertical, NW-striking, reverseoblique (right-lateral) fault. As proposed, the Dorchester fault is a 

subsurface feature that extends from a depth of about 8 km (5 mi.) below 

the ground surface downward to a depth between 13 and 25 km (8 and 15.5 

mi.). The existence of this proposed fault is not based on direct evidence, 

but rather is inferred based on the analysis of (1) cracks in the walls of 

colonial Fort Dorchester; (2) local and regional stress orientations, including 

borehole breakouts; and (3) fault plane solutions from local microseismicity. 

There is no direct geologic or geomorphic evidence for the Dorchester fault, 

thus the existence of this structure is assessed to be questionable.

Behrendt and Yuan 

(1987)

The Helena Banks Strike-Slip (?) Fault 

Zone in the Charleston, South Carolina, 

Earthquake Area; Results from a Marine, 

High-Resolution, Multichannel, SeismicReflection Survey

Data from 24 marine seismic-reflection profiles totaling ~600 km (373 mi.) 

offshore from Charleston across strands of the Helena Banks fault zone 

show Miocene strata that are warped in a reverse-faulting sense. Helena 

Banks fault is described as 110 km (68.4 mi.) long, ~N66°E-striking, and 

comprising several segments 10–40 km (6.2 to 25 mi.) long. Interpreted as 

compressional reactivation of an extensional Mesozoic basin-bounding 

fault. 

Behrendt et al. 

(1981)

Cenozoic Faulting in the Vicinity of the 

Charleston, South Carolina, 1886 

Earthquake

Data from onshore multichannel seismic-reflection profiles in the 1886 

meizoseismal area show evidence of Cenozoic faulting, including the NEstriking reverse (?) Cooke fault. Data suggest that most recent slip on the 

Cooke fault is Eocene or later. Data from offshore multichannel seismicreflection profiles and single-channel high-resolution data show the Helena 

Banks fault as a 30+ km (18.5+ mi.) long structure with most recent 

movement in post-Miocene or Pliocene time. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-18 

Citation Title Description and Relevance to SSC

Behrendt et al. 

(1983)

Marine Multichannel Seismic-Reflection 

Evidence for Cenozoic Faulting and Deep 

Crustal Structure Near Charleston, South 

Carolina

Seismic-reflection data collected offshore from Charleston show Helena 

Banks fault as NE-striking, west-dipping reverse fault that extends upward 

to about 10 km (6.2 mi.) from the sea bottom. Interpreted as a Mesozoic 

extensional fault reactivated as reverse-oblique fault at least as young as 

Miocene or Pliocene. Also interpreted a subhorizontal detachment at 11.4 ±

1.5 km (7 ± 1 mi.) depth. Suggested Charleston seismicity is primarily 

caused by movement along the detachment and that movement on highangle reverse faults (e.g., the Helena Banks fault and others) may also 

cause earthquakes. 

Chapman et al. 

(2007)

Attenuation in the Atlantic Coastal Plain of 

Virginia and Cenozoic Faulting Imaged in 

the Epicentral Area of the 1886 

Charleston, South Carolina Earthquake, 

Using Data from Seismic Reflection 

Profiles

Reprocessed seismic-reflection lines near Charleston reveal presence of 

―fault C,‖ interpreted as reactivated Mesozoic normal fault (reactivated in 

oblique-reverse sense, up to the east). Fault C is traced upward into 

Eocene-age deposits in line VT-3b, but cannot be traced higher in section

due to poor data resolution in shallow section. Fault C postulated to be the 

fault that ruptured in 1886 Charleston earthquake. Strike, length, and age of 

feature unresolved. See also Chapman and Beale (2008).

Chapman and Beale 

(2008)

Mesozoic and Cenozoic Faulting Imaged 

at the Epicenter of the 1886 Charleston, 

South Carolina, Earthquake

Reprocessed seismic-reflection lines near Charleston reveal presence of 

―fault C,‖ interpreted as reactivated Mesozoic normal fault (reactivated in 

oblique-reverse sense, up to the east). Fault C is traced upward into 

Eocene-age deposits in line VT-3b, but cannot be traced higher in section 

due to poor data resolution in shallow section. Fault C is postulated to be 

the fault that ruptured in 1886 Charleston earthquake. Strike, length, and 

age of feature unresolved. See also Chapman et al. (2007).
Table D-6.1.2 Data Summary 

Charleston RLME 

D-19 

Citation Title Description and Relevance to SSC

Chapman and Beale 

(2009)

Results of Reprocessing Seismic 

Reflection Data near Summerville, SC

Similar to Chapman and Beale (2008), reprocessed seismic-reflection lines 

near Summerville reveal Cenozoic compressional reactivation of a 

Mesozoic extensional basin, suggesting 1886 epicentral area lies within a 

zone of extensively faulted upper crust. These reflection data essentially 

reveal point images of fault at widely scattered locations, roughly coincident 

with the recently proposed Woodstock South, Woodstock North, and 

Sawmill Branch faults, inferred from a combination of earthquake 

hypocenters, focal mechanisms, geologic and geomorphic evidence, and 

intensity reports from 1886 (Dura-Gomez and Talwani, 2009; Talwani and 

Dura-Gomez, 2009). These faults strike NE and form a right-oblique (thrust) 

system. Woodstock North fault is a few km SE of the Cenozoic disturbance 

near Summerville imaged in lines VT4 and VT5, and crosses SC6 near the 

Cenozoic disturbance imaged in CMP 340. Seismicity attributed to Sawmill 

Branch fault is coincident with faults imaged in line VT3.

Chapman and Beale 

(2010)

On the Geologic Structure at the 

Epicenter of the 1886 Charleston, South 

Carolina, Earthquake

Reprocessed seismic-reflection lines near Summerville reveal Cenozoic 

compressional reactivation of a Mesozoic extensional basin, suggesting 

1886 epicentral area lies within zone of extensively faulted upper crust. 

These reflection data essentially reveal point images of fault at widely 

scattered locations, roughly coincident with recently proposed Woodstock 

South, Woodstock North, and Sawmill Branch faults, inferred from a 

combination of earthquake hypocenters, focal mechanisms, geologic and 

geomorphic evidence, and intensity reports from 1886 (Dura-Gomez and 

Talwani, 2009; Talwani and Dura-Gomez, 2009). These faults strike NE and 

form a right-oblique (thrust) system. The Woodstock North fault is a few km 

SE of the Cenozoic disturbance near Summerville imaged in lines VT4 and 

VT5, and crosses SC6 near the Cenozoic disturbance imaged in CMP 340. 

Seismicity attributed to Sawmill Branch fault is coincident with faults imaged 

in line VT3.

Colquhoun et al. 

(1983)

Surface and Subsurface Stratigraphy, 

Structure and Aquifers of the South 

Carolina Coastal Plain

Early mapping of the proposed Charleston and Garner-Edisto faults based 

on subsurface stratigraphy and borehole control. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-20 

Citation Title Description and Relevance to SSC

Crone and Wheeler 

(2000)

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic Features 

in the Central and Eastern United States, 

East of the Rocky Mountain Front

Review of potential Quaternary tectonic features in the CEUS. Includes 

description of and primary reference citations for Charleston area 

liquefaction and paleoliquefaction features, Helena Banks fault, Cape Fear 

arch, and Cooke fault. 

Doar and 

Willoughby (2006)

Revision of the Pleistocene Dorchester 

and Summerville Scarps, the Inland Limits 

of the Penholoway Terrace, Central South 

Carolina

Detailed and updated mapping of geomorphic scarps and terraces in the 

Coastal Plain of central South Carolina are interpreted as resulting from 

Pleistocene sea-level high stands, not tectonic activity. These include the 

Surry, Dorchester, Summerville, Macbeth, Bethera, Suffolk, and Awendaw 

scarps. 

Dura-Gomez and 

Talwani (2008)

A Revised Seismotectonic Framework for 

the Charleston, South Carolina 

Earthquakes

Proposes a slightly revised depiction of faults spatially associated with 

Middleton Place–Summerville seismic zone and the roughly 6 km (3.7 mi.) 

wide stepover zone of the Woodstock fault. In this revised depiction, three 

NW-striking faults accommodate the stepover, the (1) Sawmill Branch; (2) 

Lincolnville; and (3) Charleston faults. This depiction of the Sawmill Branch 

fault is similar to that proposed by Talwani and Katuna (2004). The 

Lincolnville and Charleston faults newly proposed structures (the latter is 

not the same as the Charleston fault described by Lennon (1986) and 

Weems and Lewis (2002)). No figures accompany this abstract. See DuraGomez and Talwani (2009) and Talwani and Dura-Gomez (2009) for 

relevant maps. 

Dura-Gomez and 

Talwani (2009)

Finding Faults in the Charleston Area, 

South Carolina: 1. Seismological Data

Article describes relocated microseismicity (1974–2004) in the Charleston 

area. These data are used to (1) refine mapping of and to characterize the 

proposed Woodstock, Sawmill Branch, and Ashley River faults; and (2) 

identify two proposed new faults, the Lincolnville and Charleston faults. 

Note: this is not the same Charleston fault described by Lennon (1986) and 

Weems and Lewis (2002). Each of these structures is located within or near 

the 1886 meizoseismal area and the Middleton Place–Summerville seismic 

zone. The Woodstock fault is described as a NE-striking, steeply NWdipping oblique (right-lateral) reverse fault. The Woodstock fault in the near 

surface is divided into northern and southern segments by a ~6 km (3.7 mi.) 

wide left (compressional) step. The Sawmill Branch, Lincolnville, and 

Charleston faults are described as NW-striking faults within or near the 

stepover zone. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-21 

Citation Title Description and Relevance to SSC

Gangopadhyay and 

Talwani (2005)

Fault Intersections and Intraplate 

Seismicity in Charleston South Carolina: 

Insights from a 2-D Numerical Model

A simple 2-D numerical model comprising blocks with elastic properties 

representing simplified geology of the Middleton Place–Summerville seismic 

zone is used to explain observed seismicity and interpreted fault motions. 

Model is used to support idea that fault intersections act as stress 

concentrators and that these intersections may be loci of earthquakes.

Hamilton et al. 

(1983)

Land Multichannel Seismic-Reflection 

Evidence for Tectonic Features Near 

Charleston, South Carolina, Studies 

Related to the Charleston, South 

Carolina, Earthquake of 1886—Tectonics 

and Seismicity

Data from onshore seismic-reflection profiles show evidence for three 

postulated faults in the Charleston area: the Cooke, Gants, and Drayton 

faults. The postulated Cooke fault shows ~50 m of vertical displacement 

(SE-side-down) of a Jurassic basalt layer, with displacement decreasing 

upward within Cenozoic sediments. The strike of the Cooke fault is not well 

constrained but estimated at NE. The length of the Cooke fault is not 

defined. The postulated Gants fault shows similar vertical displacement and 

orientation as the Cooke fault and likewise shows displacement decreasing 

upward within Cenozoic sediments. The age of the NE-striking Drayton fault 

is constrained to the Late Cretaceous. 

Hibbard et al. (2006) Lithotectonic Map of the Appalachian 

Orogen, Canada–United States of 

America

Lithotectonic mapping at 1:1,500,000 scale of the Appalachian Mountains in 

the U.S. and Canada, including faults and shear zones. Mapped area does 

not cover the Coastal Plain.

Horton and Dicken 

(2001)

Preliminary Digital Geologic Map of the 

Appalachian Piedmont and Blue Ridge, 

South Carolina Segment

Geologic mapping at 1:500,000 scale of the South Carolina, excluding the 

Coastal Plain. 

Lennon (1986) Identification of a Northwest Trending 

Seismogenic Graben Near Charleston, 

South Carolina

Based on shallow (to 85 m) drilling and gamma logging in the 1886 

meizoseismal area, inferred a NW-trending graben lying between 

Charleston and Kiawah Island, South Carolina. The proposed graben is 

bounded by three postulated faults: the Woodstock, Ashley River, and 

Charleston faults. Note: this is not the same Charleston fault as described 

by Dura-Gomez and Talwani (2009) and Talwani and Dura-Gomez (2009). 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-22 

Citation Title Description and Relevance to SSC

Marple and Miller 

(2006)

Association of the 1886 Charleston, South 

Carolina, Earthquake and Seismicity Near 

Summerville with a 12o Bend in the East 

Coast Fault System and Triple-Fault 

Junctions

Seismic-reflection data, microseismicity, and other geologic and 

geophysical data are used to map faults near Charleston, including the 

newly postulated NW-striking Berkeley fault. These data also are 

interpreted to show a 12° bend in the southern segment of the East Coast 

fault system. Ongoing microseismicity in the Middleton Place–Summerville 

seismic zone and the 1886 Charleston earthquake are interpreted as 

related to: (1) this fault bend; and (2) fault intersections between the East 

Coast fault system and the Ashley River, Charleston, Summerville, and 

Berkeley faults in the Summerville area. Paper includes useful summary of 

data used to constrain faults near Charleston. As part of this summary, 

Marple and Miller (2006) call into question the existence of the Adams Run 

fault of Weems and Lewis (2002). 

Marple and Talwani 

(1990)

Field Investigations of the Woodstock 

Lineament

Abstract describing preliminary geologic field investigations of the 

Woodstock lineament. Results and additional work are described in greater 

detail in subsequent publications (e.g., Marple and Talwani 1993; 2000). 

Marple and Talwani 

(1993)

Evidence for Possible Tectonic Upwarping 

Along the South Carolina Coastal Plain 

from an Examination of River Morphology 

and Elevation Data

Identifies the Zone of River Anomalies as possible geomorphic expression 

of ongoing slip and surface deformation related to the underlying 

Woodstock fault. Zone of River Anomalies defined as N-NE-trending

alignment of subtle topographic highs and morphologic changes in rivers 

(including river bends, incised channels, and convex-up longitudinal 

profiles) in the South Carolina Coastal Plain between the Edisto and Little 

Pee Dee Rivers. Suggests that the 1886 Charleston earthquake may have 

occurred on Woodstock fault. Additional studies are described in Marple 

and Talwani (2000).
Table D-6.1.2 Data Summary 

Charleston RLME 

D-23 

Citation Title Description and Relevance to SSC

Marple and Talwani 

(2000)

Evidence for a Buried Fault System in the 

Coastal Plain of the Carolinas and 

Virginia—Implications for Neotectonics in 

the Southeastern United States

Identifies and describes the postulated East Coast fault system as a N-NEstriking, roughly 600 km (373 mi.) long buried fault in the Coastal Plain of 

the Carolinas and Virginia. This fault system extends from south of 

Charleston, South Carolina, to east of Richmond, Virginia, as series of three 

right-stepping en echelon fault segments. Evidence for the existence of 

these faults segments weakens progressively to the north. Evidence for the 

southern segment is equivocal and includes the Zone of River Anomalies 

(see also Marple and Talwani 1993), linear magnetic anomalies, and 

seismicity and seismic-reflection data in the Middleton Place–Summerville 

area. Suggests the 1886 Charleston earthquake may have occurred on the 

southern segment of the East Coast fault system.

Marple and Talwani 

(2004)

Proposed Shenandoah Fault and East 

Coast-Stafford Fault System and Their 

Implications for Eastern U.S. Tectonics

Identifies postulated NW-striking Shenandoah fault in Virginia that coincides 

with an apparent ~110 km (68 mi.) wide left step separating East Coast fault 

system from Stafford fault. Implication is that the postulated East Coast fault 

system and the Stafford fault form a ~1,100 km (684 mi.) long fault system. 

McCartan et al. 

(1984)

Geologic Map of the Area Between 

Charleston and Orangeburg, South 

Carolina

Geologic mapping at 1:250,000 scale of greater Charleston area. No faults 

mapped. 

Nystrom (1996) Earthquake Hazards Map of the South 

Carolina Coastal Plain

Compilation at 1:400,000 scale showing previously mapped 1886 

liquefaction and paleoliquefaction features, and areas susceptible to 

landsliding and collapse. Map also shows areas of potential liquefaction, 

which are generally confined to an area within roughly 50 km (31 mi.) of the 

coast and farther inland along active rivers and streams. 

Prowell (1983) Index of Faults of Cretaceous and 

Cenozoic Age in the Eastern United

States

Map and brief descriptions of postulated Cretaceous and Cenozoic-age 

faults in eastern U.S.

Seeber and 

Armbruster (1981)

The 1886 Charleston, South Carolina 

Earthquake and the Appalachian 

Detachment

Judging by coseismic and post-seismic strain indicators, back slip over a 

portion of the Appalachian detachment may have caused 1886 Charleston 

earthquake, similar to the great Indian detachment earthquakes of 1905 

(M ~ 8) and 1934 (M ~ 8.3). 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-24 

Citation Title Description and Relevance to SSC

Talwani and DuraGomez (2009)Finding Faults in the Charleston Area, 

South Carolina: 2. Complementary Data

This companion paper to Dura-Gomez and Talwani (2009) includes data 

other than relocated microseismicity used to (1) refine mapping of and to 

characterize the proposed Woodstock, Sawmill Branch, and Ashley River 

faults; and (2) identify two proposed new faults, the Lincolnville and 

Charleston faults. Note: this is not the same Charleston fault described by 

Lennon (1986) and Weems and Lewis (2002). Each of these structures is 

located within or near the 1886 meizoseismal area and the Middleton 

Place–Summerville seismic zone. Woodstock fault is described as a NEstriking, steeply NW-dipping oblique (right-lateral) reverse fault. Woodstock 

fault in the near-surface is divided into northern and southern segments by 

a ~6 km (3.7 mi.) wide left (compressional) step. Sawmill Branch, 

Lincolnville, and Charleston faults are described as NW-striking faults within 

or near the stepover zone.

Talwani and Katuna 

(2004)

Macroseismic Effects of the 1886 

Charleston Earthquake

Field trip guidebook describes four locations near Charleston where surficial 

effects of the 1886 earthquake can be seen. Liquefaction features formed 

during the 1886 earthquake are described at one location near Hollywood. 

The three remaining locations are described as locations of possible 

evidence for primary 1886 surface rupture. However, the cracks in Drayton 

family tomb at Magnolia Gardens, cracks in walls of Colonial Fort 

Dorchester, and apparent clockwise rotation of St. Paul’s Episcopal Church 

in Summerville likely are result of strong ground shaking and not primary 

surface rupture. 

Trenkamp and 

Talwani (n.d.)

GPS Derived Strain and Strain Zonation 

near Charleston, South Carolina

This as-yet-unpublished study presents campaign GPS data from a 20-

station grid near Charleston that suggest average shear strain rate (~10–9to 

10–7radians/yr) that is one to two orders of magnitude higher than the

surrounding region. Measurements were taken in three surveys between 

1994 and 2000, and are combined with National Geodetic Survey data that 

were collected from 1920s to 1990s. Study suffers from admitted monument 

instability, small number of surveys (three), and short period of GPS 

measurements (six years). Strain orientations generally consistent with SH 

max (~N60°E). Largest strains located in the Middleton Place–Summerville 

seismic zone and attributed to local fault intersections.
Table D-6.1.2 Data Summary 

Charleston RLME 

D-25 

Citation Title Description and Relevance to SSC

Weems and Lewis 

(2002)

Structural and Tectonic Setting of the 

Charleston, South Carolina, Region:

Evidence from the Tertiary Stratigraphic 

Record

Using borehole data and structure contour maps on the Coastal Plain 

sedimentary units, Weems and Lewis (2002) map the NW-striking

Charleston and Adams Run faults. Viable alternate (nontectonic) 

explanations exist for these features. Marple and Miller (2006) call into 

question existence of Adams Run fault. 

Weems and 

Obermeier (1990)

The 1886 Charleston Earthquake—An 

Overview of Geological Studies

Article provides review of geological data describing 1886 Charleston 

earthquake. Indicates that there is no known surface or near-surface 

expression of the causative fault. Suggests that the only evidence for 

geologically recent (upper Pleistocene?) tectonic deformation near 

Charleston comes from domal features (including the Bonneau, Mt, Holly, 

and Fort Bull domes) recognized in subsurface Coastal Plain sediments. 

These domes are not associated with any microseismicity. Describes

evidence for three, and possibly four, middle to late Holocene earthquakes 

preserved in geologic record as paleoliquefaction features, as well as 

evidence for events as old as 30 ka. 

Wentworth and 

Mergner-Keefer 

(1983)

Regenerate Faults of the Southeastern 

United States

Proposes that Mesozoic normal faults in the Piedmont and Coastal Plain 

have been reactivated as reverse and reverse-oblique faults. Suggests the 

1886 Charleston earthquake may have occurred on a NE-striking

reactivated Mesozoic normal fault. Also suggests that, based on the 

existence of Mesozoic normal faults throughout much of the Atlantic Coastal 

Plain, earthquakes at least as large as 1886 Charleston may occur 

elsewhere in the domain. 

Wheeler (2005) Known or Suggested Quaternary Tectonic 

Faulting, Central and Eastern United 

States—New and Updated Assessments 

for 2005

Updated review of potential Quaternary tectonic features in the CEUS. 

Includes description of and primary reference citations for the East Coast 

fault system. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-26 

Citation Title Description and Relevance to SSC

Wildermuth and 

Talwani (2001)

A Detailed Gravity Survey of a Pull-Apart 

Basin in Northeast South Carolina

Marple and Talwani (2000) propose the East Coast fault system as a rightlateral reverse oblique fault comprising three segments (south, central, and 

north) configured in a right-stepping en echelon pattern. As such, the right 

stepover separating the southern and central segments should form an area 

of extension. Wildermuth and Talwani (2001) test this hypothesis by 

performing a microgravity survey in the vicinity of the stepover. Their data 

are consistent with presence of a pull-apart basin, but few details are 

provided in this abstract. 

Willoughby and 

Nystrom (2005)

Generalized Geologic Map of South 

Carolina

Generalized geologic mapping at 1:1,000,000 scale of South Carolina, 

including Coastal Plain wave-cut scarps. No faults mapped in Coastal Plain. 

Mapping too simplified to be of use in source characterization. 

Seismicity and 1886 Earthquake Intensity

Bakun and Hopper 

(2004b)

Magnitudes and Locations of the 1811-

1812 New Madrid, Missouri, and the 1886 

Charleston, South Carolina, Earthquakes

Intensity-based study of 1886 Charleston earthquake. Intensity center 

computed to be located offshore, but preferred estimate is at Middleton 

Place–Summerville seismic zone. Magnitude of 1886 Charleston 

earthquake is estimated to be between Mw 6.4 and 7.2 (at 95% confidence 

level), with preferred estimate of Mw 6.9. 

Bakun and McGarr 

(2002)

Differences in Attenuation Among the 

Stable Continental Regions

Systematic differences in the attenuation of large earthquake ground 

motions exist between different stable continental regions (SCRs) 

worldwide. Eastern North America attenuation in seismic waves is less than 

that for other SCRs. As such, some previous studies of 1886 Charleston 

earthquake that used worldwide average SCR attenuation (e.g., Johnston,

1996c) overestimate the magnitude of this earthquake. 

Bollinger (1977) Reinterpretation of the Intensity Data for 

the 1886 Charleston, South Carolina, 

Earthquake

MMI isoseismals for the 1886 Charleston earthquake based primarily on 

original observations in Dutton (1889). Highest intensities (MMI X) at/near 

Charleston.

Bollinger (1983) Speculations on the Nature of Seismicity 

at Charleston, South Carolina

Estimates 1886 earthquake at mb 6.7, with rupture length approximately 25 

km (15.5 mi.), width approximately 12 km (7.5 mi.), average slip 1 m (3.3 

ft.), based on empirical relations. Notes ongoing microseismicity 

concentrated in 1886 meizoseismal area. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-27 

Citation Title Description and Relevance to SSC

Johnston (1996c) Seismic Moment Assessment of 

Earthquakes in Stable Continental 

Regions—III. New Madrid 1811-1812, 

Charleston 1886, and Lisbon 1755

Using isoseismal-area-regression methods, the magnitude of the 1886 

Charleston earthquake is estimated at Mw 7.3 ± 0.26. Bakun and McGarr 

(2002) argue that Johnston (1996c) overestimates the magnitude of the 

1886 Charleston earthquake. 

Madabhushi and 

Talwani (1990)

Composite Fault Plane Solutions of 

Recent Charleston, South Carolina, 

Earthquakes

Reassessment of Middleton Place–Summerville seismic zone seismicity 

suggests two distinct groups of seismicity: (1) composite focal mechanism 

with right-lateral strike-slip motion, small dip-slip component, nodal plane 

oriented N-NE, and hypocentral depths from 3 to 8 km (2 to 5 mi.); and (2) 

composite focal mechanism with NW-oriented thrust dipping SW and 

hypocentral depths from 4 to 10 km (2.5 to 6.2 mi.). Data are interpreted as 

indicating microseismic activity on the postulated intersecting Woodstock 

and Ashley River faults. 

Madabhushi and 

Talwani (1993)

Fault Plane Solutions and Relocations of 

Recent Earthquakes in Middleton Place–

Summerville Seismic Zone Near 

Charleston, South Carolina

Single fault-plane solutions obtained for 35 earthquakes in Middleton 

Place–Summerville seismic zone and grouped into five subsets. Seismicity 

is attributed to reverse faulting on NW-striking, SW-dipping Ashley River 

fault and right-lateral strike-slip on the N-NE-striking vertical Woodstock 

fault. Seismicity is interpreted as concentrated near the intersection of these 

two faults. 

Smith and Talwani 

(1985)

Preliminary Interpretation of a Detailed 

Gravity Survey in the Bowman and 

Charleston, S.C. Seismogenic Zones

Gravity surveys conducted in the vicinity of the Bowman seismic zone 

suggest presence of NW-trending features, as previously interpreted from 

magnetic anomaly data.

South Carolina 

Seismic Network 

(2005) 

List of Earthquakes in Charleston 

Between 1974 and 2002

Tabulation of microseismicity in the local Charleston area, recorded 

between 1974 and 2002. Useful to show local Charleston earthquakes with 

magnitudes smaller than those listed in the CEUS SSC earthquake catalog. 

Talwani (1982) An Internally Consistent Pattern of 

Seismicity Near Charleston, South 

Carolina

Relocated seismicity in the 1886 meizoseismal area suggests (1) rightlateral strike-slip events on NE-striking Woodstock fault, and (2) SW-side-up 

thrust events on NW-striking Ashley River fault. 

Talwani (1999) Fault Geometry and Earthquakes in 

Continental Interiors

Intersecting faults are proposed as the loci of strain accumulation and 

seismicity in the upper crust of continental interiors. Postulated Woodstock 

and Ashley River faults near Charleston are cited as an example of fault 

intersection model. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-28 

Citation Title Description and Relevance to SSC

Tarr and Rhea 

(1983)

Seismicity Near Charleston, South 

Carolina, March 1973 to December 1979

Description of microseismicity defining the Middleton Place–Summerville, 

Bowman, and Adams Run seismic zones based on a temporary seismic 

network installed in 1973 and a permanent network installed in 1974. 

Tarr et al. (1981) Results of Recent South Carolina 

Seismological Studies

Description of microseismicity defining the Middleton Place–Summerville, 

Bowman, and Adams Run seismic zones based on a temporary seismic 

network installed in 1973 and a permanent network installed in 1974. 

Suggests that 1886 earthquake occurred within the Middleton Place–

Summerville seismic zone. Observes that, whereas earthquakes in the 

Piedmont tend to be scattered, those in the Coastal Plain tend to cluster. 

This is interpreted as the result of localized stresses on or near intersecting 

faults or in zones of weakness between crustal blocks. 

Liquefaction and Paleoliquefaction

Ambraseys (1988) Engineering Seismology Presents a magnitude-bound relation for liquefaction.

Amick (1990) Paleoliquefaction Investigations Along the 

Atlantic Seaboard with Emphasis on the 

Prehistoric Earthquake Chronology of 

Coastal South Carolina

Search for paleoliquefaction features along U.S. East Coast at over 1,000 

sites from southern Georgia to New Jersey. Features found only in coastal 

Carolinas. Includes rough maps of areas searched in which no features 

found, as well as sketches and photographs of selected features. Describes

evidence for six Mw 7+ earthquakes near Charleston in the past ~2 kyr.

Return period estimated at roughly 500–600 years. Includes discussion of 

criteria by which seismically induced liquefaction features may be 

distinguished from ―pseudoliquefaction‖ features.

Amick and Gelinas 

(1991)

The Search for Evidence of Large 

Prehistoric Earthquakes Along the Atlantic 

Seaboard

Search for paleoliquefaction features along U.S. East Coast at over 1,000 

sites from southern Georgia to New Jersey. Features found only in coastal 

Carolinas. Return period estimated at 500–600 years. In general, largest 

paleoliquefaction features are at sites near Charleston, suggesting repeated 

large earthquakes near Charleston. Majority of paleoliquefaction features 

can be explained by a source near Charleston, but the possibility of a 

separate (moderate?) source located ~100 km (62 mi.) NE is suggested. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-29 

Citation Title Description and Relevance to SSC

Amick, Gelinas, et 

al. (1990)

Paleoliquefaction Features Along the 

Atlantic Seaboard

Search for paleoliquefaction features along U.S. East Coast at over 1,000 

sites from southern Georgia to New Jersey. Features found only in coastal 

Carolinas. In general, largest paleoliquefaction features are at sites near 

Charleston, suggesting repeated large earthquakes near Charleston. 

Includes rough maps of areas searched in which no features found, as well 

as sketches and photographs of selected features. Describes evidence for 

six Mw 7+ earthquakes near Charleston in the past ~2 kyr. Return period 

estimated at roughly 500–600 years. Includes discussion of criteria by 

which seismically induced liquefaction features may be distinguished from 

―pseudoliquefaction‖ features. 

Amick, Maurath, 

and Gelinas (1990)

Characteristics of Seismically Induced 

Liquefaction Sites and Features Located 

in the Vicinity of the 1886 Charleston, 

South Carolina Earthquake

Describes evidence for six Mw 7+ earthquakes near Charleston in the past 

~2 kyr. Return period estimated at roughly 500–600 years. Includes 

discussion of criteria by which seismically induced liquefaction features may 

be distinguished from ―pseudoliquefaction‖ features. Similar to Amick (1990) 

and Amick, Gelinas, et al. (1990), but with less detail.

Andrus and Heidari 

(2009)

Crone and Wheeler 

(2000)

Mapping Liquefaction Potential of Soil 

Deposits near Charleston, SC

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic Features 

in the Central and Eastern United States, 

East of the Rocky Mountain Front

Both reports review potential Quaternary tectonic features in the CEUS. 

These include description of and primary reference citations for Charleston 

area liquefaction and paleoliquefaction features, Helena Banks fault, Cape 

Fear arch, and Cooke fault. 

Dutton (1889) The Charleston Earthquake of August 31, 

1886

Near-contemporary report of macroseismic effects of 1886 Charleston 

earthquake, including intensity observations, isoseismal maps (Rossi-Forrel 

scale), and distribution of sandblow ―craterlets.‖ Highest intensities and 

greatest number of craterlets found in/near Charleston, decreasing with 

distance up and down coast. Suggests 1886 epicentral location at 

Charleston. 

Gassman et al. 

(2009)

Magnitudes of Charleston, South Carolina 

Earthquakes from In Situ Geotechnical 

Data

Abstract describing geotechnical analyses of paleoliquefaction in 

Charleston area. Based on standard penetration test (SPT), cone 

penetration test (CPT), and shear-wave velocity (VS) data, Gassman et al. 

(2009) suggest a preferred magnitude range of Mw 6.7 to 7.0 for prehistoric, 

historic, and future earthquakes in Charleston seismic zone.
Table D-6.1.2 Data Summary 

Charleston RLME 

D-30 

Citation Title Description and Relevance to SSC

Gelinas et al. (1998) Paleoseismic Studies in the Southeastern 

United States and New England

Search for paleoseismic and paleoliquefaction features along U.S. East 

Coast, focusing on South Carolina and New England. Numerous features 

documented in coastal Carolinas. In general, largest paleoliquefaction 

features are at sites near Charleston, suggesting repeated large 

earthquakes near Charleston. Inland search for paleoliquefaction features 

was performed on 3.2 km (2 mi.) stretch of Big Browns Creek in Union 

County, South Carolina. No features identified. 

Hu et al. (2002a) In-Situ Properties of Soils at 

Paleoliquefaction Sites in the South 

Carolina Coastal Plain

Geotechnical estimates of in situ soil properties (including depth and 

thickness of source layer, normalized shear-wave velocity, percent fines, 

etc.) at Charleston paleoliquefaction sites. Data not useful for characterizing 

Charleston paleoearthquake source, but are used by Hu et al. (2002b).

Hu et al. (2002b) Magnitudes of Prehistoric Earthquakes in 

the South Carolina Coastal Plain from 

Geotechnical Data

Magnitude estimates for Charleston paleoearthquakes based on 

geotechnical estimates of in situ soil properties described in Hu et al. 

(2002a). Magnitude estimates range from Mw 6.8–7.8 for ―large‖ regional 

Charleston events to Mw 5.5–7.0 for ―moderate‖ local events at Georgetown. 

Leon et al.’s (2005) subsequent study, with two of the same three coauthors 

as Hu et al. (2002a, 2002b), presents lower magnitude estimates for 

prehistoric Charleston earthquakes. 

Leon (2003) Effect of Aging of Sediments on 

Paleoliquefaction Evaluation in the South 

Carolina Coastal Plain

Magnitude estimates for Charleston paleoearthquakes based on 

geotechnical assessments accounting for the effects of sediment age. 

Magnitude estimates range from Mw 5.5–7.2 for ―large‖ regional Charleston 

events to Mw 4.3–6.4 for ―moderate‖ local events at Bluffton and 

Georgetown. These estimates are lower than those presented in a previous 

study by Hu et al. (2002b). 

Leon et al. (2005) Effect of Soil Aging on Assessing 

Magnitudes and Accelerations of 

Prehistoric Earthquakes

Magnitude estimates for Charleston paleoearthquakes based on 

geotechnical assessments accounting for effects of sediment age. 

Magnitude estimates range from Mw 5.5–7.2 for ―large‖ regional Charleston 

events to Mw 4.3–6.4 for ―moderate‖ local events at Bluffton and 

Georgetown. These estimates are lower than previous studies, including 

that of Hu et al. (2002b), which had two of the same three coauthors 

(Gassman and Talwani).
Table D-6.1.2 Data Summary 

Charleston RLME 

D-31 

Citation Title Description and Relevance to SSC

Martin and Clough 

(1994)

Seismic Parameters from Liquefaction 

Evidence

Based on geotechnical analyses and critiques of previous estimates, 

preferred magnitude estimate for 1886 earthquake is ―...no larger than 

M = 7.5, possibly as low as M = 7...‖ (p. 1360).

Noller and Forman 

(1998)

Luminescence Geochronology of 

Liquefaction Features Near Georgetown, 

South Carolina

Interprets liquefaction evidence for 1886 earthquake and two or three

paleoliquefaction events at Gapway Ditch site, where Amick, Gelinas, et al. 

(1990); Amick, Maurath, and Gelinas (1990); and Talwani and Schaeffer 

(2001) interpreted one paleoliquefaction event. 

Obermeier (1996b) Using Liquefaction-Induced Features for 

Paleoseismic Analysis

Describes criteria for recognizing earthquake-induced liquefaction features 

in the geologic record, with discussion of Charleston paleoliquefaction data. 

Shows distribution of 1886 liquefaction and paleoliquefaction sites in coastal 

South Carolina and southernmost coastal North Carolina, and rough outline 

of area searched. Large diameters (3+ m) of some prehistoric craters 

suggest that these likely were caused by earthquakes ―...much stronger 

than M 5 to 5.5...‖ (p. 350). Also observes that sandblow craters that formed 

roughly 600 and 1,250 yr BP extend along the coast at least as far as 1886 

features, suggesting that some prehistoric earthquakes likely were at least 

as large as 1886.

Obermeier and 

Pond (1999)

Issues in Using Liquefaction Features for 

Paleoseismic Analysis

Summary paper describing issues regarding the use of paleoliquefaction 

data as evidence of strong ground shaking.

Obermeier et al. 

(1989)

Liquefaction Evidence for Repeated 

Holocene Earthquakes in the Coastal 

Region of South Carolina

Describes distribution of paleoliquefaction features throughout much of 

coastal South Carolina and southernmost North Carolina. Estimates at least 

three prehistoric earthquakes in past 7.2 kyr with mb > ~5.5. Notes that size 

and spatial concentration of both 1886 liquefaction and paleoliquefaction 

features are greatest near Charleston, and decrease with distance up and 

down the coast, despite similarities in liquefaction susceptibility throughout 

region. This indicates repeated large earthquakes located at or near 

Charleston. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-32 

Citation Title Description and Relevance to SSC

Obermeier et al. 

(1990)

Earthquake-Induced Liquefaction 

Features in the Coastal Setting of South 

Carolina and in the Fluvial Setting of the 

New Madrid Seismic Zone

Describes criteria for recognizing earthquake-induced liquefaction features 

in the geologic record, with discussion of Charleston paleoliquefaction data. 

Describes possible origins other than earthquakes for sand-blow craters 

and vented sand volcanoes, including compaction-induced dewatering, 

landslides, artesian springs, and ground disruption by fallen root-wadded 

trees. Estimates spatial extents of 1886 and prehistoric liquefaction fields. 

Estimates at least three prehistoric earthquakes in past 7.2 k.y with mb > 

~5.5. Notes that the abundance and diameters of prehistoric sandblow 

craters are greatest within the 1886 meizoseismal zone for a given age of 

craters, indicating repeated large earthquakes located at or near 

Charleston.

Olson et al. (2005b) Revised Magnitude Bound Relation for 

the Wabash Valley Seismic Zone of the 

Central United States

Presents an updated magnitude-bound relationship for paleoliquefaction in 

the CEUS.

Talwani (2000) The Charleston Earthquake Cycle Radiocarbon dating of paleoliquefaction features in coastal South Carolina 

suggests return period of Mw 7+ earthquakes is approximately 500 years. 

Campaign GPS survey suggests strain rate of 0.04 p rad/year (uncertainty 

unspecified). This is interpreted as consistent with ~2 m slip events every 

500 years at Charleston. 

Talwani and 

Schaeffer (2001)

Recurrence Rates of Large Earthquakes 

in the South Carolina Coastal Plain Based 

on Paleoliquefaction Data

Compilation of paleoliquefaction feature locations and radiocarbon age 

constraints from sites throughout coastal South Carolina and southernmost 

coastal North Carolina. Construction of earthquake chronology based on 

radiocarbon ages with 1-sigma error bounds. Considered scenarios with (1) 

mix of large (Mw ~ 7) regional and moderate (Mw ~ 6) local events; and (2) 

large regional events only. Paleoliquefaction record judged to be complete 

for past ~2 kyr, possibly complete for past ~6 kyr. Preferred estimate of 

500–600 years for recurrence of large (Mw ~ 7) earthquakes. 

Talwani et al. (2008) Studies Related to the Discovery of a 

Prehistoric Sandblow in the Epicentral 

Area of the 1886 Charleston SC 

Earthquake: Trenching and Geotechnical 

Investigations

Description of newly discovered paleoliquefaction feature near Fort 

Dorchester, South Carolina. Feature is undated but, based on burial depth 

and soil formation, estimated to pre-date the 1886 Charleston earthquake. 

Paleoearthquake magnitude estimated at ~6.9 (scale unspecified) based on 

unspecified geotechnical analyses. 
Table D-6.1.2 Data Summary 

Charleston RLME 

D-33 

Citation Title Description and Relevance to SSC

Recent Source Characterizations

Bollinger (1992) Specification of Source Zones, 

Recurrence Rates, Focal Depths, and 

Maximum Magnitudes for Earthquakes 

Affecting the Savannah River Site in 

South Carolina

Seismic source characterization for the Savannah River Site describes input 

parameters for PSHA. Local Zone 1 (LZ1, Charleston) Mmax = mb 6.9. 

Seismogenic thickness estimated at 14 and 25 km (9 and 15.5 mi.), 

respectively, for ―Local Charleston‖ and ―SC Piedmont and Coastal Plain‖ 

seismic sources.. 

Chapman and 

Talwani (2002)

Seismic Hazard Mapping for Bridge and 

Highway Design in South Carolina

Charleston source characteristic earthquakes (Mw 7.0–7.5) modeled as 

combination of one area source (―coastal‖) and two line (―ZRA‖ and ―three

parallel faults‖) sources. Magnitudes (Mw) [and weights]: 7.1 [0.2]; 7.3 [0.6];

and 7.5 [0.2]. Mean return period: 550 years. 

Frankel et al. (1996) National Seismic-Hazard Maps: 

Documentation

Charleston source characteristic earthquakes modeled by one areal source 

zone drawn to encompass (1) a narrow source zone defined by P. Talwani 

(to represent the Woodstock fault and the Zone of River Anomalies); and (2) 

a larger zone drawn by S. Obermeier and R. Weems constrained by the 

areal distribution of paleoliquefaction locations, although the source zone 

does not encompass all the paleoliquefaction sites.

A characteristic rupture model of Mw 7.3 earthquakes is assumed, based on 

the estimated magnitude of the 1886 event (Johnston, 1996). Assumes

recurrence time of 650 years, based on dates of paleoliquefaction events. 

Assumes vertical faults with random strikes distributed throughout the areal 

source zone when calculating the hazard. Each of these fictitious faults is 

centered on a grid cell within the source zone.
Table D-6.1.2 Data Summary 

Charleston RLME 

D-34 

Citation Title Description and Relevance to SSC

Frankel et al. (2002) Documentation for the 2002 Update of the 

National Seismic Hazard Maps

Charleston source characteristic earthquakes (Mw 6.8–7.5) modeled by two 

areal source zones, weighted at 0.50 each: (1) a narrow zone representing 

Woodstock lineament and a portion of Zone of River Anomalies; and (2) the 

same broader zone used in the 1996 model. Assumes a mean recurrence 

time of 550 years for characteristic earthquakes in the Charleston, South 

Carolina, region, as presented in the description of paleoseismic evidence 

by Talwani and Schaeffer (2001). This average recurrence time is derived 

from the recurrence intervals determined from the 1886 event and three

earlier earthquakes of similar size, based on the areal extent of their 

paleoliquefaction effects. For both areal zones, faults are oriented with 

strikes parallel to long axis of narrow areal zone. Fault lengths are 

determined from Wells and Coppersmith (1994). Some of the faults extend 

outside of source zone boundary. Magnitudes (Mw) [and weights] based on 

expert opinion and recent work by Bakun and Hopper (2002): 6.8 [0.2], 7.1 

[0.2], 7.3 [0.45], 7.5 [0.15]. 

Petersen et al. 

(2008)

Documentation for the 2008 Update of the 

United States National Seismic Hazard 

Maps

Charleston source characteristic earthquakes (Mw 6.8–7.5) modeled by two 

areal source zones, weighted 50/50: (1) a geographically narrow zone that 

follows the Woodstock lineament and an area of river anomalies, and (2) a 

broader zone that encompasses many of the known liquefaction features 

resulting from past earthquakes. At the urging of NSHMP Advisory Panel, 

the SE edge of the larger zone has been extended offshore (relative to 

2002 zone) to capture the Helena Banks fault. Assumes a mean recurrence 

time of 550 years for characteristic earthquakes in the Charleston, South 

Carolina, region, as presented in description of paleoseismic evidence by 

Talwani and Schaeffer (2001). Each zone combines a characteristic model 

with same magnitudes and weights as 2002 model. Additionally, a truncated 

Gutenberg-Richter model with mbLg from 5.0 to 7.5 accounts for background 

events in the extended margin, including Charleston zone. The background 

seismicity has random fault strike.

Silva et al. (2003) Ground Motion and Liquefaction 

Simulation of the 1886 Charleston, South 

Carolina, Earthquake

Simulations of an Mw 7.3 ―1886 Charleston-like‖ earthquake. Rupture plane 

of 1886 earthquake modeled as (1) 100 km—or 62 mi.—long, 20 km—or 

12.5 mi.--wide (static stress drop 27 bars) fault; and (2) 50 km—or 31 mi.--

long, 16 km—or 10 mi.—wide (static stress drop 107 bars) fault. Fault 

assumed coincident with the Woodstock fault. 
Table D-6.1.3 Data Summary 

Cheraw Fault RLME

D-35 

Citation Title Description and Relevance to SSC

Fault Geometry

Crone (1997) Fault Number 2330, Cheraw Fault, 

in Quaternary Fault and Fold 

Database of the United States

Cheraw fault was first recognized during regional geologic mapping in late 1960s 

and 1970s (Sharps, 1976). Structurally, fault is located above W-NW-sloping 

basement surface between N-trending Las Animas arch to the east and the Denver 

basin to the NW. Down-to-the-NW sense of motion that occurred during late 

Quaternary faulting events has same vertical sense as cumulative tectonic relief on 

Precambrian crystalline rocks. The Las Animas arch is a prominent, but relatively 

low-relief, 300 km (186.5 mi.) long positive structural element in SE Colorado. Crest 

of the arch is approximately 20–40 km (12.5–25 mi.) east of the fault. Minor uplift 

probably occurred along the arch in late Paleozoic time, but most of present relief is 

Laramide in age.

Fault does not appear to have a long history of recurrent movement. Interpretation of 

structure contours on top of Lower Cretaceous Dakota sandstone shows a similar 

offset (6–8 m [19.7–26.2 ft.] of down-to-the-NW throw) to that of early Quaternary 

alluvial deposits along the fault.

Length: 44 km (89.5 mi.), avg. strike: N44°E; sense of movement: not well known, 

inferred to be down-to-the-NW motion on a normal fault based on the attitude of 

near-surface faults exposed in trench across the fault.

The only detailed paleoseismic study of the fault is that by Crone, Machette, Bradley, 

et al. (1997).

Timing of the latest Pleistocene displacements raises possibility that surface-faulting 

earthquakes have occurred as a temporal cluster. Cumulative vertical offset on the 

Pleistocene erosional surface cut on Cretaceous shale is 3.2–4.1 m (10.5–13.5 ft.), 

which represents the total offset from the three post-latest Quaternary (<25 ka) 

displacements.

Lower Pleistocene Rocky Flats Alluvium, which has an estimated age of about 1.2 

m.y., is only offset about 7–8 m (23–26 ft.) by the fault. Displacement events older 

than about 25 ka probably occurred before about 100 ka, based on estimated time 

needed to incise, widen, and backfill the paleostream channel that is now filled with 

latest Pleistocene deposits.

Temporal clustering of earthquakes, in which relatively short time intervals of activity 

(e.g., 15–20 k.y.) are separated by long intervals of quiescence (e.g., 100 k.y.) are 

suggested. A suggested 8 k.y. average recurrence interval is based solely on 
Table D-6.1.3 Data Summary 

Cheraw Fault RLME

D-36 

Citation Title Description and Relevance to SSC

estimated timing of the latest Pleistocene and Holocene displacement events 

documented in trenching study. During a quiescent phase, surface-faulting 

earthquakes may not occur for hundreds of thousands of years. Best estimate of a 

long-term slip rate is less than or equal to 0.007 mm/yr, based on a cumulative offset 

of about 8 m (26 ft.) on the 1.2 Ma Rocky Flats Alluvium. Latest PleistoceneHolocene slip rates are between 0.14 and 0.18 mm/yr (determined by dividing the 

amount of offset, 3.6 m (11.8 ft.), on oldest faulted deposits by the age of deposits,

20–25 k.y.). 

A. Crone (pers. 

comm., March 3, 

2010)

Crone provided a DEM (originally from Dan Clark of Geoscience Australia) showing 

the Cheraw fault scarp, which may extend farther to the NE than previously thought. 

He noted that possible NE extension of the Cheraw remains unconfirmed, and its 

existence was originally suggested based on analysis of SRTM topographic data by 

Dan Clark (Geoscience Australia). Crone agreed with the TI team’s observations that 

sections of feature are suspiciously parallel and close to cultural features, so SRTM 

data could easily be capturing cultural effects that fortuitously align with a projection 

of the fault. Given the highly uncertain nature of possible NE extension, he agrees

that it should be assigned low weight in a logic tree evaluation.

A. Crone (pers. 

comm., April 21, 

2010)

After reexamination of Crone et al. (1997) and original trench logs and field photos, 

Dr. Crone concluded that neither the two-event nor three-event scenario can be 

ruled out, and that logic tree assessment should reflect this uncertainty. He agreed

with TI team‘s conclusion that ―out of cluster‖ event(s) are mostly unconstrained, and 

he stated that it seems wise to weight shorter-term history more heavily.

In response to a query about age of Rocky Flats Alluvium, Crone stated that ―the 1.2 

Ma number that we used was the conventional thinking at the time we did our report 

15 years ago. Folks have pondered this question for decades, and apparently the 

latest information is that the age of the deposit varies depending on distance from 

the mountain front. In a 2006 paper in Geomorphology, Riihimaki et al. use TCN 

analyses to estimate the age of the Rocky Flats Alluvium between Boulder and 

Golden. They conclude that the Rocky Flats is as young as 400 ka near the 

mountains and as old as 2 Ma farther to the east. This is certainly a much wider age 

range than anyone would have guessed in the past. So, if this conclusion can be 

extrapolated as far east as the Cheraw area, then our age guesstimate could be too 

young.‖ Crone concluded that ―overall, the logic tree you've constructed is 

reasonable and captures the options and uncertainties that are associated with the 

Cheraw fault.‖
Table D-6.1.3 Data Summary 

Cheraw Fault RLME

D-37 

Citation Title Description and Relevance to SSC

Crone et al. (1997) Late Quaternary Surface Faulting 

on the Cheraw Fault, Southeastern 

Colorado

Provides information on a 110 m (361 ft.) long trench excavated across Cheraw fault. 

Evidence for three episodes of surface faulting was revealed and age dates were 

obtained. Ages of the surface-rupturing events were estimated to occur at about 8 k, 

12, and 20–25 ka (one early Holocene and two latest Pleistocene events). 

Interpretation of amounts of vertical offset on Cheraw fault is as follows:

Most recent event: ~0.5–1.1 m (~1.6–3.6 ft.)

Penultimate event: ~1.1–1.6 m (~3.6–5.2 ft.)

Oldest event: ~1.5 m (~5 ft.)

Crone and Wheeler 

(2000)

Data for Quaternary Faults, 

Liquefaction Features, and 

Possible Tectonic Features in the 

Central and Eastern United States, 

East of the Rocky Mountain Front

This fault is classified as Class A. The fault is located about 140 km (87 mi.) east of 

the range front of Rocky Mountains and was originally mapped in 1970s as part of a 

regional mapping program. In 1994, a trench was excavated across the scarp, 

exposing a record of late Quaternary surface ruptures. Sense of motion on fault is 

inferred to be down-to-the-NW on a normal fault. Length of fault is about 45 km (28 

mi.). Average recurrence interval is about 8 kyr, with 4–12 kyr between individual 

displacement events, in the past about 25 kyr. 

Petersen et al. 

(2008)

Documentation for the 2008 

Update of the United States 

National Seismic Hazard Maps

Cheraw fault in eastern Colorado shows evidence of Holocene and earlier faulting, 

based on a study by Crone, Machette, Bradley, et al. (1997). They infer that surfacerupturing earthquakes on fault occurred about 8, 12, and 20–25 ka, which may 

represent an active earthquake phase. In contrast, displacement events older than 

about 25 ka must have occurred prior to 100 ka, thus representing a quiescent 

period of some 75 kyr or more. All parameters for Cheraw fault are retained from 

2002; fault was modeled using slip rate of 0.15 mm/yr, based on data from the last 

two displacement events and maximum magnitude of 7.0 ± 0.2 determined from the 

Wells and Coppersmith (1994) fault length for all slip types relation. A fixed 

recurrence time of 17.400 kyr is used with a truncated Gutenberg-Richter model from 

M 6.5–7.0. This yields mean recurrence time of 5 kyr for earthquakes with minimum 

magnitude of 6.5.
Table D-6.1.4 Data Summary 

Oklahoma Aulacogen RLME

D-38 

Citation Title Description and Relevance to SSC

General for Region

Luza and Lawson 

(1993)

Oklahoma Seismic Network Describes local network funded to investigate seismicity in Oklahoma, in 

particular, seismicity potentially related to Nemaha uplift. Presents 

earthquakes recorded from 1987 through 1992. Discusses association of 

seismicity with the Anadarko basin, Arkoma-Ouachita region, and other areas. 

Loose associations are made between earthquakes and structures, but there 

is no strong argument for activity on any structure. The depth distributions of 

earthquakes are likely not well constrained, but they suggest the seismic 

depth within Oklahoma extends to 15–20 km (9.3–12.4 mi.).

Meers Fault

Burrell (1997) Evaluation of Faulting Characteristics and 

Ground Acceleration Associated with 

Recent Movement Along the Meers Fault, 

Southwestern Oklahoma

Investigated the potential for strong earthquakes along Meers fault based on 

analyses of balanced granite boulders, stream deflections and offsets, and 

excavation of a fault exposure. Concludes that the presently observable scarp 

formed in four events with a return period of approximately 2.6–4.3 kyr, with 

less slip per event then previously suggested, and that magnitudes were 

significantly less than predicted by other researchers.

Cetin (2003) Comment on ―Known and Suggested 

Quaternary Faulting in the Midcontinent 

United States‖ by Russell L. Wheeler and 

Anthony Crone‖

Summarizes evidence for a 30 km (18.6 mi.) extension of Meers fault to the 

NW of extent mapped by Ramelli et al. (1987) in an attempt to refute 

conclusion of Wheeler and Crone (2001) that the Holocene scarp does not 

extend further to NW.

Crone (1994) Fault Number 1031b, Meers Fault, 

Southeastern Section, in Quaternary Fault 

and Fold Database of the United States

Provides summary of published information on the characteristics of 

Quaternary activity on Meers fault.

Crone and 

Wheeler (2000)

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic Features 

in the Central and Eastern United States, 

East of the Rocky Mountain Front

Provides summary of published information on the characteristics of 

Quaternary activity on Meers fault.
Table D-6.1.4 Data Summary 

Oklahoma Aulacogen RLME

D-39 

Citation Title Description and Relevance to SSC

Jones-Cecil (1995) Structural Controls of Holocene 

Reactivation of the Meers Fault, 

Southwestern Oklahoma, from Magnetic 

Studies

Used local magnetic data obtained perpendicular to the Meers fault trace to 

constrain fault structure. Concludes that magnetic data suggests (1) slip is 

occurring on the Paleozoic fault, (2) splays along the SW end of the fault are 

not controlled by Paleozoic structure, and (3) the NW end of the fault appears 

to be a rupture barrier.

Kelson and Swan 

(1990)

Swan et al. (1993)

Paleoseismic History of the Meers Fault, 

Southwestern Oklahoma, and Its 

Implications for Evaluations of Earthquake 

Hazards in the Central and Eastern United 

States

Draft Report: Investigation of the 

Quaternary Structural and Tectonic 

Character of the Meers Fault 

(Southwestern Oklahoma)

These two publications present the results of the same study, but the report of 

Swan et al. (1993) is the most detailed. They present the results of an 

extensive study of Quaternary faulting history of Meers fault based on 

trenching, soil pits, auger samples, geomorphic analysis, and radiocarbon 

dating. They identify two Holocene events on the fault (approximately 1,300–

1,400 yr BP and 2,100–2,900 yr BP) and a quiescence of approximately 200–

500 kyr before the previous events. Swan et al. (1993) also discuss potential 

evidence for activity along the Criner fault and other portions of the Wichita 

frontal fault system.

Luza et al. (1987a)

Luza et al. (1987b)

Crone and Luza 

(1990)

Investigation of the Meers Fault in 

Southwestern Oklahoma 

Investigation of the Meers Fault, 

Southwestern Oklahoma 

Style and Timing of Holocene Surface 

Faulting on the Meers Fault, Southwestern 

Oklahoma

These three publications report the results of the same trenching and 

excavation study of Meers fault. They identify one Holocene surface-rupturing 

event. Their best estimate for the date of the event based on stratigraphic 

relationships and radiocarbon dating is 1,200–1,300 yr BP.

Madole (1986)

Madole (1988)

The Meers Fault: Quaternary Stratigraphy 

and Evidence for Late Holocene Movement

Stratigraphic Evidence of Holocene 

Faulting in the Mid-Continent: The Meers 

Fault, Southwestern Oklahoma

These two publications report the results of the same study. They identify one 

Holocene event on the Meers fault, and constrain the age of the event to 

approximately 1,280 yr BP (C-14 years), based on stratigraphic relations and 

radiocarbon dating of deposits distal (tens to hundreds of meters) from the 

scarp.

Miller et al. (1990) Shallow Seismic Reflection Survey Across 

the Meers Fault, Oklahoma

A high-resolution reflection survey was conducted to investigate shallow 

structure of the fault. Survey elucidated local splay faults off the Meers and 

demonstrated the presence of high-angle to vertical up-to-the-north 

displacement along fault.
Table D-6.1.4 Data Summary 

Oklahoma Aulacogen RLME

D-40 

Citation Title Description and Relevance to SSC

Ramelli and 

Slemmons (1990)

Implications of the Meers Fault on Seismic 

Potential in the Central United States

General discussion of the state of knowledge of Meers fault at time of study, 

including hazard implications. A significant contribution from this study is 

discussion of surface rupture length and the possibility that the easternmost 

extension of the fault may not have the same slip history as the better-studied 

western portion.

Ramelli et al. 

(1987)

Ramelli and 

Slemmons (1986)

The Meers Fault: Tectonic Activity in 

Southwestern Oklahoma

Neotectonic Activity of the Meers Fault

Provides detailed mapping of Meers fault scarp based on low-sun-angle aerial 

photography. Based on this mapping, the Holocene scarp of Meers fault was 

extended further to SE than previously identified. Also documents search for 

other scarps along northern edge of Wichita Uplift. Digitized trace of fault 

used for CEUS SSC Project taken from compilation of USGS Quaternary 

Fault and Fold Database.

Wheeler and 

Crone (2001)

Known and Suggested Quaternary Faulting 

in the Midcontinent United States

Summarizes evidence for Quaternary faulting throughout CEUS. With respect 

to Meers fault, evaluates the suggestion of one researcher that the Holocene 

scarp associated with Meers fault extends 48 km (30 mi.) to NW of scarp 

defined by Ramelli et al. (1987), and concludes that there is no strong 

evidence to support this postulated NW extension of the Holocene scarp.

Wheeler and 

Crone (2003)

Reply to ―Comment on Evaluation of Meers 

Fault, Oklahoma in  ̳Known and Suggested 

Quaternary Faulting in the Midcontinent 

United States‘ by Russell L. Wheeler and 

Anthony Crone‖

Provides further justification for decision not to extend to the NW the 

Holocene Meers fault scarp beyond that mapped by Ramelli et al. (1987), 

refuting claims of Cetin (2003) that scarp extends further.

Oklahoma Aulacogen Source Zone

Axtman (1983) Structural Mechanisms and Oil 

Accumulation Along the Mountain ViewWayne Fault, South-Central Oklahoma, 

Part I

Examines structural and stratigraphic relationships of Mountain View fault and 

discusses the displacement history of fault in relation to structural and tectonic 

history of Oklahoma aulacogen.

Brewer (1982) Study of Southern Oklahoma Aulacogen, 

Using COCORP Deep Seismic-Reflection 

Profiles

Summarizes how COCORP reflection data constrains timing and structural 

style of the Oklahoma aulacogen and Wichita uplift. Provides support for 

interpretation that the aulacogen extends from Hardeman basin (south of 

Wichita uplift) to Anadarko basin (north of Wichita uplift).
Table D-6.1.4 Data Summary 

Oklahoma Aulacogen RLME

D-41 

Citation Title Description and Relevance to SSC

Brewer et al. 

(1981)

Proterozoic Basin in the Southern 

Midcontinent of the United States Revealed 

by COCORP Deep Seismic Reflection 

Profiling

Provides summary of COCORP data from Oklahoma aulacogen showing 

layered ~1.2 Ga deposits south of Wichita uplift. Makes preliminary 

conclusions that these deposits suggest the aulacogen is more expansive or 

older than previously thought. Ideas are refined in later papers by Brewer.

Brewer et al. 

(1983)

COCORP Profiling Across the Southern 

Oklahoma Aulacogen: Overthrusting of the 

Wichita Mountains and Compression Within 

the Anadarko Basin

Uses COCORP reflection data to detail structure and timing of deformation 

related to formation of Oklahoma aulacogen and Wichita uplift. Suggests that 

extent of Oklahoma aulacogen may be more restricted than previously 

considered.

Coffman et al. 

(1986)

An Interpretation of the Crustal Structure of 

the Southern Oklahoma Aulacogen 

Satisfying Gravity Data

Presents cross section of crustal structure across Oklahoma aulacogen based 

on gravity data.

Gilbert (1983b) Timing and Chemistry of Igneous Events 

Associated with the Southern Oklahoma 

Aulacogen

Summarizes timing of Oklahoma aulacogen formation as recorded in the 

record of igneous rocks.

Good et al. (1983) COCORP Deep Seismic Reflection 

Traverse Across the Southern Oklahoma 

Aulacogen

Summarizes initial results of COCORP study of Oklahoma aulacogen. Results 

and conclusions are similar to papers by Brewer and others (in this table). 

Main conclusions are the presence of a Proterozoic basin to the south of the 

Wichita uplift and thrust faults that accommodate overthrusting of the Wichita 

mountains over the Anadarko basin.

Ham et al. (1964) Basement Rocks and Structural Evolution 

of Southern Oklahoma

Provides maps of basement structure and faults of the Amarillo-WichitaArbuckle uplift.

Hanson et al. 

(1997)

Quaternary Deformation Along the Criner 

Fault, Oklahoma: A Case Study for 

Evaluating Tectonic Versus Landslide 

Faulting

Concludes that earlier investigations suggesting Quaternary activity of the 

Criner fault had misinterpreted landslide deposits and that, in fact, there have 

been no Holocene events along the Criner.

Keller and 

Stephenson (2007)

The Southern Oklahoma and DnieperDonets Aulacogens: A Comparative 

Analysis

Summarizes geophysical studies of the Oklahoma aulacogen and provides 

synthesis velocity and gravity models of the aulacogen and surrounding 

basins. Interprets base of the Anadarko basin as having rift-fill deposits.
Table D-6.1.4 Data Summary 

Oklahoma Aulacogen RLME

D-42 

Citation Title Description and Relevance to SSC

Larson et al. 

(1985)

Petrologic, Paleomagnetic, and Structural 

Evidence of a Paleozoic Rift System in 

Oklahoma, New Mexico, Colorado, and 

Utah

Presents petrologic and paleomagnetic data supporting interpretation that 

rifting related to the Oklahoma aulacogen extended into New Mexico, 

Colorado, and Utah.

Liang and 

Langston (2009)

Three-Dimensional Crustal Structure of 

Eastern North America Extracted from 

Ambient Noise

Maps three-dimensional shear-wave velocity throughout the CEUS and 

discusses presence of rifting episodes apparent in the data.

McConnell (1989) Determination of Offset Across the 

Northern Margin of the Wichita Uplift, 

Southwest Oklahoma

Uses well data to constrain structural relationships of Wichita uplift frontal 

thrust system. Derives estimates of direction and amount of slip along frontal 

thrust faults during the Ouachita orogeny.

McConnell and 

Gilbert (1990)

Cambrian Extensional Tectonics and 

Magmatism Within the Southern Oklahoma 

Aulacogen

Uses presence of Cambrian igneous rocks to interpret history of aulacogen 

formation. Uses gravity and magnetic signature of these rocks to define extent 

of the Cambrian aulacogen.

Perry (1989) Tectonic Evolution of the Anadarko Basin 

Region, Oklahoma

Summarizes tectonic history of Anadarko basin on north side of Oklahoma 

aulacogen.

Pratt et al. (1992) Widespread Buried Precambrian Layered 

Sequences in the U.S. Mid-Continent: 

Evidence for Large Proterozoic 

Depositional Basins

Discusses previously published COCORP data for Hardeman basin, south of 

Wichita uplift. Uses correlation with borings to suggest the basin is potentially 

filled with 1.3–1.5 Ga felsic igneous rocks interbedded with sedimentary 

rocks. No real discussion of subsidence history or formation of the aulacogen.

Swan et al. (1993) Draft Report: Investigation of the 

Quaternary Structural and Tectonic 

Character of the Meers Fault 

(Southwestern Oklahoma)

Assessed the potential for Quaternary activity along Wichita frontal fault 

system, with emphasis on Meers and Criner faults. Meers fault is discussed in 

that section of this data summary table. Concludes that only the Meers fault, 

and potentially the Criner fault, has evidence of Quaternary activity.

Texas BEG (1997) Tectonic Map of Texas Provides updated maps of basement structure and faults of the AmarilloWichita-Arbuckle uplift.

Viele and Thomas 

(1989)

Tectonic Synthesis of the Ouachita 

Orogenic Belt

Presents idea that Oklahoma aulacogen is a ―leaky transform‖ and not a failed 

rift arm. Cites the existence of extensive volcanism and plutonism and the 

absence of rift-related sedimentary facies.
Table D-6.1.4 Data Summary 

Oklahoma Aulacogen RLME

D-43 

Citation Title Description and Relevance to SSC

Walker (2006) Structural Analysis of the Criner Hills, 

South-Central Oklahoma

Constructed a detailed subsurface structural model of the Criner fault in the 

region where Quaternary activity had previously been suggested. 

Demonstrates that Criner fault is a relatively small secondary fault branching 

off the major Kirby fault. Based on these structural relationships, concludes 

that Criner had not slipped since the last activity on the Kirby (early

Pennsylvanian).

Williamson (1996) Observations on the Capability of the Criner 

Fault, Southern Oklahoma

Conducted a detailed analysis of previously cited evidence of 

Holocene/Quaternary activity of the Criner fault and determined that there is 

no evidence of Quaternary activity along the fault.

Zhang et al. 

(2009b)

Tomographic Pn Velocity and Anisotropy 

Structure in the Central and Eastern United 

States

Maps Pn (upper mantle) velocity structure throughout the CEUS and 

hypothesizes a potential correlation between edges of high-velocity zones 

and locations of intraplate seismic zones.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-44 

Geologic Structures Interpreted from Geologic, Gravity, Magnetic, and Seismic-Profile Data

Braile et al. (1986) Tectonic Development of the New Madrid Rift 

Complex, Mississippi Embayment, North 

America

Geological and geophysical studies of NMSZ have revealed a buried late 

Precambrian rift beneath the upper Mississippi embayment area. The rift 

has influenced tectonics and geologic history of the area since late 

Precambrian time and is presently associated with contemporary 

earthquake activity of the NMSZ. The rift formed during late Precambrian 

to earliest Cambrian time as a result of continental breakup and has 

been reactivated by compressional or tensional stresses related to plate 

tectonic interactions. Configuration of the buried rift is interpreted from 

gravity, magnetic, seismic-refraction, seismic-reflection, and stratigraphic 

studies. The increased mass of crust in the rift zone, which is reflected by 

regional positive gravity anomalies over the upper Mississippi 

embayment area, has resulted in periodic subsidence and control of 

sedimentation and river drainage in this cratonic region since formation 

of the rift complex. Correlation of the buried rift with contemporary 

earthquake activity suggests that earthquakes result from slippage along 

zones of weakness associated with ancient rift structures. Slippage is 

due to reactivation of the structure by the contemporary, nearly E-W 

regional compressive stress, which is the result of plate motions.

Braile et al. (1997) New Madrid Seismicity, Gravity Anomalies, 

and Interpreted Ancient Rift Structures

Epicentral patterns, correlative geophysical data, and historical seismic 

energy release indicate significance of New Madrid area seismicity, both 

within Reelfoot segment of rift structures and in areas outside of this 

segment, particularly to the north. Deep structure of the crust, including 

thickness variations in the upper crust and the presence of a high-density 

lower-crustal layer, is a controlling factor in New Madrid seismicity.

Clendenin et al. 

(1989)

Reinterpretation of Faulting in Southeast 

Missouri

Mine, field, and borehole core observations are reported for late 

Proterozoic–early Cambrian rift-related faulting in SE Missouri. The 

principal fault set is composed of NW-striking transfer faults. Initial late 

Cambrian reactivations extended faults NW across Midcontinent and 

formed several major lineaments. Transpressive wrench-fault 

reactivations during late Pennsylvanian–Early Permian time uplifted St. 

Francois igneous terrane into a positive flower structure. During 

Cretaceous rifting, the faults acted as transfer faults, and intersections 

with related extension faults localized associated intrusive activity.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-45 

Csontos et al. 

(2008)

Reelfoot Rift and Its Impact on Quaternary 

Deformation in the Central Mississippi River 

Valley

A structure-contour map and 3-D computer model of the top of 

Precambrian crystalline basement define the NE-trending Reelfoot rift, 

which is crosscut by SE-trending basement faults. Reelfoot rift consists 

of two basins separated by intra-rift uplift that are further subdivided into 

eight subbasins bounded by NE- and SE-striking rift faults. The rift is 

bounded to the south by White River fault zone and to the north by 

Reelfoot normal fault. Reelfoot thrust fault is interpreted as an inverted 

basement normal fault.

A structure-contour map of the Pliocene-Pleistocene unconformity (top of 

Eocene base of Mississippi River alluvium) reveals both river erosion and 

tectonic deformation. Deformation of the unconformity appears to be 

controlled by NE- and SE-trending basement faults. NE-trending rift 

faults have undergone Quaternary dextral transpression that has resulted 

in displacement of two major rift blocks (uplift in SE half; subsidence in 

NW half) and formation of the Lake County uplift, Joiner Ridge, and 

southern half of Crowley’s Ridge as compressional stepover zones, 

which appear to have originated above basement fault intersections. 

Lake County uplift has been tectonically active over the past ~2,400 

years. The aseismic Joiner Ridge and southern portion of Crowley’s 

Ridge may reflect earlier uplift, thus indicating Quaternary strain 

migration within Reelfoot rift. 

Dart and Swolfs 

(1998)

Contour Mapping of Relic Structures in the 

Precambrian Basement of the Reelfoot Rift, 

North American Midcontinent

Presents contour map of the basement of the Reelfoot rift constructed 

from drillhole and seismic-reflection data and showing the general 

surface configuration as well as several major and minor structural 

features. Major features are two asymmetric intrarift basins, bounded by 

three structural highs, and the rift margins. The basins are oriented 

normal to NE trend of rift. Two of the highs appear to be ridges of 

undetermined width that extend across the rift; the third high is an 

isolated dome or platform located between the basins. Minor features are 

three linear structures of low relief oriented subparallel to trend of rift. 

Two of these, located within the rift basins, may divide the rift basins into 

paired subbasins. These mapped features may be remnants of initial 

extensional rifting, half graben faulting, and basement subsidence. The 

rift basins are reinterpreted as having formed as opposing half grabens, 

and the structural highs are interpreted as having formed associated 

accommodation zones. Some of these features appear to be reactivated 

seismogenic structures within the modern Midcontinent compressional 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-46 

stress regime.

Hildenbrand (1982) Model of the Southeastern Margin of the 

Mississippi Valley Graben near Memphis, 

Tennessee, from Interpretation of TruckMagnetometer Data

Modeling of data from detailed magnetic-anomaly profiles suggests (1) 

that graben margins represent both structural boundaries and conduits 

for ascending magma and (2) that about 2 km (1.2 mi.) of vertical offset 

associated with normal faulting occurs within an interpreted 5.5 km (3.4 

mi.) wide zone in which magnetic basement has an average dip of 

20°NW into the graben. The high apparent susceptibility of magnetic 

basement associated with this fault zone and with the uplifted block 

suggests either that ascending magma intruded the upblock or that the 

two blocks differed lithologically prior to formation of the graben.

Hildenbrand and 

Hendricks (1995)

Geophysical Setting of the Reelfoot Rift and 

Relations Between Rift Structures and the 

New Madrid Seismic Zone

Provides discussion of several potential field features inferred from 

magnetic and gravity data that may focus earthquake activity in the 

northern Mississippi embayment and surrounding region. Summarizes 

complex tectonic and magmatic history of the rift.

Hildenbrand et al. 

(2001)

Geologic Structures Related to New Madrid 

Earthquakes near Memphis, Tennessee, 

Based on Gravity and Magnetic 

Interpretations

Defines boundaries of regional structures and igneous complexes in the 

region north of Memphis, Tennessee, and south of latitude 36° that may 

localize seismicity. 

Langenheim and 

Hildenbrand (1997)

Commerce Geophysical Lineament—Its 

Source, Geometry, and Relation to the 

Reelfoot Rift and New Madrid Seismic Zone

The Commerce geophysical lineament (CGL) is a NE-trending magnetic 

and gravity feature that extends from central Arkansas to southern Illinois 

over a distance of >400 km (>250 mi.). The CGL is parallel to trend of 

Reelfoot graben, but offset >40 km (25 mi.) to the NW of the western 

margin of rift floor. Modeling indicates that the source of the magnetic 

and gravity anomalies is probably a mafic dike swarm. Age of the source 

of the CGL is not known, but the linearity and trend of the anomalies 

suggest a relationship with Reelfoot rift, which has undergone episodic 

igneous activity. The CGL coincides with several topographic lineaments, 

movement on associated faults at least as young as Quaternary, and 

intrusions of various ages. Several earthquakes (mb > 3) coincide with 

the CGL, but the diversity of associated focal mechanisms and the 

variety of surface structural features along the length of the CGL obscure 

its relation to the release of present-day strain. With the available 

seismicity data, it is difficult to attribute individual earthquakes to a 

specific structural lineament such as the CGL.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-47 

McKeown et al. 

(1990)

Diapiric Origin of the Blytheville and Pascola 

Arches in the Reelfoot Rift, East-Central 

United States: Relation to New Madrid 

Seismicity

Earthquakes in the NMSZ correlate spatially with the Blytheville arch and 

part of the Pascola arch, which are interpreted to be the same structure. 

Both arches were formed by diapirism. Rocks in the arch are more highly 

deformed, and are therefore weaker, than adjacent rocks. Seismicity is 

hypothesized to be localized in these weaker rocks. 

Mooney et al. 

(1983)

Crustal Structure of the Northern Mississippi 

Embayment and a Comparison with Other 

Continental Rift Zones

Information on the deep structure of the northern Mississippi embayment, 

gained through an extensive seismic refraction survey, supports a rifting 

hypothesis. The confirmation and delineation of a 7.3 km/s layer, 

identified in previous studies, implies that lower crust has been altered by 

injection of mantle material. Results indicate that this layer reaches a 

maximum thickness in the north-central embayment and thins gradually 

to the SE and NW, and more rapidly to the SW along axis of graben. The 

apparent doming of 7.3 km/s layer in the north-central embayment 

suggests that rifting may be the result of a triple junction located in the 

Reelfoot basin area.

Nelson and Zhang 

(1991)

A COCORP Deep Reflection Profile Across 

the Buried Reelfoot Rift, South-Central United 

States

Deep reflection profile line reveals features of the late Precambrian 

(?)/early Paleozoic Reelfoot rift. The Blytheville arch, an axial antiformal 

feature, as well as lesser structures indicative of multiple episodes of 

fault reactivation, is evident on profile.

Odum et al. (1995) High-Resolution, Shallow, Seismic Reflection 

Surveys of the Northwest Reelfoot Rift 

Boundary near Marston, Missouri

Presents and discusses interpretation of six high-resolution seismicreflection profiles in the epicentral area of the 1811-1812 earthquakes. 

Three profiles show a master and antithetic fault pair that can be traced 

for 6 km (3.7 mi.). Geomorphic evidence suggests that the structures are 

at least 15 km (9 mi.) long. Trend of the fault pair (N50°–55°N) 

subparallels the magnetically defined Reelfoot rift boundaries and other 

major structures.

Normal and reverse displacement of a Paleozoic surface reflector 

decreases from 30 m (98 ft.) upward toward the surface. There is 

evidence for minor amounts of movement into the Eocene. Lack of 

surface and near-surface deformation may indicate that strike-slip 

movement became prevalent in the late Tertiary.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-48 

Odum et al. (2003) Variable Near-Surface Deformation Along the 

Commerce Segment of the Commerce 

Geophysical Lineament, Southeast Missouri 

to Southern Illinois, USA

Concludes that there is a plausible link between surface and nearsurface tectonic features and the vertical projection of the Commerce 

geophysical lineament (CGL). The CGL is a 5–10 km (3–6 mi.) wide 

zone of basement magnetic and gravity anomalies traceable for more 

than 600 km (373 mi.), extending from Arkansas, through SE Missouri 

and southern Illinois, and into Indiana. Interprets 12 km (7.5 mi.) of highresolution seismic-reflection data, collected at four sites along a 175 km 

(109 mi.) segment of the projection, to show varying amounts of 

deformation involving Tertiary and some Quaternary sediments. Some of 

the locally anomalous geomorphic features in the northern Mississippi 

embayment region (i.e., paleoliquefaction features, anomalous 

directional changes in stream channels, and areas of linear bluff 

escarpments) overlying CGL can be correlated with specific faults and/or 

narrow zones of deformed (faulted and folded) strata that are imaged on 

high-resolution seismic-reflection data. There is an observable change in 

near-surface deformation style and complexity progressing from SW to 

NE along trace of CGL. The seismic-reflection data corroborate mapping 

evidence that suggests that this region has undergone a complex history 

of deformation, some of which is documented to be as young as 

Quaternary, during multiple episodes of reactivation under varying stress 

fields. 

Potter et al. (1995) Structure of the Reelfoot–Rough Creek Rift 

System, Fluorspar Area Fault Complex, and 

Hicks Dome, Southern Illinois and Western 

Kentucky—New Constraints from Regional 

Seismic Reflection Data

Interprets an 83 km (51.5 mi.) segment of seismic-reflection data across 

the northern part of the Reelfoot rift—Fluorspar Area fault complex 

(FAFC)—in SE Illinois and western Kentucky. Notes that NMSZ appears 

bounded on the north and south by Cambrian accommodation zones that 

linked segments with differing rift geometry. A series of grabens and 

horst in the FAFC document a late Paleozoic reactivation of Cambrian 

rift. Beneath two of the FAFC grabens, the bounding faults meet within 

the Knox Group and do not continue to depth. Other normal faults in the 

FAFC clearly offset the top of Precambrian basement.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-49 

Pratt (2009) Insights into the Structure and Long-Term 

Deformation in the New Madrid Region from 

Seismic Reflection Profiles

Summarizes general observations and interprets all available seismicreflection profiles in the New Madrid region (including Vibroseis profiles 

acquired by USGS, industry Vibroseis profiles purchased by USGS, 

COCORP profile across the embayment, and shallow seismic-reflection 

profiles acquired by USGS). The Blytheville arch is the most prominent 

feature that can be associated with the NMSZ. The arch is an antiform in 

Precambrian and early Paleozoic rift strata (as much as 20 km, or 12 mi.,

wide and 200 km, or 124 mi., long) that coincides with the SE arm of 

seismicity. The prominent erosional surface that truncates the top of the 

arch indicates that the arch was largely formed before the erosional 

surface was cut in the Paleozoic. This erosional surface is slightly folded 

(Quaternary or Holocene in age). Prominent faults include one coinciding 

with the Bootheel lineament and one with the SE arm of seismicity; other 

faults are evident over a wider area of the embayment. The arch appears 

to coincide with a major crustal boundary. Data are consistent with a rift 

model in which middle- and lower-crustal reflectivity are associated with 

rifting, and deformation is distributed across rift zone.

Van Arsdale and 

TenBrink (2000)

Late Cretaceous and Cenozoic Geology of 

the New Madrid Seismic Zone

Presents structure-contour maps constructed from well, seismicreflection, and outcrop data of the tops of the Paleozoic section, Upper 

Cretaceous section, Paleocene Midway Group, and Eocene section used 

to illustrate post-Paleozoic structure of the NMSZ region. Maps reveal 

reactivation of the underlying late Precambrian to Cambrian Reelfoot rift 

during Midway Group deposition, but no reactivation during Late 

Cretaceous or Eocene deposition. The maps indicate a subtle, southplunging depression on the tops of the Paleozoic, Upper Cretaceous, 

and Midway Group along axis of northern Mississippi embayment that is 

referred to as a trench. This trench is 50 km (31 mi.) wide, has a 

maximum depth of 100 m (328 ft.), and appears to have formed during 

the Eocene. The trench’s western boundary coincides with Blytheville 

arch/Lake County uplift, and its SE margin underlies Memphis. The SE

margin, like the NW margin, may be fault-controlled.

Van Arsdale et al. 

(2007)

Upland Complex of the Central Mississippi 

River Valley: Its Origin, Denudation, and 

Possible Role in Reactivation of the New 

Madrid Seismic Zone

Summarizes information on the distribution of the Upland Complex 

(Lafayette gravel) in early Pliocene (5.5–4.5 Ma) and what sea level was 

(+100 m, or 328 ft.) at time of deposition. Subsequent sea-level lowering 

to –20 m (–65.5 ft.) at 4 Ma resulted in incision that formed the high-level 

terrace; subsequent denudation of up to 100 m (328 ft.) of sediment may 

have perturbed the local stress field, possibly reactivating the NMSZ.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-50 

Wheeler (1996) Relative Seismic Hazards of Six Iapetan Rifts 

and Grabens in Southeastern North America

Ranks six Iapetan rifts and grabens according to their seismic hazard 

based on seismicity and geologic criteria. Criteria include activity rate 

(seismicity), indirect evidence that their faults extend to the depths at 

which earthquakes typically occur in eastern North America, and 

evidence for Mesozoic extension. From most hazardous to least, the 

rankings are as follows: Reelfoot rift and Ottawa rift (highest); southern 

Oklahoma aulacogen and Saguenay rift (intermediate hazard); and 

Rough Creek and Rome trough (lower relative hazard indistinguishable 

from that of sparsely seismic cratonic interior regions). 

Wheeler et al. 

(1994)

Map Showing Structure of the Mississippi 

Valley Graben in the Vicinity of New Madrid, 

Missouri

Compilation map showing bedrock geology; epicenters; geologic and 

subcrop contacts; structure contours; radon concentrations; selected 

wells; selected faults; and arches, troughs, and faulted boundaries of 

Mississippi Valley graben. 

Williams et al. 

(2009)

Post-Eocene Deformation Observed in 

Seismic Profiles Across the Southwestern 

Blytheville Arch, Crowley’s Ridge, and 

Western Reelfoot Rift Margin, Arkansas

Interpretation of three high-resolution minivibe P-wave reflection profiles 

in NE Arkansas about 70 km (43.5 mi.) NW of Memphis. Profiles are 

higher resolution than previously acquired in this area. Preliminary 

results from Crowley’s Ridge, an anomalous topographic high, are 

consistent with previous COCORP and USGS reflection data and 

strongly suggest that the 50 m (164 ft.) high topography of the ridge is 

caused by post-Eocene tectonic uplift related to near-vertical ridgebounding faults. The Lepanto profile images a monocline in Paleozoic 

and younger reflectors within a seismically active area on eastern margin 

of buried Blytheville arch (maximum uplift on the Paleozoic through 

Eocene reflector sequence is 100 m, or 328 ft.). Above the Eocene and 

possibly into the Quaternary, the sediments thicken east of the 

monocline, suggesting ongoing growth. Along western Reelfoot rift 

margin, a 2 km (1.2 mi.) wide zone of deformation is observed, with 

faulting that displaces Paleozoic and Eocene reflectors about 20–30 m 

(66–98 ft.) in an up-to-the-west sense. Across the 11 km (7 mi.) length of 

the profile (that crosses other small faults), the Paleozoic-Cretaceous 

section gradually rises to the west about 75 m (246 ft.).
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-51 

Zoback et al. 

(1980)

Recurrent Intraplate Tectonism in the New 

Madrid Seismic Zone

Provides information on subsurface structure revealed through a 

program of seismic-reflection profiling. These data show that New Madrid 

seismicity can be linked to specific structural features. Major faults are 

coincident with the main earthquake trends in the area and with structural 

deformation apparently caused by repeated episodes of igneous activity. 

Notes that the zones of intense seismicity in the CEUS are associated 

with ancient rift zones that are favorably oriented for failure relative to the 

current stress field.

Northern Terminus of Reelfoot Rift

Bear et al. (1997) Seismic Interpretation of the Deep Structure 

of the Wabash Valley Fault System

Interpretation of recently compiled seismic-reflection data suggests that 

structures associated with the Wabash Valley fault system may not be 

directly linked to NE-trending structures in New Madrid area. The authors 

note that a graben may exist within the southern Indiana arm (Braile et 

al., 1982), but it is limited in geographic extent and is not structurally 

continuous with the Reelfoot rift–Rough Creek graben.

Heigold and Kolata 

(1993)

Proterozoic Crustal Boundary in the Southern 

Part of the Illinois Basin

Concludes that structures associated with the NMSZ may be distinct 

from structures to the NE (in the Wabash Valley zone), as evidenced by 

the E-SE-trending geophysical anomaly that separates two areas of 

distinctly different crust.

Hildenbrand and 

Hendricks (1995)

Geophysical Setting of the Reelfoot Rift and 

Relations Between Rift Structures and the 

New Madrid Seismic Zone

Inspection of regional magnetic and gravity anomaly maps suggests that 

NW margin does not continue northeastward into southern Indiana. A 

preferred geometry is that both the NW and SE margins bend to the east 

and merge with the Rough Creek graben.

Hildenbrand and 

Ravat (1997)

Geophysical Setting of the Wabash Valley

Fault System

Concludes from high-resolution magnetic data and the lack of regional 

potential-field features extending south from Wabash Valley that the 

Wabash Valley fault system apparently is not structurally connected to 

the faults related to the NMSZ.

Kolata and 

Hildenbrand (1997)

Structural Underpinnings and Neotectonics of 

the Southern Illinois Basin: An Overview

Summarizes geologic and geophysical information that suggests that 

cause of earthquakes in the NMSZ is unrelated to that in the region north 

of Reelfoot rift system.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-52 

Pratt et al. (1989) Major Proterozoic Basement Features of the 

Eastern Midcontinent of North America 

Revealed by Recent COCORP Profiling

Interpretation of deep seismic-reflection data from southern Illinois and 

southern Indiana indicates the absence of a thick section of rift-related 

sedimentary rocks.

Wheeler (1997) Boundary Separating the Seismically Active 

Reelfoot Rift from the Sparsely Seismic 

Rough Creek Graben

Concludes that the structural boundary between the relatively high 

hazard of the Reelfoot rift and low hazard of the Rough Creek graben is 

marked by bends and ends of large faults, a Cambrian transfer zone, and 

the geographic extent of alkaline igneous rocks. 

Seismogenic Faults

Baldwin et al. 

(2002)

Preliminary Paleoseismic and Geophysical 

Investigation of the North Farrenburg 

Lineament: Primary Tectonic Deformation 

Associated with the New Madrid North Fault?

Presents geomorphic, geologic, seismic-reflection, trench, and 

microtextural data that strongly suggest that the North Farrenburg 

lineament, as well as the South Farrenburg lineament, may be the 

surface expression of an underlying tectonic fault that ruptured during

January 23, 1812, earthquake. NE-trending contemporary 

microseismicity beneath Sikeston Ridge and previously inferred New 

Madrid North locations align partly with the lineaments.

Baldwin et al. 

(2005)

Constraints on the Location of the Late 

Quaternary Reelfoot and New Madrid North 

Faults in the New Madrid Seismic Zone, 

Central United States 

Synthesis of existing unpublished and published data with subsurface 

and geomorphic information to clarify locations of Reelfoot and New 

Madrid North faults. The Reelfoot fault is interpreted to trend NW across 

the Kentucky Bend of the Mississippi River as a NW-facing scarp 

coincident with a slough near New Madrid, Missouri, and anomalous 

elevated topography on southern Sikeston Ridge NW of New Madrid. 

Quaternary faulting and folding imaged from seismic-reflection profiles 

coincide with bedrock structural lineaments, a NE-trending band of 

contemporary microseismicity, and a distinct NW-trending post-Tertiary 

change in alluvial thickness. The Reelfoot fault is traced as much as 

several kilometers NW of the Mississippi River, where it either dies out or 

steps N-NE to merge with the New Madrid North fault. The New Madrid 

North fault appears to be expressed geomorphically as left-stepping, en 

echelon NE-trending fractures preserved in Pleistocene glacial outwash 

material comprising Sikeston Ridge. The fractures coincide with 

Quaternary faults and folds, as well as deeper Cretaceous and Paleozoic 

faults and flexures, imaged in geophysical profiles.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-53 

Baldwin et al. 

(2006)

Geological Characterization of the Idalia Hill 

Fault Zone and Its Structural Association with 

the Commerce Geophysical Lineament, 

Idalia, Missouri

Recent geologic and geophysical studies along faults overlying the 

Commerce geophysical lineament (CGL) support the notion that the 

prominent geophysical anomaly may be a source of future largemagnitude earthquakes. Results of geomorphic mapping and acquisition 

of seismic-reflection and ground-penetrating-radar data, together with 

paleoseismic trenching and borehole investigations, provide evidence of 

late Pleistocene to early Holocene deformation on Idalia Hill fault zone.

Seismic-reflection data image a 0.5 km (0.3 mi.) wide zone of NEstriking, near-vertical faults that offset Tertiary and Quaternary reflectors 

and coincide with near-surface deformation. The regional NE strike of the 

fault zone, coupled with the presence of near-vertical faults and complex 

flowerlike structures, and preferential alignment with the contemporary 

central U.S. stress regime, indicate that the fault zone likely 

accommodates right-lateral transpressive deformation.

Stratigraphic and structural relationships in trenches provide evidence for 

at least two late Quaternary faulting events on the Idalia Hill fault zone 

overlying Commerce section of the CGL. The penultimate event occurred 

in the late Pleistocene (prior to 23.6–18.9 ka). The most recent event 

occurred in the late Pleistocene to early Holocene (18.5–7.6 ka). The 

events overlap in age with two prehistoric events interpreted by Vaughn 

(1994) that occurred 23–17 ka and 13.4–9 ka and one event recognized 

by Harrison et al. (1999) that occurred 35–25 ka. The results of this study 

and previous studies provide evidence of late Pleistocene to early 

Holocene deformation along approximately 75 km (46.6 mi.) of the CGL.

Baldwin et al. 

(2008)

Geophysical and Paleoseismic Evaluation of 

the Penitentiary Fault and Its Association with 

the Commerce Geophysical Lineament, 

Tamms, Southern Illinois

Results of study provide evidence for linking observed PleistoceneHolocene deformation with previously mapped faults overlying the CGL. 

The fault is accommodating dextral transpression based on interpretation 

of seismic data, regional focal mechanisms data, geomorphic data (i.e., 

deflected streams), regional topography, and previous studies.

Data suggest that Penitentiary fault is likely a Paleozoic (?) fault that 

developed into a fault-line scarp during pre-Quaternary time and has 

been reactivated in late Quaternary time.

Faults project upsection into the latest Pleistocene Henry Formation 

(older than ~25 kyr) and possibly Holocene Cahokia Formation. Vertical 

offset of reflectors ranges from 2 to 6 m (6.5 to 20 ft.).
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-54 

Champion et al. 

(2001)

Geometry, Numerical Models and Revised 

Slip Rate for the Reelfoot Fault and Trishear 

Fault-Propagation Fold, New Madrid Seismic 

Zone

Analysis of trench excavations, shallow borings, a digital elevation model 

of topography, and bathymetry shows that Reelfoot monocline is a 

forelimb on a fault-propagation fold that has accommodated relatively 

little shortening. Reelfoot fault is a reactivated Paleozoic structure. A late

Holocene fault slip rate of 3.9 0.1 mm/year is based on 9 m (29.5 ft.) of 

structural relief, the 2,290 60 yr BP age of folded sediment, and a 75°

dip for the fault. The fault tip is 1,016 m (3,333 ft.) beneath the surface. 

The thrust is flatter at deeper levels (5–14 km, or 3.1–8.7 mi.) based on 

the location of earthquake hypocenters (~40°SW for northern segment, 

~35°W for central segment, ~45°SW for southern segment).

Chiu et al. (1997) Seismicity of the Southeastern Margin of 

Reelfoot Rift, Central United States

Coincidence of seismicity along SE flank of Reelfoot rift suggests that 

this rift flank is seismically active but at a lower level than main intra-rift 

NMSZ. Style of faulting as inferred from seismicity is complex, the 

dominant pattern being right-lateral strike-slip with reverse movement. 

Authors conclude that seismic data is sufficient to show that SE rift 

margin contains seismically active faults and has the potential of 

producing a major (M ~ 7) earthquake.

Cox, Van Arsdale, 

and Harris (2001)

Identification of Possible Quaternary 

Deformation in the Northeastern Mississippi 

Embayment Using Quantitative Geomorphic 

Analysis of Drainage-Basin Asymmetry

The SE Reelfoot rift margin coincides with a 150 km (93 mi.) long linear 

topographic scarp from near Memphis to the Tennessee-Kentucky line.

S-wave reflection profiles, auger data, and a trench excavation reveal 

late Wisconsinan to early Holocene surface faulting and late Holocene 

liquefaction associated with this fault-line scarp. Variation in sense of 

throw along strike and flower-structure geometry suggest that this is a 

strike-slip fault. Temporal shifts in strain accommodation may give rise to 

short-term seismicity patterns and/or geodetic velocities that do not 

reveal long-term tectonic patterns.

Cox, Van Arsdale,

et al. (2001)

Neotectonics of the Southeastern Reelfoot 

Rift Zone Margin, Central United States, and 

Implications for Regional Strain 

Accommodation

Suggests that the 150 km (93 mi.) long SE Reelfoot rift margin fault 

system may be accommodating significant northeastward transport as a 

right-lateral fault capable of producing earthquakes of M 7. Results of 

paleoseismological investigations show the following: no Holocene 

movement at the Union City site (north of intersection with Reelfoot 

fault); ≥3 m vertical displacement of ~Peoria loess (~20 ka) at the Porter 

Gap site (south of intersection with Reelfoot fault); and approximately

9.68 ka deposits postdate main events, while minor liquefaction 

postdates ~4.3 ka.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-55 

Cox, Van Arsdale, 

and Larsen (2002)

Paleoseismology of the Southeastern Margin 

of the Reelfoot Rift in the Vicinity of Memphis, 

Tennessee

Confirms that SE Reelfoot rift margin is a fault zone with multiple highangle faults and associated folding based on shallow seismic profiles and 

paleoseismological investigations. Documents evidence for 8–15 m 

(26.2–49.2 ft.) of right-lateral offset of a late Wisconsinan paleochannel 

(~20 ka) at a site near Porter Gap, suggesting an average slip rate of 

between 0.85 and 0.37 mm/year. 

Provides evidence for an earthquake ca. 2,500–2,000 yr BP on SE

Reelfoot rift margin that ruptured ≥80 km (50 mi.) from Shelby County 

(15–25 km, or 9.3–15.5 mi., north of Memphis metropolitan area) to 

Porter Gap (just south of intersection with Reelfoot fault).

Cox et al. (2006) Paleoseismology of the Southeastern 

Reelfoot Rift in Western Tennessee and 

Implications for Intraplate Fault Zone 

Evolution

Analysis of shallow S-wave reflection profiles, coring, and trenches show 

that SE Reelfoot rift is a right-lateral system with high-angle faults 

showing both up-to-the-NW and down-to-the-NW separations.

Offset of a Wisconsinan paleochannel at Porter Gap indicates 8–15 m 

(26–49 ft.) of right-lateral strike-slip, suggesting that this rift margin may 

have accommodated much of the regional strain. Age constraints from 

paleoseismic investigations at Shelby County and at the Porter Gap site 

are consistent with an earthquake ca. 2,500–2,000 years ago (most 

recent event) that ruptured ≥80 km (50 mi.).

Late Wisconsinan and Holocene faulting along SE rift margin fault 

system is observed adjacent to the hanging wall of the Reelfoot thrust, 

but only Wisconsinan faulting is noted adjacent to the footwall of the 

thrust. It is hypothesized that the NE segment of the SE rift margin turned 

off in Holocene when the Reelfoot stepover thrust turned on.

Cramer et al. 

(2006)

The Possibility of Northeastward Unilateral 

Rupture for the January 23, 1812 New Madrid 

Earthquake

Suggests that unilateral rupture within New Madrid fault zone led to 

extraordinary strong motions to the NE. This explanation is compatible 

with observations of triggered earthquakes in northern Kentucky and 

liquefaction in the northern New Madrid region and White County, Illinois. 

This rupture hypothesis cannot be unequivocally established due to lack 

of intensity data to the SW with which to show an asymmetric pattern of 

intensities.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-56 

Crone (1992) Structural Relations and Earthquake Hazards 

of the Crittenden County Fault Zone, 

Northeastern Arkansas

Interpretation of about 135 km (84 mi.) of seismic-reflection data provides 

information on the structural relations between the Crittenden County 

fault zone (CCFZ) and subjacent rift-bounding faults along SE margin of 

Reelfoot rift in the NMSZ.

Rift margin is 4–8 km (2.5–5 mi.) wide and coincides with the margin 

defined by magnetic data.

The CCFZ is a NE-trending zone of high-angle (up-to-the-NW throw) 

reverse faulting that extends at least 32 km (20 mi.). The fault zone 

(varying from well-developed reverse faults to 1–3 km [0.6–1.9 mi.] wide 

zone of warped and disrupted reflectors) is structurally linked to the 

subjacent rift-bounding faults. Estimated vertical displacement of 

Cretaceous marker horizon measured across multiple seismic varies 

from 10 to 49 m (32.8 to 160.8 ft.). Evidence for a history of recurrent 

reverse slip that began shortly before deposition of the Upper 

Cretaceous sedimentary rocks and extended into at least the Eocene. 

The reverse slip may be related to bending-moment faulting in a 

localized compressional stress field that developed in response to 

subsidence of the Mississippi embayment. 

The CCFZ may have the potential for generating major earthquakes, or 

conversely; however, the possibility that the CCFZ is a bending-moment 

fault argues against its being an extremely hazardous fault. 

Crone (1998a) Defining the Southwestern End of the 

Blytheville Arch, Northeastern Arkansas: 

Delimiting a Seismic Source Zone in the New 

Madrid Region

Interprets Vibroseis seismic-reflection profiles to document the 

southwesterly extent of the Blytheville arch and the length (134 km, or 83 

mi.) of a fault zone that coincides with the arch.

Crone and Schweig 

(1994)

Fault Number 1023, Reelfoot Scarp and New 

Madrid Seismic Zone

The Crittenden County fault zone (feature 1023-6) in NE Arkansas has 

no known surface expression, but extensive seismic-reflection studies 

suggest that Quaternary sediments are deformed by movement on the 

fault (Luzietti et al., 1992). The fault zone, in part, coincides with SE

margin of Reelfoot rift and has sense of vertical offset that is opposite to 

the net structural relief in the underlying rift (Crone, 1992). Drillhole and 

seismic-reflection data show that the top of Paleozoic rocks is vertically 

offset about 80 m (262 ft.) across the fault zone and that shallower strata 

are offset progressively less (Luzietti et al., 1992; Crone, 1992). 

Deformation associated with the fault zone can be confidently traced 

through Tertiary rocks that fill the Mississippi embayment (Luzietti et al., 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-57 

1992). Very high-resolution reflection data confirm that late Quaternary 

deposits are faulted, and a deformed reflector as shallow as 6 or 7 m (20

or 23 ft.) could be resolved with these data (Williams et al., 1995). Lack 

of nearby stratigraphic control precluded determining if this reflector 

represented Holocene strata. An exploratory trench coincident with the 

very high-resolution reflection profile failed to find any unequivocal 

evidence of Holocene movement on the fault zone (Crone et al., 1995).

Crone et al. (1995) Paleoseismic Studies of the Bootheel 

Lineament, Southeastern Missouri, and the 

Crittenden County Fault Zone, Northeastern 

Arkansas, New Madrid Seismic Zone, Central 

United States

Presents results of trenching studies across structures previously 

identified from interpretation of high-resolution seismic-reflection data: (1) 

Bootheel lineament and (2) Crittenden County fault zone (CCFZ). The 

absence of conclusive evidence of faulting associated with the Bootheel 

lineament was possibly due to young age of sediments (1,000–200 years 

old) and characteristics of surficial deposits that limit the likelihood of 

finding evidence of brittle failure (faulting). Liquefaction features in the 

trench were attributed to the 1811-1812 earthquakes: the site had not 

been subjected to comparable ground motion for over 1,500 years.

Data from the CCFZ trench do not provide absolute evidence for the 

origin of a monoclinal warp in an unconformity exposed in trench 

excavations; relief on the unconformity could relate to a paleochannel, or 

alternatively, could be related to deformation observed in the underlying 

deeper sediments as imaged in seismic data. 

Fischer-Boyd and 

Schumm (1995)

Geomorphic Evidence of Deformation in the 

Northern Part of the New Madrid Seismic 

Zone

Based on geomorphic evaluation, several locations of anomalous surface 

features within the NMSZ are identified. These include (1) anomalies in 

the slope, course, sinuosity, and dimensions of the Mississippi River 

related to the Lake County uplift; (2) anomalous channel behavior near 

Caruthersville, Missouri, and Barfield, Arkansas, suggestive of structural 

control; (3) angular course in the Black River suggestive of fracture 

control; (4) course changes of the Black, St. Francis, and Little rivers that 

may be tectonically controlled; and (5) topography along Crowley’s Ridge 

that suggests it is composed of at least three structural blocks that are 

bounded by NE-trending faults. Some can be directly linked to mapped 

structures in the region, whereas others may result from previously 

unidentified areas of surface deformation.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-58 

Gomberg and Ellis 

(1994)

Topography and Tectonics of the Central 

New Madrid Seismic Zone: Results of 

Numerical Experiments Using a ThreeDimensional Boundary Element Program

Presents results of numerical experiments using seismicity and subtle 

topographic constraints. Surface displacement fields are calculated for 

the NMSZ under both far-field (plate tectonic scale) and locally derived 

driving strains. Results demonstrate that surface displacement fields 

cannot distinguish between either a far-field simple or pure shear strain 

field or one that involves a deep shear zone beneath the upper crustal 

faults. Thus neither geomorphic nor geodetic studies alone are expected 

to reveal the ultimate driving mechanism behind present-day 

deformation. Results of testing hypotheses about strain accommodation 

within the New Madrid contractional stepover by including linking faults, 

two SW-dipping and one vertical, show that only those models with 

stepover faults are able to predict the observed topography. These 

models suggest that the gently dipping central stepover fault is a reverse 

fault and that the steeper fault, extending to the SE of the stepover, acts 

as a normal fault over the long term.

Guccione (2005) Late Pleistocene and Holocene 

Paleoseismology of an Intraplate Seismic 

Zone in a Large Alluvial Valley, the New 

Madrid Seismic Zone, Central USA

Summary paper that provides overview of paleoseismic investigations 

that have identified and characterized seven fault segments within the 

NMSZ. Three of the segments (Reefoot fault, New Madrid North fault, 

and Bootheel fault) have recognized surface deformation. The Reefoot 

fault is a compressive stepover along the strike-slip fault and has up to 

11 m (36 ft.) of surface relief (Guccione et al., 2002). The New Madrid 

North apparently has only strike-slip motion and is recognized by modern 

microseismicity, geomorphic anomalies, and sand cataclasis (Baldwin et 

al., 2002). The Bootheel fault, which is not associated with present 

microseismicity, is associated with extensive liquefaction and offset 

channels (Guccione et al., 2005); it is dominantly strike-slip but also has 

a vertical component of slip. Other recognized surface deformation 

includes relatively low-relief folding at Big Lake/Manila high (Guccione et 

al., 2000) and Lake St. Francis/Marked Tree high (Guccione and Van

Arsdale, 1995), both along the Blytheville arch. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-59 

Harris and Street 

(1997)

Seismic Investigation of Near-Surface 

Geological Structure in the Paducah, 

Kentucky Area

In this study, P- and S-wave seismic-refraction and seismic-reflection 

data were used to characterize shallow geological conditions in Paducah, 

Kentucky, area for use in earthquake hazard studies. Structure maps of a 

shallow unconformity and the Paleozoic bedrock surface show 

subsurface structural variability throughout the area. Ranges of shearwave velocity for the sediments and bedrock, as well as estimates of the 

shear-wave velocity contrast at the unconformity and the bedrock, have 

been determined for the area. These two surfaces are important 

variables in site response analysis to evaluate ground motion 

amplification in the Paducah area. 

Harrison and 

Schultz (1994)

Strike-Slip Faulting at Thebes Gap, Missouri 

and Illinois: Implications for New Madrid 

Tectonism

Documents evidence for Quaternary faulting in trenches in the Benton 

Hills of SE Missouri. Shows 12 earthquakes near the proposed trace of 

the Commerce geophysical lineament (CGL) and suggests that these 

earthquakes can be related to movement along structures associated 

with CGL. 

Harrison and 

Schultz (2002)

Tectonic Framework of the Southwestern 

Margin of the Illinois Basin and Its Influence 

on Neotectonism and Seismicity

Describes neotectonism along the Commerce geophysical lineament 

(CGL). The CGL is interpreted to consist of en echelon faults and 

intrusions in basement related to the Neoproterozoic to early Paleozoic 

Reelfoot rift, but may have older ancestry. Faults in Thebes Gap and 

English Hills overlie the CGL; the faults cut Paleozoic, Mesozoic, and 

Cenozoic deposits and have had a long-lived and episodic tectonic 

history, including Pleistocene and Holocene activity. In the past 25 years, 

several dozen mb 2–4 earthquakes have occurred along or near CGL.

Harrison et al. 

(1999)

An Example of Neotectonism in a Continental 

Interior:Thebes Gap, Midcontinent, United 

States

Documents evidence for four episodes of Quaternary faulting: one in late 

to post-Sangamon, pre- to early Roxana time (~60–50 ka), one in syn- or 

post Roxana, pre-Peoria time (~35–25 ka), and two in Holocene time 

(middle to late Holocene and possibly during 1811-1812 earthquake 

sequence). The overall style of neotectonic deformation is interpreted as 

right-lateral strike-slip faulting. 

Harrison et al. 

(2002)

Geologic Map of the Scott City 7.5-Minute 

Quadrangle, Scott and Cape Girardeau 

Counties, Missouri

Provides description of geomorphology and surficial geology, general 

structural geology, and results of trenching investigations at localities 

within the English Hills. At least two events may have occurred in the 

latest Holocene (just after 2σ calibrated calendar ages of 3747 to 3369 

BC and AD 968 to 639).
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-60 

Johnston and 

Schweig (1996)

The Enigma of the New Madrid Earthquakes 

of 1811-1812

Associated each of three 1811-1812 earthquakes with a specific fault by 

using historical accounts and geologic evidence:

Event D1—BA/CDF or BL

Event J1—East Prairie fault

Event F1—RF

Luzietti et al. (1992) Shallow Deformation Along the Crittenden 

County Fault Zone near the Southeastern 

Boundary of the Reelfoot Rift, Northeast 

Arkansas

Interpretation of nine Mini-Sosie seismic-reflection profiles (sedimentary 

strata imaged to a depth of 800 m [2,625 ft.]). Estimates of structural 

relief across the Crittenden County fault zone (CCFZ) at the Paleocene

level range between 14 and 70 m (46 and 230 ft.). Overlying Middle-toLate Eocene section shows a similar or slightly smaller amount of 

thinning, indicating that much of the movement on the CCFZ dates from 

Middle to Late Eocene. Displacement, flexure, and thinning in the 

geologic section increases as CCFZ converges with Reelfoot rift 

boundary (SW). Reflections from the Quaternary-Eocene unconformity 

show warping, dip, or interruptions in places over the CCFZ that suggest 

at least 16 km (10 mi.) of near-surface deformation; this deformation may 

represent possible Quaternary or Holocene movement.

B. Magnani (pers. 

comm. May 29, 

2009)

[Preliminary map showing locations of 

interpreted faults]

Presents map showing preliminary interpretation of near-surface faults 

observed in high-resolution seismic-reflection profile along the 

Mississippi River from Caruthersville, Missouri, to Helena, Missouri. 

Results of the survey suggest that the eastern Reelfoot margin fault may 

extend south from Memphis along the river (east of the boundary of the 

Reelfoot rift).

Magnani et al. 

(2009)

Long-Term Deformation History in the 

Mississippi Embayment: The Mississippi 

River Seismic Survey

Seismic survey collected a 300 km (186 mi.) long high-resolution 

seismic-reflection profile along the Mississippi River from Helena, 

Arkansas, to Caruthersville, Missouri. Identified three zones of 

deformation and faulting involving quaternary sediments. Two areas lie 

outside the NMSZ, suggesting that the long-term seismic activity in this 

area might extend over a broader region than previously suspected.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-61 

McBride et al. 

(2003)

Variable Post-Paleozoic Deformation 

Detected by Seismic Reflection Profiling 

Across the Northwestern Prong of New 

Madrid Seismic Zone

High-resolution shallow seismic-reflection profiles in the vicinity of the 

Olmstead fault (which is close to and parallel with the straight segment of 

the Ohio River) on trend with the westernmost of two groups of NEaligned prongs of epicenters) show Tertiary reactivations of complex 

Cretaceous deformations (including normal graben faults). A possible 

fault-propagation fold associated with one of these faults appears to 

affect Holocene sediments near the ground surface.

McBride, Nelson, 

and Stephenson 

(2002)

Integrated Geological and Geophysical Study 

of Neogene and Quaternary-Age Deformation 

in the Northern Mississippi Embayment

Presents results of program of shallow drilling, trenching, outcrop 

mapping, and seismic-reflection acquisition in southern Illinois just north 

of NMSZ. Detailed structural cross sections over five NE-trending faults 

that continue from the Fluorspar Area fault complex (FAFC) southward 

into the embayment indicate narrow grabens into which latest 

Cretaceous, Paleocene, and Eocene sediments were dropped and 

protected from erosion. Bounding faults were active during Neogene 

through middle Pleistocene time. 

Definitive faulting of Wisconsinan loess or Holocene alluvium is not 

observed at any site, which would indicate that the faults have been 

inactive for at least 55 ka (basal loess ages) to 128 ka (youngest Illinoian 

age). Seismic profiles indicate that faults in Quaternary sediment 

penetrate Paleozoic bedrock, and thus are tectonic. Faults exhibit vertical 

to steeply dipping normal and occasional reverse displacements that 

outline a variety of structures, including a series of narrow grabens and 

local folding.

Proposes a dynamic structural model that suggests a mechanism by 

which seismicity and active (Holocene) faulting have shifted within the 

central Mississippi Valley (away from the FAFC) over the last several ten 

thousand years.

Mihills and Van 

Arsdale (1999)

Late Wisconsin to Holocene Deformation in 

the New Madrid Seismic Zone

Interprets a structure-contour map of the unconformity between the 

Eocene strata and overlying Quaternary Mississippi River alluvium as 

representing the late-Wisconsinan-to-present strain field of the NMSZ. 

Areas of Holocene uplift include the Lake County uplift, Blytheville arch, 

and Crittenden fault. Areas of Holocene subsidence include Reelfoot 

Lake, historical Lake Obion, the Sunklands of NE Arkansas, and possibly 

areas east and west of the Crittenden County fault. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-62 

Mueller and Pujol 

(2001)

Three-Dimensional Geometry of the Reelfoot 

Blind Thrust: Implications for Moment 

Release and Earthquake Magnitude in the 

New Madrid Seismic Zone

According to seismicity data and structural analysis, the Reelfoot blind 

thrust is a complex fault that changes in geometry along-strike. The 

thrust is bounded to the north by an east-trending strike-slip fault. The 

southern end is defined by seismicity; it is not truncated by a known 

transverse fault. The northern part of the thrust steepens to 75°–80° at 

shallow depths (within upper 4 km, or 2.5 mi.), forming a listric shape. 

The center of the central part of the thrust strikes N-S and dips between 

31° and 35° west; the north and south segments strike between N10 W 

and N22 W, respectively. The SE fault segment is oriented N28 W and 

dips 48°–51° SW. Available data suggest that the thrust flattens to <35°

between about 2 and 4 km (1.2 and 2.5 mi.) depth (possibly at the 

Precambrian basement/Paleozoic cover contact at about 3 km, or 1.9 

mi., depth). 

Mueller et al. 

(1999)

Fault Slip Rates in the Modern New Madrid 

Seismic Zone

Estimates slip rate of 6.1 0.7 mm/year for the past 2,300 100 years,

based on structural and geomorphic analysis of late Holocene sediments 

deformed by fault-related folding above the blind Reelfoot thrust fault. 

Calculates slip rate of 4.8 0.2 mm/year using an alternative method 

based on the structural relief across the scarp and the estimated dip of 

the underlying blind thrust. Geometric relations suggest that right-lateral 

slip rate on the NMSZ is 1.8–2.0 mm/year.

The onset of shortening across the Lake County uplift is estimated to be 

between 9.3 and 16.4 ka, with a preference for the younger age. 

Nelson et al. (1997) Tertiary and Quaternary Tectonic Faulting in 

Southernmost Illinois 

Interprets the Fluorspar Area fault complex (FAFC) as a series of strikeslip pull-apart grabens bounded by N20 E–N40 Estriking normal and 

reverse faults. The faults probably originated as normal faults during an 

episode of crustal rifting of latest Proterozoic to early Cambrian time that 

formed the Reelfoot rift (locally, the Lusk Creek fault zone). Evidence 

exists for episodic reactivation of these faults in post-Pennsylvanian, preCretaceous, and again in late Neogene to Quaternary time. 

Results of shallow drilling, trenching, outcrop mapping, and seismicreflection acquisition in southern Illinois just north of New Madrid zone 

show evidence for Quaternary-age faulting on larger mapped faults in the 

FAFC in southernmost Illinois. NE-trending faults downdrop Mounds 

Gravel of Late Miocene to early Pleistocene age (1 Ma to 11 ka) 

approximately 150 m (490 ft.) in the deepest graben and locally displace 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-63 

Metropolis terrace gravel believed to be Illinoian (~185–128 ka) or older. 

FAFC faults are oriented for reactivation as strike-slip or oblique-slip 

faults in current stress field: apparent extensional component of slip not a 

good match for the nearly E-W maximum horizontal stress direction.

Nelson et al. (1999) Quaternary Grabens in Southernmost Illinois: 

Deformation near an Active Intraplate Seismic 

Zone

Grabens are part of the Fluorspar Area fault complex (FAFC), which has 

been recurrently active throughout Phanerozoic time. The FAFC strikes 

directly toward the NMSZ, and both the NMSZ and FAFC share origin in 

a failed Cambrian rift (Reelfoot rift). Every major fault zone of the FAFC 

in Illinois exhibits Quaternary displacement. The structures appear to be 

strike-slip pull-apart grabens, but magnitude and direction of horizontal 

slip and their relationship to the current stress field are unknown. Upper 

Tertiary strata are vertically displaced more than 100 m (328 ft.); Illinoian 

and older Pleistocene strata 10–30 m (33–98 ft.); and Wisconsinan 

deposits 1 m (3.3 ft.) or less. No Holocene deformation has been 

observed. Average vertical slip rates are estimated at 0.01–0.03 

mm/year, and recurrence intervals for earthquakes of M 6–7 are on the 

order of tens of thousands of years for any given fault.

Odum et al. (1998) Near-Surface Structural Model for 

Deformation Associated with the February 7, 

1812, New Madrid, Missouri, Earthquake

Integrates geomorphic data and documentation of differential surficial 

deformation (supplemented by historical accounts) with interpretation of 

seismic-reflection data to develop a tectonic model of near-surface 

structures in New Madrid area. Model consists of two primary 

components: a N-NW-trending thrust fault (Reelfoot fault) and a series of 

NE-trending strike-slip tear faults. The authors estimate an overall length 

of at least 30 km (18.6 mi.) and a dip of ~31° for the Reelfoot fault.

Odum et al. (2001) High-Resolution Seismic-Reflection Imaging 

of Shallow Deformation Beneath the 

Northeast Margin of the Manila High at Big 

Lake, Arkansas

The authors interpret 7 km (4.3 mi.) of high-resolution seismic-reflection 

data across NE margin of the Manila high to examine its near-surface 

bedrock structure and possible association with underlying structures 

such as the Blytheville arch. The Manila high is an elliptical area 19 km

(11.8 mi.) long (N-S) by 6 km (3.7 mi.) wide (E-W) located W-SW of Big 

Lake, Arkansas, that has less than 3 m (10 ft.) of relief. Sense of 

displacement and character of imaged faults support interpretations for 

either a NW-trending 1.5 km (0.9 mi.) wide block of uplifted strata or a 

series of parallel NE-trending faults that bound horst and graben 

structures. The favored interpretation is that deformation of the Manila 

high resulted from faulting generated by reactivation of right-lateral strikeslip fault motion along this portion of the Blytheville arch.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-64 

Odum et al. (2002) Near-Surface Faulting and Deformation 

Overlying the Commerce Geophysical 

Lineament in Southern Illinois

Seismic-reflection and microgravity data demonstrate post-Devonian 

displacement associated with the Commerce geophysical lineament in 

the Tamms area of southern Illinois. Several faults are imaged to the 

Paleozoic/Quaternary interface, and at one site, deformed Quaternary 

strata may have been faulted 5–10 m (16.4–32.8 ft.).

Odum et al. (2010) Multi-Source, High-Resolution SeismicReflection Imaging of Meeman-Shelby Fault 

and Possible Tectonic Model for a Joiner 

Ridge–Manila High Structure in the Upper 

Mississippi Embayment Region

Reinterpretation of the Meeman-Shelby fault (MSF) based on highresolution seismic-reflection profiles, combined with existing industry 

data and recent structural interpretations. MSF fault trace above the 

Paleozoic surface is constrained to having an up-to-the-west reverse 

displacement along a near-vertical (80°) plane that projects to the 

surface just east of the profiles. Using seismic-reflection data that were 

both reinterpreted and newly acquired, the authors interpret an 

orientation of approximately N13°W for the MSF and provide evidence to 

support an interpretation that the MSF forms the eastern boundary of 

Joiner Ridge tectonic structure. The authors suggest that Joiner Ridge 

and Manila high surfical uplift may collectively be considered as 

segments of a tectonic structure similar to the Reelfoot fault stepover. 

They concur with Csontos et al. (2008) that Joiner Ridge is a right-lateral 

compressional stepover between the Eastern Reelfoot Rift margin and 

the axial fault zone that formed in response to Quaternary N60°E 

maximum horizontal compressive stress field. Scientific knowledge is not 

sufficient to speculate about seismic hazard significance of the 50 km 

(31 mi.) long Joiner Ridge–MSF structure. 

Palmer, Hoffman,

et al. (1997)

Shallow Seismic Reflection Profiles and 

Geological Structure in the Benton Hills, 

Southeast Missouri

Two shallow, high-resolution seismic-reflection surveys (Mini-Sosie 

method) across southern escarpment of the Benton Hills segment of 

Crowley’s Ridge imaged numerous post-Late Cretaceous faults and 

folds. The survey did not resolve reflectors within upper 75–100 m (246–

328 ft.) of two-way travel time (about 60–100 m, or 197–328 ft.), which 

would include all of Tertiary and Quaternary and most of Cretaceous. 

The Paleozoic-Cretaceous unconformity produced an excellent 

reflection, and locally a shallower reflector within the Cretaceous was 

resolved. The English Hill fault zone, striking N30°E–N35°E, imaged in 

one of the seismic lines, has been observed by previous workers to have 

Pleistocene loess faulted against Eocene sands. The Commerce fault 

zone, striking N50°E, overlies a major regional basement geophysical 

lineament and is present on both seismic lines at southern margin of 

escarpment. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-65 

Palmer, 

Shoemaker, et al. 

(1997)

Seismic Evidence of Quaternary Faulting in 

the Benton Hills Area, Southeast Missouri

Seismic profiles show English Hill area to be tectonic in origin. Individual 

faults have near-vertical displacements with maximum offsets on the 

order of 15.2 m (50 ft.). Faults are interpreted as flower structures with 

N-NE-striking, vertically dipping, right-lateral oblique-slip faults. These 

data suggest that previously mapped faults at English Hill are deepseated and tectonic in origin.

Parrish and Van 

Arsdale (2004)

Faulting Along the Southeastern Margin of 

the Reelfoot Rift in Northwestern Tennessee 

Revealed in Deep Seismic-Reflection Profiles

Deep seismic-reflection profiles in NW Tennessee reveal structure of SE

margin of Reelfoot rift. Rift margin consists of at least two major down-tothe-west late Precambrian to Cambrian normal faults. Dominantly 

reverse faulting, folding, and positive flower structures in the shallow 

section indicate Eocene and younger transpression. Numerous faults 

displace the youngest reflectors, and therefore the age of most recent 

faulting is not known. SE rift margin is subject to right-lateral movement 

and transpression within current stress field. 

Pujol et al. (1997) Refinement of Thrust Faulting Models for the 

Central New Madrid Seismic Zone

Seismicity cross sections define the downdip geometry of the Reelfoot 

thrust.

Purser and Van 

Arsdale (1998)

Structure of the Lake County Uplift: New 

Madrid Seismic Zone 

Lake County uplift, which includes the Tiptonville dome and Ridgely 

Ridge, is interpreted to be a consequence of deformation in the hanging 

wall above the NW-striking, SW-dipping Reelfoot reverse fault. The 

Reelfoot fault dips 73° from the surface to the top of the Precambrian at a 

depth of approximately 4 km (2.5 mi.). From 4 to 12 km (2.5 to 7.5 mi.) 

depth, the fault dips 32° and is seismically active. Based on a fault-bend 

fold model, the Reelfoot fault becomes horizontal and aseismic at the top 

of the quartz brittle-ductile transition zone, at approximately 12 km (7.5 

mi.) depth. Western margin of the Tiptonville dome–Ridgely Ridge and 

western margin of the Lake County uplift are bounded by east-dipping 

kink bands (backthrusts). The Reelfoot fault, which is postulated to be 

the source of the February 7, 1812, M 8 earthquake, has less surface 

area than is necessary for an M 8 earthquake. A possible solution to this 

discrepancy between magnitude and fault plane area is that the 

associated backthrusts are seismogenic.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-66 

Russ (1979) Late Holocene Faulting and Earthquake 

Recurrence in the Reelfoot Lake Area, 

Northwestern Tennessee

Discusses results of trenching investigations across Reelfoot scarp in 

NW Tennessee. In excess of 3 m (10 ft.) of vertical displacement 

believed to be of deep-seated origin occurs across a 0.5 m wide zone of 

east-dipping normal faults near scarp base. Stratigraphic and 

geomorphic relationships suggest that little (<0.5 m) or no near-surface 

fault movement occurred across the zone during 1811-1812 earthquake 

sequence. Faults, folds, and sand dikes were identified in the trench. 

Crosscutting geologic features and local geomorphic history suggest that 

at least two periods of faulting predate sediments deposited before AD 

1800. A recurrence interval of approximately 600 years or less is 

suggested for large earthquakes in the New Madrid area.

Russ (1982) Style and Significance of Surface 

Deformation in the Vicinity of New Madrid, 

Missouri

Lake County uplift is an elongate, composite Quaternary structure 

associated with faults and modern seismicity. It is subdivided into 

Tiptonville dome, Ridgely Ridge, and the south end of Sikeston Ridge.

The Tiptonville dome is an asymmetrical monocline; the steep eastern 

flank is bounded by Reelfoot scarp, a complex monoclinal fold that has a 

zone of normal faults (displacement about 3 m, or 10 ft.) at its base. The 

zone of faults overlies, and is probably continuous, with Reelfoot fault, a 

high-angle dip-slip fault that offsets Paleozoic, Mesozoic, and Tertiary 

rocks. Surface uplift accounts for about 1/5 of the displacement. Most of 

Tiptonville dome formed between 200 and 2,000 years ago.

Ridgely Ridge is a NE-trending symmetrical buldge underlain by a 

similarly oriented zone of faults. Much of the ridge appears older than 

Tiptonville dome, but younger than 6,000 yr BP. 

The southern end of Sikeston Ridge and adjoining areas has undergone 

broad shallow warping. Deformation probably occurred in late 

Wisconsinan or early Holocene time.

The New Madrid region has been shaken by at least three earthquakes 

of mb ≥ 6.2 in the past 2,000 years.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-67 

SAIC (2002) Seismic Investigation Report for Siting a 

Potential On-Site CERCLA Waste Disposal 

Facility at the Paducah Gaseous Diffusion 

Plant, Paducah, Kentucky

Conclusions from this study are as follows:

Field observations made along Ohio River in the vicinity of the 

Paducah Gaseous Diffusion Plant (PGDP) found no large liquefaction 

features. 

The absence of large paleoliquefaction features within 24 km (15 mi.) 

of PGDP suggests that local strong ground motion has not occurred 

within the past few thousand years

The literature does report some small liquefaction features located 

along the banks of the Ohio River, about 13 km (8 mi.) NE of PGDP, 

and along the Post Creek Cutoff, about 19 km (12 mi.) NW of PGDP.

The site-specific fault study identified a series of faults beneath Site 

3A. For most of the faults beneath Site 3A, relative movement along 

main fault plane is normal, with the downthrown side to the east. 

These normal faults, along with their associated splays, either form a 

series of narrow horst and graben features or divide local sediments 

into a series of rotated blocks. Several of the faults extend through 

Porters Creek Clay and into materials underlying the surficial loess of 

latest Pleistocene age (radiocarbon dated at 13,500–15,600 yr BP). 

Three of these faults extend to within 6 m (20 ft.) of ground surface. 

This study did not find Holocene displacement of faults at Site 3A. 

At the Barnes Creek site located 18 km (11 mi.) NE of PGDP, this study 

found the following:

The relative timing of observed deformations in the geologic 

structures varies. 

Radiocarbon ages confirm that repeated deformation has occurred 

along some of the observed faults. Deformation began prior to 

deposition of the lower Metropolis (late Pleistocene), continued during 

deposition of the upper Metropolis (5,000–7,000 years old) and most 

recently occurred in the middle Holocene, after deposition of the 

upper Metropolis (within the last 5,000 years). Therefore, faults 

observed at Barnes Creek site did extend into Holocene-age 

deposits. 

The maximum displacement observed in a single event is 

approximately 0.3 m (1 ft.) in the lower Metropolis. 

Investigation of the terrace graben area concluded that observed

stratigraphy is consistent with a combination of two models: (1) a 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-68 

graben with up to 15 m (50 ft.) of displacement within the past 12,000 

years, and (2) an erosional feature with up to 15 m (50 ft.) of infilling 

within the past 12,000 years. Radiocarbon ages in the terrace graben 

area at the Barnes Creek site indicate that deep fine-grained 

sediments beneath the Metropolis are approximately 11,000 years 

old, suggesting that overlying Metropolis dates from late Pleistocene 

or early Holocene.

Schumm and Spitz 

(1996)

Geological Influences on the Lower 

Mississippi River and Its Alluvial Valley:

Identifies different reaches of the Mississippi River based on studies of 

photographs, maps, and channel morphology. The river is not 

monotonous in appearance, and therefore, it is not completely controlled 

by hydrology and hydraulics. Results of the study suggest that the 

Mississippi River has reacted to uplift, faults, clay plugs, outcrops of 

Tertiary clay, and Pleistocene gravel in its bed and tributaries. 

Schweig and Ellis 

(1992)

Distributed Faulting Along the Bootheel 

Lineament—Smoothing Over the Rough 

Spots in the New Madrid Seismic Zone

Shallow seismic-reflection work in the area of the Bootheel lineament 

shows that the lineament is underlain by a complex zone of deformation 

consisting of multiple flower structures and fractured rock that show up to 

25 m (82 ft.) of vertical relief. Flower structures and lineament occur over 

a zone at least 5 km (3 mi.) wide. Their discontinuous nature strongly 

resemble physical models in which flower structures form in less rigid 

material in response to low finite displacement across a discrete strikeslip shear zone in a rigid basement. The Bootheel lineament links two 

well-established, seismically active strike-slip zones in the New Madrid 

region and may be acting to smooth the trace of the NMSZ as 

displacement increases.

Schweig and Ellis 

(1994) 

Reconciling Short Recurrence Intervals with 

Minor Deformation in the New Madrid Seismic 

Zone

Comparison of present-day strain rates to long-term geologic offsets 

suggests that the NMSZ is a young feature, possibly as young as several 

tens of thousands of years and no older than a few million years.

Schweig and 

Marple (1991)

A Possible Coseismic Fault of the Great New 

Madrid Earthquakes

Identifies the Bootheel lineament from a remote sensing examination of 

the NMSZ. The lineament may be the surface expression of one of the 

coseismic faults of the 1811-1812 New Madrid earthquakes. It extends 

for about 135 km (84 mi.) in a N-NE direction. Morphology suggests that 

it is a strike-slip fault. The lineament does not coincide with any of the 

major arms of seismicity. A possible inference is that the arms of 

seismicity do not precisely reflect the faults that ruptured in 1811-1812.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-69 

Schweig and Van 

Arsdale (1996)

Neotectonics of the Upper Mississippi 

Embayment

Summarizes geologic and geophysical evidence of neotectonic activity, 

including faulting in Benton Hills and Thebes Gap, paleoliquefaction in 

Western Lowlands, subsurface faulting beneath and tilting of Crowley’s 

Ridge, subsurface faulting along the CCFZ, and numerous indicators of 

historical and prehistoric large earthquakes in NMSZ.

Schweig et al. 

(1992)

Shallow Seismic Reflection Survey of the 

Bootheel Lineament Area, Southeastern 

Missouri 

The pattern and character of geomorphic features associated with the 

Bootheel lineament traces are very similar in geometry to a right-lateral 

strike-slip fault. Seismic-reflection profiles are interpreted to show a 

complex zone of deformation consisting of multiple flower structures and 

fractured rock, with deformation at least as young as the base of the 

Quaternary.

Sexton and Jones 

(1986)

Evidence for Recurrent Faulting in the New 

Madrid Seismic Zone from Mini-Sosie HighResolution Reflection Data

Interpretation and integration of three seismic-reflection data sets 

provides evidence for recurrent movement along the Reelfoot fault, the 

major reverse fault associated with the Reelfoot scarp. Estimated 

displacements vary from 61 m (200 ft.) for late Paleozoic rocks to 15 m 

(50 ft.) for Late Eocene sedimentary units. A graben structure is 

interpreted to be caused by tensional stresses resulting from uplift and 

folding of the sediments. The location of the graben coincides with 

normal faults in Holocene sediments observed in trenches. These 

features are interpreted to be related and caused by reactivation of the 

Reelfoot fault.

Spitz and Schumm 

(1997)

Tectonic Geomorphology of the Mississippi 

Valley Between Osceola, Arkansas, and 

Friars Point, Mississippi

A geomorphic study of the Mississippi River and its alluvial valley 

identified anomalous surface features indicative of relatively recent 

deformation that can be linked to the following known geological 

structures: Big Creek fault zone, White River fault zone, BolivarMansfield tectonic zone, Blytheville arch, Crittenden County fault zone, 

and Reelfoot Rift margins. Faults and plutons appear to affect drainage 

networks, and the morphology of Crowleys Ridge suggests significant 

fault control. The authors conclude that (1) many anomalies probably 

reflect a fractured sub-alluvial surface, and (2) although movement along 

these fractures will most likely occur in seismically active areas, the 

probability of movement elsewhere is high.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-70 

Stephenson et al. 

(1995)

Characterization of the Cottonwood Grove 

and Ridgely Faults near Reelfoot Lake, 

Tennessee, from High-Resolution Seismic 

Reflection Data

High-resolution seismic-reflection data delineate Cottonwood Grove and 

Ridgely faults, as well as a new, potentially major fault with 

approximately 40 m (131 ft.) of apparent vertical displacement east of 

Ridgely fault. The new fault trends NW—opposite in trend direction to the 

Cottonwood Grove and Ridgely faults—and dips vertically.

The NE-trending Cottonwood Grove fault has as much as 30 m (98.5 ft.)

of apparent vertical displacement of all imaged strata, from the 

Cretaceous/Paleozoic boundary to the Middle Eocene horizon; this 

suggests faulting began post-Middle Eocene.

The NE-trending Ridgely fault appears to be a zone of faults bounding a 

horst-like feature; apparent vertical displacements across easternmost 

strand suggest recurrent displacement, with roughly 22–26 m (72.2–85.3

ft.) of apparent offset on Cretaceous/Paleozoic boundary and 18–22 m 

(59–72.2 ft.) of apparent offset on Middle Eocene deposits. The 

Quaternary/Eocene boundary was not sufficiently imaged to determine 

whether faulting has occurred later than post-Middle Eocene.

Stephenson et al. 

(1999)

Deformation and Quaternary Faulting in 

Southeast Missouri Across the Commerce 

Geophysical Lineament

High-resolution seismic-reflection data at three sites along the 

Commerce geophysical lineament (CGL) reveal post-Cretaceous faulting 

extending into Quaternary. At Qulin site, ~20 m (65.5 ft.) of apparent 

Quaternary vertical displacement is observed. At Idalia Hill, a series of 

reverse and possibly right-lateral strike-slip faults with Quaternary 

displacement are imaged. At Benton Hills, a complicated series of 

anticlinal and synclinal fault-bounded blocks occur directly north of CGL. 

Van Arsdale (2000) Displacement History and Slip Rate on the 

Reelfoot Fault of the New Madrid Seismic 

Zone

Develops a displacement history and slip rates for the Reelfoot fault in 

the NMSZ from a seismic-reflection profile and trench data.

Average slip rate estimates—seismic profile:

0.0009 mm/year (past 80 Ma)

0.0007 mm/year (late Cretaceous)

0.002 mm/year (Paleocene Midway Group)

0.001 mm/year (Paleocene-Eocene Wilcox Form)

0.0003 mm/year (post-Wilcox/pre-Holocene)

1.8 mm/year (Holocene)
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-71 

Average slip rate estimates—trench data:

4.4 mm/year (past 2,400 years based on 10 m [33 ft.] of topographic 

relief and a fault dip of 73°)

6.2 mm/year (maximum; estimated 5.4 m [17.7 ft.] cumulative 

displacement for two events between AD 900 and 1812).

Van Arsdale et al. 

(1999)

Southeastern Extension of the Reelfoot Fault This evaluation of microseismicity, seismic-reflection profile data, and 

geomorphic anomalies indicates that prehistoric and 1811-1812 

coseismic uplift in the hanging wall of the Reelfoot fault has produced 

subtle surface warping that extends from Reelfoot Lake to Dyersburg, a 

total distance of 70 km (43.5 mi.). 

Van Arsdale et al. 

(2002)

Investigation of Faulting Beneath the City of 

Memphis and Shelby County, Tennessee

Two N-NE-trending faults marked by 20 m (66 ft.) steps, referred to as 

the Memphis and Ellendale faults, are identified from structure-contour 

maps on Plio-Pleistocene to Eocene datums. Quaternary activity on both 

faults is indicated from analysis of the structure-contour maps and from 

topographic, drainage, and paleodrainage analyses. An anticlinal fold in 

floodplain sands is observed along the Ellendale fault. Radiocarbon 

dates indicate that folding occurred between AD 390 and 450 and 

liquefaction observed in the crest of the anticline occurred after AD 450. 

Modeling of the fold, which appears to be tectonic, is consistent with 5 m 

of right-lateral offset. 

Velasco et al. 

(2005)

Quaternary Faulting Beneath Memphis, 

Tennessee

Structure-contour maps and cross sections of the top of the PliocenePleistocene Upland Complex (Lafayette gravel), Eocene Upper Claiborne 

Group, and Eocene Lower Claiborne Group reveal two 20 m (66 ft.)

down-to-the-NW faults that strike approximately N30°E. Western fault is 

called the Memphis fault, and eastern fault is the Ellendale fault. 

Anticlinal folding and liquefaction features are observed coincident with 

the Ellendale fault. Radiocarbon dates indicated that folding occurred 

between AD 390 and 450, and that liquefaction occurred after AD 450. 

Seismic-reflection lines indicate that the fold extends to more than 60 m 

(197 ft.) depth in the Lower Claiborne Group, has a length of more than 1 

km (0.6 mi.), and is therefore judged to be tectonic. It is postulated that 

the anticline formed during ~5 m (16.5 ft.) of Quaternary right-lateral 

strike-slip movement on the N25°E-trending fault. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-72 

William Lettis & 

Associates (2006)

Investigation of Holocene Faulting at 

Proposed C-746-Landfill Expansion

Unpublished report presents findings of a fault hazard investigation for 

C-746-U landfill’s proposed expansion at the Department of Energy’s 

Paducah Gaseous Diffusion Plant (PGDP), in Paducah, Kentucky, within 

the Fluorspar Area fault complex. The geologic assessment was based 

on (1) review of relevant geologic and geotechnical data from the site 

vicinity, (2) analysis of aerial photography, (3) field reconnaissance, (4) 

collection and stratigraphic analysis of 86 subsurface sediment cores, 

and (5) laboratory chronological (dating) analyses. 

Geologic cross sections prepared from the direct-push technology core 

data identified laterally continuous horizontal strata for assessing 

possibility of fault displacement, and for evaluating timing of such 

displacements. Deposits encountered in the cores range in age from 

about 16 ka to greater than 125 ka. Upper three units (15.4–50.7 ka) 

generally are flat-lying and they mantle preexisting topography. The 

lower, older units (53.6–75.5 and ≥125–180 ka) exhibit occasional subtle 

to abrupt undulations of basal contacts, which may reflect fluvial 

processes and/or tectonic-related deformation.

If late Quaternary displacement has occurred beneath the site, the mostrecent displacement occurred following deposition of the Unnamed 

Intermediate Silt between 53.6 and 75.5 ka. Although unlikely, the data 

do not preclude possibility of displacement of the Roxana Silt beneath 

the site, which is approximately 34.6–47.2 ka. There is no perceptible 

displacement of the base of the Upper Peoria Loess, which is 

approximately 16.6–23.5 ka. If late Pleistocene faulting occurred at the 

site, age of such deformation would be similar to youngest age of faulting 

previously interpreted along NE-striking faults in southern Illinois.

As part of this study, reconnaissance-level review of exposures where 

SAIC (2004) reported evidence for Holocene faulting was reviewed with 

John Nelson. Based on (1) an apparent absence of faulting observed in 

upper, younger deposits (i.e., presence of only a fracture); (2) uncertain 

origin of observed fractures (e.g., possibly related to roots); and (3) 

absence of distinct stratigraphic offset of Holocene deposits, it was 

concluded that while relatively young geologic deformation is present, the 

interpretation of Holocene faulting is equivocal.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-73 

Williams et al. 

(1995)

High-Resolution Seismic Imaging of 

Quaternary Faulting in the Crittenden County 

Fault Zone, New Madrid Seismic Zone, 

Northeastern Arkansas

Interpretation of three very high-resolution compressional-wave seismicreflection profiles across surface projections of faults observed on 

coincident Mini-Sosie and Vibroseis seismic-reflection profiles. 

Deformation at and above the Quaternary-Eocene unconformity 

suggests that Crittenden County fault zone (CCFZ) has been active 

during the latest Quaternary and may be a possible source of 

earthquakes. Some evidence supports recurrent events in the 

Quaternary. There is a lack of clear connection between the faults 

observed in high-resolution data and the deeper faults imaged in other 

seismic data. Cites preliminary results of trenching that did not show 

evidence for faulting in a 2.5–3 m (8.2–9.8 ft.) deep trench excavated 

across the 7 m (23 ft.) deep fault as imaged in the seismic data. Possible 

explanation for this is that the shallow, rootless faults are bendingmoment faults that relate to monoclinal bulge associated with the CCFZ. 

Evidence is cited for preference for tectonically driven deformation on the 

CCFZ. Some aspects of the fault observations fit a strike-slip faulting 

regime.

Williams et al. 

(2001)

Seismic-Reflection Imaging of Tertiary 

Faulting and Post-Eocene Deformation 20 km 

North of Memphis, Tennessee

Interprets a 4.5 km (2.8 mi.) long Mini-Sosie seismic-reflection profile 

across eastern bluff along Mississippi River in the Meeman-Shelby 

Forest State Park north of Memphis. Identifies the Meeman-Shelby fault 

(MSF), a high-angle (75°) reverse fault that displaces Paleozoic and 

Cretaceous rocks and upwarps Tertiary deposits. Paleozoic and 

Cretaceous rocks are vertically faulted about 70 and 40 m (230 and 131

ft.), respectively, in an up-to-west sense of displacement. Overlying 

Paleocene and Eocene deposits, which are probably the youngest 

deposits imaged, are upwarped about 50–60 m (164–197 ft.) with the 

same sense of displacement. Sense of displacement, amplitude, and 

appearance of the fault in seismic data are very similar to the Crittenden 

County fault zone (CCFZ), 15 km (9 mi.) west of this profile. Projecting a 

fault trend of N33°E (same general trend as the CCFZ), a similar fault is 

observed in a seismic profile 33 km (20.5 mi.) NE of MSF fault pick. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-74 

Woolery and Street 

(2002)

Quaternary Fault Reactivation in the 

Fluorspar Area Fault Complex of Western 

Kentucky—Evidence from Shallow SH-Wave 

Reflection Profiles

Interpreted shallow shear-wave seismic-reflection profiles collected over 

SW projection of the Fluorspar Area fault complex in the northern 

Jackson Purchase Region of western Kentucky image clear evidence of 

fault and apparent fold propagation into the near-surface Quaternary 

units (less than 10 m [32.8 ft.] below ground surface). Profiles show 

evidence of various structural styles associated with episodic movement. 

The exact timing of the latest tectonic episode exhibited on the profiles is 

not known because of the lack of more accurate stratigraphic detail 

coincident with the lines. Instrumentally recorded seismic events are 

located in the immediate vicinity of study area.

Woolery et al. 

(2009)

Site-Specific Fault Rupture Hazard 

Assessment—Fluorspar Area Fault Complex, 

Western Kentucky

Assesses location and recency of faulting at one location along southerly 

projection of the Fluorspar Area fault complex. Evidence for stratigraphic 

anomalies associated with five high-angle geophysical anomalies (in a 1 

km, or 0.6 mi., long seismic-reflection profile). A total of 86 closely 

spaced 9.1 m (30 ft.) deep continuous cores were collected above 

seismic profile anomalies. Interpretation of the resultant geologic cross 

sections identified stratigraphic anomalies. Stratigraphic anomalies were 

generally constrained to postdate a 53.6–75.5 ka loess deposit: no 

perceptible displacement was found at the base of younger loess dated 

between 16.6 and 23.5 ka.

Magnitude Estimates

Atkinson and 

Hanks (1995)

A High-Frequency Magnitude Scale Based on a high-frequency magnitude scale the 1812 New Madrid event 

is estimated to be M 7.7 0.3.

Bakun and Hopper 

(2004b)

Magnitudes and Locations of the 1811-12 

New Madrid, Missouri, and the 1886 

Charleston, South Carolina, Earthquakes

Estimates M for the three largest events in the 1811-1812 New Madrid 

sequence. (MIis intensity magnitude based on inverting observations of 

intensity.)

MI 7.6 (M 6.8–7.9 at 95% confidence level) for December 16, 1811, 

event (NM1) that occurred in the NMSZ on the Bootheel lineament or 

on the Blytheville seismic zone.

MI 7.5 (M 6.8–7.8 at 95% confidence level) for January 23, 1812, event 

(NM2) for a location on the New Madrid north zone of the NMSZ.

MI 7.8 (M 7.0–8.1 at 95% confidence level) for February 7, 1812, event 

(NM3) that occurred on the Reelfoot blind thrust of the NMSZ.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-75 

Hough (2009) The 1811-1812 New Madrid Sequence: 

Mainshocks, Aftershocks, and Beyond

Discusses uncertainties associated with intensity assignments, and 

development of a set of consensus intensities for the four principal New 

Madrid events, based on independent assignments of four researchers 

(with experience analyzing historical earthquakes). The consensus 

values from these assessments are generally lower than those assigned 

by Hough et al. (2000).

Using the Bakun and Wentworth (1997) method with two published 

attenuation models for the CEUS, intensity magnitude estimates range 

from MI 6.5 to 7.0 for the December main shock, ―dawn aftershock,‖ and 

January main shock, and from MI 7.3 to 7.6 for the February main shock. 

Magnitude estimates based on assignments by individual experts for the 

December 16, 1811, and February 7, 1812, main shocks vary over a 

range of 0.3 to 0.4 units. Using revised magnitudes, distribution is 

characterized by a b-value of 1 between roughly M 6 and 7.5.

The modern instrumental catalog also reveals that, in low strain-rate 

regions, moment release will be strongly controlled by the tendency of 

seismicity to cluster, and an a-value inferred from a short instrumental 

record will tend to significantly underestimate the long-term rate of small 

events in the region.

Hough and Martin 

(2002)

Magnitude Estimates of Two Large 

Aftershocks of the 16 December 1811 New 

Madrid Earthquake

Estimates locations and magnitudes for two large aftershocks:

NM1-A: M ~ 7, thrust mechanism on a SE limb of the Reelfoot fault.

NM1-B: M 6.1 ± 0.2, location of event not well constrained, but 

probably beyond the southern end of the NMSZ, near Memphis, 

Tennessee (within the SW third to half of the band of seismicity 

identified by Chiu et al. [1997]).

Hough et al. (2000) On the Modified Mercalli Intensities and 

Magnitudes of the 1811-1812 New Madrid, 

Central United States, Earthquakes

Reinterprets intensity data, obtaining maximum magnitude estimates 

from 7.0 to 7.5 for the main three events in the 1811-1812 earthquake 

sequence:

December 16, 1811: M 7.2–7.3

January 23, 1812: M 7.0

February 7, 1812: M 7.4–7.5 (thrust event)
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-76 

Hough et al. (2005) Wagon Loads of Sand Blows in White 

County, Illinois

Based on anecdotal accounts of possible liquefaction that occurred at 

several sites in southern Illinois during the 1811-1812 New Madrid 

sequence, the authors conclude that (1) either large NMSZ events 

triggered substantial liquefaction at distances greater than hitherto 

realized, or (2) at least one large ―New Madrid‖ event occurred 

significantly north of the NMSZ. Neither can be ruled out, but the 

following lines of evidence suggest that January 23, 1812, main shock 

occurred in White County, Illinois, near the location of the 1968 mb 5.5 

southern Illinois earthquake and recent microearthquake activity. 

Descriptions report substantial liquefaction (sand blows) as well as a 3.2 

km (2 mi.) long E-W-trending crack along which 0.6 m (2 ft.) of southside-down displacement occurred. A modest offset in Paleozoic strata is 

observed in seismic-reflection survey data at this location. Additional field 

investigations are needed to further document extent and size of 

paleoliquefaction features and demonstrate the presence or absence of 

an E-W fault. 

Johnston (1996b) Seismic Moment Assessment of Earthquakes 

in Stable Continental Regions—III. New 

Madrid 1811-1812, Charleston 1886, and 

Lisbon 1755

Estimates magnitudes for the three largest events of the 1811-1812 

earthquake sequence based on intensity data:

D1 (December 16, 1811): M 8.1 0.3

J1 (January 23, 1812): M 7.8 0.3

F1 (February 7, 1812): M 8.0 0.3

Johnston and 

Schweig (1996)

The Enigma of the New Madrid Earthquakes 

of 1811-1812

This review paper focuses on the 1811-1812 earthquakes, their 

geophysical setting, fault rupture scenarios, and magnitude estimates 

based on intensity data. Using historical accounts and geologic evidence, 

the authors associate the three main 1811-1812 earthquakes with 

specific structures.

Mueller and Pujol 

(2001)

Three-Dimensional Geometry of the Reelfoot 

Blind Thrust: Implications for Moment 

Release and Earthquake Magnitude in the 

New Madrid Seismic Zone

The area of the blind thrust (1,301 km2 [502.3 mi.2]), coupled with 

estimates of displacement in the February 7, 1812, earthquake, is used 

to estimate values of seismic moment from 6.8 × 1026 to 1.4 × 1027dynecentimeters, with preferred values between 6.8 × 1026 and 8.7 × 1026

dyne-centimeters. Computed Mw for this event ranges from Mw 7.2 to 7.4, 

with preferred values between Mw 7.2 and 7.3. The moment magnitude 

for the AD 1450 event is computed as Mw 7.3.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-77 

Mueller et al. 

(2004)

Analyzing the 1811-1812 New Madrid 

Earthquakes with Recent Instrumentally 

Recorded Aftershocks

Instrumentally recorded aftershock locations and models of elastic strain 

change are used to develop a kinematically consistent rupture scenario 

for three of the four largest earthquakes of the 1811-1812 earthquake 

sequence. Three events (NM1, NM1-A, and NM3) likely occurred on two 

contiguous faults (the strike-slip Cottonwood Grove fault and the Reelfoot 

thrust fault). The third main shock (NM2), which occurred on January 23, 

1812, is inferred to be a more distant triggered event that may have 

occurred as much as 200 km (124.3 mi.) to the north in the Wabash 

Valley of southern Illinois-southern Indiana. Magnitudes assigned to each 

of these events are NM1 (M 7.3); NM1-A (M 7.0); NM2 (M 6.8); and NM3 

(M 7.5). 

Tuttle (2001) The Use of Liquefaction Features in 

Paleoseismology: Lessons Learned in the 

New Madrid Seismic Zone, Central United 

States

Uses two approaches to estimate magnitude:

Magnitude-bound—estimates minimum magnitude for AD 900 and 

1450 events of M 6.9 and M 6.7, respectively, based on Ambraseys’s 

(1988) relationship between M and epicentral distance to surface 

manifestations of liquefaction.

Energy stress—estimates M 7.5 to 8.3 from in situ geotechnical 

properties similar to M 7.6 from Ambraseys’s relation for largest 

1811-1812 earthquakes.

Tuttle et al. (2002) The Earthquake Potential of the New Madrid 

Seismic Zone

Size, internal stratigraphy, and spatial distributions of prehistoric sand 

blows indicate that AD 900 and 1450 earthquakes had source zones and 

magnitudes similar to those of the three largest shocks in the 1811-1812 

sequence.

Recurrence

Cramer (2001) A Seismic Hazard Uncertainty Analysis for 

the New Madrid Seismic Zone

A 498-year mean recurrence interval is obtained based on a Monte Carlo 

sampling of 1,000 recurrence intervals and using the Tuttle and Schweig 

(2000) uncertainties as a range of permissible dates ( two standard 

deviations). From these results, 68% confidence limits range from 267 to 

725 years; 95% confidence limits range from 162 to 1,196 years (one 

and two standard deviation ranges, respectively).
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-78 

Holbrook et al. 

(2006) 

Stratigraphic Evidence for Millennial-Scale 

Temporal Clustering of Earthquakes on a 

Continental-Interior Fault: Holocene 

Mississippi River Floodplain Deposits, New 

Madrid Seismic Zone, USA

Presents reconstruction of Holocene Mississippi River channels from 

maps of floodplain strata to identify channel perturbations reflective of 

major displacement events on Reelfoot thrust fault. Provides evidence of 

temporal clustering of earthquakes in a compressive Midcontinent 

intraplate on short-term cycles (months), as well as evidence for longerterm reactivation cyles (104

–106). The study makes a case for a ~1,000-

year cluster of earthquakes with 102yr spacing on the Reelfoot fault,

beginning with a coseismic slip event near end of the middle Holocene at 

~2200 to ~1600 BC. This Holocene cluster appears separated from the 

modern episode of seismicity (beginning ~AD 900) by at least 1,700 

years of tectonic quiescence.

Kelson et al. (1996) Multiple Late Holocene Earthquakes Along 

the Reelfoot Fault, Central New Madrid 

Seismic Zone

Based on seismic-reflection data, the authors interpret the scarp as a 

fault propagation fold over a west-dipping reverse fault. Trench 

exposures provide evidence for three episodes of deformation in the past 

2,400 years: between AD 780 and 1000, between AD 1260 and 1650, 

and during AD 1812. Each episode had a slightly different style of 

deformation. The relations suggested that graben development 

increased through time concomitant with growth of monocline or that the 

earthquakes are of different magnitude. 

Al-Shukri et al. 

(2005)

Spatial and Temporal Characteristic of 

Paleoseismic Features in the Southern 

Terminus of the New Madrid Seismic Zone in 

Eastern Arkansas

Results of this study show that the 10 km (6.2 mi.) long lineament is 

associated with sand blows. A fracture that crosscuts the sand blows has 

a strike similar to that of the lineament and may be related to faulting. Its 

length and morphology as well as parallelism to the nearby White River 

fault zone suggest that the lineament is fault controlled. However, 

additional work, including geophysical and geological investigations, is 

needed to verify presence of a fault below the layer that liquefied.

There appears to be at least a 5–10 kyr long history of strong ground 

shaking along the Daytona Beach lineament and possibly across the 

Marianna area. At Daytona Beach SE2 site, trench observations confirm 

interpretations of geophysical data of at least one major sand dike and a 

large sand blow at this site. Not imaged by ground-penetrating radar, the 

trenches revealed additional smaller sand dikes and an older sand blow. 

Both generations of liquefaction features are very weathered, like the 

sand blow at the original Daytona Beach site, suggesting they may be as 

oldh as 5.5 ka. Radiocarbon dating of buried silt loam soil provides 

maximum age constraint of 10.1 kyr for the younger of the two sand 

blows and minimum age constraint for the older sand blow. Optically
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-79 

stimulated luminescence dating is under way and should help to further 

constrain ages of the sand blows.

Sand blows in the Marianna area predate those in the NMSZ and are 

much more weathered. No sand blows have yet been found in the area 

that are less than 5 ka and could have formed during the AD 900, 1450, 

and 1811-1812 New Madrid earthquakes. Therefore, the Marianna sand 

blows do not represent distant effects of earthquakes generated by the 

NMSZ. Instead, their large size and spatial relations to local faults 

suggest that the causative earthquakes were centered in Marianna. 

Furthermore, the compound nature of some of the Marianna sand blows 

are indicative of sequences of large earthquakes resulting from complex 

fault interaction similar to the behavior of the New Madrid fault zone. 

Al-Shukri et al. 

(2006) 

Three-Dimensional Imaging of EarthquakeInduced Liquefaction Features with Ground 

Penetrating Radar near Marianna, Arkansas

High-resolution 3-D ground-penetrating radar (GPR) surveys, together 

with a profiling survey conducted at three sites to study earthquakerelated sand blows in east-central Arkansas, were used to site trenches. 

Trench results confirmed presence of sand dikes at the locations 

interpreted from GPR results. 

Tuttle (2001) The Use of Liquefaction Features in 

Paleoseismology: Lessons Learned in the 

New Madrid Seismic Zone, Central United 

States

Major earthquakes occurred in New Madrid region in AD 900 100 years 

and AD 1450 150 years. There is evidence for earlier events, but age 

estimates and areas affected are poorly constrained. Judging by

similarities in size and spatial distribution of paleoliquefaction features 

from these events and close spatial correlation to historical features, 

NMSZ was the probable source of two of these. This study is consistent 

with other paleoliquefaction studies in the region and with studies of faultrelated deformation along Reelfoot scarp (e.g., Kelson et al., 1996).

Tuttle et al. (2002) The Earthquake Potential of the New Madrid 

Seismic Zone

Recurrence intervals are based on studies of hundreds of earthquakeinduced paleoliquefaction features at more than 250 sites. The fault 

system responsible for New Madrid seismicity generated very large 

earthquakes temporally clustered in AD 900 100 years and AD 1450 

150 years, as well as 1811-1812. Given uncertainties in dating 

liquefaction features, the time between the past three events may be as 

short as 200 years or as long as 800 years, with an average of 500 

years. Evidence suggests that prehistoric sand blows probably are either 

compound structures, resulting from multiple earthquakes closely 

clustered in time, or earthquake sequences. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-80 

Tuttle et al. (2006) Very Large Earthquakes Centered Southwest 

of the New Madrid Seismic Zone 5,000–7,000 

Years Ago

Large earthquake-induced sand blows and related sand dikes are 

present at two sites in Marianna area about 180 km (112 mi.) SW of 

center of the NMSZ (80 km, or 50 mi., SW of the southern limit of NMSZ). 

Based on radiocarbon dating, liquefaction features at the Daytona Beach 

and St. Francis sites formed about 3500 and 4800 BC (5 and 7 ka), 

respectively. These events predate paleoearthquakes attributed to NMSZ 

faults.

The Marianna sand blows are similar in size to NMSZ sand blows, 

suggesting that they formed as the result of very large earthquakes 

centered near Marianna and outside NMSZ. 

Liquefaction features similar in age to, but smaller than, the Daytona 

Beach sand blow occur near Blytheville (150 km, or 93.2 mi., NE of 

Marianna) and Montrose, Arkansas (175 km, or 108.7 mi., SE of 

Marianna). A very large (M > 7.2) earthquake centered near Marianna 

about 3500 BC may account for liquefaction in all three areas. 

The large sand blows at the St. Francis site are similar to compound 

sand blows in the NMSZ, suggesting that a NMSZ-type earthquake 

sequence was centered near Marianna about 4800 BC.

Several faults in the Marianna area (including the Eastern Reelfoot rift 

margin [ERRM], the White River fault zone [WRFZ], and Big Creek fault 

zone [BCFZ]), are thought to be active, based on apparent influence on 

local topography and hydrography. ERRM appears to be the most likely 

source of very large earthquakes during middle Holocene. 

Vaughn (1991) Evidence for Multiple Generations of 

Seismically Induced Liquefaction Features in 

the Western Lowlands, Southeast Missouri 

Identifies evidence for as many as three to four major (M ≥ 5.5) 

earthquakes: the great 1811-1812 New Madrid event and two to three 

prehistoric events. Preliminary estimates of the ages based on 

archaeological data and radiocarbon dates on materials associated with 

buried or truncated liquefaction features suggest the following: (1) event 

F, 22.75 to 357 ka, and very likely more than 13.4 ka; (2) event L, with 

maximum timing of 13.43 ka and minimum timing of ca. 5.0 ka; and (3) 

event R, 12.57 to 0.59 ka, probably closer to 0.59 ka. Potentially, event R 

could correlate with one of the two major prehistoric earthquakes on the 

Reelfoot scarp. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-81 

Seismicity—Focal Mechanisms and Fault Geometry

Bakun and Hopper 

(2004a)

Catalog of Significant Historical Earthquakes 

in the Central United States 

Modified Mercalli intensity assignments are used to estimate source 

locations and moment magnitude M for 18 nineteenth-century and 20 

early twentieth-century earthquakes in the central U.S. for which 

estimates of M are otherwise not available. The 1811-1812 New Madrid 

earthquakes apparently dominated CUS seismicity in the first two 

decades of nineteenth century. M 5–6 earthquakes occurred in the 

NMSZ in 1843 and 1878, but none have occurred since 1878. 

Chiu et al. (1990) High-Resolution PANDA Experiment in the 

Central New Madrid Seismic Zone

Accurate earthquake locations from PANDA seismic array deployed in 

mid-October of 1989 define a narrow and clustered seismic zone. 

Seismicity is concentrated in upper crust beneath the sedimentary layer 

and above 15 km (9.3 mi.). Single-event fault plane solutions are well 

constrained by P-wave first motion and S-wave polarities, which suggest 

predominantly strike-slip motion with some thrust-component in the 

region.

Chiu et al. (1992) Imaging the Active Faults of the Central New 

Madrid Seismic Zone Using PANDA Array 

Data 

PANDA data clearly delineate planar concentrations of hypocenters that 

allow for interpretation as active faults. The results corroborate the 

vertical (strike-slip) faulting of SW (axial), N-NE, and western arms and 

define two dipping planes in the central segment. Seismicity in the leftstep zone between the two NE-trending vertical segments is 

concentrated around a plane that dips at ~31°SW; a separate zone to the 

SE of the axial zone defines a plane that dips at ~48°SW. These planes 

project updip to surface along the eastern boundary of Lake County uplift 

and the western portion of Reelfoot Lake. 

Seismic activity in the central NMSZ occurs continuously between ~5 and 

14 km (3.1 and 8.7 mi.) depth.

Csontos and 

VanArsdale (2008)

New Madrid Seismic Zone Fault Geometry In this study, 1,704 earthquake hypocenters obtained between 1995 and 

2006 were analyzed in 3-D space to more accurately map fault geometry 

in the NMSZ. Most of the earthquakes appear to align along fault planes. 

Identifies New Madrid North (29°, 72°SE), Risco (92°, 82°N), Axial (46°, 

90°), Reelfoot North (167°, 30°SW), and Reelfoot South (150°, 44°SW) 

faults. A diffuse zone of earthquakes exists where the Axial fault divides 

the Reelfoot fault into Reelfoot North and Reelfoot South faults. Regional 

mapping of the top of the Precambrian crystalline basement indicates 

that the Reelfoot North fault has an average of 500 m (1,640 ft.) and the 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-82 

Reelfoot South fault has 1,200 m (3,937 ft.) of down-to-the-SW normal 

displacement. Since previously published seismic-reflection profiles 

reveal reverse displacement on top of the Paleozoic and younger strata, 

the Reelfoot North and South faults are interpreted to be inverted 

basement normal faults. Reelfoot North and South faults differ in strike, 

dip, depth, and displacement, and only the Reelfoot North fault has a 

surface scarp (monocline). Thus the Reelfoot fault is actually composed 

of two left-stepping restraining bends and two faults that together extend 

across entire width of Reelfoot rift.

Herrmann and 

Ammon (1997)

Faulting Parameters of Earthquakes in the 

New Madrid, Missouri, Region

Combines traditional regional seismic network observations with direct 

seismogram modeling to improve estimates of small earthquake faulting

geometry, depth, and size. Evaluates three earthquakes that occurred 

within the vicinity of the NMSZ. Comparing new and revised results with 

existing earthquake mechanisms in the region, this paper concludes that 

tension axes are generally aligned in a N-S to NW-SE direction, while 

compression axes are aligned in a NE to E direction. Interesting 

exceptions to this pattern are the March 3, 1963, earthquake, and two 

nearby earthquakes that lie within a well-defined 30 km (18 mi.) long left 

step in seismicity near New Madrid. Depth of well-located events in the 

Reelfoot rift is ≤16 km (10 mi.).

Himes et al. (1988) Indications of Active Faults in the New Madrid 

Seismic Zone from Precise Locations of 

Hypocenters 

Based on examination of hypocenters for more than 500 earthquakes in 

the NMSZ, the relocated earthquakes are separated into three trends: (1) 

ARK, the SW-trending zone from Caruthersville, Missouri, to Marked 

Tree, Arkansas; (2) DWM, the NE-trending zone from New Madrid to 

Charleston, Missouri; and (3) CEN, the central, left-stepping offset zone 

from Ridgely, Tennessee, to New Madrid, Missouri. Vertical profiles 

along and across the ARK and DWM trends verify the strike and dip of 

dominantly strike-slip motion on near-vertical active faults along these 

trends—in agreement with previously determined composite focal 

mechanism solutions for these trends. No coherent picture for CEN is 

obtained. Velocity models from the inversion are found to be reasonably 

uniform throughout the NMSZ and support the presence of a shallow 

low-velocity zone in the central part of Mississippi embayment. 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-83 

Shumway (2008) Focal Mechanisms in the Northeast New 

Madrid Seismic Zone

Earthquakes in NE part of the NMSZ from June 1995 to June 2006 were 

relocated using a velocity model of the Mississippi embayment with 

appropriate depths to bedrock beneath seismic stations. Focal 

mechanisms were generated for events on NE-trending alignments. 

Results show that approximately half the focal mechanisms have a 

N-NE-striking nodal plane and a right-lateral strike-slip component 

consistent with earlier studies of the NMNF to the SW. This shows that 

this part of the NE NMSZ (1) is influenced by the same fault pattern and 

stress regime as the NMNF, (2) may be an extension of the NMSZ, and 

(3) therefore may represent alternate locations of January 23, 1812,

rupture. Focal depths for 19 earthquakes range from about 3 to 15 km 

(1.9 to 9.3 mi.).

Stauder (1982) Present-Day Seismicity and Identification of 

Active Faults in the New Madrid Seismic 

Zone

Results of four years of data from a regional seismic network established 

in 1974 showed the following:

a diffuse seismicity over the regional area; 

NE-SW trends of faulting within the network varying in length from 25

to 120 km (15.5 to 75 mi.) from Cairo, Illinois, into NW Arkansas; 

a major offset in these trends in region between New Madrid, Missouri, 

and Ridgely, Tennessee; 

focal mechanism studies indicate right-lateral, predominantly strike-slip 

motion on the major NE-trending seismic trend; and 

a low-velocity zone extends at least 150 km (93.2 mi.) into upper 

mantle beneath the region of highest seismicity.

Geodetic and Modeling Studies-Hypotheses for Causes of Intraplate Seismicity

Calais and Stein 

(2009)

Time-Variable Deformation in the New Madrid 

Seismic Zone

This paper speculates that earthquake hazard estimates—assuming that 

recent seismicity reflects long-term steady-state behavior—may be 

inadequate for plate interiors and may overestimate hazard near recent 

earthquakes and underestimate it elsewhere.

Recent geodetic results in the NMSZ have shown motions between 0 

and 1.4 mm/yr, allowing opposite interpretations. The upper bound is 

consistent with steady-state behavior, in which strain accumulates at a 

rate consistent with repeat time for M ~ 7 earthquakes of about 600–

1,500 years, as seen in the earthquake record. The lower bound cannot 

be reconciled with this record, which implies that the recent cluster of 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-84 

large-magnitude events does not reflect long-term fault behavior and 

may be ending. New analysis suggests strain rates lower than 1.3 ×

10–9/yr, less than predicted by a model in which large earthquakes occur 

because the NMSZ continues to be loaded as a deeper weak zone 

relaxes (e.g., Kenner and Segall, 2000). At a steady state, a rate of 0.2 

mm/yr implies a minimum repeat time of 10,000 years for low M = 7 

earthquakes with ~2 m (~6.6 ft.) of coseismic slip and one longer than 

100,000 years for M = 8 events. Strain in the NMSZ over the past several 

years has accumulated too slowly to account for seismicity over past 

~5,000 years; hence steady-state fault behavior is excluded.

Elsewhere throughout the plate interior, GPS data also show average 

deformation less than 0.7 mm/yr, and paleoseismic records show 

earthquake migration and temporal earthquake clustering. These imply 

that fault loading, strength, or both vary with time in the plate interior. 

Time variations in stress could be due to local loading and unloading 

from ice sheets or sediments or after earthquakes on other faults.

Calais et al. (2006) Deformation of the North American Plate 

Interior from a Decade of Continuous GPS 

Measurements

Two independent geodetic solutions using data from close to 300 

continuous GPS stations covering CEUS show that surface deformation 

in the plate interior is best fit by a model that includes rigid rotation of 

North America with respect to International Terrestrial Reference Frame 

(ITRF) 2000 and a component of strain qualitatively consistent with that 

expected from glacial isostatic adjustment. No detectable residual motion 

at the 95% confidence level is observed in the NMSZ.

On the basis of a 0.7 mm/yr weighted RMS value for the residual 

velocities of NMSZ sites, random deviations from a rigid plate model in 

the NMSZ region do not exceed 1.4 mm/yr, the 95% confidence level. 

This is assumed to represent a conservative upper bound on the 

magnitude of any long-term slip in the study area. Assuming a simple 

model where characteristic earthquakes repeat regularly on a given 

active fault, the results imply a minimum repeat time of about 3,000–

8,000 years for future M 8 earthquakes with 5–10 m (16–33 ft.) of 

coseismic slip, and a minimum repeat time of 600–1,500 years for future 

M 7 earthquakes with 1–2 m (3.3–6.6 ft.) of coseismic slip. This is 

consistent with recent and historical earthquake catalogs, which predict a 

recurrence interval that exceeds 1,000 years for M 7 earthquakes, and 

10,000 years for M 8 earthquakes, and is consistent with paleoseismic 

data, which imply recurrence intervals of 400–1,000 years.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-85 

Calais et al. (2009) Time-Variable Deformation in the New Madrid 

Seismic Zone

New analysis of GPS measurements across the NMSZ shows that 

deformation accumulates at a rate indistinguishable from zero and less 

than 0.2 mm/yr. At steady state, a (maximum) rate of 0.2 mm/yr implies a 

(minimum) repeat time of 10,000 years for low M 7 earthquakes, in 

contrast with the 500- to 900-year repeat time of paleoearthquakes. This, 

along with geological observations that large earthquakes and significant 

motions on Reelfoot fault started in the Holocene, suggests a transient 

burst of seismic activity rather than steady-state behavior.

The authors postulate a model in which stress changes are caused by 

the Quaternary denudation/sedimentation history of the Mississippi 

Valley. Flexural stresses are sufficient to trigger earthquakes in a 

continental crust at failure equilibrium. Resulting viscoelastic relaxation 

leads to failure again on the main fault (lower strength threshold) and on 

neighboring faults. In the absence of significant far-field loading, this 

process can only maintain seismic activity for a few thousand years.

Crone et al. (2003) Paleoseismicity of Two Historically Quiescent 

Faults in Australia: Implications for Fault 

Behavior in Stable Continental Regions

Temporal clustering, in which faults turn on to generate a series of large 

earthquakes and then turn off for a long time, may reflect the evolution of 

pore fluid pressure in the fault zone. In this model, low-permeability seals 

form around the fault zone as stress accumulates, raising pore pressure 

until an earthquake happens and each of the temporally clustered 

earthquakes relaxes some of the accumulated strain, and eventually the 

surrounding crust is sufficiently relaxed to make the fault quiescent.

Forte et al. (2007) Descent of the Ancient Farallon Slab Drives 

Localized Mantle Flow Below the New Madrid 

Seismic Zone

Viscous flow models based on high-resolution seismic tomography show 

that descent of the ancient Farallon slab into deep mantle beneath 

central North America induces a highly localized flow directly below the 

NMSZ. This localization arises because of structural variability in the 

Farallon slab and low viscosity of the sublithospheric upper mantle, and it 

represents a heretofore unrecognized and possibly significant driving 

mechanism for the enigmatic intraplate seismicity in CEUS.

Grana and 

Richardson (1996)

Tectonic Stress Within the New Madrid 

Seismic Zone

Refraction data indicate a significant high-density rift pillow beneath the 

NMSZ. Linear and nonlinear viscoelastic finite-element modeling was 

conducted to determine whether support of the rift pillow may contribute 

significantly to the total present-day stress field. Results indicate that the 

nonlinear viscoelastic model with rheological stratification based on 

composition and temperature agrees well with observed deformation 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-86 

within the zone, and with estimates of regional stress magnitudes.

The model predicts maximum compression of 30–40 megapascals above 

the rift pillow in the center of the rift axis. If the magnitude of local 

compression predicted by the nonlinear model produces inferred 

clockwise rotation on the order of 10°–30° in the direction of SHmax 

(maximum horizontal compression) near the rift axis, the magnitude of 

regional compression is a factor of one to two times that of local 

compression and is consistent with an origin due to ridge push forces. 

Addition of local stress associated with the rift pillow, however, results in 

an approximately 30% reduction in the resolved maximum horizontal 

shear stress. Thus, while the stress associated with the rift pillow can 

rotate the stress field to an orientation favorable for failure, reduction in 

the resolved shear stress requires a separate mechanism for strength 

reduction.

Results of the modeling indicate that stresses from the load of the rift 

pillow may still be present in upper crust even after 100 Myr and may still 

play a role in present-day deformation and seismicity of the NMSZ. Local 

stress fields of significant tectonic magnitudes may also occur around 

other ancient rift pillows and help explain the observed correlation 

between intraplate seismicity and failed rift zones.

Grollimund and 

Zoback (2001)

Did Deglaciation Trigger Intraplate Seismicity 

in the New Madrid Seismic Zone?

Modeling of the removal of the Laurentide ice sheet ca. 20 ka changed 

the stress field in the vicinity of New Madrid and caused seismic strain to 

increase by about three orders of magnitude. The high rate of seismic 

energy release observed during late Holocene is likely to remain 

essentially unchanged for the next few thousand years.

Kenner and Segall 

(2000)

A Mechanical Model for Intraplate 

Earthquakes: Application to the New Madrid 

Seismic Zone

Postulates a time-dependent model for the generation of repeated 

intraplate earthquakes in which seismic activity is driven by localized

transfer of stress from a relaxing lower-crustal weak body. Given 

transient perturbation to the stress field, the seismicity is also transient, 

but can have a significantly longer duration. This model suggests that 

interseismic strain rates computed between damaging slip events would 

not be geodetically detectable.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-87 

Li et al. (2007) Stress Evolution and Seismicity in the 

Central-Eastern United States: Insights from 

Geodynamic Modeling

Explores evolution of stress and strain energy in intraplate seismic zones 

and contrasts it with interpolate seismic zones using simple viscoelastic 

finite-element models. General observations are as follows:

Large intraplate earthquakes can significantly increase Coulomb stress 

and strain energy in surrounding crust.

Inherited strain energy may dominate the local strain energy budget for 

thousands of years following main shocks, in contrast to interplate 

seismic zones, where strain energy is dominated by tectonic loading.

Strain energy buildup from the 1811-1812 large events in NMSZ may 

explain some of the moderate-sized earthquakes in this region since 

1812.

Inherited strain energy is capable of producing some damaging 

earthquakes (M > 6) today in southern Illinois and eastern Arkansas, 

even in the absence of local loading.

Without local loading, however, the NMSZ would have remained in a 

stress shadow where stress has not been fully restored from the 1811-

1812 events.

Results from compilation of a Pn (upper mantle) velocity map of the 

CEUS using available seismic data do support the NMSZ’s being a 

zone of thermal weakening. 

Predicted high Coulomb stress concentrates near margins of North 

American tectosphere, correlating spatially with most seismicity in the 

CEUS.

Li et al. (2009) Spatiotemporal Complexity of Continental 

Intraplate Seismicity: Insights from 

Geodynamic Modeling and Implications for 

Seismic Hazard Estimation

Explores the complex spatiotemporal patterns of intraplate seismicity 

using a 3-D viscoelastic-plastic finite-element model. The model 

simulates tectonic loading, crustal failure in earthquakes, and coseismic 

and postseismic stress evolution. For a laterally homogeneous 

lithosphere with randomly pre-specified perturbations of crustal strength, 

the model predicts various spatiotemporal patterns of seismicity at 

different time scales, spatial clustering in narrow belts and scattering 

across large regions over hundreds of years, connected seismic belts 

over thousands of years, and widely scattered seismicity over tens of 

thousands of years.

The orientation of seismic belts coincides with the optimal failure 

directions associated with assumed tectonic loading. Stress triggering 
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-88 

and migration cause spatiotemporal clustering of earthquakes. Fault 

weakening can lead to repeated earthquakes on intraplate faults. The 

predicted patterns vary with the weakening history. Clusters of large 

intraplate earthquakes can result from fault weakening and healing, and 

these clusters can be separated by long periods of quiescence.

The complex spatiotemporal patterns of intraplate seismicity predicted in 

this simple model suggest that assessment of earthquake hazard based 

on the limited historical record may be biased toward overestimating the 

hazard in regions of recent large earthquakes and underestimating the 

hazard where seismicity has been low during historical time.

Liu and Zoback 

(1997)

Lithospheric Strength and Intraplate in the 

New Madrid Seismic Zone

Proposes a simple hypothesis to explain occurrence of localized zones of 

tectonic deformation and seismicity within intraplate regions subjected to 

relatively uniform far-field tectonic stresses. The contrast in integrated 

lithospheric strength between the NMSZ and the surrounding continental 

region appears to be the principal reason why the New Madrid area is 

the most active intraplate seismic area in eastern North America. The 

lower lithosphere's strength in the NMSZ appears to be controlled by a 

slightly thickened crust and slightly higher heat-flow values compared to 

surrounding regions. This conclusion is supported by a contrast in Pn 

(upper mantle) velocity structure, the silica geothermometry, and the rate 

of Cenozoic subsidence and recurrence of late Mesozoic and possible 

Cenozoic magmatic activity. Because of localized deformation in the 

lower crust of the NMSZ, repeated earthquakes occur with recurrence 

times that are relatively short for intraplate areas.

McKenna et al. 

(2007) 

Is the New Madrid Seismic Zone Hotter and 

Weaker Than Its Surroundings?

Evaluates sparse heat-flow data in the New Madrid area and concludes

that there is no compelling case for assuming that the NMSZ is 

significantly hotter and weaker than its surroundings, and that this result 

is consistent with the migrating seismicity model and the further 

possibility that the NMSZ is shutting down, which is suggested by the 

small or zero motion observed geodetically. In this model, the present 

seismicity is aftershocks of the large earthquakes of 1811-1812, and 

such large earthquakes will not recur there for a very long time.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-89 

Newman et al. 

(1999)

Slow Deformation and Lower Seismic Hazard 

at the New Madrid Seismic Zone

Recent geodetic measurements indicate that the rate of strain 

accumulation is less than the current detection threshold. Global 

positioning system (GPS) data show no significant differences in 

velocities on either side of southern arm of NMSZ. Near-field and 

intermediate-field (primarily hard-rock) sites yield measurements of 0.6 

3.2 and –0.9 2.2 mm/year, respectively. They are consistent with both 0 

and 2 mm/year at 2-sigma. 

GPS data for upper Mississippi embayment show that interior of the 

Reelfoot rift is moving NE relative to the North American Plate. Modeling 

stable North America as a single rigid plate fits the site velocities, with a 

mean residual of 1.0 mm/year. 

The authors conclude that the present GPS data imply that 1811-1812-

sized earthquakes are either much smaller or far less frequent than 

previously assumed (i.e., smaller than M 8 [5–10 m, or 16.4–32.8 ft., 

slip/event], or longer than a recurrence interval of 400–600 years).

Smalley et al. 

(2005)

Space Geodetic Evidence for Rapid Strain 

Rates in the New Madrid Seismic Zone of 

Central USA

Recent analysis of geodetic measurements from a permanent GPS array 

in mid-America installed in the mid- to late 1990s provides evidence for 

rapid strain rates in the NMSZ. Rates of strain are on the order of 10–7

per year, comparable in magnitude to those across active plate 

boundaries. The rates are consistent with known active faults in the 

region. Relative convergence across the Reelfoot fault is ~2.7 ± 1.6 

mm/year. Relative fault-parallel, right-lateral motion of ~1 mm/year is 

measured across southern right-lateral strike-slip fault zone, which is 

highlighted by a prominent NE-trending and vertical zone of 

microseismicity and right-lateral focal mechanisms. Surface velocities at 

distances beyond a few fault dimensions (far-field) from active faults do 

not differ significantly from zero. It is not certain whether the driving force 

behind current surface velocities is related to post-1811-1812 

postseismic processes or to accumulation of a locally sourced strain. 

Data indicate, however, that aseismic slip is almost certainly required 

across faults (or shear zones) within upper few kilometers of the surface.
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-90 

Stuart et al. (1997) Stressing of the New Madrid Seismic Zone by 

a Lower Crust Detachment Fault

The authors suggest that the cause of stress concentration onto the 

NMSZ is slip on a weak subhorizontal detachment fault or equivalent 

shear zone in the lower crust where high temperatures reduce rock

strength. The proposed detachment fault is placed at or just above the 

top surface of a layer of lower crust with anomalous high-density and 

seismic velocity called the ―rift pillow‖ or ―rift cushion.‖ Regional horizontal 

compression induces slip on the fault, and the slip creates a stress 

concentration in upper crust above rift pillow dome. The model implies 

that rift pillow geometry is a significant influence on the maximum 

possible earthquake magnitude.

Zhang et al. 

(2009a)

Lithospheric Velocity of the New Madrid 

Seismic Zone: A Joint Teleseismic and Local 

P Tomographic Study

Inversion of teleseismic P and local P first-arrival times from a nine-year 

data set are used to infer the lithospheric velocity structure beneath the 

NMSZ. Results show that the seismically active zone is associated with a 

local NE-SW-trending low-velocity anomaly in the lower crust and upper 

mantle, instead of high-velocity intrusive bodies proposed in previous 

studies. The low-velocity anomaly is on the edge of a high-velocity 

lithospheric block, consistent with notion of stress concentration near 

rheological boundaries. This lithospheric weak zone may shift stress to 

upper crust when loaded, thus leading to repeated shallow earthquakes.

Seismic Source Characterization Models

Cramer (2001) A Seismic Hazard Uncertainty Analysis for 

the New Madrid Seismic Zone

Develops a logic tree of possible alternative parameters to characterize 

earthquake sources in the NMSZ. Source model alternatives include 

fictional faults from Frankel et al. (1996) and actual faults (Bootheel 

lineament, eastern rift boundary, NE arm, SW arm, Reelfoot fault, west 

arm, and western rift boundary).

Frankel et al. 

(2002)

Documentation for the 2002 Update of the 

National Seismic Hazard Maps

Identifies three alternative fault sources: a fault trace matching recent 

microearthquake activity, and two adjacent sources situated near borders 

of the Reelfoot rift. The center fault is given twice the weight of the other 

two. Mean recurrence interval = 500 years:

M 7.3: (0.15 wt)

M 7.5: (0.20 wt)

M 7.7: (0.50 wt)

M 7.9: (0.15 wt)
Table D-6.1.5 Data Summary 

Reelfoot Rift–New Madrid Seismic Zone (NMSZ) Region

D-91 

Petersen et al. 

(2008)

Documentation for the 2008 Update of the 

United States National Seismic Hazard Maps

Revisions to the characterization of the NMSZ include the following:

Reduced magnitudes in northern NMSZ by 0.2 unit and added logictree branch for recurrence rate of 1/750 years.

Added logic-tree branch for 1/1,000-year recurrence rate of 

earthquakes in New Madrid (recommended by advisory panel).

Implemented temporal cluster model for New Madrid earthquakes. 

Modified fault geometry for New Madrid to include five hypothetical 

strands and increased weight on central strand to 0.7.

Revised dip of Reelfoot fault to 38°.

Toro and Silva 

(2001)

Scenario Earthquakes for Saint Louis, MO, 

and Memphis, TN, and Seismic Hazard Maps 

for the Central United States Region Including 

the Effect of Site Conditions

Develops alternative geometries for NMSZ. Uses fault sources identified 

by Johnston and Schweig (1996), augmented by alternative fault source 

model to the north (East Prairie extension), to represent more diffuse 

patterns of seismicity. Assumes that a large seismic-moment release in 

the region involves events on all three NMSZ faults occurring within a 

short interval. Occurrences of large earthquakes in the NMSZ are not 

independent in time. Uses mean recurrence intervals of 500 to 1,000 

years.
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Citation Title Description and Relevance to SSC

General for Region

Basement Structure

Drahovzal et al. 

(1992)

The East Continent Rift Basin: A 

New Discovery

Integration of lithologic, stratigraphic, geochemical, gravity, magnetic, structural, and 

seismic data resulted in recognition of an eastern arm of the Midcontinent rift 

system named the East Continent rift basin (ECRB). An elongate N-S-trending

Precambrian rift basin is present from SE Michigan through Ohio and Indiana, into 

central Kentucky. The ECRB is filled with red continental lithic arenites, minor red 

siltstones and shales, and volcanics. Gravity, magnetic, and seismic data indicate 

that the basin is composed of several subbasins.

The basin is bounded by the Grenville Front to the east and by normal block faults 

to the west. The basin narrows to the north; the southern boundary is not well 

constrained. The basin is interpreted to be Keweenawan in age and associated with 

the middle Proterozoic Midcontinent rift system. The ECRB predates the Grenville 

orogeny, which resulted in folding and faulting of the rift-fill sequence. Post-Grenville 

erosion, Paleozoic inversion, and wrench faulting resulted in the present 

configuration of the basin.

Drahovzal (1994) Basin-Floor Fan Complexes: A 

New Exploration Strategy for the 

Rough Creek Graben

Extent of possible extended basement crust below the southern Illinois basin is 

inferred from seismic-reflection data. 

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

The authors propose that along the SW margin of the Illinois basin, the Commerce 

geophysical lineament (CGL) to the south and the St. Charles lineament (SCL) to 

the north divide the region into three distinct tectonic domains. The authors suggest 

that these lineaments represent ancient shear zones, or accommodation zones, that 

juxtapose different-aged Proterozoic crustal blocks, and that these accommodation 

zones have partitioned strain throughout the Phanerozoic, which is reflected in the 

northward decrease of seismic activity in the region. The authors report that 

structural features within each of the three tectonic domains vary in deformational 

styles and orientations, reflecting decoupling of deformation across the two 

lineaments. (See also Midcontinent Data Summary Table for description of CGL 

and SCL.)
Table D-6.1.9 Data Summary 

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Citation Title Description and Relevance to SSC

Harrison and 

Schultz (2008)

A Tectonic Model for the 

Midcontinent U.S. Lithosphere 

Based on Structural Analyses of 

Mesoproterozoic Through 

Cenozoic Deformation

The general conclusion from this abstract is that in the midcontinent U.S., some 

seismicity can be attributed to reactivation of vertical strike-slip fault zones that are 

not associated with any rift. Furthermore, some seismically active, old rift structures 

in the Midcontinent may be inherently related to an even older strike-slip fault 

system. 

Mesoproterozoic basement rocks of the St. Francois terrane possess an orthogonal 

pattern of vertical NW- and NE-trending strike-slip fault zones. The NW trend 

dominates Mesoproterozoic deformation and is inherent from an older fabric that 

controlled the location of Mesoproterozoic igneous activity.

The assembly and breakup of Rodinia is recorded by accumulative left slip of 60–75 

km (37.3–46.6 mi.) and 30–75 km (19–47 mi.) on NW-trending structures, pre-Late 

Cambrian vertical, right-lateral, strike-slip faulting on NW-trending in the St. 

Francois terrane, emplacement of dominantly NE-trending, 1.33 Ga mafic dikes, 

and uplift and erosion of ~2–4 km (~1.2–2.5 mi.) of rocks. Reactivation of NEtrending structures in the Late Cambrian resulted in formation of the Reelfoot rift 

and was accompanied by reactivation of vertical NW-trending structures with leftlateral displacement. Faulting in the Paleozoic, Mesozoic, and Cenozoic cover 

sequences documents reactivation of both vertical trends as far-field strike-slip 

faults during the Acadian, Taconic, Ouachita, Alleghany, and Laramide orogenies. 

Stepovers within the strike-slip fault system produced local uplift along restraining 

bends and subsidence in pull-apart grabens and basins. A tectonic model of the 

Midcontinent lithosphere is best portrayed as consisting of an orthogonal mosaic of 

vertical zones of shear that presumably penetrate the crust and upper mantle and 

are long-lived and prone to reactivation under lithospheric stresses.
Table D-6.1.9 Data Summary 

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D-94 

Citation Title Description and Relevance to SSC

Hildenbrand and 

Ravat (1997)

Geophysical Setting of the 

Wabash Valley Fault System

Analyses of gravity and magnetic data have been used to evaluate the geologic 

framework of the northern Mississippi embayment and Illinois basin regions. 

Inversion of high-resolution aeromagnetic data shows that interpreted ultramafic 

dikes closely follow mapped faults; their abundance suggests that the Wabash 

Valley fault system (WVFS) contains more faults than those mapped. Both dike 

pattern and mapped WVFS terminate near the Reelfoot–Rough Creek–Rome rift 

system. The Grayville graben (~20 km [~12.5 mi.] wide, ~700 m [~2,297 ft.] 

maximum basement relief, and <40 km [<25 mi.] long) underlying the Wabash 

Valley developed during rifting, perhaps in response to stress concentrations 

generated by a bend in the rift system.

The Wabash Valley faults are interpreted to be minor tectonic structures (relative to 

the Reelfoot rift and Rough Creek graben) and probably do not represent a failed rift 

arm. There is a lack of any obvious relation between the WVFS and the epicenters 

of historical and prehistoric earthquakes. Five prehistoric earthquakes lie near 

structures associated with the Commerce geophysical lineament.

Hildenbrand et al. 

(2002)

The Commerce Geophysical 

Lineament and Its Possible 

Relation to Mesoproterozoic 

Igneous Complexes and Large 

Earthquakes in the Central Illinois 

Basin

Inversions of magnetic and gravity data provide insights on upper-crustal structures 

in the central Illinois basin. The results of 2-D and 3-D inversion techniques suggest 

that the source of the Commerce geophysical lineament (CGL) follows the SE

boundary of a dense, magnetic, NE-trending igneous center named the Vincennes 

igneous center. The CGL, defining the 5–10 km (3–6 mi.) wide Commerce 

deformation zone (CDZ), appears to have influenced the structural development of 

the Vincennes igneous center. Overlying the igneous center is the Centralia 

seismic-reflection sequence, expressed as highly coherent reflectors.

It is hypothesized that (1) the Vincennes igneous center is the source of inferred 

volcanic units of the Centralia sequence and is related to a rifted margin or a 

Proterozoic plate boundary; (2) the CDZ evolved in the Mesoproterozoic (1.1–1.5 

Ga) as a major cratonic rheological boundary (possible rifted margin, suture, or 

accreted belt) and was the focus of episodic reactivation related to varying stress 

regimes throughout its history; and (3) spatial relations of the CDZ with large 

Pleistocene and Holocene earthquakes suggest that this major rheological 

boundary is intimately related to both surface and deep structures and to the

seismic hazard of the Illinois basin region. Assuming recent right-lateral slip along 

the CDZ, a jog or left step in the Vincennes area leads to thrusting or a restraining 

bend, where associated stress accumulations may have resulted in nearby large 

prehistoric earthquakes.
Table D-6.1.9 Data Summary 

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Citation Title Description and Relevance to SSC

Kolata and 

Hildenbrand 

(1997)

Structural Underpinnings and 

Neotectonics of the Southern 

Illinois Basin: An Overview

The southern end of the Illinois basin is one of the most structurally complex regions 

in the midcontinent U.S. Two major structural elements exist: (1) a broad SWplunging cratonic depression across central Illinois and SW Indiana is characterized 

by moderate to high earthquake potential and enigmatic earthquake sources; and 

(2) the southernmost part is underlain by the Reelfoot rift and Rough Creek graben, 

a rift system that formed during late Precambrian to middle Cambrian time. 

Geological and geophysical information suggests that the cause of earthquakes in 

the New Madrid seismic zone is unrelated to that of the region north of the rift 

system.

Kolata and Nelson 

(1991)

Tectonic History of the Illinois 

Basin

The Illinois basin is a polyhistory basin that formed primarily during the Paleozoic 

era. The basin began as a failed rift concurrent with the breakup of a supercontinent 

during latest Precambrian or early Cambrian time. Following the rift basin phase, 

which lasted from early to middle Cambrian, the tectonic setting changed to a broad 

cratonic basin centered over the rift. Plate tectonic interactions along the eastern

and southern margins of North America have repeatedly reactivated the rift and 

have influenced basin subsidence, sedimentation, formation of geologic structures, 

migration of subsurface fluids, and contemporary earthquake activity. 

McBride and 

Kolata (1999)

Upper Crust Beneath the Central 

Illinois Basin, United States

Interpretation of industry seismic-reflection data provides information for 

understanding the structure and origin of the upper crust (0–12 km [0–7.5 mi.] 

depth) beneath the central Illinois basin. Highly coherent basement reflectivity is 

expressed as a synformal wedge of dipping and subhorizontal reflections situated 

beneath the center of the Illinois basin that thickens and deepens to the northeast 

(e.g., 0–5.3 km—or 0–3.3 mi.—thickness along a 123 km—76.5 mi.—N-S line). The 

boundaries of an anomalous subsequence of disrupted reflections located along the 

southern margin of this wedge are marked by distinct steeply dipping reflections 

(possible thrust faults) that continue or project up to antiformal disruptions of lower 

Paleozoic marker reflectors, suggesting Paleozoic or possibly later tectonic 

reactivation of Precambrian structures. There are multiple hypotheses for the origin 

of the Precambrian reflectivity, including basaltic flows or sills interlayered with 

clastic sediments and/or emplaced within felsic igneous rocks.
Table D-6.1.9 Data Summary 

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Citation Title Description and Relevance to SSC

McBride et al.

(2001)

Refining the Target for 

EarthScope in the Central 

Midcontinent

Overview summary stating that new images (industry data) of deep structure, 

extending at least as deep as about 65 km (40.5 mi.), represent the largest 

concentration of deep seismic-reflection profiles between the Appalachians and the 

Rockies. Interpretation of these data shows the presence of three highly coherent 

Precambrian ―stratigraphic‖ sequences beneath the Paleozoic Illinois basin that 

continue down to 15–20 km (9–12.5 mi.) depth. Review of 3-D mapping of these 

sequences reveals broad ―basinal‖ packages that may be related to a Proterozoic 

rift and/or volcanic episode. 

Normal-fault reflector offsets that progressively disrupt the sequences with depth 

are possibly related to a Proterozoic rift and/or volcanic episode related to the 

original thermal event that produced the Granite-Rhyolite province. These 

sequences may be analogous to younger Keweenawan-type rift-related volcanism 

and sedimentation that affected the central Midcontinent during the Proterozoic. The 

circular-to-oval shape of the sequences in plan view seems to argue against a linear 

rift origin and is more suggestive of a large rhyolitic collapsed caldera complex that 

could have developed in association with the Granite-Rhyolite province. 

The deeper parts of the seismic sequences correspond to subdued geopotential 

field values and spatial wavelengths, meaning that the seismic sequences are 

lacking in widespread high-density, high-magnetization rocks relative to the 

surrounding region. The outer margins, especially to the west and south, are 

marked by prominent coincident closed-contour magnetic and gravity anomalies, 

which do indicate mafic igneous source intrusions (expressed as highly diffractive 

zones on the deep-reflection profiles. The continuation of the subdued magnetic 

intensity character (as expressed in the first vertical derivative) to the north and east 

may point to the extension of the upper-crustal layering in those directions, beyond 

where regional seismic data are available. The geopotential field data preclude a 

large mafic igneous component to the crust, except for isolated igneous centers, 

suggesting that the rifting or volcanic episode must not have tapped deeply or 

significantly into the lower crust or upper mantle.

The presence of newly observed mantle reflectivity beneath the Illinois basin 

indicates significant upper-mantle heterogeneity relative to other parts of the U.S.

studied using reflection methods. The mantle reflectors do not obviously correlate to 

any particular geologic feature. 

The reprocessed profiles suggest that the seismogenic source beneath the 

seismically active southern Illinois basin may be closely associated with (1) 
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-97 

Citation Title Description and Relevance to SSC

midcrustal dipping reflectors associated with thrust-mechanism earthquakes and (2) 

seismically imaged steep faults in basement associated with strike-slip-mechanism 

earthquakes.

McBride et al. 

(2007)

Deep Faulting and Structural 

Reactivation Beneath the 

Southern Illinois Basin

Integrates seismicity, borehole, geophysical, and seismic profile data to create a 

2.5-dimensional picture down to local seismogenic depth (0–15 km, or 0–9.3 mi.) 

along western flanks of two of the major structures within the Illinois basin: Wabash 

Valley fault system (WVFS), and La Salle anticlinal belt (LSA). The results of 

reprocessing seismic-reflection profiles, combined with earthquake hypocenter 

parameters, suggest three distinct seismotectonic environments in the upper crust. 

1. A fault pattern that appears to correspond to the steep nodal plane of a strike-slip 

mechanism is delineated for the April 3, 1974, mb = 4.7 earthquake. The focal 

mechanism is consistent with a dominant stress system of NE-striking dextral 

strike-slip. The fault pattern is interpreted to be a deeply buried rift zone or zone 

of intense normal faulting underpinning a major Paleozoic depocenter of the 

Illinois basin (Fairfield basin). 

2. A similar earthquake (June 10, 1987, mb = 5.2) and its well-located aftershocks 

define a narrow zone of deformation that occurs along and parallel to the frontal 

thrust of the LSA. The strike and dip of the NW-trending nodal plane were 

reported by Langer and Bollinger (1991) to be 312° and 80°SW, respectively.

This frontal thrust is associated with an asymmetric Laramide-style fold in the 

Paleozoic section. The NW trend of local epicenters and the steep rupture plane 

are both consistent with the basement fault, defined from seismic-reflection

profiles that core the monocline flexure within the basin sediments.

3. The hypocenter of largest earthquake (November 9, 1968; mb = 5.5) may be 

spatially associated with a prominent zone of dipping middle-crustal reflections, 

just west of WVFS, which have been interpreted as a deeply buried blind thrust 

(McBride, Hildenbrand, et al., 2002). This may indicate that shallow Paleozoic 

structures are effectively decoupled from deeper seismogenic structure in this 

case. The earthquake was originally interpreted to have occurred on a N15°Etrending reverse fault dipping about 45°W; interpretation of seismic data 

indicates it may have occurred on a more NE-trending blind reverse fault in the 

basement (fault F).

The geopotential field data display trends that mimic structural trends interpreted 

from reflection profiles and earthquake information. The proposed correlation of 

preexisting structures with earthquakes having consistently oriented structural 
Table D-6.1.9 Data Summary 

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D-98 

Citation Title Description and Relevance to SSC

parameters supports the reactivation of old deformation zones by contemporary 

stresses. The degree to which deformation has propagated upward from 

Precambrian basement into Paleozoic rocks varied significantly even over a small 

study area. 

Pratt et al. (1992) Widespread Buried Precambrian 

Layered Sequences in the U.S. 

Mid-Continent: Evidence for Large 

Proterozoic Depositional Basins

Seismic-reflection data in the Illinois region show a Precambrian layered 

assemblage extending 320 km (199 mi.) in an E-W direction and 200 km (124.3 mi.)

in an N-S direction. The assemblage is approximately 12 km (7.5 mi.) thick. 

Apparent sequence boundaries (onlap, downlap) within the assemblage suggest 

they are part of a large depositional basin with diffractions and dipping strata due to 

faulting. The layered sequence correlates with regions of relatively long-wavelength 

and low-amplitude magnetic anomalies; the extent of this magnetic signature 

suggests that about 200,000 km2(77,220 sq. mi.) of Illinois, Indiana, and western 

Ohio may be underlain by similar Precambrian strata.

Sparlin and Lewis 

(1994)

Interpretation of the Magnetic 

Anomaly over the Omaha Oil 

Field, Gallatin County, Illinois

A magnetic anomaly identified in an aeromagnetic survey over southern Illinois is 

expressed in contours as a localized magnetic high on the west flank of a regional 

magnetic low. An industry well drilled near the apex of the Omaha structural dome, 

which is coincident with the anomaly, encountered two zones of ultramafic intrusive 

rock identified as mantle-derived ultramafic rock that can be associated with 

incipient stages of crustal rifting. The anomaly is modeled using two ultramafic sills 

with an igneous feeder plug.

PALEOZOIC STRUCTURES (Evidence for Reactivation)

La Salle Anticlinorium

Marshak and 

Paulsen (1997)

Structural Style, Regional 

Distribution, and Seismic 

Implications of Midcontinent Faultand-Fold Zones, United States

This paper interprets the La Salle deformation belt as consisting of three segments 

composed of north-trending fault arrays. Each segment terminates at a NW-trending

discontinuity. The authors note that this geometry resembles the pattern of rift 

segments linked at accommodation zones, typical of low-strain rifts. 

McBride and 

Nelson (1999)

Style and Origin of MidCarboniferous Deformation in the 

Illinois Basin, USA—Ancestral 

Rockies Deformation?

Interprets the La Salle anticlinorium as the product of Late Paleozoic displacements 

on high-angle reverse faults in crystalline basement that propagated upward to 

monoclines and asymmetrical anticlines in Paleozoic sedimentary cover. This paper 

presents reflection profiles in the Fairfield basin that do not support the hypothesis 

presented by Marshak and Paulsen (1997).
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Nelson (1995) Structural Features in Illinois Introduces the name La Salle anticlinorium for the feature that previously had been 

referred to as the La Salle anticlinal belt. The feature trends N-NW and extends for 

more than 320 km (200 mi.) from Lee County in the northwest to Lawrence County 

in the southeast. It comprises numerous subparallel anticlines, domes, monoclines, 

and synclines, several dozen of which are individually named. The pattern of the 

individual structures comprising the feature has previously been described as en 

echelon. The author, however, states that this term is misleading, that in a true 

en echelon fold belt the structures are aligned at an angle to the overall trend of the 

system, reflecting strike-slip deformation. The author reports that in the La Salle 

anticlinorium, individual folds are oriented predominantly parallel to the trend of the 

larger system. He also describes the individual folds as being offset from one 

another and partially overlap; toward the north, individual folds generally step to the 

west. The La Salle anticlinorium is described as locally exhibiting a branching 

pattern. 

The author reports that the primary uplift of the La Salle anticlinorium occurred in 

the Late Paleozoic. An angular unconformity at the base of Pennsylvanian-age 

strata is observed along the entire length of the structure. Seismic-reflection profiles 

across the Charleston monocline indicate that the entire Paleozoic sedimentary 

column (pre-Pennsylvanian) is folded and that the amount of structural relief does 

not change significantly with depth.

High-angle reverse faults are documented at depth in several places along the 

southern part of the La Salle anticlinorium. The author’s proprietary seismicreflection profiles reveal faults on the west flank of the Lawrenceville dome, the east 

flank of the Bridgeport anticline, and the SW flank of the Hardinville anticline. These 

faults displace the top of Precambrian basement and overlying Cambrian strata, 

dying out at or below the Ordovician Knox Group. About 152 m (500 ft.) of 

displacement occurs on the basement surface of the Bridgeport anticline, and the 

largest fault on the Hardinville anticline has about 91–122 m (300–400 ft.) of throw.

Based on borehole data in Cambrian sandstone at the northern part of the 

anticlinorium, several E-W-trending faults defining a graben are shown on the west 

side of the dome east of the Peru monocline. Borehole data in Coles County also 

indicate faulting in Mississippian strata near the west flank of Ashmore dome (a 

small dome near the southern end of the Murdock syncline). No orientations of 

these faults are reported.

The author interprets the La Salle anticlinorium as the product of Late Paleozoic 
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displacements on high-angle reverse faults in crystalline basement that propagated 

upward to monoclines and asymmetrical anticlines in Paleozoic sedimentary cover. 

The faults could be classified as drape folds or fault-propagation folds. The complex 

arrangement of folds in the La Salle anticlinorium suggests a mosaic of faults in the 

basement of eastern Illinois.

Peru Monocline

Heigold (1972) Notes on the Earthquake of 

September 15, 1972, in Northern 

Illinois

Based on the proximity of this earthquake to the Peru monocline, this paper 

suggests that the earthquake was the result of faulting related to a zone of 

weakness near the region where the monocline merges with the Ashton anticline. 

Herrmann (1979) Surface Wave Focal Mechanisms 

for Eastern North American 

Earthquakes with Tectonic 

Implications

The 1972 earthquake occurred about 16 km (10 mi.) SE of the 1999 earthquake. A 

focal mechanism solution from the 1972 earthquake indicates movement on a highangle strike-slip fault, either right-lateral to the N-NW or left-lateral to the E-NE.

Larson (2001)

Larson (2002)

The Earthquake of September 2, 

1999, in Northern Illinois: Big 

Lessons from a Small Earthquake

The Earthquake of 2 September 

1999 in Northern Illinois: 

Intensities and Possible 

Neotectonism

Descriptions of two recent earthquakes that have been associated with the Peru 

monocline: a September 1972 magnitude mb 4.6 earthquake and a September 1999

magnitude mb 3.5 earthquake. Within the precision of the seismographic data, the 

1999 and 1972 earthquakes were located 5 and 13 km (3 and 8 mi.), respectively, 

below the Peru monocline. A third earthquake, which occurred May 27, 1881, also 

might be related to the Peru monocline, based on damage reports from La Salle, 

which sits directly on the structure, but an exact location for this earthquake is not 

known. The 2002 paper concludes that the spatial association of recent seismicity 

may suggest that Peru monocline is a reactivated Paleozoic structure.

Nelson (1995) Structural Features in Illinois Describes the Peru monocline, which lies within the northern La Salle deformation 

belt, as a 105 km (65 mi.) long NW-SE-trending fold belt in which the rocks dip 

steeply to the southwest into the Illinois basin. The structure is most prominent in La 

Salle County, where the relief on the SW limb is as much as 396 m (1,300 ft.). In 

some area coal mines, the coal beds dip 45° on the steep flank of the monocline. 

The Peru monocline is less pronounced to the northwest, where the relief 

decreases and the dip becomes very gentle as the structure merges with the 

Ashton anticline. 
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Du Quoin Moncline

Marshak and 

Paulsen (1997)

Structural Style, Regional 

Distribution, and Seismic 

Implications of Midcontinent Faultand-Fold Zones, United States

This paper includes the Du Quoin monocline within the broad southern La Salle 

deformation belt. 

Nelson (1995) Structural Features in Illinois The Du Quoin monocline of southern Illinois trends N-S and warps Paleozoic strata 

down to the east. Normal faults of the Dowell and Centralia fault zones are 

coincident with the dipping flank of the fold, and displace strata down to the west. 

The paper reports that several high-resolution seismic lines across the Centralia 

fault zone indicate a normal fault dipping 70°–75° toward the west, affecting all 

reflectors down to Ordovician strata. Infers that the fault has undergone two 

episodes of movement. The greatest displacements on the structures took place 

during early to middle Pennsylvanian, with intermittent and lesser movements 

continuing into late Pennsylvanian and possibly Permian time. Post-Pennsylvanian 

extension and normal faulting occurred along the Centralia fault. 

Su and McBride 

(1999)

Final Technical Report—Study of 

a Potential Seismic Source Zone 

in South-Central Illinois

This paper reports that low-resolution seismic-reflection data reveal a west-dipping 

reverse fault in the Precambrian basement beneath the monocline that cuts the top 

of the basement-cover contact. Faulting affects the upper Mississippian to 

Ordovician strata. The Centralia fault zone probably represents extensional 

reactivation of the basement structure beneath the Du Quoin monocline, and these 

structures likely connect at depth. The authors consider the Du Quoin monocline—

and related Centralia fault—as a potential source for an earthquake that could have 

produced middle Holocene paleoliquefaction features in SW Illinois and possibly SE

Missouri. 

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

This paper, like Su and McBride (1999), considers the Du Quoin monocline, and 

related Centralia fault, as a potential source for an earthquake that could have 

produced middle Holocene paleoliquefaction features in SW Illinois and possibly SE

Missouri. The conclusions are based on paleoliquefaction studies in southern 

Missouri and southern Illinois.
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Louden Anticline

Su and McBride 

(1999)

Final Technical Report—Study of 

a Potential Seismic Source Zone 

in South-Central Illinois

Reports that recent digital Vibroseis data over this feature, which is located directly 

NE of the Du Quoin monocline, reveals a major deep basement fault that projects to 

a depth of about 12 km (7.5 mi.) from the forward hinge point of the east-facing 

flexure of the dipping limb. A surface area of 252 km2(97 sq. mi.) for the fault is 

estimated based on the axial length of the anticline, 29 km (18 mi.), and the vertical 

length of the basement fault, 8.7 km (5.4 mi.). This associated basement fault may 

be a source structure for paleoliquefaction events.

Waterloo-Dupo Anticline

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

The Waterloo-Dupo anticline is a N-NW-trending asymmetrical anticline that has 

been interpreted to be a southern continuation of the Cap au Gres structures. 

Similar to the Cap au Gres structure, it experienced at least two periods of 

deformation: moderate folding in the Late Devonian and a major episode of folding 

during late Mississippian to early Pennsylvanian. Apparent offset of the WaterlooDupo anticline suggests right-lateral slip on the St. Louis fault. The authors 

conclude that this offset of the Waterloo-Dupo anticline is consistent with late 

Mississippian to early Pennsylvanian NE-SW compression.

Nelson (1995) Structural Features in Illinois The Waterloo-Dupo anticline has a steep western limb, >45° in places, and a gentle 

east limb. Slight post-Pennsylvanian folding may have occurred on the structure.

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

Based on the spatial distribution of prehistoric liquefaction features, the paper 

indicates that the Waterloo-Dupo anticline, Valmeyer anticline, and St. Louis fault 

are possible sources for paleoearthquake features observed in eastern Missouri, 

but also emphasizes that other scenarios relying on sources farther east are equally 

possible (i.e., on the Du Quoin monocline–Centralia fault).
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Farmington Anticline

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

The Farmington anticline/Avon block is a broad (up to 19.3 km [12 mi.] wide) NWtrending low-relief structural feature that lies between Ste. Genevieve and Simms 

Mountain faults. Weak to moderate seismicity is clustered around this structure, 

which has been interpreted to occur above buried faults cutting middle Proterozoic 

basement rock. A zone of NW-trending horsts and grabens with subsidiary and 

contemporaneous NE-striking oblique-slip faults coincides with axis of the fold.

Peoria Folds

Nelson (1995) Structural Features in Illinois Designates a series of subtle anticlines and synclines, originally identified in 1957, 

as the Peoria folds. Individual folds named are the Astoria, Farmington, Littleton, 

Bardolph, Brereton, St. David, Sciota, Seville, and Versailles anticlines and the 

Bryant, Bushnell, Canton, Elmwood, Fairview, Ripley, and Table Grove synclines; 

they were mapped from surface and subsurface data on various Pennsylvanian and 

Mississippian horizons. Nearly all strike slightly north of east. They are linear to 

slightly arcuate, with the convex side to the north. The folds plunge eastward, as 

does the regional dip. Most have less than 30 m (100 ft.) of structural relief. 

This paper notes the correspondence of these minor folds with topography, in 

particular the E-NE alignment of small streams. This is the only region in Illinois 

where topography appears to be so strongly influenced by bedrock structure 

through glacial drift. The source of the horizontal compression that may have 

formed these folds is unknown.

Sandwich Fault

Kolata et al. 

(1978) 

The Sandwich Fault Zone of 

Northern Illinois

The NW-trending Sandwich fault zone, which also lies within the northern La Salle 

deformation belt in NE Illinois, has a maximum vertical displacement of about 244 m 

(800 ft.). 

Larson (2002) The Earthquake of 2 September 

1999 in Northern Illinois: 

Intensities and Possible 

Neotectonism

Notes that two historical earthquakes (in 1909 and 1912) may be associated with 

the Sandwich fault zone, and that these two earthquakes may indicate reactivation 

of a fault within the Precambrian basement associated with the Sandwich fault 

zone.
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Nelson (1995) Structural Features in Illinois Movement along Sandwich fault zone may have been contemporaneous with 

formation of Peru monocline.

Plum River Fault Zone

Bunker et al. 

(1985)

The Plum River Fault Zone and 

the Structural and Stratigraphic 

Framework of Eastern Iowa

Describes northward dips of late Quaternary loess-covered terraces along an 

ancient, south-flowing channel of Mississippi River where terraces cross Plum River 

fault zone. Although the northward dips could be interpreted as evidence of 

Quaternary slip on the fault zone, they could also be explained by terrace erosion 

and subsequent burial beneath a blanket of loess. 

Crone and 

Wheeler (2000)

Wheeler and 

Crone (2001)

Data for Quaternary Faults, 

Liquefaction Features, and 

Possible Tectonic Features in the 

Central and Eastern United 

States, East of the Rocky 

Mountain Front

Known and Suggested 

Quaternary Faulting in the 

Midcontinent United States

Geologic evidence is insufficient to demonstrate Quaternary slip or deformation 

associated with the feature; therefore, the fault is characterized as non-Quaternary.

Nelson (1995) Structural Features in Illinois Plum River fault zone strikes E-W across NW Illinois and into NE Iowa. The author 

reports that primary movements on Plum River faults were post-Devonian and prePennsylvanian. Structural relationships between Pennsylvanian strata and the fault 

zone preclude more than about 10 m (30 ft.) of post-Pennsylvanian movement. 

Centralia Fault Zone

Nelson (1995) Structural Features in Illinois Normal faults of Centralia fault zone are coincident with dipping flank of Du Quoin 

monocline and displace Paleozoic strata down to the west. The author reports that 

several high-resolution seismic lines across Centralia fault zone indicate a normal 

fault dipping 70°–75° toward the west, affecting all reflectors down to Ordovician 

strata. The author and Su and McBride (1999) infer that the zone has undergone 

two episodes of movement: reverse (west side up) during the Pennsylvanian to form 

Du Quoin monocline, and normal (west side down) after the Pennsylvanian. 
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Su and McBride 

(1999)

Final Technical Report—Study of 

a Potential Seismic Source Zone 

in South-Central Illinois

Observes similar displacement of 30–49 m (100–160 ft.) for all levels imaged (upper 

Mississippian to Ordovician). The authors suggest that the Centralia fault zone 

represents extensional reactivation of the basement structure beneath the Du Quoin 

monocline, and that these structures likely connect at depth. Possible association of 

earthquakes located near the structural axis of the Centralia fault and Du Quoin 

monocline with focal mechanisms is consistent with strike-slip along north-trending 

structures. The Centralia fault zone may be the source of earthquakes that 

produced paleoliquefaction features in the region. Like Nelson (1995), this paper 

infers that the fault has undergone two episodes of movement: reverse (west side 

up) during the Pennsylvanian to form the Du Quoin monocline, and normal (west 

side down) after the Pennsylvanian.

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

In agreement with Su and McBride (1999), this paper suggests that the Centralia 

fault may be the source of earthquakes that produced paleoliquefaction features in 

the region.

Rend Lake Fault

Nelson (1995) Structural Features in Illinois The Rend Lake fault zone parallels the west flank of the Benton anticline, which is 

located directly east of the Du Quoin monocline. 

Su and McBride 

(1999) 

Final Technical Report—Study of 

a Potential Seismic Source Zone 

in South-Central Illinois

Reports that seismic-reflection data indicate a pattern of basement-penetrating 

faulting in and near the Rend Lake fault zone that probably is a product of the same 

post-Pennsylvanian, E-W extensional stress regime that created the Centralia fault 

zone.

Cap au Gres Structure

Harrison and 

Shultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

Strikes of the axial surface of the fold and related faults range from N5°W to 

N85°W. The Cap au Gres structure, the north-striking Florissant dome, the 

Waterloo-Dupo anticline, and the Lincoln fold are all parts of the same 

deformational system. 

Although the feature has undergone recurrent movement, initial uplift occurred in 

Devonian and early Mississippian time. This paper summarizes studies related to 

the early deformational events on this structure. Based on kinematic indicators on 

faults and layer-parallel shortening associated with folding, the authors conclude 

that two episodes of deformation occurred along the Cap au Gres structure during 
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the late Mississippian and earliest Pennsylvanian. The initial episode, which was 

relatively minor, resulted from N-S compression and produced extension along N-S

segments of the structure. The next phase was a major episode of NE-SW 

compression that produced most of the deformational features along the structure. 

Following this period of deformation, some NW-striking segments of the structure 

were reactivated as high-angle normal faults. This deformation, which probably was 

of early Pennsylvanian age, appears to be the product of NW-SE maximum 

horizontal stress.

The authors note that interpretation of possible deformation of Quaternary gravels 

(see Nelson, 1995, below) is tentative because of uncertainties in correlating 

individual erosional surfaces that may not represent contiguous or equivalent 

contacts, and the fact that the Grover Gravel occurs at various elevations.

Mateker and 

Segar (1965)

Gravity Investigation Along the 

Eastern Flank of the Ozark Uplift

Geophysical surveys (gravity) along the structure indicate that the faults are nearly 

vertical and extend at least several kilometers into the crust.

Nelson (1995) Structural Features in Illinois The Cap au Gres structure is a faulted monocline that exhibits an overall W-NW 

trend in Missouri and an E-W trend in Illinois. The north side has been raised as 

much as 366 m (1,200 ft.) relative to the south side. Various workers have 

concluded that this structure corresponds to a high-angle, north-dipping reverse 

fault in Precambrian basement rocks and the associated locally fractured fold near 

the surface. Apparent displacement of the Plio-Pleistocene Grover Gravel and its 

underlying peneplain indicates possible Tertiary tectonic activity on this structure. 

The gravel and underlying erosional surface on the south side of the flexure lie 

about 45.7 m (150 ft.) lower than on the north. 

Eureka–House Springs Structure 

Clendenin et al. 

(1993) 

Sequencing Reelfoot Extension 

Based on Relations from 

Southeast Missouri and 

Interpretations of the Interplay 

Between Offset Preexisting Zones 

of Weakness

Interprets Middle and Late Ordovician, Middle Devonian, and post-Mississippian 

episodes of deformation on the Eureka–House Springs structure, suggesting that it 

experienced a minimum of 10 km (6 mi.) of left-lateral strike-slip motion. 
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Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

This paper summarizes the various interpretations of the complex NW-striking

Eureka–House Springs structure in eastern Missouri. The structure has been 

described as a doubly plunging anticline and associated faults or, alternatively, as 

three right-stepping en echelon fault segments. In addition, the Valmeyer anticline in 

Illinois may be an en echelon segment of the Eureka–House Springs structure. The 

general conclusion of this paper is that the zone may have originated as a 

Proterozoic structure and may extend north of the St. Charles lineament, although 

only those segments south of this lineament were reactivated at various times in the 

Phanerozoic. 

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

Estimates of significant lateral strike-slip motion are considered tentative given the 

lack of piercing points and insufficient strike length for that displacement. The 

authors observe no clear evidence of recent fault activity associated with the Eureka 

fault system, but note that proximity to their Meramec River liquefaction site and the 

uncertainties regarding the exact nature of this structure may warrant additional 

study.

Ste. Genevieve Fault Zone

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

Detailed studies of this fault zone document contractional, extensional, and strikeslip movement along high-angle faults, as well as multiple periods of movement. 

The zone dies out near both the St. Charles and Commerce lineaments (see 

Midcontinent-Craton Data Summary Table), suggesting a genetic link and 

demonstrating the influence of these structural features on tectonism in the region. 

Deformation along this structure is correlative to the late Mississippian to middle 

Pennsylvanian tectonic episode identified elsewhere in the Midcontinent. The paper 

provides evidence for a period of extension probably of Late Pennsylvanian to 

Permian age.

Detailed and reconnaissance mapping along the SGFZ for more than 75 years has 

revealed no evidence for Tertiary or Quaternary faulting. 

Heigold and 

Kolata (1993)

Proterozoic Crustal Boundary in 

the Southern Part of the Illinois 

Basin

The fault may have originated as a crustal plate boundary or suture zone during the 

Proterozoic. 
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Nelson (1995)

Nelson et al. 

(1997)

Structural Features in Illinois

Tertiary and Quaternary Tectonic 

Faulting in Southernmost Illinois

The Ste. Genevieve fault zone (SGFZ) is mapped for approximately 193 km (120 

mi.) along strike from SE Missouri into SW Illinois. It consists of numerous 

en echelon strands and braided segments having variable deformation styles and a 

complex history of reactivation. Displacement across the zone ranges from less 

than 198 m (650 ft.) to as much as 1,189 m (3,900 ft.). Detailed studies of this fault 

zone document contractional, extensional, and strike-slip movement along highangle faults, as well as multiple periods of movement. 

In Illinois, compressional deformation is documented along the Ste. Genevieve fault 

in early Pennsylvanian rocks (Nelson, 1995). The later report, Nelson et al. (1997), 

however, indicates that some faults along the SE part of the SGFZ in Illinois 

displace Cretaceous and Tertiary sediments, but Quaternary deposits are not 

faulted. 

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

Identifies soft-sediment deformation that could be related to low levels of ground 

shaking at one location along a strand of the fault. Diffuse seismicity occurs in the 

block between the SGFZ and Simms Mountain fault system. However, no evidence 

has been documented of any tectonic deformation of Quaternary deposits, nor has 

convincing evidence for paleoliquefaction been observed in this area.

Simms Mountain Fault System 

Clendenin et al. 

(1993)

Sequencing Reelfoot Extension 

Based on Relations from 

Southeast Missouri and 

Interpretations of the Interplay 

Between Offset Preexisting Zones 

of Weakness

Faults along the entire system were active in the late Cambrian as transfer faults 

related to Reelfoot rift extension.

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

The Simms Mountain fault system in SE Missouri consists of numerous braided and 

en echelon fault strands that are continuous southward into the Cape Girardeau 

fault system. Together these fault systems extend more than 106 km (66 mi.), and 

in places reach as wide as 79 km (24 mi.). Left-lateral strike-slip movement 

occurred on the fault system, primarily before formation of Mississippi Valley–type 

ore deposits of Permian age, although some are later or of unknown age.
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Bodenschatz-Lick Fault System

Clendenin et al. 

(1993)

Sequencing Reelfoot Extension 

Based on Relations from 

Southeast Missouri and 

Interpretations of the Interplay 

Between Offset Preexisting Zones 

of Weakness

Similarities in strike, dip, and early Paleozoic history suggest that this fault system 

may be related to the Greenville fault, which has been interpreted as a major early 

Paleozoic extensional fault associated with the Reelfoot rift.

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

The Bodenschatz-Lick fault system is a complex NE-striking zone that has been 

mapped for approximately 40 km (25 mi.) in SE Missouri and southern Illinois. 

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

Two clusters of low-magnitude seismicity have been recorded by the New Madrid 

network near the SW part of the Bodenschatz-Lick fault system near its intersection 

with the Simms Mountain–Cape Girardeau fault systems. Field investigations in the 

areas of seismicity found no evidence of earthquake-induced paleoliquefaction in 

Holocene deposits. 

Cape Girardeau Fault System

Harrison and 

Schultz (2002)

Tectonic Framework of the 

Southwestern Margin of the 

Illinois Basin and Its Influence on 

Neotectonism and Seismicity

The Cape Girardeau fault system, which is a continuation of the Simms Mountain 

fault system, consists of numerous branching and anastomosing, dominantly NWstriking near-vertical faults. Although NE and N-NW-striking faults are less common, 

they appear to show evidence for the most recent deformation. There are rhombshaped pull-apart grabens related to strike-slip faulting that can be divided into three 

groups: (1) those that contain only Paleozoic rocks, (2) those that contain Upper 

Cretaceous and lower Tertiary formations, and (3) those that contain Quaternary 

strata. 

Unequivocal evidence of faulting of Quaternary gravel has been observed in a 

quarry and roadcut at the SE end of the fault system near its intersection with the 

Commerce geophysical lineament. Results of recent trenching show evidence for 

Quaternary faulting, possibly post-Sangamon in age. Unfaulted Peoria Loess (late 

Wisconsinan in age) and possibly Roxana Silt overlie the fault and graben fill. The 

authors interpret the Quaternary deformation to have formed under E-NE horizontal 

maximum principal stress. They favor erosion and fill as an alternative to the finding 
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by Tuttle, Chester, et al. (1999) of a source of possible faulting in Quaternary gravel 

discovered on part of the Cape Girardeau fault system approximately 14.5 km 

(9 mi.) to the NW.

Wabash Valley Fault System

Bear et al. (1997) Seismic Interpretation of the Deep 

Structure of the Wabash Valley 

Fault System

This paper concludes that the fault system is not a northward continuation of the 

Reelfoot rift, because fault displacements of the WVFS decrease southward in the 

direction of the rift complex. Analysis of industry reflection data across the fault 

system indicates Cambrian fault movements as well as early Paleozoic dextral 

strike-slip along some of the faults. 

Bristol and 

Treworgy (1979)

The Wabash Valley Fault System 

in Southeastern Illinois

Major structures within the Illinois portion of the Wabash Valley fault system are 

identified from interpretation of drillhole and downhole geophysical logs. The WVFS 

is about 90–100 km (55–60 mi.) long and as much as 48 km (30 mi.) wide. The 

faults of the WVFS outline elongate, gently tilted or arched horsts and grabens, with 

the axial part of the system down-faulted relative to the margins. Drillhole data 

indicate predominantly normal movement with vertical offset of as much as 146 m 

(480 ft.) along the faults that is post-late Pennsylvanian. The faults die out 

downward; some may reach basement but do not necessarily penetrate it.

Counts, Durbin, 

and Obermeier 

(2008)

Seismic Ground-Failure Features 

in the Vicinity of the Lower 

Wabash and Ohio River Valleys

Field trip guidebook that describes tectonically induced ground failures of Tertiary 

and Quaternary age in the lower Wabash River and Ohio River valleys of southern 

Illinois, SW Indiana, and western Kentucky.

Counts et al. 

(2009a)

Investigation of Quaternary 

Displacement on the Uniontown 

Fault, Western Kentucky

Paleoseismic investigations (trenching and boreholes) of a prominent north-trending 

scarp on the floodplain of the Ohio River suggest that the scarp is tectonic rather 

than erosional. The trench across the scarp exposed flat-lying floodplain strata east 

of the scarp and a 3 m (9.8 ft.) down-to-the-west monoclinal flexure at the scarp. 

The scarp displaces Quaternary sediment and thus represents Quaternary folding. 

Shallow seismic-reflection lines reveal faulting that extends from the Paleozoic 

bedrock, up into the Quaternary alluvium, to near the base of the scarp. The 

monoclinal flexure is interpreted to have formed as a consequence of underlying 

Quaternary reverse faulting. The fault, referred to as the Uniontown fault, is part of 

the Wabash Valley fault system. Movement on the Uniontown fault appears to have 

controlled the course of the Ohio River in a fashion similar to the New Madrid bend 

of the Mississippi River around the north-trending Reelfoot fault in SW Kentucky. 
Table D-6.1.9 Data Summary 

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D-111 

Citation Title Description and Relevance to SSC

Counts et al. 

(2009b)

Paleoseismic Features Within the 

Wabash Valley Seismic Zones in 

Western Kentucky

Identifies several large clastic dikes in the banks of the Green River in Davies 

County. The largest was a weakly cemented gravel dike, 4–7 cm (1.6–2.8 in.) wide

and 3.3 m (10.8 ft.) high, that was injected upward into silty floodplain deposits. The 

base of this dike penetrated clay bed containing 9,850 ± 70 yr BP wood, indicating 

that the earthquake occurred during the early to middle Holocene.

A fault scarp 5 km (3 mi.) long was mapped in the Ohio River floodplain. The scarp 

trends north, faces west, and is 2.5 m (8.2 ft.) high at its southern end. Seismicreflection profiles across the scarp show that faulting in the Paleozoic bedrock 

extends upward and offsets Quaternary sediments just below the base of the scarp. 

A monoclinal flexure 3 m (9.8 ft.) down to the west was exposed at the base of the 

scarp in a trench. Radiocarbon dates indicate that the strata were folded between 

3,500 and 295 yr BP, so the scarp represents Holocene folding. 

Fraser et al. 

(1997)

Geomorphic Response to 

Tectonically-Induced Ground 

Deformation in the Wabash Valley

In the restraining bend region along the western edge of the Commerce deformation 

zone, morphometric analysis of the land surface, detailed geologic mapping, and 

structural analysis of bedrock indicate west-dipping surfaces in the Wabash Valley.

Heigold and 

Larson (1994)

Geophysical Investigations of 

Possible Recent Ground 

Deformation and Neotectonism in 

White County, Illinois

At a locality in the lower Wabash Valley, the authors investigated two sites where 

suspected neotectonism and ground deformation were associated with historical 

seismicity. One of the sites experienced liquefaction during the 1811 New Madrid 

earthquake. The other was an escarpment (referred to as the Meadow Bank) along 

a projection of the Herald-Phillipstown fault zone. Vertical electrical soundings, 

seismic refraction profiling, resistivity profiling, and boreholes were used to evaluate 

the depth to Pennsylvanian bedrock across the escarpment. It was concluded that 

the escarpment probably formed as a result of erosion, possibly along the fault 

zone. The study found no evidence to support recent movement along preexisting 

or newly formed faults.

Nelson and Lumm 

(1987)

Nelson (1995)

Structural Geology of 

Southeastern Illinois and Vicinity

Structural Features in Illinois

The Wabash Valley fault system (WVFS) is a major zone of NE-trending, high-angle 

normal and strike-slip faulting along the border area of Illinois, Kentucky, and 

Indiana. These faults lie within and form the borders of the NE-trending Grayville 

graben. The WVFS includes the following faults: Albion-Ridgeway, Cottonwood, 

Herald-Phillipstown, Inman, Inman West, Inman East, Junction, Maunie, Mt. 

Carmel–New Harmony, North Fork, Pitcher Lake, and Ribeyre Island. The Grayville 

graben and WVFS are bounded to the south by the Rough Creek–Shawneetown 

fault system. 
Table D-6.1.9 Data Summary 

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D-112 

Citation Title Description and Relevance to SSC

The authors suggest that the WVFS most likely developed in the Early Permian and

is therefore the same age as the Cottage Grove fault system. They note that 

individual faults within the zone are characterized by slightly arcuate segments that 

overlap. They also conclude that the WVFS does not cross the Rough Creek–

Shawneetown fault zone.

Based on previous interpretations of WVFS structures as primarily normal faults 

(Bristol and Treworgy, 1979), the conclusion of Nelson and Lumm (1987) is that the 

WVFS developed in response to W-NW and E-SE extension. Nelson (1995) 

proposes that the faults originated from a deformation episode that initially produced 

doming along a N-NE-trending axis. 

Sexton et al. 

(1986)

Seismic Reflection Profiling 

Studies of a Buried Precambrian 

Rift Beneath the Wabash Valley 

Fault Zone

Based on interpretation of seismic-reflection profiles, this paper argues that the 

faults of the WVFS developed by reactivation of a Precambrian rift zone (Grayville 

graben) that was the northern extension of the Reelfoot–Rough Creek system. The 

paper also discusses regional and detailed gravity and magnetic anomaly data. 

Regional data sets had previously been used to infer the existence of a NE-trending

rift beneath the Wabash Valley in SW Indiana and SE Illinois. Detailed gravity and 

magnetic profile data collected along the Wabash Valley seismic-reflection lines 

were also examined. Calculations of theoretical gravity anomalies associated with 

the locations of the Wabash Valley faults suggest that due to the small amplitude of 

the offsets, no identifiable anomalies would be expected in the detailed gravity 

anomaly data. Large, observed regional gravity and magnetic anomalies over the 

Wabash Valley fault area are almost certainly caused by density contrasts 

associated with the pre-Mt. Simon rocks and intrabasement sources.

Van Arsdale et al. 

(2009)

Quaternary Displacement Along 

the Hovey Lake Fault of Southern 

Indiana and Western Kentucky

A shallow S-wave seismic-reflection line acquired across the Hovey Lake fault in 

southern Indiana and western Kentucky reveals Paleozoic bedrock that is folded 

and normal faulted 10.5 m (34.4 ft.). The overlying Quaternary alluvium has 2 m 

(6.6 ft.) of reverse displacement at a depth of 5 m (16.4 ft.), thus revealing structural 

inversion. Although there is no surface scarp, a line of shallow borings, acquired 

across the seismically identified fault, indicates that the faulting may come to the 

surface. Trenching was not permitted at this site.

Folding and faulting in Paleozoic bedrock and overlying Quaternary alluvium also 

was observed in a shallow S-wave seismic-reflection line that was acquired across 

a down-to-the-west scarp within the Hovey Lake fault system in western Kentucky. 

A trench exposed folded 3,500 yr BP Ohio River alluvium. The down-to-the-west 

fold, which has an amplitude of 3 m (9.8 ft.), is believed to have formed in response 
Table D-6.1.9 Data Summary 

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D-113 

Citation Title Description and Relevance to SSC

to underlying down-to-the-west Holocene fault displacement. Fractures within an 

undeformed unit that laps onto the scarp indicate that minor fault reactivation may 

have occurred within the last 295 years.

Wheeler et al. 

(1997)

Seismotectonic Map Showing 

Faults, Igneous Rocks, and 

Geophysical and Neotectonic 

Features in the Vicinity of the 

Lower Wabash Valley, Illinois, 

Indiana, and Kentucky

Describes possible neotectonic points in the lower Wabash Valley based on Heigold 

and Larson (1994).

Woolery (2005) Geophysical and Geological 

Evidence of Neotectonic 

Deformation Along the Hovey 

Lake Fault, Lower Wabash Valley 

Fault System, Central United 

States

High-resolution seismic (shear-wave) reflection profiles collected along the Hovey 

Lake fault, a known Paleozoic fault within a system of faults in the southernmost 

Wabash Valley fault system in an area of recognized prehistoric and contemporary 

seismicity, show high-angle deformation extending above the Paleozoic bedrock 

and into Upper Quaternary sediment. Time-displacement calculations from the data 

show approximately 10.5 m (34.4 ft.) of offset on the top-of-bedrock horizon, located 

7.7 m (25.3 ft.) below ground surface, suggesting fault movement at this site as late 

as ~37 ka.

Paleoliquefaction Studies (See also Table 6.1.9-1)

Chester and Tuttle 

(2000)

Paleoseismology Study in the 

Cach River Valley, Southern 

Illinois

Six sand dikes were observed at four locations. The sand dikes range from 1 to 9 

cm (0.4 to 3.5 in.) wide and pinch upward, extending to 1.1 m (3.6 ft.) above the 

water table or 2.4 m (7.9 ft.) below the top of the cutbank. Differences in weathering 

characteristics may indicate two generations of sand dikes. A radiocarbon date of 

AD 1020–1250 represents a maximum age for the younger generation, and possibly 

the older generation as well. The results are consistent with ground shaking of 

modified Mercalli intensity VIII-IX. 

Counts et al. 

(2009b)

Paleoseismic Features Within the 

Wabash Valley Seismic Zones in 

Western Kentucky

Identifies several large clastic dikes in the banks of the Green River in Davies 

County. The largest was a weakly cemented gravel dike, 4–7-cm (1.6–2.8 in.) wide 

and 3.3 m (10.8 ft.) high, that was injected upward into silty floodplain deposits. The 

base of this dike penetrated clay bed containing 9,850 ± 70 yr BP wood, indicating 

that the earthquake occurred during the early to middle Holocene.
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-114 

Citation Title Description and Relevance to SSC

Green et al. 

(2005)

Engineering Geologic and 

Geotechnical Analysis of 

Paleoseismic Shaking Using 

Liquefaction Effects: Field 

Examples

This paper cites the assessment of the Vincennes paleoearthquake as a case study 

for implementing the methods outlined in Olson et al. (2005a) for assessing 

uncertainties in (1) the significance of changes in the geotechnical properties of 

post-liquefied sediments (e.g., aging and density changes); (2) the selection of 

appropriate geotechnical soil indices from individual paleoliquefaction sites; and (3) 

the methodology for integration of back-calculated results of strength of shaking 

from individual paleoliquefaction sites into a regional assessment of paleoseismic 

strength of shaking.

Twelve sites that are at scattered locations in the Wabash Valley and that exhibit 

paleoliquefaction features are analyzed. The features are first provisionally 

attributed to the Vincennes earthquake, which occurred around 6,100 yr BP, and 

are used to illustrate the proposed approach for selecting representative soil indices 

of the liquefied sediments. These indices are used in back-calculating the strength 

of shaking at the individual sites, the results from which are then incorporated into a 

regional assessment of the moment magnitude, M, of the Vincennes earthquake. 

The regional assessment validated the provisional assumption that the 

paleoliquefaction features at the scattered sites were induced by the Vincennes 

earthquake, in the main, which was determined to have a magnitude of M ~ 7.5.

Hajic et al. (1995) Distribution and Dating of 

Prehistoric Earthquake 

Liquefaction in Southeastern

Illinois, Central U.S.

Presents results of a paleoliquefaction survey along streams in SE and central 

Illinois. A total of 127 paleoliquefaction sites are identified. Relatively wide dikes in 

the Sangamon and Kaskaskia river valleys at distances of 200 and 175 km (124.3 

and 108.7 mi.) from Vincennes suggest either shaking from multiple sources or a 

noncircular distribution of features associated with the Vincennes earthquake.

Stratigraphic, geomorphic, pedologic, archaeological, and preliminary radiocarbon

evidence indicates that SE Illinois was shaken by substantial earthquakes at a 

minimum two, and possibly six, times in the past: possibly around 18,500 yr BP, 

around 6,100 yr BP, possibly around 3,750 yr BP, and during the 1811-1812 New 

Madrid earthquakes. Two additional Holocene earthquakes are possibly 

represented by liquefaction features along the Sangamon River (<9,200 yr BP) and 

lower Kaskaskia River.
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-115 

Citation Title Description and Relevance to SSC

Hajic and Wiant 

(1997)

Dating of Prehistoric Earthquake 

Liquefaction in Southeastern and 

Central Illinois

Presents results of an additional stream bank survey along reaches of Big Muddy, 

Miller, Mill, and Big creeks and an unnamed ditch in the Little Wabash Valley, all in 

SE Illinois. An additional stream bank survey along reaches of rivers and creeks in

central and west-central Illinois and east-central Missouri resulted in negative 

evidence for any paleoliquefaction features, suggesting that the part of west-central 

Illinois north of St. Louis covered by these surveys was not struck by an earthquake 

of sufficient magnitude to cause liquefaction during the Holocene.

The majority of paleoliquefaction observed in SE Illinois is attributable to the 

Vincennes earthquake. An earthquake near Mt. Auburn (subsequently referred to by 

McNulty and Obermeier (1999) as the Springfield earthquake) occurred after around 

7,400 yr BP and before around 4,500 yr BP. Two other sites in Illinois are possibly 

attributable to the Skelton–Mt. Carmel earthquakes. Dikes at two SE Illinois sites 

most likely were emplaced about 19,800 ± 1,100 yr BP; these may be related to 

features observed in SW Indiana or they may be glaciotectonic.

McNulty and 

Obermeier (1999)

Liquefaction Evidence for At Least 

Two Strong Holocene 

Paleoearthquakes in Central and 

Southwestern Illinois

Discusses evidence for the timing and magnitude of two middle Holocene 

earthquakes in Illinois: the Springfield and Shoal Creek earthquakes. The 

Springfield earthquake occurred between 5,900 and 7,400 yr BP; dikes are as much 

as 0.4 m (1.3 ft.) in width near the presumed energy center about 35 km (21.7 mi.) 

NE of Springfield, Illinois; the magnitude is estimated to be at least M 6.2 and less 

than M 6.8. The Shoal Creek earthquake occurred around 5,700 yr BP; dikes 

probably extend approximately 35 km (22 mi.) from the energy center (assumed to 

be approximately 65 km, or 40.5 mi., E-SE of St. Louis, Missouri; dikes as wide as 

0.5 m (1.6 ft.) are observed; the magnitude is estimated to be M 6.0 or greater.

Munson et al. 

(1997)

Liquefaction Evidence for 

Holocene and Latest Pleistocene 

in the Southern Halves of Indiana 

and Illinois—A Preliminary 

Overview

Identifies evidence for at least eight paleoearthquakes having magnitudes stronger 

than any in the historical era in southern Illinois and southern Indiana. At least six 

prehistoric earthquakes occurred during the Holocene and at least two others 

occurred during the latest Pleistocene. The two largest paleoearthquakes were 

centered in the lower Wabash Valley. The estimated magnitude of the largest 

earthquake, which occurred 6,100 ± 200 yr BP, is M 7.5–7.8. The next largest 

earthquake, an estimated M 7.1–7.3 earthquake, occurred 12,000 ± 1,000 yr BP. 

Two other paleoearthquakes likely had magnitudes of M ≥ 6.8.

It is likely that liquefaction evidence has been discovered for all Holocene and latest 

Pleistocene paleoearthquakes with M ≥ 7 (radius of liquefaction effects > 50 km

[31 mi.]) in southern Illinois and Indiana. However, in addition to the six or more 

M 6.0–7.0 earthquakes that have been discovered, numerous other earthquakes 
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-116 

Citation Title Description and Relevance to SSC

strong enough to potentially induce limited liquefaction could have struck other 

areas but, based on the lack of liquefiable deposits, left no evidence. In some parts 

of the southern halves of Indiana and Illinois, an earthquake with a potential radius 

of liquefaction effects of 30–40 km (18.6–25 mi.) could have struck without leaving 

liquefaction evidence. 

Obermeier et al. 

(1993)

Liquefaction Evidence for One or 

More Strong Holocene 

Earthquakes in the Wabash 

Valley of Southern Indiana and 

Illinois, with a Preliminary 

Estimate of Magnitude

Provides criteria for interpreting an earthquake origin for dikes observed in the 

Wabash Valley. Concludes that virtually all of the dikes were formed by a single 

large earthquake that took place between 1.500 and 7.5 ka. The epicenter of the 

strongest earthquake(s) was near Vincennes, Indiana. The strength of the 

earthquake far exceeds the level of shaking and magnitude of the 1895 M 6.8 

Charleston, Missouri, earthquake; the magnitude of the Vincennes earthquake

appears to have been similar to that of the 1886 Charleston, South Carolina, 

earthquake (M ~ 7.5). 

Obermeier (1998) Liquefaction Evidence for Strong 

Earthquakes of Holocene and 

Latest Pleistocene Ages in the 

States of Indiana and Illinois, USA

Major conclusions outlined in this summary paper are as follows:

Virtually all dikes observed are from seismic liquefaction. Dikes were induced by 

prehistoric earthquakes whose energy centers (and epicenters) were almost 

exclusively in Indiana and Illinois (with the exception of some features in Cache 

Valley related to 1811-1812 New Madrid earthquakes).

Probably nine paleoearthquakes larger than historical earthquakes are identified,

at least seven and probably eight Holocene earthquakes of which have a 

magnitude of M 6 or higher.

The largest, which occurred ~6,100 ± 100 yr BP, was on the order of M 7.5; the 

next largest (M ~ 7.1) occurred ~12,000 ± 1,000 yr BP. Three more had 

magnitudes of M > 6.5.

The two strongest were in proximity to each other and took place in the general 

vicinity of the most numerous and strongest historical earthquakes (M 4–5.5) in 

the lower Wabash Valley of Indiana and Illinois. Paleoearthquakes of lower 

magnitudes are more randomly distributed and have struck in regions having no 

significant historical seismicity.

Probably all earthquakes of M > 7 have been identified in Illinois and Indiana.

A significant number (10 or more) of moderate to strong paleoearthquakes

(M 6–7) likely occurred during Holocene and latest Pleistocene time but are not 

recorded in paleoliquefaction record because of a lack of liquefiable deposits. 
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-117 

Citation Title Description and Relevance to SSC

Olson et al. 

(2005a)

Geotechnical Analysis of 

Paleoseismic Shaking Using 

Liquefaction Effects: A Major

Updating

Describes a new methodology proposed for the geotechnical analysis of strength of 

paleoseismic shaking using liquefaction effects. The proposed method provides 

recommendations for the selection of both individual and regionally located test 

sites, provides techniques for the validation of field data for use in back-analysis, 

and presents a recently developed energy-based solution to back-calculate paleoearthquake magnitude and strength of shaking. The proposed method allows 

investigators to qualitatively assess the influence of post-earthquake density change 

and aging. The proposed method also describes how the back-calculations from 

individual sites should be integrated into a regional assessment of paleoseismic 

parameters.

Olson et al. 

(2005b)

Revised Magnitude Bound 

Relation for the Wabash Valley 

Seismic Zone of the Central 

United States

Provides a revised regional magnitude-bound curve for the central U.S. using a 

consistent site-to-source distance measure, a detailed review of liquefaction 

accounts resulting from historical earthquakes, and magnitude estimates for those 

historical earthquakes that have factored in data from recent seismological studies. 

Reassessed magnitudes for four paleoearthquakes in the Wabash Valley are 

approximately 0.5–0.7 magnitude units smaller than previously suggested. The 

revised magnitude estimates are M 7.3 (Vincennes earthquake), M 6.7 (Skelton 

earthquake), M 6.3 (Vallonia earthquake), and M 6.2 (Waverly earthquake).

Olson et al. (2007) Quantifying Uncertainties in 

Paleoliquefaction Studies

A preliminary M 7.99 ± 0.27 is estimated for the Vincennes paleoearthquake 

(around 6,100 yr BP) using simplified and rigorous statistical and probabilistic 

methods to quantify uncertainties in liquefaction susceptibility (aging and density 

change, liquefaction severity, fines content adjustment, and overburden stress 

correction); field data quality (field observations and in situ test measurement, 

ground failure mechanism, and field setting); seismicity and seismic demand 

(attenuation relationships, magnitude scaling factor, depth reduction factor, and 

local site response); and a Bayesian updating framework that uses the magnitude 

bound method to estimate a prior distribution,.

Pond and Martin 

(1997)

Estimated Magnitudes and 

Accelerations Associated with 

Prehistoric Earthquakes in the 

Wabash Valley Region of the 

Central United States

Presents results of a geotechnical study of soil conditions at paleoliquefaction sites 

to estimate both the magnitude and accelerations of four prehistoric earthquakes. 

Using an energy-stress approach, the geotechnical and seismological estimates of 

surface accelerations suggest M 6.9 (Waverly earthquake), M 7.1 (Vallonia 

earthquake), M 7.3 (Skelton earthquake), and M 7.8 (Vincennes earthquake).
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-118 

Citation Title Description and Relevance to SSC

Su and McBride 

(1999)

Final Technical Report—Study of 

a Potential Seismic Source Zone 

in South-Central Illinois

Discusses interpretation of reprocessed seismic-reflection profiles across the Du 

Quoin monocline–Louden anticline region and paleoliquefaction reconnaissance 

along 90 km (56 mi.) of the Big Muddy River and its tributaries in the vicinity of 

these structures. No new paleoliquefaction features were observed, but this may be 

due to lack of liquefiable sediments. The report concludes that all previously

recognized paleoliquefaction features in the study region could be induced by 

earthquakes on the Du Quoin monocline–Louden anticline structures.

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest 

of the New Madrid Seismic Zone

The results of this study are summarized and updated in Tuttle (2005b); see below.

Tuttle (2005b) Paleoseismological Study in the 

St. Louis Region: Collaborative 

Research

This paper summarizes and updates observations reported by Tuttle, Chester, et al. 

(1999). At least two generations of Holocene earthquake-induced liquefaction 

features, including sand and silt dikes and sills, and only two sand blows, are 

identified in the St. Louis region. Some features probably formed during the 1811-

1812 or earlier New Madrid earthquakes, and others formed during a middle 

Holocene earthquake in 4520 BC ± 160 years. Late Holocene sand dikes, up to 26 

cm (10.2 in.) in width, occur along the Kaskaskia River and its tributaries, Crooked, 

Shoal, and Silver creeks, as well as along Cahokia and Piasa creeks and the 

Cache, Castor, Marys, and Meramec rivers. The 4250 BC earthquake may or may 

not have been responsible for all of the middle Holocene features. The relatively 

large size of features identified near Germantown, Illinois, suggests that the 

earthquake source may be located east of St. Louis. Alternative sizes and locations 

are suggested. The Meramec River features could have formed as a result of a 

moderate-to-large earthquake centered in the St. Louis area or a very large 

earthquake centered 80–100 km (50–62 mi.) east of St. Louis.

Seismicity

Bakun and 

Hopper (2004a)

Catalog of Significant Historical 

Earthquakes in the Central United 

States

Modified Mercalli intensity assignments are used to estimate source locations and 

moment magnitude M for 18 nineteenth-century and 20 early twentieth-century 

earthquakes in the central U.S. for which estimates of M are otherwise not 

available. There has been persistent seismic activity in the Illinois basin in southern 

Illinois and Indiana, with M > 5.0 earthquakes in 1895, 1909, 1917, 1968, and 1987. 

Historical earthquakes (pre-1952) in the Illinois basin have been associated with the 

Wabash Valley fault zone, the Cottage Grove fault zone, the Du Quoin monocline, 

the Ste. Genevieve fault zone, and the La Salle anticlinorium. 
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-119 

Citation Title Description and Relevance to SSC

Hamburger et al. 

(2008)

Geodetic Observations from the 

Region Surrounding the M 5.2 Mt. 

Carmel, Illinois Earthquake

The April 18, 2008, M 5.2 earthquake was located close to the New Harmony fault 

at ~14 km (~8.7 mi.) depth. Analysis of GPS data suggests systematic NW motion 

of about 0.5–0.7 mm/yr with respect to the Stable North American Reference 

Frame. Block models, which assume boundaries along the Cottonwood Grove–

Rough Creek Graben (CGRCG) and the WVFS, indicate marginal block velocities 

with possible strike-slip motion along the WVFS, and E-W motions along the 

CGRCG.

Hamburger et al. 

2009)

Is There a Connection Between 

Seismicity and Deformation in the 

New Madrid and Wabash Valley 

Seismic Zones?

Comparison of geodetic and geophysical data between WVSZ and NMSZ. In both 

cases, regional seismic and potential field data provide evidence for high-angle, 

basement-penetrating faults that define narrow, elongate Precambrian grabens that 

lie beneath relatively undeformed Paleozoic or Mesozoic rocks. Data from a 56-sitecampaign GPS geodetic network in the southern Illinois basin indicate systematic 

NW motion of about 0.5–0.7 mm/yr with respect to the Stable North American 

Reference Frame. Average results for the entire network show marginally significant 

strains, with an orientation rotated 45° from the overall direction of intraplate stress 

in the U.S. Midcontinent.

Kim (2003) The 18 June 2002 Caborn, 

Indiana, Earthquake: Reactivation 

of Ancient Rift in the Wabash 

Valley Seismic Zone?

The June 18, 2002, Mw 4.6 earthquake occurred on a steeply dipping fault at a 

depth of about 18 km (11.2 mi.; better than ±2 km—or ±1.2 mi.—horizontal and 

vertical location accuracy). The source mechanism determined from regional 

waveform analysis is predominantly strike-slip along near-vertical nodal planes (dips 

82° and 84°) striking 28° and 297°. The close proximity of the epicenter to the trace 

of the Caborn fault, and good agreement between the strike and dip of that fault and 

source mechanism for the June 18, 2002, earthquake suggest that the earthquake 

occurred on that fault. This earthquake may suggest that buried faults associated 

with a possible Precambrian rift system are being reactivated by the contemporary 

E–E-NE-trending regional horizontal compressive stress.

Larson et al. 

(2009)

Analysis of Effects from the April 

18, 2008 Illinois Earthquake

Analyzes the April 18, 2008, M 5.4 earthquake that occurred in the Wabash Valley 

seismic zone at depth of 11.6 km (7.2 mi.). The earthquake was located in a mature 

oil and coal production region; E-W elongation of the Intensity IV and higher 

regions. Some of the E-W elongation may be attributed to the E-W focal mechanism 

of the earthquake, whereas other patterns coincide with major river channels (soil 

amplification) and a geologic structure.
Table D-6.1.9 Data Summary 

Wabash Valley RLME

D-120 

Citation Title Description and Relevance to SSC

McBride et al. 

(2007)

McBride, 

Hildenbrand, et al. 

(2002)

Deep Faulting and Structural 

Reactivation Beneath the 

Southern Illinois Basin

Interpreting the Earthquake 

Source of the Wabash Valley 

Seismic Zone (Illinois, Indiana, 

and Kentucky) from Seismic 

Reflection, Gravity, and Magnetic 

Intensity

Seismotectonic implications described above (Basement Structure section). 

McBride, Hildenbrand, et al. (2002) provide a table summarizing depths and 

magnitudes for instrumentally recorded earthquakes of the Wabash Valley seismic 

zone (mbLg 3.1–5.2) that range from 4.9 ± 14.1 km (3 ± 8.8 mi.) to 23.4 ± 2.1 km

(14.5 ± 1.3 mi.).

Withers et al. 

(2009)

Introduction and Background for 

the April 18, 2008 Illinois 

Earthquake

Discusses the April 18, 2008, Mt. Carmel, Illinois, earthquake, the largest 

earthquake in the Wabash Valley seismic zone in the past 20 years. The 

earthquake took place near Mt. Carmel, Illinois; the magnitude was Mw 5.2 (Mw 5.4 

according to GCMT [http://www.global cmt.org]); a relatively long-lasting aftershock 

sequence included 37 earthquakes located by the network, with 3 earthquakes 

greater than magnitude 4).

Yang et al. (2009) Determination of the Fault Plane 

for the April 18, 2008 Illinois 

Earthquake by Detecting and 

Relocating Aftershocks

Analysis of aftershocks using the sliding-window cross-correlation technique and 

the double-difference relocation algorithm gives a best-fit plane having a nearly E-W 

trend with an orientation of 248 and a dip angle of 81. The fault is nearly vertical 

down to ~20 km (~12.4 mi.).

Seismic Hazard Models 

Petersen et al. 

(2008)

Documentation for the 2008 

Update of the United States 

National Seismic Hazard Maps

Although the Wabash Valley region in southern Indiana and Illinois is part of the 

craton, M 7.5 is used for Mmax there, based on the distribution of paleoliquefaction 

features resulting from past large earthquakes.

Wheeler and 

Cramer (2002)

Updated Seismic Hazard in the 

Southern Illinois Basin: Geological 

and Geophysical Foundations for 

Use in the 2002 USGS National 

Seismic-Hazard Maps

Based on estimates of the magnitudes (M 7.1 and M 7.5) of prehistoric earthquakes 

in the southern Illinois basin, this paper outlines three alternative source 

configurations that can be combined in a logic tree: the oval tri-state seismicity 

source zone that is centered on the two energy centers; a narrow source zone that 

follows the Vincennes bend in the Commerce geophysical lineament; and the 

Grayville graben. Mmax is set at 7.5 inside each alternative source.
Table D-7.3.1 Data Summary 

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Citation Title Description and Relevance to SSC

Initiation of Iapetan Rifting

Abdel-Rahman and 

Kumarapeli (1998)

Geochemistry of Mantle-Related 

Intermediate Rocks from the Tibbit Hill 

Volcanic Suite, Quebec Appalachians

Major and trace-element geochemistry of intermediate volcanic rocks of the 

Tibbit Hill volcanic suite provide evidence for anorogenic A1 type suites, 

consistent with the earlier interpretation of an Iapetan triple junction. Traceelement modeling suggests that these intermediate magmas were produced by 

up to 20% fractional crystallization of alkaline to transitional basaltic melts, 

representing differentiates of basalts related to hotspot plumes or continental 

rift zones. The authors also suggest that the intermediate rocks of the Tibbit Hill 

volcanic suite are comagmatic and coeval with the Adirondack dike swarm and 

formed shortly before the onset of seafloor spreading.

Abdel-Rahman and 

Kumarapeli (1999)

Geochemistry and Petrogenesis of 

the Tibbit Hill Metavolcanic Suite of 

the Appalachian Fold Belt, Quebec–

Vermont: A Plume-Related and 

Fractionated Assemblage

Presents the geochemistry of the Tibbit Hill mafic to felsic volcanic assemblage 

based on data presented in previous studies. The study concludes that the 

mafic basalts from the Tibbit Hill volcanic suite crystallized from basaltic 

magma produced by approximately 2.5% batch partial melting of garnet 

lherzolite with a final basaltic melt segregation depth of 80–100 km (50–62 mi.), 

which is consistent with melting within a rising mantle plume below the Sutton 

Mountains triple junction. Twenty-five percent fractionation of these basaltic 

magmas produced the intermediate melts.

The Adirondack dike swarm is geochemically similar to the Tibbit Hill basalt 

and both differ from the geochemically depleted Grenville dike swarm, 

suggesting that Tibbit Hill (and therefore the Adirondack dike swarm) represent 

the youngest, pre-breakup, extension-related volcanism prior to the initiation of 

seafloor spreading. 

This paper does not consider the results of other Iapetan volcanics in the 

region—specifically, the work of McCausland and Hodych (1998). 

Bédard and 

Stevenson (1999)

The Caldwell Group Lavas of 

Southern Quebec: MORB-Like 

Tholeiites Associated with the 

Opening of Iapetus Ocean

Trace-element and Nd isotopic data were obtained for the Caldwell Group 

lavas of southern Quebec. These undated rocks, which belong to the internal 

nappe domain of the Humber zone, were deformed during the Taconic 

orogeny. These rocks initially formed at an advanced stage in the transition 

from rift to drift along the Iapetan margin. Despite exhibiting clear evidence of 

hydrothermal alteration, several conclusions were inferred from the 

geochemistry of these basalts. These basalts crystallized from melts derived 

from normal mid-ocean ridge basalt (MORB) at low to medium pressure 
Table D-7.3.1 Data Summary 

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D-122 

Citation Title Description and Relevance to SSC

fractional crystalization. Most lavas represent about 20% melting from a source 

slightly less depleted than fertile MORB mantle (asthenospheric mantle),

whereas subpopulations of the Caldwell lavas are characterized by 6%–15% 

melting of the same source mantle. These data are substantiated by Ndisotope data that indicate derivation from a light rare-earth-element-depleted 

mantle that is more radiogenic than other Iapetus basalts, implying that other 

basalts in the region were derived from a more enriched source. Sedimentary 

samples reflect a mixture of old (Archean) and juvenile (Iapetan) crustal 

sources for the basin. 

Cawood et al. (2001) Opening Iapetus: Constraints from the 

Laurentian Margin in Newfoundland

Evaluates the age relationships of the Skinner Cove Formation (550.5 +3/–2 

Ma), the Lady Slipper pluton (555 +3/–5 Ma), and the youngest marine 

carbonate sediments (540–535 Ma) interpreted as the rift drift transition from 

within the Humber zone of the Appalachian orogen in Newfoundland. 

Compares these age relationships with the paleomagnetic data of McCausland 

and Hodych (1998) and data for other igneous activity on the eastern margin of 

Laurentia. Attributes these data to a two-stage rifting process along the eastern 

margin of Laurentia.

Igneous activity 760–700 Ma in the Appalachian Blue Ridge corresponds with 

the opening of the proto-Pacific between East Australia /West Antarctic 

conjugate margins. The younger set of igneous activity observed in eastern 

Laurentia between 620 and 550 Ma involves rifting and separation of Laurentia 

from the West Gondwana cratons corresponding to the closure of the 

Mozambique Ocean and assembly of East and West Gondwana; initiation of 

subduction of the proto-Pacific beneath East Gondwana; and rifting of Baltica 

and Siberia from Laurentia and Gondwana. The Iapetus Ocean was initiated 

between Laurentia and Gondwana by 570 Ma, while Baltica had already 

separated from Laurentia. A proto-Pacific spreading center may have also 

propagated at that time. 

Faill (1997a) A Geologic History of the NorthCentral Appalachians. Part 1. 

Orogenesis from the Mesoproterozoic 

Through the Taconic Orogeny

Crustal extension and rifting late in the Neoproterozoic and into the earliest 

Cambrian separated the Neoproterozoic supercontinent Rodina into East 

Gondwana, West Gondwana, and Laurentia. This rifting event resulted in the 

development of the St. Lawrence rift system. The breakup of Rodinia spanned 

approximately 200 Myr, with separation of East Gondwana from western 

Laurentia approximately 750 million years ago and rifting of eastern Laurentia 

from West Gondwana resulting in the opening of several intervening oceans. 
Table D-7.3.1 Data Summary 

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Citation Title Description and Relevance to SSC

The Iapetus Ocean was initially defined as the early Paleozoic ocean between 

Baltica and Laurentia (Greenland); the Theic Ocean was defined as the ocean 

between Laurentia and Gondwana; and the Rheic Ocean between Baltica and 

Gondwana.

Emphasizes that the subsequent usage of the name ―Iapetus‖ to refer to the 

Paleozoic ocean off the Laurentia east margin became nearly universal, and 

that sensu stricto the Iapetus Ocean was closed in the Late Silurian Caledonia 

orogeny during the docking of Avalonia microcontinents with Laurentia. The 

remaining ocean that lay east of Avalonia is generally called Theic, leading the 

author to recognize the Paleozoic ocean east of Laurentia as Theia. This 

discussion uses the name Iapetus as given by various authors cited by Faill 

(1997a), recognizing the distinction between these three Paleozoic oceans.

Higgins and van 

Breemen (1998)

The Age of the Sept Iles Layered 

Mafic Intrusion, Canada: Implications 

for the Late Neoproterozoic/Cambrian 

History of Southeastern Canada

Authors obtained U-Pb ages of 565 ± 4 Ma for the Sept Iles layered mafic 

pluton located on islands and peninsulas of the Gulf of St. Lawrence. 

Combining these results with other published ages for Neoproterozoic to 

Cambrian igneous rocks from the Laurentian margin suggests three phases of 

magmatism:

1. Tholeiitic dike emplacement was diachronous along the Laurentian margin: 

the Long Range dike swarm in Newfoundland was dated at 615 ± 2 Ma over 

a distance of 400 km (249 mi.; Kamo et al., 1989); Grenville dike swarm 

formed synchronously with the Ottawa graben at 590 +2/–1 Ma over a 

distance of 400 km (249 mi.; Kumarapeli, 1993; Kamo et al., 1995). These 

dike swarms may have been produced by one or two mantle plumes 

between 615 and 590 Ma, possibly one at Sept Iles.

2. Following dike emplacement, alkaline plutons intruded into a relatively large 

region spanning Quebec, Ontario, Greenland, and Scandinavia as early as 

578 Ma and as late as the Sept Iles intrusion (565 Ma). The authors 

attribute these plutons to a major plume and triple junction located at Sept 

Iles instead of the location below the Sutton Mountains proposed by 

Kumarapeli (1993), but acknowledge that the two dike swarms could be the 

result of two mantle plumes separated by 25 Myr. The authors also observe 

that the alkaline plutons were intruded along rift faults that developed after 

the emplacement of dikes. 

3. Undated diabase dikes and metabasaltic flows occur throughout the 
Table D-7.3.1 Data Summary 

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D-124 

Citation Title Description and Relevance to SSC

Northern Appalachians, indicating the earliest stages of the formation of the 

Iapetus Ocean. Tholeiitic lavas of the Tibbit Hill Formation have U-Pb zircon 

ages of 554 +4/–2 Ma (Kumarapeli et al., 1989), and alkaline volcanic rocks 

at Skinners Cove, Newfoundland, have U-Pb ages of 550 +3/–2 Ma 

(McCausland et al., 1997). 

Hodych and Cox 

(2007)

Ediacaran U-Pb Zircon Dates for the 

Lac Matapédia and Mt. St.-Anselme 

Basalts of the Quebec Appalachians: 

Support for a Long-Lived Mantle 

Plume During the Rifting Phase of 

Iapetus Opening

U-Pb zircon ages for the Lac Matapédia basalt (565 ± 6 Ma and 556 ± 5 Ma) 

and the Mt. St.-Anselme basalt (550 ± 7 Ma) support the interpretation of a 

long-lived Sutton Mountains mantle plume. These data close the gap between 

the end of flood basalt and the beginning of plume magmatism and support a 

rift-drift transition at 540 Ma as opposed to 570 Ma (McCausland and Hodych, 

1998). This hypothesis implies that Laurentia drifted northward more slowly 

than was suggested by McCausland and Hodych (1998).

Kamo et al. (1995) Age of the Grenville Dyke Swarm, 

Ontario–Quebec: Implications for the 

Timing of Iapetan Rifting

Improves the geochronology of the Grenville dike swarm by obtaining U-Pb 

baddeleyite ages from the widest dikes throughout the Ottawa graben. These 

results give an age of 590 Ma, implying that the Grenville dike swarm was 

emplaced within a relatively short time span. These dikes are thought to have 

formed at the onset of rifting within the Ottawa graben, the Sutton Mountains 

triple junction, and the related segment of the Iapetan margin. Comparison with 

ages of similar rift-related igneous rocks along the Iapetan margin of Laurentia, 

including the Bakersville dike swarm of the Blue Ridge (570 Ma), Franklin 

swarm of northern Canadian Shield (723 Ma), and Long Range dikes of SE

Labrador and Newfoundland (615 Ma), indicate that Iapetan rifting occurred 

along vast distances of the northern and eastern margins of Laurentia.

The timing of initial rifting within the Ottawa graben is somewhat earlier than 

other parts of North America, suggesting that rift initiation progressed from the 

northern Laurentia margin at 723 Ma to Labrador and Newfoundland at 615 

Ma, followed by the Grenville dike swarm at 590 Ma. 
Table D-7.3.1 Data Summary 

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D-125 

Citation Title Description and Relevance to SSC

Kumarapeli (1985) Vestiges of Iapetan Rifting in the 

Craton West of the Northern 

Appalachians

Proposes that a mantle plume produced the initial ruptures of Iapetan rifting 

along a triple junction that led to continental fragmentation and the 

development of an aulacogen in the Ottawa graben. Carbonatite complexes of 

the Ottawa and Saguenay grabens with ages of 565 and 564 Ma, respectively, 

support the view that these two rifts formed as parts of a single event. Alkaline

to transitional bimodal volcanic rocks of the Tibbit Hill volcanics are deposited 

within the Sutton Mountains salient, east of the Ottawa graben, and are thought 

to be coeval with the Grenville dike swarm within the Ottawa graben. Interprets 

the Sutton Mountains as the triple junction that initiated Iapetan rifting.

Kumarapeli (1993) A Plume-Generated Segment of the 

Rifted Margin of Laurentia, Southern 

Canadian Appalachians, Seen 

Through a Completed Wilson Cycle

Improves upon the model presented by the author in 1983 with the addition of 

geochronology of dike swarms and volcanic rocks. Proposes that initiation of 

rifting was accompanied by the emplacement of the 590 Ma Grenville mafic 

dike swarm of tholeiitic composition. Rifting continued for 35 million years until 

554 Ma when alkaline to transitional basalts erupted at the Sutton Mountains 

triple junction. This was quickly followed by a short period of rift-facies clastic 

sedimentation consisting of conglomerates attributed to a large river delta. The 

rift-drift transition is indicated by the deposition of open marine sedimentation, 

thought to have occurred 550 Ma because of the presence of early Cambrian 

fauna above this transition. 

Kumarapeli et al. 

(1988)

Volcanism on the Passive Margin of 

Laurentia: An Early Paleozoic 

Analogue of Cretaceous Volcanism 

on the Northeastern American Margin

Transitional to alkaline basalts and mid-ocean ridge basalts (MORBs) found 

within the Granby nappe of SE Quebec provide evidence for late Cambrian to 

Early Ordovician volcanism within transverse fracture zones analogous to Early 

Cretaceous volcanism in the Atlantic. The authors acknowledge that this data 

set is not sufficient to determine whether the volcanism took place during the 

drifting phase of the continental margin, because the precise age of these 

rocks is not known. These allochthonous blocks are thought to represent slabs 

dislodged from the ancient shelf-margin sequence, possibly by faults of the 

Ottawa graben in addition to NE-trending faults. 
Table D-7.3.1 Data Summary 

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D-126 

Citation Title Description and Relevance to SSC

McCausland and 

Hodych (1998)

Paleomagnetism of the 550 Ma 

Skinner Cove Volcanics of Western 

Newfoundland and the Opening of the 

Iapetus Ocean

Authors obtained paleomagnetic data for volcanic flows and volcaniclastic 

sediments of the Skinner Cove Formation in western Newfoundland dated at 

550 Ma that point to a paleolatitude of 19°S ± 9°. This result represents the 

paleolatitude of the Iapetan margin at that time. Comparison of these results to 

the 577 Ma Callander Complex of Ontario indicates rapid northward drift of 

Laurentia at approximately 570 Ma resulting from the opening of the Iapetus 

Ocean, which continued to the rift drift transition at approximately 550 Ma. 

Puffer (2002) A Late Neoproterozoic Eastern 

Laurentian Superplume: Location, 

Size, Chemical Composition, and 

Environmental Impact

Compiles a database of high field-strength elements for late Neoproterozoic to 

early Paleozoic flood basalts and dike swarms in eastern North America. 

Displaying these results on spider diagrams normalized to the bulk composition 

of the earth confirms that these rocks are derived from a mantle plume. The 

spatial distribution of these data reveals a peak concentration at the inferred 

Sutton Mountains triple junction, indicating that superplume magmatic activity 

peaked at 550 Ma. A second, earlier population of less geochemically enriched 

melts was derived from a subcontinental lithospheric mantle source mixed with 

mantle from a plume source. These older rocks (615–564 Ma) represent early 

lavas extruded from rifts, consistent with the early stages of mantle plume 

upwelling. The author favors the interpretation that these rocks are the result of 

one superplume as opposed to two plumes. 

Ratcliffe (1987) Basaltic Rocks in the Rensselaer 

Plateau and Chatham Slices of the 

Taconic Allochthon: Chemistry and 

Tectonic Setting

Tholeiitic to transitional alkaline basalts flows, sills, and metasedimentary rocks 

represent a restricted period of basaltic volcanic activity associated with 

Iapetan rifting. These volcanic rocks are interbedded with greywacke 

interpreted as turbidite fan complexes extending into deeper water. These 

assemblages are thought to form as short-lived rift-stage volcanics on a 

structurally evolving cratonic margin. 

The author proposes that these rocks formed in a fault-controlled continental 

margin with high relief and a narrow shoreline. Continental flood basalts 

capped the basement rocks, with flows erupting through local fissures into the 

water, and flowed onto greywacke fans. 

St. Seymour and 

Kumarapeli (1995)

Geochemistry of the Grenville Dyke 

Swarm: Role of Plume-Source Mantle 

in Magma Genesis

Confirms a mantle source for the synrift Grenville dike swarm, suggesting that 

the triple junction formed over a mantle plume, with dikes crystallizing from 

melts derived from the cooler plume head. 
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-127 

Citation Title Description and Relevance to SSC

Walsh and Aleinikoff 

(1999)

U-Pb Zircon Age of Metafelsite from 

the Pinney Hollow Formation: 

Implications for the Development of 

the Vermont Appalachians

U-Pb zircon age of 571 ± 5 Ma for metafelsite from the Pinney Hollow 

Formation of Vermont records the age of rhyolitic volcanism and deposition in a 

largely pelitic sequence interpreted as a pre-shelf rift-clastic sequence. This 

age agrees with other ages from rift-clastic volcanic rocks in the Appalachians. 

The relative distribution and thickness of metavolcanic and metafelsic sections 

throughout the Appalachians suggest that the basin that the Pinney Hollow 

Formation was deposited into was already well developed when the 571 Ma 

metafelsite was deposited. Therefore, the 554 Ma age for the Tibbit Hill 

volcanic suite at the Sutton Mountains triple junction does not represent the 

first pulse of volcanic activity during the initial opening of the Iapetan basin in 

the Vermont and Quebec Appalachians. This age also validates that the Wood 

Peak fault is a significant thrust fault separating the autochthonous and paraautochthonous cover sequence rocks, which supports the interpretation that 

the Taconic root zone is located in the hinterland of the Vermont Appalachians 

on the eastern side of the Green Mountain massif.

Faulting in St. Lawrence

Faure et al. (1996b) State of Intraplate Stress and 

Tectonism of Northeastern America 

Since Cretaceous Times, with 

Particular Emphasis on the New 

England–Quebec Igneous Province

Along the Ottawa-Bonnechere graben, E-W-trending Cretaceous normal faults 

mark the contact between Paleozoic rocks to the south and Grenvillian 

basement to the north. The NE-SW-directed extension associated with NWSE-trending normal faults is more widespread and older than the N-S-directed 

extension associated with E-W-trending normal faults. The Ottawa-Bonnechere 

graben and associated basement faults acted as localized zones of weakness 

in the early stage of Cretaceous extension, resulting in reorientation of the 

regional stress field and formation of the localized zone of N-S-directed 

extension. 
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D-128 

Citation Title Description and Relevance to SSC

Kumarapeli and Saull 

(1966)

The St. Lawrence Valley System:

A North American Equivalent of the 

East African Rift Valley System

Proposes a rift origin for the St. Lawrence valley system, including the OttawaBonnechere and Saguenay grabens. Evidence supporting this conclusion 

includes the following: 

Escarpments on the NW side of the St. Lawrence valley, north side of the 

Ottawa Bonnechere graben, and western margin of the Champlain valley.

South of the Ottawa-Bonnechere graben, tilting of the Madawaska 

Highlands to the south, NW tilting of the Adirondack massif, north tilting of 

a Laurentian block south of the Saguenay graben, and south block tilting of 

the Gaspé Peninsula. 

En echelon normal faults along the NW boundary with vertical 

displacements between 450 and 1,200 m.

St. Barnabe fault is a 55 km (34 mi.) normal fault on the SE margin with 

600 m of downthrow to the west.

Concentrations of historical seismicity along the St. Lawrence and Ottawa 

valleys and the St. Lawrence trough.

Presence of a negative Bouguer anomaly in the rift valley.

Connection of the St. Lawrence valley with the Mississippi embayment.

Westward continuation of the Ottawa-Bonnechere graben with the 

Midcontinent rift system.

Because the publication pre-dated plate tectonics, many aspects of the 

authors’ ideas are not consistent with current tectonic models of the region.

After comparing St. Lawrence rift system to East African rift system, the 

authors suggest the Great Lakes may be analogous to Lakes Victoria and 

Kyoga. The authors also associate Monteregian alkaline intrusives with St. 

Lawrence valley. Recent work associates this with Cretaceous instrusion 

associated with reactivation of the Ottawa-Bonnechere graben. .
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-129 

Citation Title Description and Relevance to SSC

Lamontagne et al. 

(2003)

Seismotectonic Characteristics of the 

Lower St. Lawrence Seismic Zone, 

Quebec: Insights from the Geology, 

Magnetics, Gravity, and Seismics

Reviewed the seismotectonic model of the lower St. Lawrence seismic zone 

from focal depths, focal mechanisms, gravity and magnetic data, offshore 

seismic lines, and mapped onshore geology. Concluded that seismicity is 

generally located where regional Iapetan and later faults change orientation 

from SW-NE to mostly E-W. Based on the correlation of seismicity with faults 

and geopotential lineaments, small earthquakes are thought to have occurred 

in fractured rock as opposed to large normal faults. Localized seismicity of the 

lower St. Lawrence seismic zone may be the result of enhanced stress due to 

a number of factors, including change in regional fault strike, mafic rocks of the 

Sept Iles layered igneous complex, presence of fluids at depth, and low 

coefficient of friction where fault gauge exists.

Lemieux et al. (2003) Structural Analysis of Supracrustal 

Faults in the Charlevoix Area, 

Quebec: Relation to Impact Cratering 

and the St-Laurent Fault System

Two major sets of fault orientations (N290–N320 and N020–N040) are found 

outside the impact zone with minor fault sets trending N270–N280 and N000–

N020. Within the impact crater, fault orientations are more scattered but are 

similar to the NW- and NE-trending systems of the external domain. The 

spread of orientations within the central portion of the crater is attributed to the 

impact-related polygonal pattern of normal faults, whereas the NW and NE

fault sets represent the youngest reactivation.

Coarse-grained cataclastic breccias up to 50 m thick are exposed along brittle 

faults striking NE and NW outside the impact crater. Similar cataclastic 

breccias are also found within the impact crater but are usually less than a few 

meters thick. Polymictic clastic matrix breccia is found exclusively within the 

impact crater. Fragments of cataclastic breccia are present, suggesting 

recurrent brecciation during incremental faulting events. Pseudotachylyte and 

foliated gouge are locally related to the cataclastic breccia, indicating that these 

rocks originate from a post-impact, single, and progressive tectonic event along 

the St. Lawrence rift system.

The St-Laurent fault influenced the deposition of Ordovician deposits during 

late stages of the Taconian orogeny by syndepositional faulting preserved as 

major lateral thickness variations within the section, presence of slump 

deformation in almost all stratigraphic units, preservation of pseudotachylyte 

within synsedimentary breccias, and occurrence of fault breccia clasts.

However, the geometry and structural characteristics of faulting are consistent 

with Mesozoic fault reactivation due to rifting of the North Atlantic region. 
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-130 

Citation Title Description and Relevance to SSC

Rocher et al. (2003) Brittle Fault Evolution of the Montréal 

Area (St. Lawrence Lowlands, 

Canada): Rift-Related Structural 

Inheritance and Tectonism 

Approached by Palaeostress Analysis

NW-SE extension associated with the opening of the Iapetus Ocean resulted in 

the formation of N040-trending faults along the north shore of the St. Lawrence 

lowlands, the development of three major N090-trending faults that define a 

success of horsts and grabens on Montreal and Jesus islands, and N120-

trending faults in the Montreal area. The three N090-trending faults have the 

following geometries:

1. The Bas-Sainte-Rose fault zone, the northernmost series of N090-trending

faults in the Montreal area, is a steeply north-dipping fault with 

approximately 200 m of vertical displacement and nearly 3 km (2 mi.) of 

apparent left-lateral offset. Offsets on the Bas-Sainte-Rose fault zone 

decrease as the fault zone extends westward, where it apparently crosscuts 

the N020-trending Rivière-aux-Mille-Iles fault zone. 

2. Rapide-du-Cheval-Blanc consists of a series of steeply south-dipping 

normal faults (the Ile-Bizard, the Rapide-du-Cheval-Blanc, and Outremont 

faults) with a total vertical offset of approximately 100 m. 

3. The Sainte-Anne-de-Bellevue fault zone is a north-dipping normal fault with 

a left-lateral strike-slip component in the southern part of Montreal Island. Its 

vertical offset has not been precisely determined.

All three faults clearly crosscut NNE-SSW-trending folds from the Appalachian 

Chambly-Fortierville syncline system in the Trois-Rivières seismic zone. 

WNW-ESE compressions followed by minor NNW compressional events are 

associated with Appalachian thrusting. WNW compression reactivated N090-

trending faults into strike-slip right-lateral faults, and N040–070 and N120 faults 

as reverse to strike-slip faults. Subsequent NNW compression is responsible 

for strike-slip conjugate faults trending NW-SE and NNE. 

NE-SW and NNW-SSE extension is associated with the opening of the North 

Atlantic–Labrador Sea and reactivated faults with normal to strike-slip motions. 

NNW extension is responsible for the horst-and-graben geometry of the major 

N090 normal faults described above. Late NE-SW compression is recorded in 

Monteregian plutons.

NE-SW compression postdating these events is associated with the formation 

of strike-slip faults that crosscut the Monteregian intrusions and is consistent 

with the current stress regime.
Table D-7.3.1 Data Summary 

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D-131 

Citation Title Description and Relevance to SSC

Roden-Tice, Brandt, 

and Tremblay (2009)

Apatite Fission-Track Evidence for 

Late Paleozoic to Early Mesozoic 

Unroofing and Potential Fault 

Reactivation Along the Saguenay 

River Graben, Quebec

Apatite fission-track age discontinuities across the Montmorency and SaintLaurent faults are consistent with Late Jurassic to Early Cretaceous fault 

reactivation and uplift.

Spencer et al. (1989) The Extension of Grenville Basement 

Beneath the Northern Appalachians: 

Results from the Quebec-Maine 

Seismic Reflection and Refraction 

Surveys

A master decollement separating autochthonous Grenville basement from 

overlying allochthonous rocks of the Appalachian orogen extends over a 

distance of 200 km (125 mi.) and can be traced from shallow depths beneath 

the St. Lawrence lowlands SE to about 25 km (15.5 mi.) depth beneath the SE 

edge of the Chain Lakes massif. Basement is offset by closely spaced en 

echelon normal faults with displacements between 200 and 1,000 m 

interpreted as Iapetan growth faults. The Baie Verte–Brompton line, separating 

Cambrian and Ordovician continental slope and rise deposits from oceanic arc 

and magmatic assemblages to the south, including the Chain Lakes massif, is 

imaged as a shallow, thin-skinned structure. The Chain Lakes terrane is 

thought to underlie much of the Connecticut Valley–Gaspe Synclinorium. The 

Acadian Guadeloupe fault disrupts the master decollement of the Taconian 

orogeny and thrust the Connecticut Valley–Gaspe Synclinorium over the Chain 

Lakes massif. 

St. Julien and Hubert 

(1975)

Evolution of the Taconian Orogen in 

the Quebec Appalachians

Describes 11 lithostratiographic assemblages distributed among the 

autochthonous, external, and internal domains of Quebec Appalachians. 

The autochthonous domain contains Cambrian and Ordovician sandstones and 

carbonates representing transgressive shelf deposits, Middle and Upper 

Ordovician flysch deposits, and Upper Ordovician shale and sandstone 

representing the post-tectonic regressive sequence. This domain contains 

E-W- and N30E-trending normal faults active between late Precambrian and 

Late Ordovician. 
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D-132 

Citation Title Description and Relevance to SSC

Tremblay and 

Lemieux (2001)

Supracrustal Faults of the St. 

Lawrence Rift System Between CapTourmente and Baie-Saint-Paul, 

Quebec

The Cap-Tourmente and St. Lawrence faults are late Proterozoic–early 

Paleozoic normal faults attributed to rifting during the opening of the Iapetus 

Ocean. 

The St. Lawrence fault trends N020–N050 and dips 60°–70° to the SE. Fault 

rocks consist of fault breccia, cataclastite, foliated gouge, and pseudotachylyte 

with a minimum thickness of 20 m near Sault-au-Cochon. Fault rocks exposed 

at Cap-Tourmente consist of 10–15 m thick zones of protocataclasite, 

cataclasite, and fault breccia. Within the Charlevoix area, the St. Lawrence 

fault is characterized by a well-developed and extensive series of cataclastic 

rock, gouge, and associated pseudotachylyte. 

The Cap-Tourmente fault trends E-W and dips approximately 80° to the south. 

Fault rocks consist mostly of fault breccia more than 10 m thick, as well as 

cataclastic rocks and dark pseudotachylyte veins. The St. Lawrence fault is 

crosscut by the Cap-Tourmente fault at Cap-Tourmente. 

West of Cap-Tourmente, the Montmorency Falls fault occupies the same 

structural position as the St. Lawrence fault, suggesting that they formed from 

en echelon faults trending parallel to the axis of the St. Lawrence rift. 

The Cap-Tourmente fault possibly represents a transfer fault, producing an 

oblique relay between two longitudinal normal faults. 

The St. Lawrence fault crosses the Charlevoix impact crater without major 

trend deflection or fault offsets within or at the boundaries of the Devonian 

impact structure. This observation suggests that impact-related faults did not 

significantly alter the orientation of preexisting structures and that reactivation 

is younger than the impact structure, most probably concurrent with the 

opening of the Atlantic Ocean in the Mesozoic. 

Tremblay et al. 

(2003)

Supracrustal Faults of the St. 

Lawrence Rift System, Quebec: 

Kinematics and Geometry Revealed 

by Field Mapping and Marine Seismic 

Reflection Data

This paper builds on work presented by Trembley and Lemieux (2001) and 

presents strike orientations, dip angles, and pitch angles for faults with 

evidence for frictional sliding in the St. Lawrence rift system. 

NE-trending longitudinal faults show three trends (N025, N040, and N070) and 

generally dip to the SE, although a minor number dip to the NW. Transverse 

faults show two trends (N290 and N310) and dip to the NE or SW, which is 

consistent with the horst-and-graben geometry. Both sets of faults are highangle faults with dip angles averaging 75°–80°. The pitch value of fault 
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-133 

Citation Title Description and Relevance to SSC

lineations is greater than 70°, indicating that most structures are dip-slip faults. 

Longitudinal and transverse faults show mutual crosscutting relationships, 

suggesting that they represent conjugate structures related to the same 

tectonic event. 

The St-Laurent fault has experienced at least 800 m of vertical throw at Saultau-Cochon. The Cap-Tourmente fault has a minimum vertical fault throw of 

700 m. The Montmorency fault has an 80 m fault scarp near Quebec City;

stratigraphic analysis suggests that fault throw should be less than 150 m, 

which is considerably less than the other faults. Several offshore faults 

subparallel to that fault may have vertical downthrow displacements up to 1 km

(0.6 mi.). 

Longitudinal faults likely result from the development of en echelon faults 

trending parallel to the rift axis, and transfer faults represent transfer faults or 

accommodation zones. Variations in fault throw are likely a result of 

propagation of extension along transfer faults. 

The presence of cataclastic rocks, pseudotachylytes, and fault gouge is 

consistent with changes of deformation mechanics during progressive and 

incremental deformation in the upper crust.

High-resolution seismic profiles in the St. Lawrence estuary indicate that the 

Laurentian Channel trough transitions from a half graben to a graben structure 

from SW to NE. 

Tremblay et al. (2003) speculate that reactivation of the St. Lawrence rift 

system is post-Ordovician, younger than the Devonian impact cratering event, 

and experienced additional fault throw and shoulder uplift during the Mesozoic 

opening of the North Atlantic. 

Faulting in the Ottawa-Bonnechere Graben

Mereu et al. (1986) The 1982 COCRUST Seismic 

Experiment Across the OttawaBonnechere Graben and Grenville 

Front in Ontario and Quebec

Results of the 1982 Canadian Consortium for Crustal Reconnaissance Using 

Seismic Techniques (COCRUST) long-range seismic refraction experiment 

show a sharp, step-like displacement of the Moho beneath the south shoulder 

of the Ottawa graben, confirming the deep-seated nature of its faults and 

penetration of mantle melts into the crust. Furthermore, the COCRUST surveys 

show a poorly defined Moho at unusually shallow depths beneath the graben.
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-134 

Citation Title Description and Relevance to SSC

Rimando and Benn 

(2005)

Evolution of Faulting and PaleoStress Field Within the Ottawa 

graben, Canada

Authors observe three periods of faulting in Cambro-Ordovician sedimentary 

rocks within the eastern end of the Ottawa graben, near Ottawa. The oldest 

generation of faults formed in a stress field with a horizontal maximum 

compressive stress (σ1) oriented NW. These structures are kinematically 

congruent with the compression direction associated with the closing of the 

Iapetus Ocean. The second generation of faults indicates a WNW-oriented σ1

and coincides with the emplacement of Cretaceous carbonatite dikes. The third 

generation of faults has a σ1 oriented SW, which is consistent with the postCretaceous stress field in eastern North America. 

Faulting in the Saguenay Graben

Du Berger et al. 

(1991)

The Saguenay (Quebec) Earthquake 

of November 25, 1988: Seismologic 

Data and Geologic Setting

The Saguenay graben is defined by the Lac Tchitogama and Ste-Marguerite 

River normal faults on the north wall and the Lac Kénogami normal fault on the 

south wall. Ordovician limestones show downthrow of 500 m along the north 

wall. Subvertical brittle faults are found within and outside the graben. 

Lineaments in the regional cluster at 000°, 015°, 030°, 050°, 105°, and 160°. 

The 015 and 030 lineaments correspond to NNE late Grenvillian ductile belts 

and some post-Ordovician brittle faults. The St. Lawrence rift reactivated the 

030° trend and produced the 050° trend. The 160 trend is parallel to glacial 

strike. The 105° trend is prominent only in the rosette of the Saguenay graben. 

The 000° trend corresponds to a complex array of en echelon oblique short 

breaks near the St. Maurice lineament, suggesting that the St. Maurice marks 

the transition between two structural domains. 

Roden-Tice, Brandt, 

and Tremblay (2009)

Apatite Fission-Track Evidence for 

Late Paleozoic to Early Mesozoic 

Unroofing and Potential Fault 

Reactivation Along the Saguenay 

River Graben, Quebec

Apatite fission-track age discontinuities across the Sainte-Marguerite fault 

suggest Late Triassic to Early Jurassic reactivation, whereas age 

discontinuities across the Lac Kénogami fault to the south indicate Middle 

Jurassic reactivation. 
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-135 

Citation Title Description and Relevance to SSC

Stratigraphic Evidence for Fault Activity

Hersi et al. (2003) Reappraisal of the Beekmantown 

Group Sedimentology and 

Stratigraphy, Montreal Area, 

Southwestern Quebec: Implications 

for Understanding the Depositional 

Evolution of the Lower-Middle 

Ordovician Laurentian Passive Margin 

of Eastern Canada

Detailed lithostratigraphic mapping and conodont biostratigraphy of the 

Beekmantown Group of SE Quebec indicates that the platform evolved as a 

distally steepened ramp during deposition of the Lower Ordovician Theresa 

Formation and the Ogdensburg Member of the Beauharnois Formation. 

Lavoie et al. (2003) Stratigraphic Framework for the 

Cambrian-Ordovician Rift and Passive 

Margin Successions from Southern 

Quebec to Western Newfoundland

In the Quebec Reentrant, platform rocks were only marginally involved in the 

tectonic stacking of the Taconic orogeny and form a spatially restricted frontal 

Taconian deformation zone known as the para-autochthonous or imbricate 

fault domain and therefore not considered part of the Humber Zone. The 

Quebec Reentrant is rooted in the autochthonous St. Lawrence platform. 

These structural relationships allow for stratigraphic and paleogeographic 

scenarios for the early evolution of the Quebec-Newfoundland segment of the 

continental margin slope of Laurentia. Neoproterozoic to latest early Cambrian 

rift volcanics are overlain by rift-drift transition successions of the early 

Cambrian Sauk I sequence. A global sea-level lowstand resulted in an 

unconformity that separates these rocks from shallow marine middle Cambrian 

to Middle Ordovician rocks of the Sauk II and Sauk III subsequences. An 

extensive debris flow unit resedimented the middle Cambrian slope succession 

and is attributed to tectonic instability during the middle to late Cambrian. The 

authors suggest that reactivation of the Saguenay graben could be responsible 

for the anomalous upper Cambrian succession. Similar syndepositional 

tectonic activity is observed in the younger St. Lawrence platform succession in 

the Charlevoix area during the Middle to Late Ordovician. The authors present 

locations of reentrants and promontories for the eastern margin of Laurentia 

farther north than those of Thomas (1991).
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-136 

Citation Title Description and Relevance to SSC

Longuépée and 

Cousineau (2005)

Reappraisal of the Cambrian 

Glauconite-Bearing Anse Maranda 

Formation, Quebec Appalachians: 

from Deep-Sea Turbidites to Clastic 

Shelf Deposits

Paleogeographic reconstruction led to a significant reinterpretation of the 

sedimentary environment of the Anse Maranda Formation, originally explained 

as proximal turbidites of a deep-sea fan and now explained as shelf sediments

deposited in storm-influenced deep subbasins seaward of a headland 

(Montmorency promontory). These sediments were deposited along a narrow 

shelf with irregular topography south of the Saguenay graben.

Seismicity and Focal Mechanism Data

Adams and Basham 

(1991)

The Seismicity and Seismotectonics 

of Eastern Canada

The western Quebec seismic zone consists of two bands of seismicity. The 

western band trends slightly west of northwest and lies along the Ottawa River 

between Lake Timiskaming and Montreal. This portion of the western Quebec 

seismic zone is attributed to rift faults of the Ottawa graben. Focal mechanisms 

for earthquakes within this zone are consistent with thrust faulting on NWstriking faults. The authors dispute the hypothesis that Mesozoic extension in 

the St. Lawrence rift extends SE into the Great Lakes.

Baird et al. (2009) Stress Channeling and Partitioning of 

Seismicity in the Charlevoix Seismic 

Zone, Quebec, Canada

Seismicity is localized along two elongate bands of seismicity bounded by rift 

faults extending NE of the Charlevoix impact crater. In a 2-D stress model, 

faults are represented as frictional discontinuities, and the impact crater as an 

elastic continuum of reduced modulus. Stress trajectories flow around the weak 

impact crater, concentrating stress along weak faults into the impact crater, 

resulting in seismicity localized in linear bands. The asymmetric placement of 

the rift faults through the crater results in increased seismicity potential along 

the rift, north of the crater. 

Observed seismicity is therefore interpreted as a result of stress concentration 

due to the interaction of the crater (local zone of weakness) and rift faults 

(large-scale weak zone). Small to moderate seismicity occurs within the crater, 

and larger earthquakes are localized along the rift faults. 

Modeling in 3-D would be able to accurately represent the bowl shape of the 

crater but may not be able to explain why seismicity extends below the crater 

into Grenville basement. Current observations of reverse reactivation of rift 

faults associated with glacial rebound could not be assessed with the 2-D 

model presented in this paper and would need to be examined with a 3-D 

model. 
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-137 

Citation Title Description and Relevance to SSC

Bent (1992) A Re-examination of the 1925 

Charlevoix, Québec, Earthquake

Analysis of additional waveforms resulted in source parameters of strike 

42° ± 7°, dip 53° ± 7°, rake 105° ± 10°, depth 10 km (6.2 mi.), seismic moment 

3.1 ± 2.5 × 1025 dyne cm (Mw 6.2), MS 6.2 ± 0.3, mb 6.5 ± 0.4, source duration 

5 sec, and stress drop 35 bars. Due to insufficient 1-sec period data, mbLg was 

not determined; however, Street and Turcotte (1977) obtained a mbLg 6.6, and

Atkinson and Boore (1987) obtained a mbLg 6.8. Felt area estimates range from 

3.3 × 106 km2(Street and Lacroix, 1979) to 5.2 × 106 km2(Smith, 1962). 

Drysdale and Cajka (1989) obtained a mbLg 6.1 using Nuttli et al. (1979) and 

mbLg 6.2 using Toro and McGuire (1987). The dip is shallower than would be 

expected from observed surface faults but consistent with recent seismicity. 

The focal mechanism is consistent with horizontal compression in the NW-SE 

direction that is orthogonal to the regional stress field, indicating an anomalous 

stress field in Charlevoix that may be depth dependent.

Bent (1996a) An Improved Source Mechanism for 

the 1935 Timiskaming, Quebec 

Earthquake from Regional Waveforms

Analysis of seismograms from 11 stations for the November 1, 1935, 

Timiskaming earthquake led to the determination of seismic moment of 2.3 ±

1.3 × 1025 dyne cm, corresponding to Mw of 6.1 ± 0.2.

Lamontagne and 

Ranalli (1996)

Thermal and Rheological Constraints 

on the Earthquake Depth Distribution 

in the Charlevoix, Canada, Intraplate 

Seismic Zone

Compares the depth distribution of Charlevoix earthquakes to rheological 

models of the region. The maximum depth of earthquakes can be controlled by 

either the brittle-ductile transition or the velocity-weakening to velocitystrengthening fault behavior. The rheological change at the brittle-ductile 

transition was modeled by calculating geotherms assuming a variety of rock 

compositions in the upper and middle crust. The depth distribution of 

earthquakes in Charlevoix requires geotherms very close to the upper limit for 

felsic rocks and a wet lower crust. The temperature-controlled sliding stability 

transition can occur at 300°C and 450°C for quartz or feldspar plasticity. 

Hydrolytic weakening of feldspars at 350°C occurs at 25 km (15.5 mi.) for the 

upper geotherms. The maximum crustal stress difference has an upper limit of 

about 100–200 MPa, requiring high pore fluid pressure or low coefficient of 

friction in mid- to lower crust. Thrust reactivation of steeply dipping faults 

requires a low coefficient of friction. The authors attribute the presence of 

earthquakes in the Charlevoix region to brittle-ductile transition deeper than 25 

km (15.5 mi.), corresponding to higher than average geotherms, onset of 

ductility for hydrated feldspar at about 350°C, high pore-fluid pressure and a 

low friction coefficient, possibly related to unhealed zones of intense fracturing.
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-138 

Citation Title Description and Relevance to SSC

Lamontagne and 

Ranalli (1997)

Faults and Spatial Clustering of 

Earthquakes near La Malbaie, 

Charlevoix Seismic Zone, Canada

Focal mechanisms for earthquakes larger than M 3 show reverse faulting, 

whereas smaller-magnitude earthquakes indicate both normal and strike-slip 

mechanisms, suggesting that local stress and/or strength conditions control 

their occurrence. Focal mechanisms for larger events of the Charlevoix seismic 

zone, however, suggest reactivation of paleo-rift faults in response to regional 

stresses. The distribution of spatially clustered events (doublets and triplets) 

within the Charlevoix seismic zone indicates that very few events have 

occurred on the same fractures with similar focal mechanisms, implying that 

these fault zones occur in highly fractured rocks. These observations indicate 

that the Charlevoix seismic zone is characterized by highly fractured zones 

responding to regional stresses and local perturbations in stress or strength, 

possibly enhanced by pore fluid pressures.

Ma and Atkinson 

(2006)

Focal Depths for Small to Moderate 

Earthquakes (MN 2.8) in Western 

Quebec, Southern Ontario, and 

Northern New York

Performs regional depth-phase modeling of earthquakes occurring in southern 

Ontario, western Quebec, and northern New York between 1980 and 2004. 

Events with depths greater than 15 km (9.3 mi.) are restricted to the Ottawa 

graben and western Quebec seismic zone. The wide depth distribution could 

indicate faults of throughgoing crustal extent or different faults that occur at 

different depths in the crust. In the entire study region, focal depths cluster at 5, 

8, 12, 15, and 22 km (3, 5, 7.5, 9.3, and 13.7 mi.) and may reflect layering in 

seismogenic properties within the crust.

Ma and Eaton (2007) Western Quebec Seismic Zone 

(Canada): Clustered, Midcrustal 

Seismicity Along a Mesozoic Hotspot 

Track

Deep earthquakes (greater than 17 km, or 10.6 mi., in depth) are localized as 

clusters at Timiskaming, Maniwaki, Mont Laurier, and Adirondack. The 

Timiskaming cluster is located near the 1935 Timiskaming earthquake, has a 

lower b-value than the other clusters and the regional average, and is spatially 

associated with faults of the Ottawa-Bonechere graben. The authors speculate 

that heat from the hotspot track weakened faults of the Ottawa-Bonechere 

graben, which explains the lack of historical seismicity along most of the extent 

of the graben system. 
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-139 

Citation Title Description and Relevance to SSC

Paleoseismic Investigations

Aylsworth et al. 

(2000)

Did Two Massive Earthquakes in the 

Holocene Induce Widespread 

Landsliding and Near-Surface 

Deformation in Part of the Ottawa 

Valley, Canada?

Examines large prehistoric landslides in abandoned channels of the Ottawa 

River and disturbed sediment of the erosional plane adjacent to the Ottawa 

River. Radiocarbon ages for buried wood and plant material from landslide 

debris cluster at 4,550 yr BP, which are thousands of years younger than the 

age of paleochannel abandonment. This observation cannot be attributed to 

either fluvial erosion or wet-weather-induced landslides. East of the landslides, 

disturbed sediment and possible sand boils dated at 7,060 yr BP are preserved 

within the flat erosional plane adjacent to the Ottawa River. These two age 

distributions are attributed to paleoearthquakes of uncertain magnitude and 

source. 

Doig (1990) 2300 Yr History of Seismicity from 

Silting Events in Lake Tadoussac, 

Charlevoix, Quebec

Inferred a variable recurrence rate for the Charlevoix seismic zone from silt 

layers in lakes due to earthquake-induced landslides. Some silt layers in the 

section were correlated with historical earthquakes from 1638, 1663, 1791, 

1870, and 1925. From 320 BC to AD 800, determined a 120-year recurrence 

interval, 270 years from AD 800 to 1500, and 75 years from AD 1500 to the 

present.

Doig (1991) Effects of Strong Seismic Shaking in 

Lake Sediments, and Earthquake 

Recurrence Interval, Témiscaming, 

Quebec

Sampled lake sediments from Lac Tee, located within 15 km (9.3 mi.) of the 

epicenter of the 1935 magnitude 6.3 Timiskaming earthquake. Observed three 

silt layers in six sediment cores attributed to earthquake-induced landslides. A 

15–22 cm thick chaotic mixture of black to brown organic material and large, 

partly tabular fragments of previously formed silt layers is interpreted as 

sediment redeposit during the 1935 Timiskaming earthquake. The basal silt 

layer may imply a two-stage event, such as a small foreshock or a major 

aftershock. A second 6 cm thick silt layer in core 4 and a 1–2 mm thick silt 

layer in cores 2 and 6 are interpreted as the result of a distant or smaller 

earthquake. A third silt layer at 100 cm overlain by gyttja containing lumps of 

silt is interpreted as a similar-sized event as the 1935 Timiskaming earthquake. 

The upper 2–3 cm from cores 2, 4, and 6 contain brown, homogeneous 

flocculent gyttja interpreted as normal accumulation of sediment since 1935. 

This sedimentation rate was used to infer ages of 400 and 1,500 years for the 

second and third silt layers, respectively. Doig (1991) does not explicitly 

correlate the second silt layer to the 1663 Charlevoix earthquake. This data set 

suggests two magnitude 6–6.5 events in 1,500 years.
Table D-7.3.1 Data Summary 

St. Lawrence Rift Zone 

D-140 

Citation Title Description and Relevance to SSC

Doig (1998) 3000-Year Paleoseismological 

Record from the Region of the 1988 

Saguenay, Quebec, Earthquake

Author has determined a recurrence interval ranging from 350 to 1,000 years 

for the Saguenay graben based on evidence of earthquake-induced landslide 

deposits within lakes near the epicenter of the 1988 earthquake.

Filion et al. (1991) A Chronology of Landslide Activity in 

the Valley of Rivière du Gouffre, 

Charlevoix, Quebec

Samples of tree trunks buried in landslide flow materials were collected from 

four sectors along the Gouffre River between Saint-Urban and Baie-Saint-Paul. 

The age distribution of tree trunks indicates that landslides have occurred at 

5,670, 3,170, 2,500, 1,870 yr BP, with most occurring less than 600 yr BP. 

Comparison of tree-ring widths throughout the study area suggests that trees 

died during the latent period between the 1662 and 1663 growing seasons, 

possibly due to synchronous landslides. The authors interpret these two 

landslides as having been caused by the February 1663 Charlevoix 

earthquake. These results provide no evidence for the 1925 earthquake. The 

authors emphasize the importance of tree-ring techniques to delineate the 

areal extent of landslides caused by the 1663 earthquake and to caution 

against exaggerating the geomorphic consequences of earthquakes.

Tuttle and Atkinson 

(2010)

Localization of Large Earthquakes in 

the Charlevoix Seismic Zone, 

Quebec, Canada, During the Past 

10,000 Years

Provides evidence for three Holocene paleoearthquakes in Charlevoix with M ≥ 

6.2, including at least two prehistoric episodes at 5,000 and 10,000 years ago.

Tuttle et al. (1990) Liquefaction and Ground Failure 

Induced by the 1988 Saguenay, 

Quebec, Earthquake

Sand boil deposits and ground fissures were documented immediately 

following the November 25, 1988, M 5.9 Saguenay earthquake. Lateral 

spreading was the principal mode of ground failure during the 1988 earthquake 

and in the past, with displacements on the order of centimeters.

Tuttle et al. (1992) Liquefaction Induced by Modern 

Earthquakes as a Key to 

Paleoseismicity: A Case Study of the 

1988 Saguenay Earthquake

One, possibly two, earthquakes caused pre-1988 liquefaction features 

identified in Tuttle et al. (1990). One has a well-constrained age of 340 ± 70 

radiocarbon yr BP, possibly corresponding to the 1663 Charlevoix earthquake. 
Table D-7.3.2 Data Summary

Great Meteor Hotspot Zone 

D-141 

Citation Title Description and Relevance to SSC

Geologic Evidence for Hotspot Track

Adams and Basham 

(1991)

The Seismicity and Seismotectonics 

of Eastern Canada

Postulated that differential uplift of the shield may have thermally stressed and 

fractured Precambrian crust during passage of the hotspot. Attributed localized 

release of seismic energy to this weakened crust. Speculated that New 

England may not exhibit same rates of seismicity because plutonism may have 

healed deep crustal fractures.

Crough (1981) Mesozoic Hotspot Epeirogeny in 

Eastern North America

This study attributes a 600 km (373 mi.) wide zone of epeirogeny in SE

Canada and New England during the Cretaceous and early Tertiary to the 

Great Meteor hotspot as evidenced by apatite fission-track dating. 

Duncan (1984) Age Progressive Volcanism in the 

New England Seamounts and the 

Opening of the Central Atlantic Ocean

Duncan (1984) obtained radiometric ages for dredged volcanic rocks from 

seven of the New England seamounts and concluded that the seamounts 

increase in age from SE (82 Ma for the Nashville seamount) to NW (103 Ma for 

the Bear seamount). Linear rate of migration of volcanisms of 4.7 cm/yr 

determined from these ages is in agreement with age of the Corner seamounts 

(70–75 Ma) and the youngest phase of igneous activity in White Mountains 

(100–124 Ma). 

Faure et al. (1996b) State of Intraplate Stress and 

Tectonism of Northeastern America 

Since Cretaceous Times, with 

Particular Emphasis on the New 

England–Quebec Igneous Province

Performed a paleostress analysis of Cretaceous dyke trends and regional- and 

mesoscopic-scale faults from the Monteregian plutons. Dykes display ESEWNW and ENE-WSW trends and are spatially distributed in three E-W-trending

dyke swarms 75 by 300 km (47 by 186 mi.) in area. Most dykes surrounding 

Cretaceous plutons are radially distributed and perpendicular to contacts with 

hosting sedimentary rocks. Leucocratic dykes occur closer to plutons and 

disappear within 3–4 km (2–2.5 mi.), likely recording local stress effects due to 

pluton emplacement. Crosscutting dykes clearly show a dominant E-Wtrending orientation. Lamprophyre dykes occur independently of plutons and 

strike parallel to regional dyke swarms, recording regional far-field stresses.

Southwest of Mont Brome and around Mont Megantic, N-S- to NE-SW-trending

dykes found in slates strike parallel to the regional foliation of Taconic or 

Acadian metamorphic rocks. Their emplacement is controlled by preexisting 

anisotropy and, therefore, poorly records the paleostress. NW-SE-trending

dykes indicate NE-SW-striking extension with a slight clockwise rotation near 

Montreal. E-W-trending dykes indicate a N-S-striking extension. In some 
Table D-7.3.2 Data Summary

Great Meteor Hotspot Zone 

D-142 

Citation Title Description and Relevance to SSC

plutons, these E-W-trending dykes crosscut radially distributed dykes. 

Normal faults in the region display two orientations:

1. E-W-trending normal faults are found predominantly in the Montreal area 

parallel to graben boundaries and the axis of the Monteregian hills. These 

faults have vertical offsets ranging between 100 and 430 m (328 and 1,411 

ft.) and record homogeneous N-S-trending extension. 

2. NW-SE to WNW-ESE-trending normal faults record NE-SW-trending

extension and are found everywhere in Quebec. These faults trend 

obliquely to graben boundaries with less than 100 m (328 ft.) of vertical 

offset. The stress orientation varies between NNE-SSW near Ottawa and 

Montreal and ENE-WSW in southern Quebec. 

The NW-SE to WNW-ESE faults are older than the E-W-trending faults but 

exhibit crosscutting relationships, suggesting that some were reactivated 

during the formation of the E-W-trending faults. Some E-W-trending brittle 

faults and joints are observed in several Cretaceous plutons with similar 

orientations to dykes that are locally crosscut by these normal faults,

suggesting that dyke emplacement and faulting are contemporaneous. The 

NE-SW-directed extension is more widespread and older than the N-S-directed 

extension, suggesting that the Ottawa-Bonnechere graben and associated 

basement faults acted as localized zones of weakness in the early stage of 

Cretaceous extension, resulting in reorientation of the regional stress field and 

formation of the localized zone of N-S-directed extension. 

These orientations are attributed to to an initial NE-SW extension event 

associated with rifting between Labrador and Greenland at 140 Ma, opening of 

the South Atlantic at 130 Ma, and related reactivation of the Temiskaming 

graben. Subsequent N-S-oriented extension associated with the emplacement 

of the Monteregian Hills corresponds to global fragmentation of Pangaea when 

Iberia separated from Newfoundland when dominant tensional stress 

propagated along the Labrador rift. 

Conjugate sets of NE-SW dextral and ESE-WNW sinistral strike-slip faults and 

WNW-SSW reverse faults provide evidence for a compressional stress regime 

postdating emplacement of Cretaceous plutons. Stress regime shifted to ENEWSW-directed compressional in early Tertiary when oceanic spreading rate 

decreased due to an increasing number of convergent boundaries in Pacific. 
Table D-7.3.2 Data Summary

Great Meteor Hotspot Zone 

D-143 

Citation Title Description and Relevance to SSC

Faure et al. (2006) Paleostress Analysis of Atlantic 

Crustal Extension in the Quebec 

Appalachians

Fault stress tensors indicate that most E-W- to ESE-WNW-oriented stress is 

found in Montreal and Gaspe area, whereas SE-NW stress is found in SE

Quebec. Late Triassic–Jurassic dikes in New England and southern Quebec 

indicate SE-NW-oriented extension consistent with fault slip stress. The N-Strending portion of a Jurassic dike in southern Quebec is consistent with 

regional E-W extensional stress axis, whereas the NE-SW branch of this dike 

is more compatible with a local and adjacent NW-SE extension. Stress axes 

exhibit clockwise rotation in White Mountain magma series, possibly due to 

local deviatoric stresses or a NE-SW-oriented basement fault. The authors

attribute these two extensional paleostress trends to either (1) 

contemporaneous regional partitioning of ESE-WNW-oriented extension 

influenced by N-S-trending structures in Champlain Lake Valley and NE-SWtrending structures of St. Lawrence rift, or (2) an initial Late Triassic E-W 

extension related to formation of Bay of Fundy and South Georgia rift basins 

and Early Jurassic ESE-WNW extension related to central Atlantic rift system.

Heaman and 

Kjarsgaard (2000)

Timing of Eastern North American 

Kimberlite Magmatism: Continental 

Extension of the Great Meteor 

Hotspot Track?

Extends Great Meteor hotspot track NW to Rankin Inlet on west side of James 

Bay by identifying four periods of kimberlite magmatism (at 196, 180–176, 

148–146, and 142–134 Ma) from U-Pb perovskite ages that extend from NW to 

SE from Rankin Inlet through to the Attawapiskat, Kirkland Lake, and 

Timiskaming fields. These results are not consistent with Morgan’s (1983) 

study, which identified two Mesozoic hotspot tracks in New England separated 

by 40 Myr Heaman and Kjarsgaard (2000) suggest that this age progression 

and the change from kimberlitic to basaltic magmatism correspond to change 

from thick lithosphere to thinner lithosphere east of Monteregian Hills. 

Matton and Jebrak 

(2009)

The Cretaceous Peri-Atlantic Alkaline 

Pulse (PAAP): Deep Mantle Plume 

Origin or Shallow Lithospheric BreakUp?

Cretaceous magmatism occurred along widely separated peri-Atlantic 

continental margins as widespread alkaline igneous activity. This volcanism, 

along with the Central Atlantic magmatic province associated with Jurassic 

rifting, has been attributed to either deep mantle plumes or a combination of 

tensional forces, lithospheric rifting, and structural controls. Matton and Jebrak 

(2009) propose that periodic reactivation of deep-seated preexisting zones of 

weakness during major stages of Atlantic tectonic evolution, combined with 

coeval asthenospheric upwelling due to edge-driven convection and 

continental insulation flow, enhanced the ascent of alkaline magmas. The 

authors prefer shallow, small-scale upwelling during periodic structural 

reactivation to a mantle plume as a mechanism for alkaline magmas. 
Table D-7.3.2 Data Summary

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D-144 

Citation Title Description and Relevance to SSC

McHone (1996) Constraints on the Mantle Plume 

Model for Mesozoic Alkaline 

Intrusions in Northeastern North 

America

The author proposes that one or more deep-mantle plumes do not provide a 

satisfactory mechanism for distribution of Cretaceous alkaline rocks of NE New 

England. Observed that previous studies oversimplify evidence for a hotspot 

track across New England by ignoring important petrological data, including the 

following:

Jurassic syenite-monzonite-alkali granite of the White Mountain magma 

series has been described as separate province from Cretaceous intrusions,

although many Early Jurassic dikes and several mafic to felsic plutons in the 

province are petrographically and chemically similar to Early Cretaceous 

intrusions that overlap.

Early Cretaceous dikes and plutons of the New England–Quebec igneous 

province have statistically similar paleomagnetic poles between 122 and

124 Ma and show no consistent trend for published ages in any direction 

across region.

Seamount volcanism is not limited to ages defined by a linear hotspot track,

nor is it in line with the New England–Quebec province.

Cretaceous alkaline rocks do not exhibit a consistent chemical signature 

indicative of a mantle source. 

These observations indicate that lithospheric processes were necessary to 

start and stop generation of magmas from the same source in the mantle, and 

petrological studies should emphasize local and regional tectonic features.

McHone (2000) Non-plume Magmatism and Rifting 

During the Opening of the Central 

Atlantic Ocean

Presents a model for Mesozoic rifting in the Atlantic based on several 

convection cells beneath the rift zone as opposed to a mantle plume. The 

presence of dikes with lengths up to 700 km (435 mi.) displaying uniform 

composition can be explained by either (1) flow of magma away from a single, 

local magma source for each large dike or dike swarm, or (2) vertically moving 

magmas from compositionally different subhorizontal layers that are 

homogeneous across large mantle source regions. Cretaceous intraplate 

hotspots postdate Jurassic tholeiitic magmatism and Atlantic Ocean rifting by 

80 Myr or more. 

McHone (2000) proposes that rifting of Pangaea progressed through a series 

of linear zones of mantle upwelling that gradually coalesced into the modern 

segments of the mid-ocean ridges. The lithosphere promoted an increase in 
Table D-7.3.2 Data Summary

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Citation Title Description and Relevance to SSC

upper mantle temperatures beneath the incipient rift zone, culminating in the 

great Early Jurassic magmatic event. Subsequent cooling resulted in evolution 

of the rift into a zone of shallow linear upwelling and convection by which the 

mantle ejects ridge basalts and accretes new oceanic crust. This is supported 

by the presence of Cretaceous and Cenozoic alkaline igneous volcanoes in 

eastern North America, the northern North Atlantic, western Africa, South 

America, and as seamounts and islands throughout the central North Atlantic 

Ocean. 

Morgan (1983) Hotspot Tracks and the Early Rifting 

of the Atlantic

Study tested the hypothesis that hotspots are fixed in space by generating 

plate reconstructions for the Atlantic Ocean from the last 180 Myr using ages of 

known hotspot tracks. Morgan (1983) recognized two hotspot tracks passing 

through New England at different times: the Verde hotspot track at about 160 

Ma and the Meteor hotspot at about 120 Ma. The Verde hotspot traveled from 

south of Hudson Bay to the New England seamounts from 180 to 130 Ma, and 

the Meteor track parallels the Verde track through Ontario, New England, and 

the New England seamounts approximately 40 Myr after the Verde track. The 

predicted track for the Great Meteor hotspot closely follows known ages for the 

White Mountain magma series in New Hampshire, the Cretaceous seamounts 

of offshore New England, the Corner Rise (recording when the mid-Atlantic 

Ridge crossed over the hotspot), and the Great Meteor seamount (11–17 Ma) 

in the Central Atlantic. 

Poole et al. (1970) Geology of Southeastern Canada Alkaline rocks of the Monteregian Hills consist of nepheline, syenite, essexite, 

nordmarkite, pulaskite, yamaskite, and rougemontite forming circular plugs with 

steep walls and laccoliths within a 241 km (150 mi.) long west-trending line 

between Montreal and Lake Megantic in Quebec. These intrusions range in 

age from 84 to 123 Ma, with many falling between 100 and 115 Ma. Rocks may 

be related to a NW-striking kimberlite dike at Kirkland Lake (151 ± 8 Ma). 

Roden-Tice and Tice 

(2005)

Regional-Scale Mid-Jurassic to Late 

Cretaceous Unroofing from the 

Adirondack Mountains Through 

Central New England Based on 

Apatite Fission-Track and (U-Th)/He 

Thermochronology

Apatite fission-track ages and (U-Th)/He ages from the Adirondack Mountains 

and eastern New York State, Vermont, western Massachusetts and 

Connecticut, and western New Hampshire indicate that widespread unroofing

during the Middle Jurassic to Late Cretaceous occurred at a rate of 0.07 to 

0.08 km/Myr This regional uplift is attributed to remnant heating from the Great 

Meteor hotspot. Differential unroofing was accommodated by extensional fault 

reactivation. 
Table D-7.3.2 Data Summary

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D-146 

Citation Title Description and Relevance to SSC

Roden-Tice and 

Wintsch (2002)

Early Cretaceous Normal Faulting in 

Southern New England: Evidence 

from Apatite and Zircon Fission-Track 

Ages

Apatite and zircon fission-track age transects across Hartford-Deerfield basin in 

Connecticut and Massachusetts increase to the east, indicating that unroofing 

occurred during the Late Jurassic through Early Cretaceous. Age of graben 

structure of Hartford Basin is Cretaceous and may not be an early Mesozoic 

―rift‖ basin. 

Roden-Tice, West, et 

al. (2009)

Presence of a Long-Term 

Lithospheric Thermal Anomaly: 

Evidence from Apatite Fission-Track 

Analysis in Northern New England

Apatite fission-track ages across New Hampshire, NE Vermont, and western 

Maine range from 70 to 140 Ma and reflect widespread Early to Late 

Cretaceous cooling. This regional cooling and unroofing is attributed to 

passage of North America Plate over the Great Meteor hotspot, emplacement 

of White Mountain magma series in the Early Jurassic, and associated E-W 

and NW-SE extension. Regional uplift on the order of 5–7 km (3–4 mi.) may 

explain lack of rift basins in central New England and Quebec.

Sleep (1990) Monteregian Hotspot Track: A LongLived Mantle PlumeFrom modeling the buoyancy flux of the Great Meteor hotspot, the author

observed that the trace of the hotspot changes orientation, concluding that the 

plume was weak beneath Ontario and strong beneath Montreal where the track 

changed orientation through the White Mountains, and became weakened at 

the Nashville seamount where the track changed orientation to the Corner 

seamounts. Sleep (1990) also suggested that the lack of tracks west of the 

Monteregian Hills may be the result of the Canadian Shield’s being less 

vulnerable to the hotspot than the Paleozoic sediments of the Montreal area

were.

Zartman (1977) Geochronology of Some Alkalic Rock 

Provinces in Eastern and Central 

United States

Provides ages for the White Mountain plutonic suite, consisting of mildly 

alkaline rocks with compositions of granite, quartz syenite, syenite, and lesser 

amounts of intermediate and mafic units occupying a batholith, several stocks, 

and related ring dikes. The mapped relationships of these rocks indicate posttectonic character from host rocks and a relatively slow intrusion of complexly 

evolved magma chambers into shallow crust. These rocks were emplaced over 

three rather broad pulses of magmatism at 220–235 Ma, 155–200 Ma, and 95–

125 Ma but lack any regular time-transgressive pattern of ages. Alignment of 

these rocks with the Monteregian Hills of Quebec and Cretaceous seamounts 

of offshore New England can be attributed to the trace of a mantle hotspot 

between the Early Triassic to Early Cretaceous or to emplacement along 

fractures, indicative of intraplate stresses. 
Table D-7.3.2 Data Summary

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D-147 

Citation Title Description and Relevance to SSC

Geophysical Characteristics 

Eaton et al. (2006) Crustal Thickness and VP/VS

Variations in the Central Grenville 

Orogen (Ontario, Canada) from 

Analysis of Teleseismic Receiver 

Functions

Crustal thickness maps derived from teleseismic analysis and results of 

regional seismic-refraction surveys image the hotspot track NE of the OttawaBonnechere graben as minima on these maps. Thinnest crust (34.5–37.0 km) 

coincides with the elevated seismicity rates of Western Quebec seismic zone, 

NE of Ottawa-Bonnechere graben.

Li et al. (2003) Shear Velocity Structure and 

Azimuthal Anisotropy Beneath 

Eastern North America from Rayleigh 

Wave Inversion

Determined velocity structure and anisotropic variations in velocity structure 

from inversion of Rayleigh waves in order to detect asthenospheric flow 

beneath the thick continental lithosphere beneath NE United States and SE 

Canada. Rayleigh wave-phase velocity anomaly with a period of 33 s, 

corresponding to sensitivity to structure down to 40 km (25 mi.) in depth, 

indicates a low-velocity band oriented NE-SW. North American continental keel 

beneath Grenville province is imaged in the upper mantle down to roughly 200 

km (124 mi.) in depth. The North American keel has an irregular shape and a 

low-velocity zone beneath eastern New York and central New England to 200 

km (124 mi.), with particularly high amplitudes at depths of 60–140 km (37–87 

mi.). This velocity anomaly is interpreted as the lateral contrast between 

relatively thick lithosphere beneath western New York and Pennsylvania and 

the warm asthenosphere beneath the thinned New England lithosphere caused 

by thermal erosion associated with the Cretaceous hotspot. Additionally, weak 

anisotropy observed from shear-wave splitting indicates that source must be at 

least 200 km (124 mi.) deep, suggesting that a sublithospheric shear zone may 

decouple motions of lithosphere and deeper mantle. 

Rondenay et al. 

(2000)

Teleseismic Studies of the 

Lithosphere Below the 

Abitibi-Grenville Lithoprobe Transect

Travel-time inversions of teleseismic results from southern Ontario image a 

low-velocity corridor between 50 and 300 km (31 and 373 mi.) that crosscuts 

regional structures of the Grenville province and Ottawa-Bonnechere graben. 

This low-velocity corridor is coincident with northwestward continuation 

intrusions of Monteregian Hills. These results are attributed to a zone of 

contrasting thermal-compositional-anisotropic properties interpreted to have 

been formed by the same process responsible for emplacement of the 

Monteregian Hills (either a fixed mantle plume of the Great Meteor hotspot or 

rifting associated with opening of Atlantic Ocean). This anomaly is flanked on 

both sides by high seismic velocity, possibly representing zones of depleted 

residuum or transitions in mantle fabric. 
Table D-7.3.2 Data Summary

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D-148 

Citation Title Description and Relevance to SSC

Seismicity 

Adams and Basham 

(1991)

The Seismicity and Seismotectonics 

of Eastern Canada

The Western Quebec seismic zone contains two distinct bands of seismicity: a 

W-NW-trending band of seismicity along the Ottawa River between Ottawa and 

Lake Timiskaming associated with rift faults of the Ottawa River valley, and a 

N-NW-trending band extending from Montreal to the Baskatong Reservoir 

attributed to crustal fracturing associated with passage of a Cretaceous hotspot 

track. Recent seismicity of this second band includes the 1975 M 4.2 Maniwaki 

and 1978 M 4.1 St. Donat earthquakes. These two bands of seismicity 

converge near the St. Lawrence River. 

Ma and Atkinson 

(2006)

Focal Depths for Small to Moderate 

Earthquakes (MN 2.8) in Western 

Quebec, Southern Ontario, and 

Northern New York

Performed regional-depth-phase modeling of earthquakes occurring in 

southern Ontario, western Quebec, and northern New York between 1980 and 

2004. Events with depths greater than 15 km (9.3 mi.) are restricted to Ottawa 

graben and Western Quebec seismic zone (WQSZ). Hypocentral depths for 

events in WQSZ range from 2 to 25 km (1.2 to 15.5 mi.). The wide depth 

distribution could indicate faults of throughgoing crustal extent or different faults 

that occur at different depths in the crust. In entire study region, focal depths 

cluster at 5, 8, 12, 15, and 22 km (3, 5, 7.5, 9.3, and 13.7 mi.) and may reflect 

layering in seismogenic properties within the crust. 

Ma and Eaton (2007) Western Quebec Seismic Zone 

(Canada): Clustered, Midcrustal 

Seismicity Along a Mesozoic Hot Spot 

Track

The authors determined focal depths for 73 earthquakes, combined these data 

with those computed by Ma and Atkinson (2006), and compared the spatial 

distribution of earthquakes with focal mechanisms to evaluate tectonic controls 

of the Western Quebec seismic zone (WQSZ), a 160 km (100 mi.) wide band 

of intraplate seismicity extending 500 km (311 mi.) from Adirondack Highlands 

to James Bay. 

Shallow events with depths less than 8 km (5 mi.) are randomly distributed with 

reverse mechanisms attributed to glacial isostatic adjustment. Earthquakes 

with intermediate depths define a linear band of earthquakes. Deep 

earthquakes (greater than 17 km, or 10.6 mi., in depth) are localized as 

clusters at Timiskaming, Maniwaki, Mont-Laurier, and Adirondack. Timiskaming 

cluster is located near the 1935 Timiskaming earthquake, has a lower b-value 

than the other clusters and the regional average, and is associated with faults 

of the Ottawa-Bonechere graben. Adirondack cluster is located near the 1944 

Cornwall-Massena earthquake, and two events within the cluster have focal 

mechanisms with an E-W-oriented P axis. The Mont-Laurier cluster is adjacent 
Table D-7.3.2 Data Summary

Great Meteor Hotspot Zone 

D-149 

Citation Title Description and Relevance to SSC

to paleoseismic evidence near Ottawa River studied by Aylsworth et al. (2000). 

Seismicity does not generally correlate with structure in WQSZ; shear zones of 

Grenville province cut across the NW-SE trend of WQSZ at a high angle. The 

Maniwaki cluster exhibits repeating events, with deep seismicity localized 

within the footwall of the Baskatong crustal ramp, and intermediate and shallow 

seismicity localized within the hanging wall. Clustered seismicity, with the 

exception of the Timiskaming clusters, has little spatial overlap with OttawaBonnechere and Timiskaming graben structures. 

The authors speculate that localized seismicity in the WQSZ is attributed to 

either weakened faults and shear zones caused by reheating of crust by 

hotspot track, or to stress concentrations associated with the emplacement of 

major bodies in more felsic crust. Near-surface expression of the hotspot track 

progressively changes from kimberlitic melts in interior of craton to more 

voluminous crustal magmatism as the hotspot interacted with a progressively 

thinner lithosphere. The authors propose that the WQSZ represents an area of 

blind intrusions associated with entrapment of mantle-derived melt in the crust 

that is located between kimberlitic dikes to the NW and Monteregian intrusions

to the SE. 

Ma et al. (2008) Intraplate Seismicity of a Recently 

Deglaciated Shield Terrane: A Case 

Study from Northern Ontario, Canada

Determined depth phases of 537 earthquakes occurring in Northern Ontario 

between 1980 and 2006. Identified two active clusters south of James Bay and 

near Kapuskasing where focal depths range from a few km to more than 20 km

(12.4 mi.). James Bay cluster was not recognized until regional monitoring 

began in 2002. Cluster is centered around 53N, 80.7W with focal depths 

varying from 4 to 20 km (2.5 to 12.4 mi.), indicating that earthquakes occur 

along deep-rooted geologic structures. Largest magnitude observed in cluster 

is MN 3.6. Kapuskasing cluster is located 100 km (62 mi.) NW of Western 

Quebec seismic zone (WQSZ), separated by an aseismic zone. Kapuskasing 

cluster contains the December 1, 1928, ML 5.0; April 13, 1980, MN 4.1; and 

December 7, 2007, MN 4.2 earthquakes. Focal mechanisms from both clusters 

indicate thrust mechanisms with NW-striking nodal planes. Focal depths 

increase successively in time, consistent with progressive rupture migration 

down a fault. The authors attribute the Kapuskasing cluster to extension of 

WQSZ, and this seismicity to a combination of thermal rejuvenation of the crust 

and/or rheological contrast between igneous rocks and older crust resulting 

from passage of North America over the Great Meteor hotspot.
Table D-7.3.2 Data Summary

Great Meteor Hotspot Zone 

D-150 

Citation Title Description and Relevance to SSC

Paleoseismic Investigations 

Aylsworth et al. 

(2000)

Did Two Massive Earthquakes in the 

Holocene Induce Widespread 

Landsliding and Near-Surface 

Deformation in Part of the Ottawa 

Valley, Canada?

Examines large prehistoric landslides in abandoned channels of Ottawa River 

and disturbed sediment of the erosional plane adjacent to Ottawa River, south 

of Great Meteor Hotspot seismotectonic zone. Radiocarbon dates from buried 

wood and plant material that collected in landslide debris cluster at 4,550 yr 

BP, which is thousands of years younger than the age of paleochannel 

abandonment. This observation cannot be attributed to either fluvial erosion or 

wet-weather-induced landslides. East of the landslides, disturbed sediment and 

possible sand boils dated at 7,060 yr BP are preserved within flat erosional 

plane adjacent to Ottawa River. These two age distributions are attributed to 

paleoearthquakes of uncertain magnitude and source. 
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-151 

Citation Title Description and Relevance to SSC

General for Region

Adams et al. (1995) Northeastern North American 

Earthquake Potential—New 

Challenges for Seismic Hazard 

Mapping

Presents rationale for source characterization used in the seismic hazard maps 

of Canada. The Northern Appalachian zone consists of crust of the northern 

Appalachians that overrode the Iapetan passive margin. The geometry extends 

from the landward limit of Mesozoic extensional faulting to the seaward limit of 

thinned Grenville crust of the Iapetan passive margin. The Miramichi earthquake 

is considered the paradigm earthquake.

Tremblay and 

Castonguay (2002)

Structural Evolution of the Laurentian 

Margin Revisited (Southern Quebec 

Appalachians): Implications for the 

Salinian Orogeny and Successor 

Basins

The northern Appalachians consist of several tectonostratigraphic zones: 

Humber, Dunnage, Gander, Avalon, and Meguma. The external Humber zone 

consists of sedimentary rocks and mafic volcanic rocks deformed into a series of 

imbricate NW-directed thrust nappes of prehnite-pumpellyite to sub-greenschist 

facies. The internal Humber zone consists of distal facies of external Humber 

zone units of greenschist to amphibolite metamorphic grade. The Dunnage zone 

consists of ophiolites, melanges, volcanic arc sequences, and flysch deposits. 

The surface boundary between the Humber and Dunnage zones defines the 

Baie Verte–Brompton line. In southern Quebec, the Dunnage zone is overlain by 

the Connecticut Valley–Gaspe trough. 

Taconic Orogeny

Faill (1997a) A Geologic History of the NorthCentral Appalachians, Part 1:

Orogenesis from the Mesoproterozoic 

Through the Taconic Orogen

The Middle to Late Ordovician Taconic orogeny extended from Labrador to 

Alabama and is currently exposed in the southern Appalachians in the Piedmont 

and Great Valley allochthons and western New England. Assemblages in the 

southern Appalachians contain complexes formed in the Theic Ocean, whereas 

assemblages of western New England consist of two magmatic arcs: the Halwey 

arc of the Brompton-Cameron terrane and the Ammonoosuc arc of the Central 

Maine terrane.

Faill (1997b) A Geologic History of the NorthCentral Appalachians, Part 2: The 

Appalachian Basin from the Silurian 

Through the Carboniferous

Several Theic components, including microcontinents, magmatic arcs, and 

accretionary prisms were obducted along the broad carbonate shelf that existed 

on the eastern edge of Laurentia. These Taconic terranes formed a topographic 

barrier creating the Appalachian basin from Alabama to at least Quebec. 
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-152 

Citation Title Description and Relevance to SSC

Faure et al. (2004) Reconstruction of Taconian and 

Acadian Paleostress Regimes in the 

Quebec and Northern New Brunswick 

Appalachians

Paleostress analysis of brittle faults in Quebec and New Brunswick indicate that

Taconic deformation produced N-S- to NE-SW-trending reverse conjugated 

brittle faults under a pure compressional stress regime late in the development 

of the orogeny. This Taconic compressional event also resulted in reactivation of 

Iapetan faults in the St. Lawrence Lowlands as E-NE/W-SW dextral and NW-SE

sinistral faults. 

Moench and 

Aleinikoff (2003)

Stratigraphy, Geochronology, and 

Accretionary Terrane Settings of Two 

Bronson Hill Arc Sequences, Northern 

New England

Volcanic arcs of the Bronson Hill anticlinorium developed in the late Cambrian 

within the Theic Ocean during the Penobscot orogeny. They were obducted to 

the Laurentian margin during the Middle to Late Ordovician Taconic orogeny.

These arcs developed from multiple accretionary events with changing polarity 

shortly before the closing of the Iapetus Ocean at 460 Ma.

Spencer et al. (1989) The Extension of Grenville Basement 

Beneath the Northern Appalachians: 

Results from the Quebec-Maine 

Seismic Reflection and Refraction 

Surveys

A master decollement separating autochthonous Grenville basement from

overlying allochthonous rocks of the Appalachian orogen extends over a 

distance of 200 km (124 mi.) and can be traced from shallow depths beneath the 

St. Lawrence Lowlands SE to about 25 km (15.5 mi.) depth beneath the SE

edge of the Chain Lakes massif. Basement is offset by closely spaced en 

echelon normal faults, with displacements between 200 and 1,000 m interpreted 

as Iapetan growth faults. The Baie Verte–Brompton line, separating Cambrian 

and Ordovician continental slope and rise deposits from oceanic arc and 

magmatic assemblages to the south, including the Chain Lakes massif, is 

imaged as a shallow, thin-skinned structure. The Chain Lakes terrane is thought 

to underlie much of the Connecticut Valley–Gaspe synclinorium. The Acadian 

Guadeloupe fault disrupts the master decollement of the Taconian orogeny and 

thrust the Connecticut Valley–Gaspe synclinorium over the Chain Lakes massif.

St. Julien and Hubert 

(1975)

Evolution of the Taconian Orogen in 

the Quebec Appalachians

Describes 11 lithostratigraphic assemblages distributed between the 

autochthonous, external, and internal domains of the Quebec Appalachians. The 

autochthonous domain contains Cambrian and Ordovician sandstones and 

carbonates representing transgressive shelf deposits, Middle and Upper 

Ordovician flysch deposits, and Upper Ordovician shale and sandstone

representing the post-tectonic regressive sequence. This domain contains E-Wand N30E-trending normal faults active between late Precambrian and Late 

Ordovician. 

The external domain is divided into an outer belt containing imbricated thrusts 

and an inner belt composed of nappes separated by Logan’s Line. Assemblages 
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-153 

Citation Title Description and Relevance to SSC

of the autochthonous domain can be found within the thrust-imbricated belt. 

lower Cambrian clastic-carbonate, Cambrian shale-feldspathic sandstone, and 

upper Cambrian/Lower Ordovician shale-limestone conglomerate assemblages 

constitute nappes of the inner belt of the external domain. East-dipping reverse 

faults of the external belt repeat through successive imbricated structures on a 

decollement surface that cuts southeastward into progressively older rocks. 

Polarity of the nappes indicates that right-side-up nappes with the oldest rock 

assemblages always rest on nappes containing the youngest. Emplacement of 

the nappes is constrained by elevation and denudation of the nappes beginning 

in early Middle Ordovician and progressing westward until late Middle 

Ordovician and prior to dynamothermal metamorphism, as evidenced by a 

regional penetrative cleavage associated with a late fold system. 

The internal domain contains assemblages from the inner belt, and ophiolite, 

shale-melange, slate-sandstone tuff, and calk-alkaline volcanic assemblages. 

The internal domain is deformed by late recumbent folds genetically related to 

dynamothermal metamorphism in the latest Ordovician or earliest Silurian. 

Imbrication along major thrust faults likely occurred in the Upper Ordovician. 

These assemblages were accumulated on a Grenville-like basement to the west 

and newly formed oceanic crust to the east. The Taconian orogeny coincides 

with obduction of newly formed ocean crust in late Early Ordovician and 

subduction of oceanic crust during early and late Middle Ordovician. Rocks 

within the internal and external domains exhibit Devonian deformation 

associated with Acadian orogeny. 

Stewart et al. (1993) Global Geoscience Transect 8: 

Quebec-Maine-Gulf of Maine 

Transect, Southeastern Canada, 

Northeastern United States of America 

Integrates interpretations from the Maine-Quebec seismic lines and provides 

descriptions of major tectonostratigraphic terranes, including the Laurentian 

craton, the Brompton-Cameron, Central Maine, Nashoba-Casco-Miramichi, and 

Atlantica composite terranes, and the Meguma terrane. 

Salinian Orogeny

Murphy and Keppie 

(2005)

The Acadian Orogeny in the Northern 

Appalachians

Late Cambrian–Middle Ordovician Penobscottian orogeny amalgamated 

composite terranes within arcs of the Iapetus Ocean, and therefore did not result 

in deformation within Laurentia. Late Ordovician–Silurian Salinic orogeny 

accreted the Gander, Avalon, Nashoba, and Carolina terranes to Laurentia 

during closing of the Iapetus Ocean during the Laurentia-Avalonia collision.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-154 

Citation Title Description and Relevance to SSC

Tremblay and 

Castonguay (2002)

Structural Evolution of the Laurentian 

Margin Revisited (Southern Quebec 

Appalachians): Implications for the 

Salinian Orogeny and Successor 

Basins

Silurian metamorphism (430–410 Ma) in the northern Appalachians is attributed 

to retrograde metamorphism following the main compression event. The event 

involved SE-directed transport of Taconian crustal wedge followed by normal 

faulting (Saint-Joseph and Baie Verte–Brompton faults) and development of the 

fault-bounded sedimentary basins of the Connecticut Valley–Gaspé trough. This 

extension is inconsistent with coeval compression in Newfoundland, suggesting 

that the Salinian orogeny is geographically restricted or the entire Laurentian 

margin is characterized by crustal extension that induced the formation of major 

sedimentary basins during the Silurian and Devonian.

Tremblay and Pinet 

(2005)

Diachronous Supracrustal Extension in 

an Intraplate Setting and the Origin of 

the Connecticut Valley—Gaspé and 

Merrimack Troughs, Northern 

Appalachians

Attributes the late-stage extension to supracrustal extensional collapse due to 

late-stage delamination of the lithospheric mantle in a SE-dipping subduction 

zone.

Acadian Orogeny

Faill (1997b) A Geologic History of the NorthCentral Appalachians, Part 2: The 

Appalachian Basin from the Silurian 

Through the Carboniferous

The Acadian orogeny is expressed in the Appalachian basin as siliclastic 

sedimentation from the Middle to Late Devonian, with additional pulses of uplift 

occurring in the early and late Carboniferous. The principle tectonic activity 

occurred in New England. 

Faure et al. (2004) Reconstruction of Taconian and 

Acadian Paleostress Regimes in the 

Quebec and Northern New Brunswick 

Appalachians

Deformation from the Acadian orogeny is expressed as E-SE/W-NW

compression in a transpressional regime, producing E-NE/W-NW dextral and 

NW-SE sinistral strike-slip faults that crosscut Taconian thrust faults in the 

Appalachians of Quebec and New Brunswick. This deformation also resulted in 

reactivation of Iapetan structures in the St. Lawrence Lowlands.

Murphy and Keppie 

(2005)

The Acadian Orogeny in the Northern 

Appalachians

The Devonian Acadian orogeny has been attributed to either the collision of 

Avalonia with Laurentia or the accretion of the Meguma terrane; however, recent 

work indicates that the Meguma terrane is the passive margin on the southern 

margin of Avalonia. The authors interpret the Acadian orogeny as forming along 

an Andean-type margin that possibly overrides a plume and swell. 
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-155 

Citation Title Description and Relevance to SSC

Tremblay et al. 

(2000)

Acadian Metamorphism in the 

Dunnage Zone of Southern Québec, 

Northern Appalachians: 40Ar/39Ar 

Evidence for Collision Diachronism

Acadian metamorphism is well dated as 385–375 Ma in the southern part of the 

Dunnage zone.

Alleghanian Orogeny

Faill (1998) A Geologic History of the NorthCentral Appalachians, Part 3: The 

Alleghany Orogeny

The Alleghanian orogeny produced decollement tectonism in the central and 

southern Appalachians, along with early penetrative shortening, late low-angle 

thrusts, low-grade metamorphism, and transpressional shear zones. NE of the 

Pennsylvania salient, the Alleghany orogeny is confined to Carboniferous basins 

and rocks previously affected by the Taconic and Acadian orogenies. In New 

England, Alleghany tectonism was driven by docking of the Avalon terrane. The 

northern Appalachians exhibit high-pressure metamorphism of Taconic and 

Acadian crust in east-central Connecticut and Massachusetts and deformation 

of Appalachian deposits near the Hudson Valley.

Faure et al. (1996a) Alleghanian Paleostress 

Reconstruction in the Northern 

Appalachians: Intraplate Deformation 

Between Laurentia and Gondwana

Brittle faults of the northern Appalachians exhibit three phases of compression 

during the Alleghanian orogeny: an early NNW-SSE compression, a NNE-SSW 

compression, and a late WNW-ESE compression.

Murphy and Keppie 

(2005)

The Acadian Orogeny in the Northern 

Appalachians

There is general consensus that the late Carboniferous–Permian Alleghany 

orogeny was due to terminal collision between Gondwana and Laurentia-Baltica 

that closed the Rheic Ocean and resulted in the formation of Pangaea.

Opening of the Atlantic

Faure et al. (1996b) State of Intraplate Stress and 

Tectonism of Northeastern America 

Since Cretaceous Times, with 

Particular Emphasis on the New 

England–Quebec Igneous Province

Results of a paleostress analysis of brittle faults in the Quebec Appalachians 

provide evidence for two distinct phases of Cretaceous extension: an initial 

geographically widespread NE-SW phase of extension and a later N-S phase of 

extension confined to southern Quebec. The authors attributed this Cretaceous 

volcanism to continued fragmentation of Pangaea. Early NE- to E-NE-oriented 

extension and associated magmatism between 140 and 90 Ma are correlated to 

rifting between Labrador and Greenland at ~140 Ma, early breakup stages of 

South Atlantic Ocean at 130 Ma, and N-S-oriented extension and emplacement 

of dikes at 125 Ma, corresponding to separation of Iberia from Newfoundland.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-156 

Citation Title Description and Relevance to SSC

Faure et al. (2006) Paleostress Analysis of Atlantic 

Crustal Extension in the Quebec 

Appalachians

Fault stress tensors indicate that most E-W- to ESE-WNW-oriented stress is 

found in the Montreal and Gaspe area, whereas SE-NW stress is found in SE 

Quebec. Late Triassic–Jurassic dikes in New England and southern Quebec 

indicate SE-NW-oriented extension consistent with fault slip stress. The N-Strending portion of a Jurassic dike in southern Quebec is consistent with the 

regional E-W extensional stress axis, whereas the NE-SW branch of this dike is 

more compatible with a local and adjacent NW-SE extension. Stress axes 

exhibit clockwise rotation in the White Mountain magma series, possibly due to 

local deviatoric stresses or a NE-SW-oriented basement fault. 

The authors attribute these two extensional paleostress trends to either (1) 

contemporaneous regional partitioning of ESE-WNW-oriented extension that 

was influenced by N-S-trending structures in the Champlain Lake Valley and the 

NE-SW-trending structures of the St. Lawrence rift, or (2) an initial Late Triassic 

E-W extension related to the formation of the Bay of Fundy and South Georgia 

rift basins and Early Jurassic ESE-WNW extension related to the central Atlantic 

rift system.

Cretaceous Great Meteor Hotspot

Crough (1981) Mesozoic Hotspot Epeirogeny in 

Eastern North America

Attributes a 600 km (373 mi.) wide zone of epeirogeny in SE Canada and New 

England during the Cretaceous and early Tertiary to the Great Meteor hotspot,

as evidenced by apatite fission-track dating. 

Duncan (1984) Age Progressive Volcanism in the New 

England Seamounts and the Opening 

of the Central Atlantic Ocean

The author obtained radiometric ages for dredged volcanic rocks from seven of 

the New England seamounts and concluded that the seamounts increase in age 

from the SE (82 Ma for the Nashville seamount) to the NW (103 Ma for the Bear 

seamount).

Faure et al. (1996b) State of Intraplate Stress and 

Tectonism of Northeastern America 

Since Cretaceous Times, with 

Particular Emphasis on the New 

England–Quebec Igneous Province

Performed a paleostress analysis of the New England–Quebec igneous 

province that provided an alternative interpretation for the distribution of 

Cretaceous plutons. Dikes display ESE-WNW and ENE-WSW trends and are 

spatially distributed in three E-W-trending dike swarms 75 by 300 km (47 by 186 

mi.) in area. Leucocratic dikes occur closer to plutons and disappear within 3–4 

km (2–2.5 mi.), likely recording local stress affects due to pluton emplacement. 

Lamprophyre dikes occur independently of plutons and strike parallel to regional 

dike swarms, recording regional far-field stresses.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-157 

Citation Title Description and Relevance to SSC

Normal faults in the regions display two orientations: (1) E-W-trending normal 

faults found predominantly in the Montreal area are parallel to graben 

boundaries and the axis of the Monteregian hills, with vertical offsets ranging 

between 100 and 430 m; and (2) NW-SE to WNW-ESE-trending normal faults 

oblique to graben boundaries with less than 100 m of vertical offset. The NW-SE 

to WNW-ESE faults are older than the E-W-trending faults but exhibit 

crosscutting relationships, suggesting that some were reactivated during the 

formation of the E-W-trending faults. Some E-W-trending brittle faults and joints 

are observed in several Cretaceous plutons with similar orientations to dikes that 

are locally crosscut by these normal faults, suggesting that dike emplacement 

and faulting are contemporaneous. Conjugate sets of NE-SW dextral and ESEWNW sinistral strike-slip faults and NNW-SSE reverse faults provide evidence 

for a compressional stress regime postdating the emplacement of the 

Cretaceous plutons. 

The authors attribute these data to an initial NE-SW extension event associated 

with rifting between Labrador and Greenland at 140 Ma, opening of the South 

Atlantic at 130 Ma, and related reactivation of the Timiskaming graben. 

Subsequent N-S-oriented extension associated with the emplacement of the 

Monteregian Hills corresponds to global fragmentation of Pangaea when Iberia 

separated from Newfoundland when dominant tensional stress propagated 

along the Labrador rift. The stress regime shifted to ENE-ESE-directed 

compressional in the early Tertiary when the oceanic spreading rate decreased 

due to an increasing number of convergent boundaries in the Pacific. The 

authors conclude that the emplacement of Cretaceous intrusions is consistent 

with a lithospheric fracture model as opposed to a hotspot model, emphasizing 

the role of preexisting structure in the Ottawa-Bonnechere graben. 

McHone (1996) Constraints on the Mantle Plume 

Model for Mesozoic Alkaline Intrusions 

in Northeastern North America

The author proposes that one or more deep-mantle plumes do not provide a 

satisfactory mechanism for the distribution of Cretaceous alkaline rocks of NE

New England, and observes that previous studies oversimplify the evidence for 

a hotspot track across New England by ignoring important petrological data, 

including the following:

Jurassic syenite-monzonite-alkali granite of the White Mountain magma 

series has been described as a separate province from Cretaceous 

intrusions, although many Early Jurassic dikes and several mafic to felsic 

plutons in the province are petrographically and chemically similar to Early 
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-158 

Citation Title Description and Relevance to SSC

Cretaceous intrusions that overlap.

Early Cretaceous dikes and plutons of the New England–Quebec igneous 

province have statistically similar paleomagnetic poles between 122 and 124 

Ma and show no consistent trend for published ages in any direction across 

the region.

Seamount volcanism is not limited to ages defined by a linear hotspot track,

nor is it in line with the New England–Quebec province.

Cretaceous alkaline rocks do not exhibit a consistent chemical signature 

indicative of a mantle source.

These observations indicate that lithospheric processes were necessary to start 

and stop the generation of magmas from the same source in the mantle, and 

petrological studies should emphasize local and regional tectonic features.

Morgan (1983) Hotspot Tracks and the Early Rifting of 

the Atlantic

Attributes this age distribution to two hotspot tracks passing through New 

England at different times: the Verde hotspot track at about 160 Ma and the 

Meteor hotspot about 120 Ma 

Roden-Tice and Tice 

(2005)

Regional-Scale Mid-Jurassic to Late 

Cretaceous Unroofing from the 

Adirondack Mountains Through 

Central New England Based on 

Apatite Fission-Track and (U-Th)/He 

Thermochronology

Apatite fission-track ages and (U-Th)/He ages from the Adirondack Mountains 

and eastern New York state, Vermont, western Massachusetts and Connecticut, 

and western New Hampshire indicate that widespread unroofing during the 

Middle Jurassic to Late Cretaceous occurred at a rate of 0.07 to 0.08 km/Myr

This regional uplift is attributed to remnant heating from the Great Meteor 

hotspot. Differential unroofing was accommodated by extensional fault 

reactivation.

Roden-Tice, West, et 

al. (2009)

Presence of a Long-Term Lithospheric 

Thermal Anomaly: Evidence from 

Apatite Fission-Track Analysis in 

Northern New England

Apatite fission-track ages across New Hampshire, NE Vermont, and western 

Maine range from 70 to 140 Ma and reflect widespread Early to Late Cretaceous 

cooling. This regional cooling and unroofing is attributed to passage of the North 

American Plate over the Great Meteor hotspot, emplacement of the White 

Mountain magma series in the Early Jurassic, and associated E-W and NW-SE 

extension. Regional uplift on the order of 5–7 km (3–4 mi.) may explain lack of 

rift basins in central New England and Quebec.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-159 

Citation Title Description and Relevance to SSC

Sleep (1990) Monteregian Hotspot Track: A LongLived Mantle PlumeFrom modeling the buoyancy flux of the Great Meteor hotspot, the author

observed that the trace of the hotspot changes orientation, concluding that the 

plume was weak beneath Ontario and strong beneath Montreal where the track 

changed orientation through the White Mountains, and became weakened at the 

Nashville seamount where the track changed orientation to the Corner 

seamounts. The author suggests that the lack of tracks west of the Monteregian 

Hills may be the result of the Canadian Shield’s being less vulnerable to the 

hotspot than the Paleozoic sediments of the Montreal area were.

Zartman (1977) Geochronology of Some Alkalic Rock 

Provinces in Eastern and Central 

United States

The author observed that although the mapped relationships of alkalic intrusive 

rocks of New Hampshire indicate post-tectonic character from their host rocks, 

relatively shallow emplacement depths, and alignments with the Monteregian 

Hills of Quebec and Cretaceous seamounts of offshore New England, 

radiometric ages of the New Hampshire plutons range from Early Triassic to 

Early Cretaceous but lack any regular time-transgressive pattern of ages.

Geophysical Anomalies

Hughes and Luetgert 

(1991)

Crustal Structure of the Western New 

England Appalachians and the 

Adirondack Mountains

Interpreted seismic refraction data from the eastern Adirondack Mountains, 

northern Vermont, northern New Hampshire, and SE Maine. The lower crust has 

indistinct reflectors and was modeled with a velocity of 6.7 km/s. The depth to 

Moho thickens from 36 km (22 mi.) in western Maine to 40 km (25 mi.) in 

Vermont. Crust thins to the east along the transect. Coherent large-amplitude 

Moho reflections beneath Vermont and New Hampshire suggest compositional 

lamination at the base of the crust. Locally, the apparent velocity of the upper 

mantle exceeds 8.1 km/s (5 m/s). 

Li et al. (2003) Shear Velocity Structure and 

Azimuthal Anisotropy Beneath Eastern 

North America from Rayleigh Wave 

Inversion

Determined the velocity structure beneath NE United States and SE Canada 

using Rayleigh wave inversion. The North American continental keel beneath 

Grenville Province is imaged in the upper mantle down to roughly 200 km (124 

mi.) in depth. The North American keel has an irregular shape and a low velocity 

zone beneath eastern New York and central New England to 200 km (124 mi.),

with particularly high amplitudes at depths of 60–140 km (37–87 mi.). Thin 

lithosphere beneath west-central New England and easternmost New York may 

be caused by thermal erosion associated with the Cretaceous hotspot.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-160 

Citation Title Description and Relevance to SSC

Seismicity

Brown and Ebel 

(1985)

An Investigation of the January 1982 

Gaza, New Hampshire Aftershock 

Sequence

Presents source parameters for aftershocks of the January 19, 1982, Gaza, 

New Hampshire, earthquake. Arrival time data for these aftershocks indicate a 

northwestward progression of epicentral location with time, suggesting the 

potential for NW-trending basement structures in the region along with the 

presence of shallow, multidirectional fracture patterns.

Burke (2004) Historical Seismicity in the Central 

Highlands, Passamaquoddy Bay, and 

Moncton Regions of New Brunswick, 

Canada, 1817-1961

The author revised magnitudes and locations for historical earthquakes within 

the Central Highlands subzone (October 22, 1869, MN 5.7; May 16, 1896, mbLg

4.0; August 8, 1908, mbLg 4.4; July 22, 1922, mbLg 4.9; January 4,1930, mbLg 4.2;

and September 30, 1937, mbLg 4.8) and indentified additional historical 

earthquakes (March 16, 1863, mbLg 4.0; December 18, 1903, mbLg 4.2; March 

20, 1911, mbLg 4.5; June 27, 1915, mbLg 3.8; and March 30, 1925, mbLg 4.1). 

Identified the August 12, 1867, mbLg 3.7 Moncton earthquake and revised the 

time for the February 8, 1824, MN 5.2 Moncton earthquake. Also identified the 

February 25, 1935, mbLg 3.2 earthquake and revised times and locations for the 

January 1, 1883, mbLg 5.3; March 23, 1896, mbLg 4.2; and December 11, 1912,

mbLg 4.7 Passamaquoddy Bay earthquakes.

Burke (2009) Historical Earthquakes Felt in New 

Brunswick (1764, 1811-1960)

Presents a compilation of historical earthquakes in New Brunswick that updates 

findings in Burke (2004) and Leblanc and Burke (1985). The text contains a 

discussion of felt report, felt area for all events, and isoseismal area of intensity 

IV reports for selected earthquakes. 

Ebel (1996) The Seventeenth Century Seismicity 

of Northeastern North America

Places the epicenter for the June 11, 1638, earthquake in the seismically active 

part of central New Hampshire and estimates a magnitude of 6.5 ± 0.5 to 

account for felt effects in Trois Rivières, Quebec, and Boston, Massachusetts.

Ebel and Bouck 

(1988)

New Focal Mechanisms for the New 

England Region: Constraints on the 

Regional Stress Regime

Presents focal mechanisms for small to moderate events occurring in New 

England between 1981 and 1987. These mechanisms are predominantly 

reverse with a component of strike-slip. These mechanisms have variable strike 

directions, including NE-SW, NW-SW, N-S, and E-W.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-161 

Citation Title Description and Relevance to SSC

Ebel et al. (1986) A Study of the Source Parameters of 

Some Large Earthquakes of 

Northeastern North America

Examines source parameters for the two earthquakes occurring in December 

1940 near Ossipee, New Hampshire: the December 20 ML 5.3 and the 

December 24 ML 5.4 earthquakes. Synthetic seismograms for the December 20, 

1940, Ossipee earthquake provide evidence for a predominantly thrust 

mechanism with either a N-S- or E-W-striking nodal plane.

Leblanc and Burke 

(1985)

Re-evaluation of the 1817, 1855, 

1869, and 1904 Maine–New 

Brunswick Area Earthquakes

Compiled felt reports and determined magnitudes for the March 21, 1904, mbLg

5.9; October 22, 1869, mbLg 5.7; February 8, 1855, mbLg, 5.2–5.5; and May 22,

1817, mbLg 4.5–5 historical earthquakes in Maine and New Brunswick. 

Structures

Moench and 

Aleinikoff (2003)

Stratigraphy, Geochronology, and 

Accretionary Terrane Settings of Two 

Bronson Hill Arc Sequences, Northern 

New England

The Amonoosuc fault is a major Triassic normal fault extending 200 km (124 

mi.) from northern New Hampshire SW to Springfield, Vermont, with about 4 km 

(2.5 mi.) of vertical displacement. Although Triassic displacement is assumed, 

several earlier displacements may have occurred. 

Roden-Tice, West, et 

al. (2009)

Presence of a Long-Term Lithospheric 

Thermal Anomaly: Evidence from 

Apatite Fission-Track Analysis in 

Northern New England

Apatite fission-track ages across the Ammonoosuc fault in the Connecticut River 

valley do not display age discontinuities that would imply significant 

displacement; howeve, in NW New Hampshire, age discontinuities suggest 

normal displacement during the Late Cretaceous. Similar age discontinuities are 

observed between the Bill Little fault and west-dipping normal Northey Hill fault. 

Samples collected from the area between these two faults display modeled timetemperature histories representing higher structural levels that were

downdropped in a grabenlike structure during the Late Cretaceous. 

Tremblay and 

Castonguay (2002)

Structural Evolution of the Laurentian 

Margin Revisited (Southern Quebec 

Appalachians): Implications for the 

Salinian Orogeny and Successor 

Basins

The following faults have regional significance:

Logan’s Line marks the end of the Appalachian front.

The Richardson fault forms the boundary between the external and internal 

Humber zones.

The Bennett-Brome fault forms a composite structure along the NW limbs of 

the Notre Dame and Sutton Mountains anticlinoria.

Saint-Joseph fault defines the SE limb of the Notre Dame Mountains 

anticlinorium. Exhibited normal faulting during the Late Silurian to Early 

Devonian.
Table D-7.3.3 Data Summary 

Northern Appalachian Zone 

D-162 

Citation Title Description and Relevance to SSC

The Baie Verte–Brompton line forms the SE limb of the Sutton Mountains 

anticlinorium. Exhibited normal faulting during the Late Silurian to Early 

Devonian.

The La Guadeloupe fault is an Acadian reverse fault. The unusual thrust 

geometry is attributed to tectonic inversion of normal faults during Acadian 

compression.

West and Roden-Tice 

(2003)

Late Cretaceous Reactivation of the 

Norumbega Fault Zone, Maine: 

Evidence from Apatite Fission-Track 

Ages

Apatite fission-track ages across the Norumbega fault zone in southern Maine 

range from 113 to 89 Ma west of the fault and 159 to 140 Ma east of the fault. 

This age distribution is attributed to 2 km (1.2 mi.) east-side-down vertical 

displacement during the Late Cretaceous.
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-163 

Citation Title Description and Relevance to SSC

General for Region

Adams et al. (1995) Northeastern North American 

Earthquake Potential—New 

Challenges for Seismic Hazard 

Mapping

The authors developed seismic source zones based on hypothesis that stable 

continental earthquakes occur through reactivation of rift faults that break the 

integrity of continental crust, including Atlantic and Iapetan margins. 

Characterized faulted edge of Grenville continental crust that rifted during 

opening of Iapetus Ocean. Normal faults are currently reactivated as thrust 

faults within Canada and strike-slip faults in the U.S. The authors distinguish 

between Iapetan rift basins and failed Iapetan rifts.

Aleinikoff et al. 

(1995)

U-Pb Ages of Metarhyolites of the 

Catoctin and Mount Rogers 

Formations, Central and Southern 

Appalachians: Evidence for Two 

Pulses of Iapetan Rifting

The authors determined U-Pb ages for zircons sampled from Catoctin (564 ± 9 

Ma) and Mount Rogers (758 ± 12 Ma) formations. Tholeiitic flood metabasalt of 

Catoctin Formation crops out on both flanks of Blue Ridge anticlinorium from 

SE Pennsylvania to central Virginia and is overlain by Lower Cambrian rocks of 

Chilhowee Group. Catoctin Formation is underlain by rhyolite and arkose of 

Mechum River Formation, which contains clasts of Mesoproterozoic basement 

and Neoproterozoic Robertson River Igneous Suite. These rhyolites are 

thought to be the extrusive equivalent of the Battle Mountain Alkali Feldspar 

Granite of the Robertson River Igneous Suite. 

Bimodal volcanic rocks and interlayered sedimentary rocks of 760 Ma Mount 

Rogers Formation crop out in SW Virginia, North Carolina, and Tennessee. 

The Mount Rogers Formation nonconformably overlies Mesoproterozoic 

Cranberry Gneiss and is overlain by glaciogenic Konnarock Formation, which 

is overlain by the Chilhowee Group. The authors attribute these ages to two 

rifting events between 760 and 700 Ma and 570 and 560 Ma and correlate 

rifting in Sutton Mountains region with younger event. Study suggests that thick 

sediments of Ocoee Supergroup represent a long, slow episode of crustal 

extension and that Mount Rogers embayment is older than South Mountain 

and Sutton Mountains embayments. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-164 

Citation Title Description and Relevance to SSC

Bédard and 

Stevenson (1999)

The Caldwell Group Lavas of 

Southern Quebec: MORB-Like 

Tholeiites Associated with the 

Opening of Iapetus Ocean

The authors obtained trace element and Nd isotopic data for Caldwell Group 

lavas of southern Quebec. These undated rocks, within Internal Nappe domain 

of Humber zone, were deformed during the Taconic orogeny. The rocks initially 

formed at an advanced stage in transition from rift to drift along Iapetan margin. 

Despite exhibiting clear evidence of hydrothermal alteration, several 

conclusions were inferred from the geochemistry of these basalts. These 

basalts crystallized from melts derived from normal mid-ocean ridge basalt 

(MORB) at low- to medium-pressure fractional crystallization. Most lavas 

represent about 20% melting from a source slightly less depleted than fertile 

MORB mantle (asthenospheric mantle), whereas subpopulations of Caldwell 

lavas represent only 6%–15% melting of the same source mantle. These data 

are substantiated by Nd-isotope data that indicate derivation from a mantle 

depleted of light rare earth elements that is more radiogenic than other Iapetus 

basalts, implying other basalts in the region were derived from a more enriched 

source. Sedimentary samples reflect mixture of old (Archean) and juvenile 

(Iapetan) crustal sources for the basin. 

Du Berger et al. 

(1991)

The Saguenay (Quebec) Earthquake 

of November 25, 1988: Seismologic 

Data and Geologic Setting

Saguenay graben is defined by Lac Tchitogama and Ste-Marguerite River 

normal faults on north wall and Lac Kénogami normal fault on south wall. 

Ordovician limestones show downthrow of 500 m (1,640 ft.) along north wall. 

Subvertical brittle faults are found within and outside the graben. Lineaments in 

the region cluster at 000°, 015°, 030°, 050°, 105°, and 160°. The 015 and 030 

lineaments correspond to NNE late Grenvillian ductile belts and some postOrdovician brittle faults. The St. Lawrence rift reactivated 030° trend and 

produced 050° trend. The 160° trend is parallel to glacial strike. The 105° trend 

is prominent only in the Saguenay graben rosette. The 000° trend corresponds 

to a complex array of en echelon oblique short breaks near St. Maurice 

lineament, suggesting that St. Maurice marks transition between two structural 

domains. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-165 

Citation Title Description and Relevance to SSC

Faill (1997a) A Geologic History of the NorthCentral Appalachians. Part 1. 

Orogenesis from the Mesoproterozoic 

Through the Taconic Orogeny

Crustal extension and rifting late in the Neoproterozoic and into the earliest 

Cambrian separated Neoproterozoic supercontinent Rodinia into East 

Gondwana, West Gondwana, and Laurentia. Breakup of Rodinia spanned 

approximately 200 Myr, with separation of East Gondwana from western 

Laurentia approximately 750 Ma, and rifting of eastern Laurentia from West 

Gondwana resulting in the opening of several intervening oceans. Iapetus 

Ocean initially defined as early Paleozoic ocean between Baltica and Laurentia 

(Greenland); Theic Ocean defined as ocean between Laurentia and 

Gondwana, and Rheic Ocean as ocean between Baltica and Gondwana. This 

study emphasizes that subsequent universal usage of Iapetus refers to the 

Paleozoic ocean off Laurentia east margin and that sensu stricto the Iapetus 

Ocean was closed in Late Silurian Caledonia orogeny during docking of 

Avalonia microcontinents with Laurentia. The remaining ocean that lay east of 

Avalonia is generally called Theic, leading the author to recognize Paleozoic 

ocean east of Laurentia as Theia.

Evidence of initial breakup of Rodinia along western margin of Laurentia exists 

in southern Appalachian Virginia/North Carolina Blue Ridge as 760 Ma 

continental rift-facies volcanic Mount Rogers Formation and as largely 

nonvolcanic Ocoee rift deposits farther to the SW. The events may have been 

related to opening of Pacific Ocean. 

Rocks of Catoctin rift of Virginia, Maryland, and Pennsylvania comprise 

volcanic rocks of Catoctin Formation and sedimentary clastics of Chilhowee 

Group. These rocks, along with rocks of the St. Lawrence rift, suggest a fairly 

uniform-composition magma generation along eastern margin of Laurentia 

during the second phase of rifting. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-166 

Citation Title Description and Relevance to SSC

Faure et al. (2006) Paleostress Analysis of Atlantic 

Crustal Extension in the Quebec 

Appalachians

Fault stress tensors indicate that most E-W to ESE-WNW-oriented stress is 

found in Montreal and Gaspé area, whereas SE-NW stress is found in SE 

Quebec. Late Triassic–Jurassic dikes in New England and southern Quebec 

indicate SE-NW-oriented extension consistent with fault slip stress. The N-Strending portion of a Jurassic dike in southern Quebec is consistent with 

regional E-W extensional stress axis, whereas the NE-SW branch of this dike 

is more compatible with a local and adjacent NW-SE extension. Stress axes 

exhibit clockwise rotation in the White Mountain magma series, possibly due to 

local deviatoric stresses or a NE-SW-oriented basement fault. 

Faure et al. (2006) attribute these two extensional paleostress trends to either 

(1) contemporaneous regional partitioning of ESE-WNW-oriented extension 

influenced by N-S-trending structures in the Champlain Lake Valley and by NESW-trending structures of the St. Lawrence rift, or (2) an initial Late Triassic 

E-W extension related to formation of Bay of Fundy and South Georgia rift 

basins and Early Jurassic ESE-WNW extension related to central Atlantic rift 

system.

Gates and Volkert 

(2004)

Vestiges of an Iapetan Rift Basin in 

the New Jersey Highlands: 

Implications for the Neoproterozoic 

Laurentian Margin

Neoproterozoic rift basin deposits of Chestnut Hill Formation allow correlation 

between Iapetan rift basins in both northern and southern Appalachians. 

Immature, locally derived sediments of Chestnut Hill Formation were deposited 

into early alluvial, and later fluvial, lacustrine, and deltaic environments. 

Outcrops of Chestnut Hill Formation are associated with Morgan Hill and 

Chestnut Hill fault systems, which display transition in normal faulting from 

ductile to brittle moving upward in the geologic section. The authors recognize 

that Chestnut Hill basin may not be the most inboard Neoproterozoic basin,

and may in fact open the possibility that Iapetan margin contains other basins 

beneath Valley and Ridge cover. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-167 

Citation Title Description and Relevance to SSC

Higgins and van 

Breemen (1998)

The Age of the Sept Iles Layered 

Mafic Intrusion, Canada: Implications 

for the Late Neoproterozoic/Cambrian 

History of Southeastern Canada

The authors obtained U-Pb ages of 565 ± 4 Ma for Sept Iles layered mafic 

pluton located on Gulf of St. Lawrence islands and peninsulas. Combining 

these results with other published ages for Neoproterozoic to Cambrian 

igneous rocks from Laurentian margin suggests three phases of magmatism:

1. Tholeiitic dike emplacement was diachronous along Laurentian margin: 

Long Range dike swarm in Newfoundland was dated at 615 ± 2 Ma over a 

distance of 400 km (250 mi.) (Kamo et al., 1989); Grenville dike swarm 

formed synchronously with the Ottawa graben at 590 +2/–1 Ma over a 

distance of 400 km (250 mi.) (Kumarapeli, 1993; Kamo et al., 1995). These 

dike swarms may have been produced by one or two mantle plumes 

between 615 and 590 Ma, possibly one at Sept Iles.

2. Following dike emplacement, alkali plutons intruded into a relatively large 

region spanning Quebec, Ontario, Greenland, and Scandinavia as early as 

578 Ma and as late as Sept Iles intrusion (565 Ma). The authors attribute 

these plutons to a major plume located at Sept Iles instead of the location 

below the Sutton Mountains proposed by Kumarapeli (1993), but 

acknowledge that the two dike swarms could be result of two mantle plumes 

separated by 25 Myr The authors also observe that alkalic plutons were 

intruded along rift faults that developed after emplacement of dikes. 

3. Undated diabase dikes and metabasaltic flows occur throughout northern 

Appalachians, indicating earliest stages of formation of Iapetus Ocean. 

Tholeiitic lavas of Tibbit Hill Formation have U-Pb zircon ages of 554 +4/–2 

Ma (Kumarapeli et al., 1989); and alkali volcanic rocks at Skinners Cove, 

Newfoundland, have U-Pb ages of 550 +3/–2 Ma (McCausland et al., 1997). 

Hodych and Cox 

(2007)

Ediacaran U-Pb Zircon Dates for the 

Lac Matapédia and Mt. St.-Anselme 

Basalts of the Quebec Appalachians: 

Support for a Long-Lived Mantle 

Plume During the Rifting Phase of 

Iapetus Opening

U-Pb zircon ages for Lac Matapédia basalt (565 ± 6 Ma and 556 ± 5 Ma) and 

Mt. St.-Anselme basalt (550 ± 7 Ma) support interpretation of a long-lived 

Sutton Mountains mantle plume. These data close the gap between end of 

flood basalt and beginning of plume magmatism, and support a rift-drift 

transition at 540 Ma, as opposed to 570 Ma (McCausland and Hodych, 1998). 

This hypothesis implies that Laurentia drifted northward more slowly than was 

suggested by McCausland and Hodych (1998).
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Citation Title Description and Relevance to SSC

Howell and van der 

Pluijm (1999)

Structural Sequences and Styles of 

Subsidence in the Michigan Basin

Subsidence of Michigan basin began in late Cambrian to Early Ordovician. 

Subsequent episodes of subsidence responded to Appalachian tectonic 

events, resulting in evolution of the style and geometry of subsidence. These 

observations do not indicate that Iapetan rifting affected the Michigan basin.

Kanter (1994) Tectonic Interpretation of Stable 

Continental Crust

Northern and central portions of North America are an amalgamation of various 

Archean and Proterozoic domains assembled during the Mesoproterozoic. 

During the very late Neoproterozoic and continuing into the earliest Paleozoic, 

rifting occurred along eastern and southern margins, resulting in a passive 

margin. 

The author classified St. Lawrence–Ottawa domain (#227) as a Paleozoic rift,

remnant of an east-facing continental margin of an ocean basin that closed 

during formation of Appalachian Mountains, as evidenced by Appalachian 

thrust sheets overlapping eastern edge. Domain is defined on basis of 

fractures and normal faults in basement, alkalic intrusions, and Paleozoic 

sedimentary rocks that overlie basement. The presence of coarse clastics 

presumed to be of late Proterozoic age in eastern end of Ottawa graben 

implies that initiation of this rift system may have occurred in late 

Neoproterozoic. 

The author did not classify as extended any other Paleozoic domains south of 

St. Lawrence–Ottawa domain along eastern margin. The Newfoundland (#220) 

and Acadia (#222) domains consist of large clastic wedges formed as a result 

of Taconic accretionary events. Portions of Piedmont domain (#223) were 

deformed during Taconic orogeny, were accreted during Acadian strike-slip 

deformation (which affected the entire Appalachians), and experienced intense 

deformation during the widespread Alleghanian orogeny. Valley and Ridge 

province (domain #224) consists of miogeoclinal sediments overlying Grenvilleage basement deformed as a thin-skinned fold and thrust belt west of 

Piedmont domain. 

Outboard of these domains, the Eastern Seaboard domain (#218) records 

Mesozoic extension resulting from breakup of Pangaea. 

Study determined that the distinction between extended and non-extended 

domains was the only statistically significant variable on basis of maximum 

magnitude.
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Citation Title Description and Relevance to SSC

Kamo et al. (1995) Age of the Grenville Dyke Swarm, 

Ontario, Quebec: Implications for the 

Timing of Iapetan Rifting

Updates geochronology of Grenville dike swarm by obtaining U-Pb baddeleyite 

ages from widest dikes throughout Ottawa graben. Revised age of 590 Ma 

suggests Grenville dike swarm was emplaced within a relatively short time 

span. These dikes are thought to have formed at onset of rifting within Ottawa 

graben, Sutton Mountains triple junction, and the related segment of Iapetan 

margin. Comparison with ages of similar rift-related igneous rocks along 

Iapetan margin of Laurentia, including Bakersville dike swarm of the Blue 

Ridge (570 Ma), Franklin swarm of northern Canadian Shield (723 Ma), and 

Long Range dikes of SE Labrador and Newfoundland (615 Ma), indicate that 

Iapetan rifting occurred along vast distances of northern and eastern margins 

of Laurentia. The timing of initial rifting within Ottawa graben is somewhat 

earlier than other parts of North America, suggesting that rift initiation 

progressed from northern Laurentia margin at 723 Ma to Labrador and 

Newfoundland at 615 Ma, followed by Grenville dike swarm at 590 Ma. 

Kumarapeli and Saull 

(1966)

The St. Lawrence Valley System: A 

North American Equivalent of the East 

African Rift Valley System

Proposes rift origin for St. Lawrence valley system, including OttawaBonnechere and Saguenay grabens. Discusses the evidence supporting this 

conclusion, including the following:

Escarpments on NW side of St. Lawrence valley, north side of Ottawa 

Bonnechere graben, and western margin of Champlain Lake Valley.

South of Ottawa-Bonnechere graben, tilting of Madawaska Highlands to the 

south, NW tilting of Adirondack massif, north tilting of a Laurentian block 

south of Saguenay graben, and south block tilting of Gaspé Peninsula. 

En echelon normal faults along NW boundary with vertical displacements 

between 450 and 1,200 m (1,476 and 3,937 ft.).

St. Barnabe fault, a 55 km (34 mi.) normal fault on SE margin with 600 m 

(1,969 ft.) of downthrow to the west.

Concentrations of historical seismicity along St. Lawrence and Ottawa 

valleys and St. Lawrence trough.

Presence of a negative Bouguer anomaly in rift valley.

Connection of St. Lawrence valley with Mississippi embayment.

Westward continuation of Ottawa-Bonnechere graben with Midcontinent rift 

system.
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Citation Title Description and Relevance to SSC

Because the publication pre-dated plate tectonics, many aspects of the 

authors’ ideas are not consistent with current tectonic models of the region. 

After comparing St. Lawrence rift system to East African rift system, the 

authors suggest that the Great Lakes may be analogous to Lakes Victoria and 

Kyoga. The authors also associate Monteregian alkaline intrusives with St. 

Lawrence valley. Recent work associates them with Cretaceous intrusion that 

formed during reactivation of Ottawa-Bonnechere graben. 

Kumarapareli (1985) Vestiges of Iapetan Rifting in the 

Craton West of the Northern 

Appalachians

Proposes that a mantle plume produced initial ruptures of Iapetan rifting along 

a triple junction that led to continental fragmentation and development of an 

aulacogen in Ottawa graben. Alkalic to transitional bimodal volcanic rocks of 

the Tibbit Hill volcanics are deposited within Sutton Mountains salient, east of 

Ottawa graben, and are thought to be coeval with Grenville dike swarm within 

Ottawa graben. Interprets Sutton Mountains as the triple junction that initiated 

Iapetan rifting.

Kumarapeli et al. 

(1988)

Volcanism on the Passive Margin of 

Laurentia: An Early Paleozoic 

Analogue of Cretaceous Volcanism 

on the Northeastern American Margin

Transitional to alkaline basalts and mid-ocean ridge basalts (MORBs) found 

within Granby nappe of SE Quebec provide evidence for late Cambrian to 

Early Ordovician volcanism within transverse fracture zones analogous to Early 

Cretaceous volcanism in the Atlantic. The authors acknowledge that this data 

set is not sufficient to determine whether volcanism took place during drifting 

phase of continental margin because precise age of these rocks is not known. 

These allochthonous blocks are thought to represent slabs dislodged from the 

ancient shelf-margin sequence, possibly by Ottawa graben faults and NEtrending faults. 

Kumarapeli (1993) A Plume-Generated Segment of the 

Rifted Margin of Laurentia, Southern 

Canadian Appalachians, Seen 

Through a Completed Wilson Cycle

Updates mantle plume model presented by Kumarapeli (1985) with 

geochronology of dike swarms and volcanic rocks. Proposes that initiation of 

rifting was accompanied by emplacement of 590 Ma Grenville mafic dike 

swarm of tholeiitic composition. Rifting continued for 35 Myr until an outburst of 

alkaline to transitional basalts at Sutton Mountains triple junction dated at 554 

Ma. This was quickly followed by a short period of rift-facies clastic 

sedimentation consisting of conglomerates attributed to a large river delta. Riftdrift transition is indicated by deposition of open-marine sedimentation, thought 

to have occurred 550 Ma based on presence of rocks with early Cambrian 

fauna above this transition. 
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Citation Title Description and Relevance to SSC

Lavoie et al. (2003) Stratigraphic Framework for the 

Cambrian-Ordovician Rift and Passive 

Margin Successions from Southern 

Quebec to Western Newfoundland

In the Quebec Reentrant, platform rocks were only marginally involved in 

tectonic stacking of Taconic orogeny, and form a spatially restricted frontal 

Taconian deformation zone that is known as the para-autochthonous or 

imbricate fault domain, and is therefore not considered part of Humber zone. 

The Quebec Reentrant is rooted in the autochthonous St. Lawrence platform. 

These structural relationships allow for stratigraphic and paleogeographic 

scenarios for early evolution of Quebec-Newfoundland segment of continental 

margin slope of Laurentia.

Neoproterozoic to latest early Cambrian rift volcanics are overlain by rift-drift 

transition successions of early Cambrian Sauk I sequence. A global sea-level 

lowstand resulted in an unconformity that separates these rocks from shallow 

marine middle Cambrian to Middle Ordovician rocks of Sauk II and Sauk III 

subsequences. An extensive debris flow unit resedimented the middle 

Cambrian slope succession and is attributed to tectonic instability during 

middle to late Cambrian. The authors suggest that reactivation of Saguenay 

graben could be responsible for the anomalous upper Cambrian succession. 

Similar syndepositional tectonic activity is observed in the younger St. 

Lawrence platform succession in Charlevoix area during Middle to Late 

Ordovician. The authors present locations of reentrants and promontories for 

eastern margin of Laurentia farther north than those of Thomas (1991).

Lemieux et al. (2003) Structural Analysis of Supracrustal 

Faults in the Charlevoix Area, 

Quebec: Relation to Impact Cratering 

and the St-Laurent Fault System

Two major sets of fault orientations (N290°–N320° and N020°–N040°) are 

found outside impact zone, with minor fault sets trending N270°–N280° and 

N000°–N020°. Within the impact crater, fault orientations are more scattered 

but are similar to NW- and NE-trending systems of external domain. Spread of 

orientations within central portion of crater is attributed to the impact-related 

polygonal pattern of normal faults, whereas NW and NE fault sets represent 

youngest reactivation.

Coarse-grained cataclastic breccias up to 50 m (164 ft.) thick are exposed 

along brittle faults striking NE and NW outside impact crater. Similar cataclastic 

breccias are also found within the impact crater but are usually less than a few 

meters thick. Polymictic clastic matrix breccia are found exclusively within 

impact crater. Fragments of cataclastic breccia are present, suggesting 

recurrent brecciation during incremental faulting events. Pseudotachylyte and 

foliated gouge are locally related to cataclastic breccia, indicating that these 

rocks originate from a post-impact, single, and progressive tectonic event along 
Table D-7.3.4 Data Summary 

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Citation Title Description and Relevance to SSC

St. Lawrence rift system.

The St-Laurent fault influenced deposition of Ordovician deposits during late 

stages of Taconian orogeny as indicated by syndepositional faulting preserved 

as major lateral thickness variations within the section, presence of slump 

deformation in almost all stratigraphic units, preservation of pseudotachylyte 

within synsedimentary breccias, and occurrence of fault breccia clasts.

However, the geometry and structural characteristics of faulting are consistent 

with Mesozoic fault reactivation due to rifting of North Atlantic region. 

McBride et al. (2005) Integrating Seismic Reflection and 

Geological Data and Interpretations 

Across an Internal Basement Massif: 

The Southern Appalachian Pine 

Mountain Window, USA

The authors trace the master Appalachian decollement from Inner Piedmont to 

Coastal Plain. They find that beneath the Carolina terrane, the decollement 

roots to the Moho, indicating the location of Acadian-Alleghanian suture.

McCausland and 

Hodych (1998)

Paleomagnetism of the 550 Ma 

Skinner Cove Volcanics of Western 

Newfoundland and the Opening of the 

Iapetus Ocean

The authors obtained paleomagnetic data for volcanic flows and volcaniclastic 

sediments of Skinner Cove Formation in western Newfoundland dated at 550 

Ma that point to paleolatitude of 19°S ± 9°. This result represents paleolatitude 

of Iapetan margin at that time. Comparison of these results to those of 577 Ma 

Callander Complex of Ontario indicates rapid northward drift of Laurentia at 

approximately 570 Ma resulting from opening of Iapetus Ocean, which 

continued to the rift-drift transition at approximately 550 Ma.

Mereu et al. (1986) The 1982 COCRUST Seismic 

Experiment Across the OttawaBonnechere Graben and Grenville 

Front in Ontario and Quebec

Results of 1982 Canadian Consortium for Crustal Reconnaissance Using 

Seismic Techniques (COCRUST) long-range seismic refraction experiment 

show a sharp, step-like displacement of the Moho beneath south shoulder of 

Ottawa graben, confirming deep-seated nature of its faults and penetration of 

mantle melts into crust. Furthermore, COCRUST surveys show poorly defined 

Moho at unusually shallow depths beneath graben.

Petersen et al. 

(2008)

Documentation for the 2008 Update of 

the United States National Seismic 

Hazard Maps

The most recent model for the national seismic hazard maps for CEUS

incorporates maximum magnitude distributions that are considered separately 

for the craton and the Iapetan rifted margin as determined by Wheeler (1995). 

Model selects values based on analogy with other stable continental regions:

four values of moment magnitude between M 6.6 and M 7.2 (Charleston areal 

zone) for the craton, and four values of moment magnitude between M 7.1 

(Charleston main shock) and M 7.7 (Bhuj, India) for the extended margin.
Table D-7.3.4 Data Summary 

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Citation Title Description and Relevance to SSC

Pratt et al. (1988) A Geophysical Study of the Earth’s 

Crust in the Central Virginia: 

Implications for Appalachian Crustal 

Structure

The authors conclude that crustal thinning (at Taconic suture) in the Piedmont 

is responsible for Appalachian gravity gradient.

Rimando and Benn 

(2005)

Evolution of Faulting and PaleoStress Field Within the Ottawa 

Graben, Canada

The authors observe three periods of faulting in Cambro-Ordovician 

sedimentary rocks within eastern end of Ottawa graben, near Ottawa. The 

oldest generation of faults formed in stress field with a horizontal maximum 

compressive stress (σ1) oriented NW. These structures are kinematically 

congruent with the compression direction associated with closing of Iapetus 

Ocean. Second generation of faults indicates a WNW-oriented σ1 and 

coincides with emplacement of Cretaceous carbonatite dikes. Third generation 

of faults has a σ1 oriented SW, which is consistent with post-Cretaceous stress 

field in eastern North America. 

Rocher et al. (2003) Brittle Fault Evolution of the Montréal 

Area (St. Lawrence Lowlands, 

Canada): Rift-Related Structural 

Inheritance and Tectonism 

Approached by Palaeostress Analysis

NW-SE extension associated with opening of Iapetus Ocean resulted in 

formation of N040-trending faults along north shore of St. Lawrence Lowlands

and development of three major N090-trending faults that define a succession

of horsts and grabens on Montréal and Jésus islands and N120-trending faults 

in Montreal area. The N090-trending faults have the following geometries:

1. Bas-Sainte-Rose fault zone, the northernmost series of N090-trending faults 

in Montreal area, is a steeply north-dipping fault with approximately 200 m 

(656 ft.) of vertical displacement and nearly 3 km (2 mi.) of apparent leftlateral offset. Offsets on Bas-Sainte-Rose fault zone decrease as fault zone 

extends westward, where it apparently crosscuts the N020-trending Rivièreaux-Mille-Iles fault zone. 

2. Rapide-du-Cheval-Blanc consists of a series of steeply south-dipping 

normal faults (Ile-Bizard, Rapide-du-Cheval-Blanc, and Outremont) with a 

total vertical offset of approximately 100 m (326 ft.). 

3. Sainte-Anne-de-Bellevue fault zone is a north-dipping normal fault with a 

left-lateral strike-slip component in southern part of Montréal Island. Its 

vertical offset has not been precisely determined.

All three faults clearly crosscut NNE-SSW-trending folds from Appalachian 

Chambly-Fortierville syncline system in Trois-Rivières seismic zone. 

WNW-ESE compressions followed by minor NNW compressional events are 
Table D-7.3.4 Data Summary 

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Citation Title Description and Relevance to SSC

associated with Appalachian thrusting. WNW compression reactivated N090-

trending faults as strike-slip right-lateral faults, and reactivated N040-070 and 

N120 faults as reverse to strike-slip faults. Subsequent NNW compression is 

responsible for strike-slip conjugate faults trending NW-SE and NNE. 

NE-SW and NNW-SSE extension is associated with opening of North Atlantic–

Labrador Sea and reactivated faults with normal to strike-slip motions. NNW 

extension is responsible for horst-and-graben geometry of major N090 normal 

faults described above. Late NE-SW compression is recorded in Monteregian 

plutons. NE-SW compression postdating these events is associated with 

formation of strike-slip faults that crosscut Monteregian intrusions and is 

consistent with current stress regime.

Spencer et al. (1989) The Extension of Grenville Basement 

Beneath the Northern Appalachians: 

Results from the Quebec-Maine 

Seismic Reflection and Refraction 

Surveys

A master decollement separating autochthonous Grenville basement from 

overlying allochthonous rocks of Appalachian orogen extends over a distance 

of 200 km (124 mi.) and can be traced from shallow depths beneath St. 

Lawrence Lowlands SE to about 25 km (15.5 mi.) depth beneath SE edge of 

Chain Lakes massif. Basement is offset by closely spaced en echelon normal 

faults, with displacements between 200 and 1,000 m (656 and 3,281 ft.) 

interpreted as Iapetan growth faults.

The Baie Verte–Brompton line, separating Cambrian and Ordovician 

continental slope and rise deposits from oceanic arc and magmatic 

assemblages to south, including Chain Lakes massif, is imaged as shallow, 

thin-skinned structure. Chain Lakes terrane is thought to underlie much of 

Connecticut Valley–Gaspé synclinorium. Acadian Guadeloupe fault disrupts 

master decollement of Taconian orogeny and thrusts Connecticut Valley–

Gaspé synclinorium over Chain Lakes massif. 

St. Julien and Hubert 

(1975)

Evolution of the Taconian Orogen in 

the Quebec Appalachians

Describes 11 lithostratiographic assemblages distributed among 

autochthonous, external, and internal domains of Quebec Appalachians. 

The autochthonous domain contains Cambrian and Ordovician sandstones and 

carbonates representing transgressive shelf deposits, Middle and Upper 

Ordovician flysch deposits, and Upper Ordovician shale and sandstone 

representing the post-tectonic regressive sequence. This domain contains 

E-W- and N30E-trending normal faults active between late Precambrian and 

Late Ordovician.
Table D-7.3.4 Data Summary 

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D-175 

Citation Title Description and Relevance to SSC

Swanson (1986) Preexisting Fault Control for Mesozoic 

Basin Formation in Eastern North 

America

Correlates Mesozoic basin formation with reactivation of specific Paleozoic 

reverse and strike-slip faults along Appalachians.

Thomas (1991) The Appalachian-Ouachita Rifted 

Margin of Southeastern North 

America

Synthesizes available data into an interpretation of mechanisms controlling 

shape and timing of Iapetan rifted margin. NW-SE extension along entire rift 

system resulted in NE-trending rift (normal) faults and NW-trending transform 

faults. Rifting began in late Precambrian along Blue Ridge rift. By beginning of 

Cambrian, Blue Ridge progressed to a passive margin flanked by Iapetus 

Ocean, extension occurred along Mississippi Valley, Rough Creek, Rome, and 

Birmingham fault systems, and mafic magmas were emplaced along Southern 

Oklahoma fault system, suggesting the spreading center moved from Blue 

Ridge rift to Ouachita rift in early Cambrian. This was accompanied by initiation 

of Alabama-Oakland transform and Southern Oklahoma fault system. Some 

extension was propagated into Mississippi Valley, Rough Creek, Rome, and 

Birmingham fault systems, but this did not result in opening of an ocean. By 

early late Cambrian, the entire rift and transform margin evolved into passive 

margin.

Thomas (2006) Tectonic Inheritance at a Continental 

Margin

Explores tectonic inheritance of crustal structure through two Wilson cycles. 

The pre-Rodinia continental margin is unknown; however, possible inheritance 

from a dextral offset in older continental margin may result in the dextral bend 

of Grenville front beneath Gulf Coastal Plain. The New York–Alabama 

lineament, possibly an intra-Grenville suture, may represent either accretion 

along a straight segment of rifted margin or orogen-parallel slip across the 

shape of the margin. The palinspastically restored Iapetan margin consists of 

NE-striking rift segments offset by NW-striking transform faults, which in turn 

frame promontories and embayments of rifted continental margin.

The trace of Alabama-Oklahoma transform corresponds to probable location of 

a large-scale dextral bend in Grenville front. Rift-parallel graben systems, 

including Rome trough and Birmingham graben, indicate late synrift extension 

inboard from the rifted margin; their relationship to older tectonic fabrics is 

obscure and presently unrecognized. A pervasive lithospheric fabric may result 

in successive reoccupation of traces of transform faults at continental margin 

and differential crustal subsidence along transform faults at rift offsets in 

continental embayments. The shape of Iapetan margin controlled orientation of 

Appalachian-Ouchita foreland structures and subsequent continental margin of 
Table D-7.3.4 Data Summary 

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Citation Title Description and Relevance to SSC

Atlantic and Gulf Coastal Plain. 

Tremblay and 

Lemieux (2001)

Supracrustal Faults of the St. 

Lawrence Rift System Between CapTourmente and Baie-Saint-Paul, 

Quebec

The Cap-Tourmente and St. Lawrence faults are late Proterozoic–early 

Paleozoic normal faults attributed to rifting during opening of the Iapetus 

Ocean. 

The St. Lawrence fault trends N020°–N050° and dips 60°–70° to SE. Fault 

rocks consist of fault breccia, cataclastite, foliated gouge, and pseudotachylyte 

with a minimum thickness of 20 m near Sault-au-Cochon. Fault rocks exposed 

at Cap-Tourmente consist of 10–15 m thick zones of protocataclasite, 

cataclasite, and fault breccia. Within Charlevoix area, the St. Lawrence fault is 

characterized by a well-developed and extensive series of cataclastic rock, 

gouge, and associated pseudotachylyte. 

The Cap-Tourmente fault trends E-W and dips approximately 80° to the south. 

Fault rocks consist mostly of fault breccia more than 10 m thick, as well as 

cataclastic rocks and dark pseudotachylyte veins. The St. Lawrence fault is 

crosscut by Cap-Tourmente fault at Cap-Tourmente. 

West of Cap-Tourmente, the Montmorency Falls fault occupies the same 

structural position as the St. Lawrence fault, suggesting that they formed from 

en echelon faults trending parallel to axis of St. Lawrence rift. 

The Cap-Tourmente fault possibly represents a transfer fault, producing an 

oblique relay between two longitudinal normal faults. 

The St. Lawrence fault crosses the Charlevoix impact crater without major 

trend deflection or fault offsets within or at the boundaries of the Devonian 

impact structure. This observation suggests that impact-related faults did not 

significantly alter the orientation of preexisting structures and that reactivation 

is younger than the impact structure, most probably concurrent with opening of 

the Atlantic Ocean in the Mesozoic.

Tremblay et al. 

(2003)

Supracrustal Faults of the St. 

Lawrence Rift System, Quebec: 

Kinematics and Geometry Revealed 

by Field Mapping and Marine Seismic 

Reflection Data

Presents strike orientations, dip angles, and pitch angles for faults with 

evidence of frictional sliding in the St. Lawrence rift system. NE-trending

longitudinal faults show three trends (N025, N040, and N070) and generally dip 

to SE, although a minor number dip to NW. Transverse faults show two trends 

(N290 and N310) and dip to NE or SW, which is consistent with horst-andgraben geometry. Both sets of faults are high-angle faults with dip angles 

averaging 75°–80°. The pitch value of fault lineations is greater than 70°, 

indicating that most structures are dip-slip faults. Longitudinal and transverse 
Table D-7.3.4 Data Summary 

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D-177 

Citation Title Description and Relevance to SSC

faults show mutual crosscutting relationships, suggesting that they represent 

conjugate structures related to same tectonic event. 

St-Laurent fault has experienced at least 800 m (2,625 ft.) of vertical throw at 

Sault-au-Cochon. Cap-Tourmente fault has a minimum vertical fault throw of 

700 m (2,297 ft.). Montmorency fault has an 80 m (262 ft.) fault scarp near 

Quebec City; stratigraphic analysis suggests that fault throw should be less 

than 150 m (492 mi.), which is considerably less than the other faults. Several 

offshore faults subparallel to that fault may have vertical downthrow 

displacements up to 1 km (0.6 mi.). 

Longitudinal faults likely result from development of en echelon faults trending 

parallel to the rift axis, and transfer faults represent transfer faults or 

accommodation zones. Variations in fault throw are likely a result of 

propagation of extension along transfer faults. 

Presence of cataclastic rocks, pseudotachylytes, and fault gouge is consistent 

with changes of deformation mechanics during progressive and incremental 

deformation in upper crust.

High-resolution seismic profiles in St. Lawrence estuary indicate that 

Laurentian Channel trough transitions from a half graben to a graben structure 

from SW to NE. 

The authors speculate that reactivation of St. Lawrence rift system is postOrdovician, younger than the Devonian impact cratering event, and that the rift 

system experienced additional fault throw and shoulder uplift during Mesozoic 

opening of North Atlantic. 

Valentino and Gates 

(1995)

Iapetan Rift-Related Turbidite-Fan 

Deposits from the Central 

Appalachian Piedmont

Peters Creek Formation of SE Pennsylvania and northern Maryland consists of 

two submarine turbidite-fan systems. Metaclastic strata of Peters Creek 

Formation preserve primary detrital and bedding features indicative of 

deposition in turbidite-fan systems. Presence of greenstone interlayered with 

feldspathic metasandstone suggests rift-related deposition. Granitic lithic 

fragments indicate unroofing of continental crust. Peters Creek Formation may 

represent deposits transported along an Iapetan rift-related transform fault 

linking southern Lynchburg rift basin with a comparable rift basin in southern 

New England. 
Table D-7.3.4 Data Summary 

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Citation Title Description and Relevance to SSC

Walsh and Aleinikoff 

(1999)

U-Pb Zircon Age of Metafelsite from 

the Pinney Hollow Formation: 

Implications for the Development of 

the Vermont Appalachians

U-Pb zircon age of 571 ± 5 Ma for metafelsite from Pinney Hollow Formation of 

Vermont records age of rhyolitic volcanism and deposition in a largely pelitic 

sequence interpreted as pre-shelf rift-clastic sequence. This age agrees with 

other ages from rift-clastic volcanic rocks in the Appalachians. Relative 

distribution and thickness of metavolcanic and metafelsic sections throughout 

Appalachians suggest the basin that Pinney Hollow Formation was deposited 

into was already well developed when the 571 Ma metafelsite was deposited. 

Therefore, the 554 Ma age for Tibbit Hill Formation at Sutton Mountains triple 

junction does not represent first pulse of volcanic activity during initial opening 

of Iapetan basin in Vermont and Quebec Appalachians. This age also validates 

theory that Wood Peak fault is a significant thrust fault separating 

autochthonous and para-autochthonous cover sequence rocks, which in turn 

supports interpretation that the Taconic root zone is located in hinterland of 

Vermont Appalachians on eastern side of Green Mountain massif.

Wheeler (1995) Earthquakes and the Cratonward 

Limit of Iapetan Faulting in Eastern 

North America

Recognizes that seismic activity within the Charlevoix, Quebec; Giles County, 

Virginia; Eastern Tennessee; and, possibly, Clarendon-Linden seismic zones is

attributed to compressional reactivation of NE-trending Iapetan normal faults. 

Defines NW limit of potentially seismogenic Iapetan normal faults from a variety 

of data sets available at the time. This boundary, with an uncertainty of 21 km

(13 mi.), separates lower rates of seismicity to the NW from higher rates to the 

SE and suggests that seismic zones to the SE of the line can produce large 

earthquakes such as those at Charlevoix.

Whitmeyer and 

Karlstrom (2007)

Tectonic Model for the Proterozoic 

Growth of North America

Breakup of Rodinia consists of diachronous disassembly. Early stages of rifting 

resulted in opening of a paleo-Pacific Ocean along western margin of Laurentia 

between 780 and 680 Ma, corresponding to separation of Australia, Antarctica, 

south China, and Siberia, and failed rifting along eastern margin of Laurentia. 

Complete breakup along eastern margin of Laurentia initiated by 620 Ma from 

Newfoundland to southern Appalachians. This final stage of breakup involved 

rifting of Argentina Precordillera terrane from Ouachita embayment. Transfer of 

Precordillera terrane across Iapetus Ocean requires relocating Iapetus 

spreading ridge from present-day Alabama to central Texas. This change in 

spreading may have occurred because of at least two incipient triple junctions 

that combined in SE United States in early Cambrian to initiate a new 

spreading ridge-transform system.
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-179 

Citation Title Description and Relevance to SSC

Geophysical Anomalies

New York–Alabama (NY-AL) Lineament

King and Zietz (1978) The New York–Alabama Lineament: 

Geophysical Evidence for a Major 

Crustal Break in the Basement 

Beneath the Appalachian Basin

NY-AL lineament consists of series of linear magnetic gradients that 

correspond with west side of regional Appalachian gravity low. This lineament 

extends more than 1,600 km (994 mi.) from Mississippi embayment to Green 

Mountains of Vermont. It separates north-trending gravity anomalies on the 

NW from NE-trending anomalies to the SE. Magnetic gradient of NY-AL 

lineament faces SE for some sections and NE for others. Given that regions of 

high magnetic values are cut off by the lineament, it likely represents a strikeslip fault as opposed to a vertical displacement. The lineament constitutes a 

major break in crystalline basement rocks of Appalachian basement separating 

stable craton of continental interior from more mobile Appalachian block of 

continental margin. 

Steltenpohl et al. 

(2010)

New York–Alabama Lineament: A 

Buried Right-Slip Fault Bordering the 

Appalachians and Mid-continent North 

America

NY-AL lineament is a N40E-trending magnetic lineament extending 1,600 km 

(994 mi.) from Vermont to southern Tennessee. From southern West Virginia 

to Tennessee, it separates a mottled pattern of magnetic highs and lows of the 

granite-rhyolite province and Neoproterozoic mafic rocks to the NW, from NEtrending magnetic lineaments of Appalachian orogen to the SE. NY-AL 

lineament is a fundamental tectonic boundary that may represent either an 

escape strike-slip fault related to Grenvillian contractual orogenesis, an axis of 

anatectic melting following continental collision, or an intra-Grenvillian suture. 

In Eastern Tennessee seismic zone (ETSZ), the Ocoee block is bounded by 

NY-AL lineament on the north and Clingman lineament on the south. NY-AL 

lineament is interpreted as strike-slip fault zone, based on truncation of Amish 

anomaly in West Virginia and on documentation of ~220 km (~137 mi.) of rightslip displacement and a trending magnetic high-low pair in SE block in 

Tennessee, Georgia, and Alabama. Linear fault segments that border Rome 

trough are parallel to and locally coincide with NY-AL lineament. SE border 

fault parallels lineament for nearly 250 km (155 mi.) from eastern KY to SW 

Pennsylvania. This segment of lineament was reactivated as a normal fault that 

underwent west-side-down dip-slip displacement during formation of Rome 

trough. Crust NW of NY-AL lineament behaved as a coherent block.

Seismicity of ETSZ may be localized along the N15E-trending magnetic low 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-180 

Citation Title Description and Relevance to SSC

anomaly in the Ocoee block, which coincides with metasedimentary gneiss 

correlative with the Amish anomaly. Modern stress field is compatible with the 

one that initiated dextral motion along NY-AL lineament. 

Structures

Rome Trough

Drahovzal (1997) Proterozoic Sequences and Their 

Implications for Precambrian and 

Cambrian Geologic Evolution of 

Western Kentucky: Evidence from 

Seismic Reflection Data

Rough Creek graben and Rome trough exhibit Cambrian fan complexes 

deposited in a subsiding basin to the north. This subsidence likely occurred in 

late Precambrian and may represent inboard extension of Iapetan rifting along 

the Mesoproterozoic East Continent rift basin. 

Faill (1997a) A Geologic History of the NorthCentral Appalachians. Part 1. 

Orogenesis from the Mesoproterozoic 

Through the Taconic Orogeny

Rome trough consists of steep normal faults that become listric at depth, 

recording intracontinental extension during middle and late Cambrian. It acted 

as middle Cambrian sediment trap, with quartzose facies accumulating to the 

west during late Cambrian. Siliclastic deposition along eastern margin of 

Laurentia was replaced by carbonate deposition during early Cambrian.

Stark (1997) The East Continent Rift Complex: 

Evidence and Conclusions

Attributes development of Rome trough and reactivation of Kentucky River fault 

system to late Neoproterozoic extension associated with opening of Iapetus 

Ocean within East Continent rift complex.

Steltenpohl et al. 

(2010)

New York–Alabama Lineament: A 

Buried Right-Slip Fault Bordering the 

Appalachians and Mid-continent North 

America

Linear fault segments that border Rome trough parallel and locally coincide 

with the NY-AL lineament. The SE border fault is parallel to lineament for 

nearly 250 km (155 mi.) from eastern Kentucky to SW Pennsylvania. This 

segment of lineament was reactivated as a normal fault that underwent westside-down dip-slip displacement during formation of Rome trough.

Van Arsdale and 

Sergeant (1992)

Post-Pliocene Displacement on Faults 

Within the Kentucky River Fault 

System of East-Central Kentucky

Kentucky River fault system forms northern boundary of Rome trough, a 

Paleozoic aulacogen. The absence of post-Paleozoic deposits prevents 

determination of Mesozoic and early Tertiary displacements. Trenches in 

terrace materials indicate folding and faulting within last five million years, and 

probably within last million years. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-181 

Citation Title Description and Relevance to SSC

Central Metasedimentary Belt Boundary Zone

Forsyth, Milkereit, 

Davidson, et al. 

(1994)

Seismic Images of a Tectonic 

Subdivision of the Grenville Orogen 

Beneath Lakes Ontario and Erie

The authors observed extensional reactivation in Paleozoic section above 

Central Metasedimentary Belt boundary zone in eastern Lake Erie. 

O’Dowd et al. (2004) Structural Fabric of the Central 

Metasedimentary Belt of Southern 

Ontario, Canada, from Deep Seismic 

Profiling

Using results of Southern Ontario Seismic Project and analysis or regional 

magnetic data, the authors conclude that Central Metasedimentary Belt 

boundary zone must be located on west side of Mississauga domain, thereby 

placing it farther west. 

Zones of Elevated Seismicity

Clarendon-Linden Fault System

Crone and Wheeler 

(2000)

Data for Quaternary Faults, 

Liquefaction Features, and Possible 

Tectonic Features in the Central and 

Eastern United States, East of the 

Rocky Mountain Front

Crone and Wheeler (2000) identify Clarendon-Linden fault zone in New York 

as Class C tectonic feature. Assessment is based on absence of 

paleoseismological evidence that fault zone has slipped during the Quaternary.

Dineva et al. (2004) Seismicity of the Southern Great 

Lakes: Revised Earthquake 

Hypocenters and Possible Tectonic 

Controls

Hypocenters from earthquakes occurring between 1990 and 2001 were 

relocated; the redefined zones of seismicity delineate several clusters of events 

beneath Lake Ontario. The authors identified a cluster C that is parallel to 

Clarendon-Linden fault system but shifted slightly to SE by about 4 km (2.5 

mi.). They note that during the 1990–2001 recording period for this analysis, 

little seismic activity occurred along Clarendon-Linden fault system, with only 

two events near southern end.

Fakundiny and 

Pomeroy (2002)

Seismic-Reflection Profiles of the 

Central Part of the Clarendon-Linden 

Fault System of Western New York in 

Relation to Regional Seismicity

Describes Clarendon-Linden fault system as broad zone of small faults with 

small displacements in lower Paleozoic bedrock. Fault system is at least 77 km 

(48 mi.) long and 7–17 km (4.5–10.5 mi.) wide; total vertical displacement 

across the zone is small (>91 m). Fault system is spatially coincident with a 

north-trending geophysical (combined magnetic and gravity) lineament within 

basement rock. Most earthquakes in the region cannot be unequivocally 

associated spatially with individual tectonic structures and lineaments. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-182 

Citation Title Description and Relevance to SSC

Forsyth, Milkereit, 

Zelt, et al. (1994)

Deep Structure Beneath Lake 

Ontario: Crustal-Scale Grenville 

Subdivisions

Using deep crustal seismic images, at least three major shear zones are 

interpreted to underlie Lake Ontario. Elzevir-Frontenac boundary zone defined 

based on a shear zone transition exposed to north of Lake Ontario between 

these two terranes and linked to a seismically defined shear zone extending 

beneath Lake Ontario to south shore. Iroquoian high is defined on basis of 

gradual thinning of Paleozoic section over a crestal area of Elzevir-Frontenac 

boundary zone. Iroquoian high is interpreted to help explain Paleozoic fractures 

that formed Clarendon-Linden structure in New York. 

Jacobi (2002) Basement Faults and Seismicity in the 

Appalachian Basin of New York State

Evaluates regional sets of lineaments identified on Landsat images and their 

relationship to faults and earthquake epicenter locations. Identifies ClarendonLinden fault system as the most prominent of western New York State fault 

sources. A seismicity swarm is located along western flank of the gravity high 

associated with this fault system. The swarm terminates on north where gravity 

high diminishes in amplitude.

Jacobi and Fountain 

(2002)

The Character and Reactivation 

History of the Southern Extension of 

the Seismically Active ClarendonLinden Fault System, Western New 

York State

By integrating a variety of surface and subsurface data, the authors determined 

that Clarendon-Linden fault system in SW New York State consists of as many 

as 10 parallel, segmented faults. Fault segments are truncated by cross-strike 

discontinuities. The rock record indicates that fault blocks formed by the fault 

segments and that cross-strike discontinuities were active in Precambrian and 

subsequently reactivated multiple times until Late Devonian.

Ouassaa and Forsyth 

(2002)

Interpretation of Seismic and Potential 

Field Data from Western New York 

State and Lake Ontario

Lithoprobe and seismic data provide evidence of major zones of east-dipping 

Grenville deformed crust extending from north of Lake Ontario toward SW. In 

the vicinity of Clarendon-Linden fault, N-NE-trending magnetic and gravity 

anomalies are parallel to, but are not restricted to, the principal trend of this 

fault system. Surface continuity of inferred faults constituting Clarendon-Linden 

fault system is not strongly supported by reprocessed seismic data.

Paleoseismic Investigations

Seeber and 

Armbruster (1993)

Natural and Induced Seismicity in the 

Lake Erie–Lake Ontario Region: 

Reactivation of Ancient Faults with 

Little Neotectonic Displacement

Historical and recent earthquake activity is interpreted to form a prominent 

seismic zone associated with Clarendon-Linden fault. Location of 1929 mb 5.2 

Attica earthquake suggests this event could have been associated with 

Clarendon-Linden fault. Also, earthquakes induced from injection of brine into 

wells in the Dale area could be associated with Clarendon-Linden fault.
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-183 

Citation Title Description and Relevance to SSC

Tuttle, Dyer-Williams, 

and Barstow (2002) 

Paleoliquefaction Study of the 

Clarendon-Linden Fault System, 

Western New York State

Investigations indicated a lack of earthquake-induced liquefaction features in 

geologic units, which suggests the fault system did not generate large M > 6 

earthquakes in past 12,000 years. It was concluded that the fault system could 

have produced small and moderate earthquakes, but probably not large ones,

during late Wisconsinan and Holocene. 

White et al. (2000) A Seismic-Based Cross-Section of the 

Grenville Orogen in Southern Ontario 

and Western Quebec

Describes Elzevir-Frontenac boundary zone as major structural boundary zone 

based on prominent geophysical signatures. These make up a broad zone of 

SE-dipping reflections and midcrustal velocity contours that shallow at depths 

of 12–15 km (7.5–9.5 mi.). 

Giles County (Virginia) Seismic Zone (GCVSZ)

Seismicity and Fault Geometry Data

Bollinger and 

Wheeler (1988)

The Giles County, Virginia, Seismic 

Zone—Seismological Results and 

Geological Interpretations

Defines 40 km (25 mi.) long seismic zone based on instrumental seismicity. A 

damaging earthquake that occurred in 1897 in Giles County is believed to have 

occurred within this seismic zone. Compressional reactivation of an Iapetan 

normal fault is likely responsible for formation of seismic zone. 

Bollinger et al. (1991) Seismicity of the Southeastern United 

States; 1698 to 1986

Provides an overview of historical and instrumental seismicity in SE United 

States. Describes dimensions of GCVSZ and notes that zone of seismicity is 

beneath rocks detached by thrusting, thus demonstrating the lack of 

association with fault structures observed at the surface. Release of seismic 

energy in GCVSZ most likely related to reactivation of Precambrian faults.

Gresko (1985) Analysis and Interpretation of 

Compressional (P Wave) and Shear 

(SH Wave) Reflection Seismic and 

Geologic Data over the Bane Dome, 

Giles County, Virginia

Seismic-reflection data acquired in Giles County were analyzed. Interpreted 

thickening of basement rock beneath the Bane Dome is postulated to represent 

late Precambrian–early Cambrian rifting. Faults generated at that time may 

now be reactivated in the present stress regime. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-184 

Citation Title Description and Relevance to SSC

Paleoseismic Investigations

Anderson and Spotila 

(2001)

The Relationship of Geologic 

Structure to the Giles County Seismic 

Zone in Southwest Virginia, Based on 

Fracture Mapping in Allochthonous 

Paleozoic Strata

Describes study to characterize brittle fractures that occur along 7 km (4.5 mi.) 

of discontinuous outcrops in Giles County. Fractures range from diffuse hairline 

cracks to through-going, clay-filled faults. Fracture orientations have no 

apparent relationship to local topography or karst-related subsidence. 

Earthquakes in region could have ruptured entire upper crust; however, without 

age control on the fractures, a strong conclusion cannot yet be made.

Bollinger et al. (1992) Geologically Recent Near-Surface 

Faulting in the Valley and Ridge 

Province: New Exposures of 

Extensional Faults in Alluvial 

Deposits, Giles County, SW Virginia 

Describes characteristics of two extensional faults that cut a series of alluvial 

terrace deposits along north side of New River Valley near Pembroke in Giles 

County. The age of neither the faults nor the sediments is known, but both 

appear to be relatively recent (Tertiary or Quaternary). The faults are important 

because they indicate at least local occurrence of geologically recent nearsurface faulting. Seismic monitoring in area indicates earthquake hypocenters 

occur at depths greater than 5 km (3 mi.). 

Chapman and 

Krimgold (1994)

Seismic Hazard Assessment for 

Virginia

Attributes earthquakes in GCVSZ to a 40 km (25 mi.) long NNE-trending, 

steeply dipping structure oriented approximately 20° counterclockwise to 

detached sedimentary structures mapped at surface. Earthquakes occur below 

Valley and Ridge thrust sheets at depths of 5–25 km (3–15.5 mi.). Focal 

mechanisms exhibit strike-slip motions on steeply dipping northerly and 

easterly planes with a maximum compressive stress direction that is 

northeasterly and nearly horizontal. This pattern of seismicity attributed to 

reactivation of one or more Eocambrian extensional faults. On basis of this 

information, Chapman and Krimgold delineated a separate seismic zone for 

Giles County region. 

Crone and Wheeler 

(2000)

Data for Quaternary Faults, 

Liquefaction Features, and Possible 

Tectonic Features in the Central and 

Eastern United States, East of the 

Rocky Mountain Front

Describes Pembroke faults in terrace deposits of probable Quaternary age at a 

locality along north side of New River Valley near Pembroke, Virginia. These 

faults were reported but not named by others (e.g., Law et al., 1992). The faults 

overlie a steeply dipping tabular zone of hypocenters; however, it has not been 

determined whether they are tectonic or the result of solution collapse. 

Characteristics of the faults are described. Based on uncertainty in fault origin, 

Pembroke faults are assigned to Class B, 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-185 

Citation Title Description and Relevance to SSC

Granger et al. (1997) Quaternary Downcutting Rate of the 

New River, Virginia, Measured from 

Differential Decay of Cosmogenic 26Al 

and 10Be in Cave-Deposited Alluvium

Describes how cosmogenic radionuclides 26Al and 10Be in quartz can be used 

to infer time of emplacement of cave-deposited river sediment. Analyses of 

these radionuclides from caves high above New River indicate a downcutting 

rate of 27.3 + 4.5 m/Myr. A tectonic tilt rate over the late Quaternary of 1.05 + 

0.35 m km–1 Myr–1is estimated near GCVSZ. 

Law et al. (1994) Geologically Recent Near-Surface 

Faulting and Folding in Giles County, 

Southwest Virginia: New Exposures of 

Extensional and Apparent Reverse 

Faults in Alluvial Sediments Between 

Pembroke and Pearisburg

Describes faults and graben structures investigated in alluvial deposits at 

Pembroke excavation site on the New River. The ages of faults and sediments 

are unknown; however, unlithified nature of the deposits suggests relatively 

young ages (Tertiary or Quaternary). Excavation site is within defined area of 

GCVSZ. Authors use three models to explain formation of exposed fold and 

fault structures: landsliding, solution collapse, and basement faulting of tectonic 

origin.

Law et al. (2000) Folding and Faulting of PlioPleistocene Sediments in Giles 

County, SW Virginia: (1) Surface Data 

and Interpretation

Describes excavations along New River Valley that have revealed series of 

extensional and reverse faults cutting alluvial terrace deposits. Terrace 

sediments are arched into broad, gently plunging antiform. Features are 

consistent with continued sedimentation in a depression formed by progressive 

solution of limestone, followed by inversion to form the anticlinal structure. The 

fine structure preserved in some terrace deposits precludes sudden slip on the 

faults and indicates slow slip rates.

Mills (1985) Descriptions of Backhoe Trenches 

Dug on New River Terraces Between 

Radford and Pearisburg, Virginia, 

June 1981

Provides information on 20 backhoe trenches dug on terraces of the New River 

in and near Giles County. No evidence of seismic shaking, faulting, or surface 

rupture was found in the 2 trenches within GCVSZ or in 18 trenches near the 

zone.

Mills (1986) Possible Differential Uplift of New 

River Terraces in Southwestern 

Virginia

Describes studies of terrace elevations along New River in SW Virginia. 

Differences in elevation between two areas can be explained by differential 

uplift between 30 and 200 mm/ka. Uplift is consistent with probable movements 

on faults associated with GCVSZ. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-186 

Citation Title Description and Relevance to SSC

Wheeler (2005) Known or Suggested Quaternary 

Tectonic Faulting, Central and 

Eastern United States—New and 

Updated Assessments for 2005

Reviews information about GCVSZ. This seismic zone has no recognized 

geomorphic expression, and no geologic evidence has yet demonstrated 

Quaternary surface deformation caused by tectonic faulting within the zone. 

Accordingly, it is assigned to Class C. Nonetheless, occurrence of a significant

historical earthquake in 1897 (M 5.9) and of continuing smaller earthquakes 

demonstrates that a notable level of seismic hazard exists for zone. 

Geophysical Investigations

Robinson et al. 

(1993)

A Seismic Refraction and Electrical 

Resistivity Survey of Faulted Alluvial 

Deposits in Giles County, VA 

Imaged high-angle faults and a broad antiformal fold in young, unconsolidated 

sediment in Giles County, Virginia, were imaged with seismic refraction and 

electrical resistivity. Results from seismic refraction indicate the faults extend 

through sediments more than 40 m (131 ft.) thick and local topography exists at 

bedrock surface, which can be attributed to faulting, karst, or inherited 

topography. Results from resistivity survey indicate that high-angle anomalies 

are high-angle faults.

Robinson et al. 

(2000)

Folding and Faulting of PlioPleistocene Sediments in Giles 

County, SW Virginia: (3) Seismic 

Refraction, Potential Fields, and 

Borehole Data

Describes excavations along New River Valley that have revealed series of 

faults cutting alluvial terrace deposits. Terrace sediments are arched into 

broad, gently plunging antiform, with a graben in hinge zone of antiform.

Subsurface investigations indicate that terrace deposits reach maximum of 40 

m (131 ft.) thick and contain possible voids. Geophysical measurements in 

limestone basement do not reveal any features that might be related to fold 

and graben structures in overlying terrace deposits.

Williams et al. (2000) Folding and Faulting of PlioPleistocene Sediments in Giles 

County, SW Virginia: (2) GroundPenetrating Radar and Seismic 

Reflection Data 

Describes excavations along New River Valley that have revealed series of 

faults cutting alluvial terrace deposits. Terrace sediments are arched into 

broad, gently plunging antiform, with a graben in hinge zone of antiform. 

Seismic-reflection and ground-penetrating radar were used to image faults 

below excavation level. This information indicates that exposed faults are 

contained within a larger system of SSE- and NNW-dipping normal faults and 

that there is a linear depression in limestone bedrock that corresponds to the 

graben in terrace deposits. The authors note that it is unlikely that the faults 

were caused by collapse of an isolated subcircular sinkhole.
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-187 

Citation Title Description and Relevance to SSC

Eastern Tennessee Seismic Zone (ETSZ)

Seismicity and Fault Geometry Data

Bollinger et al. (1991) Seismicity of the Southeastern United 

States; 1698 to 1986

Describes seismicity in eastern Tennessee. This area is the most seismically 

active in Southeast. Largest recorded earthquake reported at time of 

publication was 1973 Ms 4.6 Maryville-Alcoa event. Active faulting is reported 

as occurring on steeply dipping fault planes, the majority of which are located 

beneath the master Appalachian decollement.

Chapman (1996) Focal Mechanisms and the Geometry 

of Basement Faults in the Eastern 

Tennessee Seismic Zone

Compares relocated hypocenters for 474 earthquakes with more than 40 focal 

mechanisms for earthquakes monitored between 1982 and 1993. Results 

indicate that earthquakes exhibit predominantly strike-slip motion that occur 

either on left-stepping en echelon basement faults striking SW-NE or on a 

conjugate system of E-W-striking faults.

Chapman et al. 

(1997)

A Statistical Analysis of Earthquake 

Focal Mechanisms and Epicenter 

Locations in the Eastern Tennessee 

Seismic Zone

Describes location and orientation of possible seismogenic basement faults 

based on information provided by focal mechanisms and earthquake 

epicenters. Spatial aspects of the seismicity are examined. Strike-slip motion 

on steeply dipping planes is dominant mode of faulting in the 300 km (186 mi.) 

long seismic zone. A series of NE-trending en echelon basement faults are 

intersected by several east-trending faults. 

Chapman et al. 

(2002)

The Eastern Tennessee Seismic 

Zone: Summary after 20 Years of 

Network Monitoring

Provides information on focal depths and mechanisms of earthquakes in ETSZ. 

Focal mechanism solutions indicate strike-slip faulting on steeply dipping 

planes. Epicenters form linear segments that may reflect basement fault 

structure being reactivated in the modern stress regime. Largest historical

earthquake in ETSZ was magnitude 4.6. Although no evidence for larger 

shocks has been found, microearthquakes suggest coherent stress 

accumulation within a large volume. The authors propose that a hydrologic 

element may link seismicity, uniform regional stress, and basement structure. 

Dunn and Chapman 

(2006)

Fault Orientation in the Eastern 

Tennessee Seismic Zone: A Study 

Using the Double-Difference 

Earthquake Location Algorithm

Uses double-difference earthquake location algorithm to examine earthquake 

hypocenter relocations and resolve fault orientations. Relocations in the most 

seismically active portion of ETSZ indicate diffuse west-striking, north-dipping 

zone of hypocenters. Zone is consistent with a structure imaged on a seismicreflection profile that appears to be a seismogenic basement fault.
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-188 

Citation Title Description and Relevance to SSC

Johnston et al. 

(1985)

Seismotectonics of the Southern 

Appalachians

Describes majority of southern Appalachian seismicity as occurring in a 

concentrated zone beneath Valley and Ridge province of eastern Tennessee. 

Zone is bounded on NW by NY-AL lineament and on SE by Clingman/Ocoee 

lineaments. Analyses indicate that seismic activity occurs beneath the 

decollement, thus supporting hypothesis that Appalachian seismicity is 

unrelated to surficial geologic or tectonic features.

Kaufmann and Long 

(1996)

Velocity Structure and Seismicity of 

Southeastern Tennessee

Describes SE Tennessee seismic zone as located at confluence of major 

crustal features. Using a velocity model, the authors demonstrate that 

seismicity is concentrated in areas of average to below average velocity and 

does not appear to be associated with a major crustal feature. Instead,

seismicity is characterized by distribution of hypocenters and their association 

with low-velocity regions at midcrustal depths. 

Keller et al. (1982) Evidence for a Major Late 

Precambrian Tectonic Event (Rifting?) 

in the Eastern Midcontinent Region

Describes large linear gravity anomaly that extends through eastern Kentucky 

and Tennessee and coincides with a zone of complex, high-amplitude 

magnetic anomalies. This area appears to have been location of an ancient rift 

that formed about 1,100 Ma and has been locally reactivated. Basement 

lithologies in area appear to be metamorphosed volcanics that are relatively 

strong.

King and Zietz (1978) The New York–Alabama Lineament:

Geophysical Evidence for a Major 

Crustal Break in the Basement 

beneath the Appalachian Basin

Defines NY-AL lineament that extends for more than 1,600 km (994 mi.), 

marked by series of magnetic gradients that trend NE. Seismic activity is 

correlated to location of lineament, with an active area to SE and an inactive 

area along NW side of lineament. 

Long and Kaufmann 

(1994)

The Velocity Structure and 

Seismotectonics of Southeastern 

Tennessee

Evaluates relationship of midcrustal structures and seismicity from a velocity 

model derived from inversion of travel-time residuals and gravity data. The 

authors observed that spatial patterns of historical seismicity correlate with low 

velocity regions at midcrustal depths, which suggests that intraplate 

earthquakes occur in weakened crust. Velocity data does not support NY-AL 

lineament as a linear feature parallel to a deep sedimentary basin. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-189 

Citation Title Description and Relevance to SSC

Powell et al. (1994) A Seismotectonic Model for the 300-

Kilometer-Long Eastern Tennessee 

Seismic Zone

Describes characteristics of seismicity in ETSZ, including the association of 

earthquakes with major potential field anomalies; greatest density of epicenters 

is near NY-AL magnetic lineament. The authors propose that ETSZ is evolving, 

with earthquakes coalescing into NE-trending zone near juncture between 

relatively weak and strong basement crustal blocks. The authors suggest that 

deformation in ETSZ may evolve eventually into a longer through-going strikeslip fault.

Powell (2002) Three-Dimensional Velocity Structure 

in the New Madrid and Other SCR 

Seismic Zones

Velocity images obtained for SCR areas reveal strong velocity contrasts that 

appear to control distribution of seismicity. Earthquakes tend to concentrate 

where strain energy is concentrated, which is in areas of low velocity or along 

edges of high-velocity zones. A prominent low-velocity zone was detected in

ETSZ; most earthquakes occur in rocks that surround the lowest-velocity 

regions of this zone. 

Tavernier and 

Williams (2002) 

The Basement Faults in the East 

Tennessee Seismic Zone: 

Observations from the Swan Creek 

Gas Field 

Seismic-reflection and well data from Swan Creek gas field in eastern

Tennessee have been used to study basement structure and its relationship to 

NY-AL lineament in ETSZ. A system of normal faults is apparent in 

Precambrian basement NW of the field; the faults are locally coincident with 

NY-AL lineament. A left-lateral strike-slip fault is also recognized in Paleozoic 

basement rock. The two directions of basement faults are consistent with those 

of faults interpreted in ETSZ from earthquake focal mechanisms. 

Teague et al. (1986) Focal Mechanism Analyses for 

Eastern Tennessee Earthquakes 

(1981-1983)

The authors determined 10 single-event and 6 composite focal mechanisms 

from 37 events in eastern Tennessee occurring between September 1981 and 

July 1983. Focal mechanisms are predominantly strike-slip along nearly 

vertical N-S- (right-lateral) or E-W- (left-lateral) oriented nodal planes,

consistent with compressionally reactivated Iapetan normal faults. The P axes 

systematically converge from N40°E to N50°E with depth. Distribution of 

P axes from this data set restricts the maximum compressive stress (σ1) 

between N30°E and N76°E with plunge angles from 15° to –40°. Result is 

similar to that determined for GCVSZ and is consistent with values derived for 

the Midcontinent.

USGS (2003) Poster of the Fort Payne, Alabama 

Earthquake of 29 April 2003—

Magnitude 4.6

Provides information on April 29, 2003, Fort Payne earthquake of M 4.6 and 

summarizes seismic hazard in SE United States. 
Table D-7.3.4 Data Summary 

Paleozoic Extended Crust Zone 

D-190 

Citation Title Description and Relevance to SSC

Vlahovic et al. (1996) P and S Wave Velocity Structure and 

Hypocenter Locations in the Eastern 

Tennessee Seismic Zone

The authors developed 3-D crustal velocity model from inversion of arrival time 

data and observed that higher velocities are associated with more seismogenic 

crust SE of NY-AL lineament, whereas lower-velocity anomalies are NW of 

lineament. Relocation of events with this model places most seismicity in a 30 

km (19 mi.) wide block between 4 and 22 km (2.5 and 14 mi.) along entire 

length of seismic zone (300 km, or 186 mi.).

Vlahovic et al. (1998) Joint Velocity Hypocenter-Velocity 

Inversion for the Eastern Tennessee 

Seismic Zone

Describes velocity structure model used to update focal mechanisms and 

hypocenters for earthquakes in ETSZ. Relocated hypocenters define a 

seismogenic volume consistent with a tectonic model of faulting along NY-AL 

lineament, which is characterized by sharp contrasts in strength of adjoining 

crustal blocks. Earthquakes tend to concentrate along steepest velocity 

gradients, suggesting they occur on ancient faults separating rocks of different 

compositions.

Wheeler (2005) Known or Suggested Quaternary 

Tectonic Faulting, Central and 

Eastern United States—New and 

Updated Assessments for 2005

Summarizes characteristics of ETSZ. Small to moderate earthquakes in zone 

demonstrate active subsurface faulting; however, zone has had no historical 

earthquakes of M 5 or larger, and there is no surficial geologic evidence for

occurrence of large earthquakes. Accordingly, ETSZ is assigned to Class C for 

lack of geologic evidence of large earthquakes.

Paleoseismic Investigations

Whisner et al. (2003) Disturbed Sediments in the East 

Tennessee Seismic Zone: Evidence 

of Large Prehistoric Earthquakes in 

East Tennessee? 

Summarizes detailed geologic studies in ETSZ focused on trying to locate 

paleoseismic features. Geologic mapping in a 300 km2(186 mi.2) area within 

most active part of ETSZ did not reveal concrete evidence of large prehistoric 

earthquakes. Information was provided from two localities in Tennessee where 

anomalously deformed sediments occur. The two localities include folded and 

faulted pebble layers at Tellico Plains site and clastic dikes in a small fault at 

Gray site (outside recognized ETSZ). Deformed sediments could indicate late 

Pleistocene or early Holocene earthquake activity. 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-191 

Citation Title Description and Relevance to SSC

General for Region

Austin et al. (1990) Crustal Structure of the Southeast Georgia 

Embayment-Carolina Trough: Preliminary 

Results of a Composite Seismic Image of a 

Continental Suture(?) and a Volcanic 

Passive Margin

The authors use multichannel seismic-reflection data to image the Carolina 

platform and conclude that observed magnetic anomaly in this region is the 

product of Mesozoic rifting processes, not Paleozoic collision.

Bird et al. (2005) Gulf of Mexico Tectonic History: Hotspot 

Tracks, Crustal Boundaries, and Early Salt 

Distribution

The authors interpret deep basement structural highs in Gulf of Mexico as 

hotspot tracks. In this interpretation, the basin began to form as the Yucatan 

experienced continental crustal extension and 22° of counterclockwise 

rotation (160–150 Ma). This was followed by a further 20° of counterclockwise

rotation and seafloor spreading in the gulf.

Cook (1984) Geophysical Anomalies Along Strike of the 

Southern Appalachian Piedmont

Documents trends in both Bouguer gravity and magnetic anomalies 

associated with the Appalachians in Georgia and Virginia. 

Crough (1981) Mesozoic Hotspot Epeirogeny in Eastern 

North America

Attributes a 600 km (373 mi.) wide zone of epeirogeny in SE Canada and 

New England during the Cretaceous and early Tertiary to the Great Meteor 

hotspot, as evidenced by apatite fission-track dating. 

Daniels et al. 

(1983)

Distribution of Subsurface Lower Mesozoic 

Rocks in the Southeastern United States, 

as Interpreted from Regional Aeromagnetic 

and Gravity Maps

Concludes that Brunswick magnetic anomaly must be older than the 

Mesozoic features that it can be traced over, and is therefore not sourced by 

South Georgia rift.

The authors performed a paleostress analysis of the New England–Quebec 

igneous province, which provides an alternative interpretation for the 

distribution of Cretaceous plutons. Dikes display ESE-WNW and ENE-WSW 

trends and are spatially distributed in three E-W-striking dike swarms 75 by 

300 km (47 by 186 mi.) in area. Leucocratic dikes occur closer to plutons and 

disappear within 3–4 km (2–2.5 mi.), likely recording local stress effects due 

to pluton emplacement. Lamprophyre dikes occur independently of plutons 

and strike parallel to regional dike swarms, recording regional far-field 

stresses. Normal faults in the regions display two orientations:

1. E-W-striking normal faults found predominantly in Montreal area are 

parallel to graben boundaries and axis of the Monteregian Hills, with 

vertical offsets ranging between 100 and 430 m (328 and 1,411 ft.).

2. NW-SE to WNW-ESE-striking normal faults are oblique to graben 

boundaries, with less than 100 m (328 ft.) of vertical offset.
Table D-7.3.7 Data Summary 

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D-192 

Citation Title Description and Relevance to SSC

NW-SE to WNW-ESE faults are older than E-W-striking faults but exhibit 

crosscutting relationships, suggesting that some were reactivated during 

formation of the E-W-striking faults. Some E-W-striking brittle faults and joints 

are observed in several Cretaceous plutons with similar orientations to dikes 

that are locally crosscut by these normal faults, suggesting that dike 

emplacement and faulting are contemporaneous. Conjugate sets of NE-WS 

dextral and ESE-WNW sinistral strike-slip faults and WNW-SSW reverse 

faults provide evidence for a compressional stress regime postdating 

emplacement of the Cretaceous plutons. 

Faure et al. (1996) State of Intraplate Stress and Tectonism of 

Northeastern America Since Cretaceous 

Times, with Particular Emphasis on the 

New England–Quebec Igneous Province

Faure et al. (1996) attribute intraplate stress and tectonism in NE America to 

an initial NE-SW extension event associated with rifting between Labrador 

and Greenland at 140 Ma, opening of South Atlantic at 130 Ma, and related 

reactivation of Timiskaming graben. Subsequent N-S-oriented extension 

associated with emplacement of the Monteregian Hills corresponds to global 

fragmentation of Pangaea when Iberia separated from Newfoundland when 

dominant tensional stress propagated along Labrador rift. The stress regime 

shifted to ENE-ESE-directed compressional stress in early Tertiary when the 

oceanic spreading rate decreased because of an increasing number of 

convergent boundaries in the Pacific. Faure et al. (1996) conclude that 

emplacement of Cretaceous intrusions is consistent with a lithospheric 

fracture model as opposed to a hotspot model, emphasizing role of 

preexisting structure in Ottawa-Bonnechere graben.

Faure et al. (2006) Paleostress Analysis of Atlantic Crustal 

Extension in the Quebec Appalachians

Identifies two phases of extension: (1) an initial Late Triassic E-W extension 

related to formation of rift basins in Bay of Fundy and southern Georgia, and 

(2) Early Jurassic ESE-WNW extension related to central Atlantic rift system.

Funck et al. (2004) Crustal Structure of the Northern Nova 

Scotia Rifted Continental Margin (Eastern 

Canada)

The authors used seismic refraction to image along-strike variation in crustal 

structure where Atlantic margin transitions from volcanic to nonvolcanic rifting 

(Nova Scotia). They find that continental crust thins from 36 to 3 km (22 to 2 

mi.) over a distance of 180 km (112 mi.). Further seaward, they find a 150 km 

(93 mi.) long section of serpentinized mantle overlain by a 3 km (2 mi.) thick 

section of continental crust. Beyond this transition zone, they find oceanic 

crust with average thickness of 4 km (2.5 mi.). These data support idea that 

Atlantic margin becomes progressively more nonvolcanic to the NE, and 

place the continent-ocean boundary 60 km (37 mi.) farther SE than did Keen 

and Potter (1995b). 
Table D-7.3.7 Data Summary 

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D-193 

Citation Title Description and Relevance to SSC

Hatcher et al. 

(1994)

E-5 Cumberland Plateau to Blake Plateau, 

Centennial Continent/Ocean Transect #18

Geologic cross section is based on surface geology, drillholes, shipboard and 

aeromagnetic anomaly data, and gravity and seismic-reflection data.

Hatcher et al. 

(2007)

Tectonic Map of the Southern and Central 

Appalachians: A Tale of Three Orogens 

and a Complete Wilson Cycle

Provides comprehensive review of formation and geologic history of 

Appalachian orogen.

Hibbard et al. 

(2004)

The Appalachian Orogen Reviews structural geology, tectonics, and history of Appalachian orogen. 

Hibbard et al. 

(2006)

Lithotectonic Map of the Appalachian 

Orogen, Canada–United States of America

Lithotectonic mapping at 1:1,500,000 scale of the Appalachians in the U.S.

and Canada, including faults and shear zones. Mapped area includes western 

portion of ECC, namely Piedmont. 

Hibbard et al. 

(2007)

A Comparative Analysis of Pre-Silurian 

Crustal Building Blocks of the Northern and 

the Southern Appalachian Orogen

The authors investigate each phase of orogeny in Appalachians and 

determine that pre-Silurian Appalachians were uniform from north to south. 

Heterogeneities must postdate Late Ordovician events.

Holbrook, Purdy, et 

al. (1994)

Seismic Structure of the U.S. Mid-Atlantic 

Continental Margin

Uses multichannel and wide-angle seismic data to investigate the nature of 

continent-ocean boundary of the Atlantic margin (Virginia). The authors find 

that continent-ocean boundary is not sharp, but is instead a 100 km (62 mi.) 

wide transition zone characterized by rift-related mafic igneous material, up to 

25 km (15.5 mi.) thick. Location of these igneous rocks also coincides with 

East Coast magnetic anomaly (ECMA), and the authors therefore conclude 

the ECMA does not mark an Appalachian suture zone, but rather is sourced 

by igneous rocks emplaced during rifting. Supports the idea that Atlantic 

margin is strongly volcanic and not consistent with plume models.

Holbrook, Reiter, et 

al. (1994)

Deep Structure of the U.S. Atlantic 

Continental Margin, Offshore South 

Carolina, from Coincident Ocean Bottom 

and Multichannel Seismic Data

Combined seismic-reflection study and wide-angle ocean-bottom seismic 

profile of Carolina Trough. Finds rifted continental crust for the first 80 km (50 

mi.) along transect, characterized by 1–4 km (0.6–2.5 mi.) of post-rift 

sediment overlying 30–34 km (19–21 mi.) thick crust. Further seaward, 

transitional crust is a 70–80 km (43–50 mi.) wide zone containing up to 12 km 

(7.5 mi.) of post-rift sediment overlying 10–24 km (6–15 mi.) thick crust. 

Beyond this, 8 km (5 mi.) thick oceanic crust is overlain by 8 km (5 mi.) of 

sediments. Transitional crust, which is the product of rifting-induced 

magmatism, produces the Brunswick and East Coast magnetic anomalies. 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-194 

Citation Title Description and Relevance to SSC

Hutchinson et al. 

(1983)

Crustal Structure Beneath the Southern 

Appalachians: Nonuniqueness of Gravity 

Modeling

The authors modeled Appalachian gravity gradient and favor the 

interpretation that it marks a suture zone.

Johnston (1994) Seismotectonic Interpretations and 

Conclusions from the Stable Continental 

Region Seismicity Database

Defines nine major and several minor stable continental regions (SCRs), 

finding that annual seismic moment released in rifted SCRs exceeds that in 

nonrifted SCR by a factor of 15.

Kanter (1994) Tectonic Interpretation of Stable 

Continental Crust

Subdivides stable continental regions in North America (and world) into 

tectonic domains based on geologic and geophysical characteristics, such as 

age and whether domain is extended or non-extended. The characterization 

of the ECC-AM seismotectonic zone is influenced by Eastern Seaboard 

domain (#218) of extended Paleozoic continental crust. 

Karner and Watts 

(1983)

Gravity Anomalies and Flexure of the 

Lithosphere at Mountain Ranges

Documents phenomenon of gravity gradients along Himalayas, Alps, and 

Appalachians and concludes that this gradient generally marks subsurface 

loads, which for Appalachians is attributed to foreland basin development.

Keen and Potter 

(1995a)

The Transition from a Volcanic to a 

Nonvolcanic Rifted Margin off Eastern 

Canada

The authors use seismic-reflection data SE of Nova Scotia to show presence 

of seaward-dipping reflectors (SDRs), also commonly found farther south 

along Atlantic margin. They interpret the SDRs to be derived by igneous and 

sedimentary material accreted into a widening, subsiding rift zone. Presence 

of both SDRs and strong East Coast magnetic anomaly (ECMA), combined 

with the disappearance of both these features farther north, suggests that

ECMA is created by igneous rocks forming the SDRs. The relative abruptness 

with which both features disappear to north also argues for small-scale 

convection to be the volcanic source along this rift zone. 

Keen and Potter 

(1995b)

Formation and Evolution of the Nova Scotia 

Rifted Margin: Evidence from Deep Seismic 

Reflection Data

The authors use seismic-reflection data to document a 100–200 km (62–124 

mi.) wide zone of thinned continental crust (factor of 3) off coast of Nova 

Scotia, which is much wider than typical width of crustal extension along 

Atlantic margin farther south (~20 km, or 12 mi.). They propose that this may 

be related to the shift from volcanic rifting (to south) to nonvolcanic rifting 

(Nova Scotia). Thinning in this study is accommodated by simple shear in 

crust and pure shear in mantle lithosphere. The authors propose that 

continent-ocean boundary lies just seaward of the limit of synrift sediments, 

adjacent to a 100 km (62 mi.) wide zone of thinned (<9 km, or 6 mi.) 

continental crust that underlies the continental slope/rise.
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-195 

Citation Title Description and Relevance to SSC

Keller and Hatcher 

(1999)

Some Comparisons of the Structure and 

Evolution of the Southern AppalachianOuachita Orogen and Portions of the 

Trans-European Suture Zone Region

Interprets Appalachian gravity gradient as marking a suture zone of the 

Alleghanian orogeny.

Klitgord et al. 

(1988)

U.S. Atlantic Continental Margin; Structural

and Tectonic Framework

Mesozoic rifting resulted in breakup of Pangaea. This rifting is associated with 

separation of the North American and African plates, producing rift basins 

along Atlantic seaboard that are situated landward of hinge zone of 

continental margin. This landward region experienced considerably less 

crustal thinning than did the region seaward of hinge zone that includes the 

deeper marginal sedimentary basins. Basement hinge zone consists of series 

of parallel half graben structures that deepen seaward. At hinge zone, 

basement deepens steeply to east by a series of downdropped fault blocks 

from about 2–4 km (1–2.5 mi.) depth to over 8 km (5 mi.) depth. The 

character of block faulting at hinge zone varies along the margin and may 

reflect influence of older crustal structure on Mesozoic rifting. Half graben 

structures with seaward-dipping border faults are observed at Georges Bank 

hinge zone, whereas faulted blocks with landward-dipping faults form hinge 

zone in Baltimore Canyon trough.

LASE Study Group 

(1986)

Deep Structure of the U.S. East Coast 

Passive Margin from Large Aperture 

Seismic Experiments (LASE)

The authors use large-aperture seismic reflection to image Baltimore Canyon 

trough, revealing a continuous high-velocity deep-crustal layer that extends 

from beneath continental crust to oceanic crust. They interpret this layer as 

having formed either late in continental rifting process or early in seafloor 

spreading process.

Li et al. (2003) Shear Velocity Structure and Azimuthal 

Anisotropy Beneath Eastern North America 

from Rayleigh Wave Inversion

The authors determined the velocity structure and anisotropic variations in 

velocity structure from inversion of Rayleigh waves in order to detect 

asthenospheric flow beneath the thick continental lithosphere beneath NE

United States and SE Canada. Rayleigh wave–phase velocity anomaly with a 

period of 33 sec, corresponding to sensitivity to structure down to 40 km (25 

mi.) in depth, indicates a low-velocity band oriented NE-SW. The North 

American continental keel beneath Grenville Province is imaged in upper 

mantle down to roughly 200 km (124 mi.) in depth. North American keel has 

an irregular shape and a low-velocity zone beneath eastern New York and 

central New England to 200 km (124 mi.), with particularly high amplitudes at 

depths of 60–140 km (37–87 mi.). This velocity anomaly is interpreted as 

lateral contrast between relatively thick lithosphere beneath western New 

York and Pennsylvania and warm asthenosphere beneath thinned New 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-196 

Citation Title Description and Relevance to SSC

England lithosphere caused by thermal erosion associated with the 

Cretaceous hotspot. Additionally, weak anisotropy that is observed from 

shear-wave splitting indicates that the source must be at least 200 km (124 

mi.) deep, suggesting that a sublithospheric shear zone may decouple

motions of the lithosphere and deeper mantle.

Manspeizer et al. 

(1989)

Post-Paleozoic Activity Reviews rifting and igneous activity in the post-Paleozoic period.

McBride and 

Nelson (1988)

Integration of COCORP Deep Reflection 

and Magnetic Anomaly Analysis in the 

Southeastern United States: Implications 

for Origin of the Brunswick and East Coast 

Magnetic Anomalies

The authors suggest three possible sources for Brunswick magnetic anomaly: 

subducted root nappes of the Inner Piedmont, obducted upper mantle, or 

Mesozoic rifting. The authors do not strongly support a particular solution, but 

do suggest that the Brunswick and East Coast magnetic anomalies may have 

a continuous, related source.

McBride et al. 

(2005)

Integrating Seismic Reflection and 

Geological Data and Interpretations Across 

an Internal Basement Massif: The Southern 

Appalachian Pine Mountain Window, USA

The authors trace the master Appalachian decollement from Inner Piedmont 

to Coastal Plain. They find that beneath the Carolina terrane, the decollement 

roots to Moho, indicating the location of Acadian-Alleghanian suture.

McHone (1996) Constraints on the Mantle Plume Model for 

Mesozoic Alkaline Intrusions in 

Northeastern North America

Proposes that one or more deep-mantle plumes do not provide a satisfactory 

mechanism for distribution of Cretaceous alkaline rocks of New England, and 

observes that previous studies oversimplify evidence for a hotspot track 

across New England by ignoring important petrological data, including the 

following:

Jurassic syenite-monzonite-alkali granite of the White Mountain magma 

series (WMMS) has been described as separate province from Cretaceous 

intrusions, although many Early Jurassic dikes and several mafic to felsic 

plutons in the province are petrographically and chemically similar to Early 

Cretaceous intrusions that overlap.

Early Cretaceous dikes and plutons of New England–Quebec igneous 

province have statistically similar paleomagnetic poles between 122 and

124 Ma and show no consistent trend for published ages in any direction 

across region.

Seamount volcanism is not limited to ages defined by linear hotspot track 

nor is it on trendwith New England–Quebec province.

Cretaceous alkaline rocks do not exhibit a consistent chemical signature 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-197 

Citation Title Description and Relevance to SSC

indicative of a mantle source.

These observations indicate that lithospheric processes were necessary to 

start and stop generation of magmas from the same source in mantle, and 

that petrological studies should emphasize local and regional tectonic 

features.

Murphy and 

Keppie (2005)

The Acadian Orogeny in the Northern 

Appalachians

Avalonia and Meguma terranes in Nova Scotia are separated by strike-slip 

system of faults.

Pe-Piper and Piper 

(2004)

The Effects of Strike-Slip Motion Along the 

Cobequid-Chedabucto-SW Grand Banks 

Fault System on the Cretaceous-Tertiary 

Evolution of Atlantic Canada

Proposes that reactivation of Cobequid–Chedabucto–SW Grand Banks fault 

system could explain several features related to Canadian Atlantic margin, 

including rapid subsidence on Scotian margin and deep-water margin off the 

SW Grand Banks.

Pratt et al. (1988) A Geophysical Study of the Earth’s Crust in 

Central Virginia: Implications for 

Appalachian Crustal Structure

Concludes that crustal thinning (at Taconic suture) in the Piedmont is 

responsible for Appalachian gravity gradient.

Shillington et al. 

(2006)

Evidence for Asymmetric Nonvolcanic 

Rifting and Slow Incipient Oceanic 

Accretion from Seismic Reflection Data on 

the Newfoundland Margin

The authors use seismic-reflection data to image Newfoundland nonvolcanic 

margin. They observe a region of extended continental crust (ECC) 

successively bordered by transitional basement and slow-spreading oceanic 

basement. They compare this structure to that of Iberian margin, the wellstudied conjugate to Newfoundland. Two important differences are noted, 

however:

1. The ECC of Newfoundland has few if any normal faults accommodating 

extension.

2. The transitional basement is not exhumed peridotite. The authors infer 

instead that the transition is thinned continental crust denuded by latestage rifting (via rolling-hinge or detachment faulting) and possibly altered 

by magmatic intrusions/oceanic accretion.

Spencer et al. 

(1989)

The Extension of Grenville Basement 

Beneath the Northern Appalachians: 

Results from the Quebec-Maine Seismic 

Reflection and Refraction Surveys

The authors image the contact between Grenville basement and overlying 

allochthonous rocks of the Appalachians.
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-198 

Citation Title Description and Relevance to SSC

Trehu et al. (1989) Structure of the Lower Crust Beneath the 

Carolina Trough, U.S. Atlantic Continental 

Margin

The authors image Carolina trough along three seismic profiles and find a 

lens of high-velocity lower-crustal material spatially correlated with East Coast 

magnetic anomaly. They conclude that this layer was caused during either 

rifting or seafloor spreading.

Van Avendonk et 

al. (2009)

Extension of Continental Crust at the 

Margin of the Eastern Grand Banks, 

Newfoundland

The authors confirm previous reports of rapidly thinning crust beneath 

continental slope of offshore Newfoundland (from about 30 to 6 km, or 19 to 4 

mi., producing a Moho dip of 50°). The thinned continental crust extends 

seaward for 80 km (50 mi.); this is interpreted as the result of strong (possibly 

gabbroic) lower crust that rotated upward during extension, localizing thinning 

to distal margin. The authors also observe high mantle seismic velocities at 

continent-ocean transition, a fairly unique observation that they interpret as 

evidence for nonserpentinized mantle. The lack of seaward-dipping normal 

faults in this region is explained by models that allow for large-scale 

detachment faults to be active during rifting.

Williams (1978) Tectonic Lithofacies Map of the 

Appalachian Orogen

Maps location of both Paleozoic thrusts and later Mesozoic basins along the 

length of Appalachians.

Williams and 

Hatcher (1983)

Appalachian Suspect Terranes Defines major suspect terranes of eastern North America and relates these to 

various orogenies responsible for uplift of Appalachians.

Zoback and 

Zoback (1989)

Tectonic Stress Field of the Continental 

United States

The authors conclude that direction of maximum horizontal compression in 

the eastern U.S. is oriented roughly NE-ENE, consistent with far-field ridgepush motion in the Atlantic.

Mesozoic Extension

Benson (1992) Map of Exposed and Buried Early Mesozoic 

Rift Basins/Synrift Rocks of the U.S. Middle 

Atlantic Continental Margin

Compilation of buried rift basins reveals high degree of parallelism with 

exposed basins and Paleozoic structural grain of Appalachians.

Cumbest et al. 

(1992)

Gravity and Magnetic Modeling of the 

Dunbarton Basin, South Carolina

Presents a model of Dunbarton extensional basin in South Carolina and 

Georgia in which gravity and magnetic anomalies are modeled 

simultaneously.

Hutchinson et al. 

(1986)

Rift Basins of the Long Island Platform The authors map rift basins of Long Island platform using seismic-reflection, 

magnetic, and gravity data. They conclude that basin formation was controlled 

by Paleozoic structural trends.
Table D-7.3.7 Data Summary 

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D-199 

Citation Title Description and Relevance to SSC

Nelson et al. 

(1985)

Profiling in the Southeastern United States.

Part I: Late Paleozoic Suture and Mesozoic 

Rift Basin

COCORP profile in western Georgia is interpreted as imaging the Paleozoic 

suture between North America and Africa.

Oh et al. (1995) Seaward-Dipping Reflectors Offshore the 

Southeastern United States: Seismic 

Evidence for Extensive Volcanism 

Accompanying Sequential Formation of the 

Carolina Trough and Blake Plateau Basin

Presents evidence to suggest that seaward-dipping reflectors represent 

voluminous volcanism beneath Carolina trough and Blake Plateau basin and 

that breakup of NW Africa and North America was time-transgressive from 

north to south during early Middle Jurrassic.

Olsen et al. (1991) Rift Basins of Early Mesozoic Age Presents summary and mapping of Mesozoic extensional basins in eastern 

U.S.

Roden-Tice and 

Tice (2005)

Regional-Scale Mid-Jurassic to Late 

Cretaceous Unroofing from the Adirondack 

Mountains Through Central New England 

Based on Apatite Fission-Track and 

(U-Th)/He Thermochronology

Apatite fission-track ages across Adirondack Mountains, eastern New York, 

Vermont, western Massachusetts and Connecticut, and western New 

Hampshire provide evidence for differential unrooting that may have been 

accommodated by fault reactivation during Late Cretaceous. The authors 

attribute this regional unroofing to a change from extension to horizontal 

compression to the Great Meteor hotspot. 

Roden-Tice and 

Wintsch (2002)

Early Cretaceous Normal Faulting in 

Southern New England: Evidence from 

Apatite and Zircon Fission-Track Ages

Apatite and zircon fission-track age transects across Hartford-Deerfield basin 

in Connecticut and Massachusetts increase to the east, indicating that 

unroofing took place during Late Jurassic through Early Cretaceous. Age of 

graben structure of Hartford Basin is Cretaceous and may not be an early 

Mesozoic ―rift basin.‖

Roden-Tice, West,

et al. (2009)

Presence of a Long-Term Lithospheric 

Thermal Anomaly: Evidence from Apatite 

Fission-Track Analysis in Northern New 

England

Apatite fission-track ages across New Hampshire, NE Vermont, and western 

Maine range from 70 to 140 Ma and reflect widespread Early to Late 

Cretaceous cooling. This regional cooling and unroofing is attributed to 

passage of North America Plate over Great Meteor hotspot, emplacement of 

White Mountain magma series in Early Jurassic, and associated E-W and 

NW-SE extension. Regional uplift on the order of 5–7 km (3–4 mi.) may 

explain lack of rift basins in central New England and Quebec.

Schlische (1993) Anatomy and Evolution of the TriassicJurassic Continental Rift System, Eastern 

North America

Maps and details evolution of Mesozoic basins along Atlantic margin.
Table D-7.3.7 Data Summary 

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D-200 

Citation Title Description and Relevance to SSC

Schlische (2003) Progress in Understanding the Structural 

Geology, Basin Evolution, and Tectonic 

History of the Eastern North America Rift 

System

Presents summary and mapping of Mesozoic extensional basins in eastern 

U.S. 

Schlische and 

Olsen (1990)

Quantitative Filling Model for Continental 

Extensional Basins with Application to the 

Early Mesozoic Rifts of Eastern North 

America

Presents quantitative model for stratigraphic evolution of extensional basins 

with the simplifying assumptions of constant volume input of sediments and

water per unit time, as well as uniform subsidence rate and fixed outlet level. 

The model makes it possible to extract from sedimentary record those events 

in the history of an extensional basin that are due solely to the filling of a 

basin growing in size through time, and those events that are due to changes 

in tectonics, climate, or sediment and water budgets.

Schlische et al. 

(1996)

Geometry and Scaling Relations of a 

Population of Very Small Rift-Related 

Normal Faults

The authors studied geometry and scaling relationships on normal faults

within Solite Quarry of Dan River rift basin. The data indicate that there is no 

significant change in displacement geometry and linear length–displacement 

scaling relation between small and large faults.

Sheridan et al. 

(1993)

Deep Seismic Reflection Data of EDGE 

U.S. Mid-Atlantic Continental-Margin 

Experiment: Implications for Appalachian 

Sutures and Mesozoic Rifting and 

Magmatic Underplating

A seismic-reflection study across Virginia continental margin that outlines a 

Paleozoic suture, buried Appalachian terranes, and Mesozoic rifting and 

magmatic events.

Smoot (1985) The Closed-Basin Hypothesis and Its Use 

in Facies Analysis of the Newark 

Supergroup

A sedimentological analysis of the Newark Supergroup using various basin 

models to decide which basins are open or closed and used to help 

reconstruct facies. 

Swanson (1986) Preexisting Fault Control for Mesozoic 

Basin Formation in Eastern North America

Correlates Mesozoic basin formation with reactivation of specific Paleozoic 

reverse and strike-slip faults along Appalachians.

Talwani and 

Abreau (2000)

Inferences Regarding Initiation of Oceanic 

Crust Formation from the U.S. East Coast 

Margin and Conjugate South Atlantic 

Margins

East Coast magnetic anomaly is associated with seaward-dipping reflectors 

that represent volcanic rocks. These reflectors and underlying intrusive rocks 

are interpreted as constituting earliest crust and upper mantle generated at 

the time of initial opening of Atlantic Ocean.
Table D-7.3.7 Data Summary 

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D-201 

Citation Title Description and Relevance to SSC

Withjack et al. 

(1998)

Diachronous Rifting, Drifting, and Inversion 

on the Passive Margin of Central Eastern 

North America: An Analog for Other 

Passive Margins

Uses new data to analyze and outline timeline of rifting along eastern North 

America (ENA). Features map of early Mesozoic rift basins of ENA. 

Withjack et al. 

(2002)

Rift-Basin Structure and Its Influence on 

Sedimentary Systems

Describes four types of rift basins based on structure and their influence on 

processes within sedimentary systems.

Central Virginia Seismic Zone (CVSZ)

Bollinger (1973) Seismicity and Crustal Uplift in the 

Southeastern United States

Defines and names CVSZ as area of persistent, low-level seismicity in central 

Virginia. 

Bollinger and 

Hopper (1971)

Virginia’s Two Largest Earthquakes—

December 22, 1875 and May 31, 1897

Largest earthquake in CVSZ occurred near center of zone on December 22, 

1875, with mb 5.0 and MMI VII. 

Bollinger and Sibol 

(1985)

Seismicity, Seismic Reflection Studies, 

Gravity, and Geology of the Central Virginia 

Seismic Zone: Part I. Seismicity

Defines CVSZ as area of persistent, low-level seismicity that extends about 

120 km (75 mi.) in N-S direction and about 150 km (93 mi.) in an E-W 

direction from Richmond to Lynchburg, Virginia. The largest historical 

earthquake in CVSZ is the December 22, 1875, mb 5.0 (MMI VII) Goochland 

County event. Roughly three-quarters of the observed seismicity is located in 

upper 11 km (7 mi.) of crust. 

Coruh et al. (1988) Seismogenic Structures in the Central 

Virginia Seismic Zone

Interprets structures from I-64 seismic-reflection line. Suggests that seismicity 

in central and western parts of zone may be associated with west-dipping 

reflectors that form roof of a detached antiform; seismicity in eastern part of 

zone near Richmond may be related to near-vertical diabase dike swarm of 

Mesozoic age. 

de Witt and Bayer 

(1986)

Seismicity, Seismic Reflection, Gravity, and 

Geology of the Central Virginia Seismic 

Zone: Part 3. Gravity

Provides clarification of figures in Keller et al. (1985).

Glover et al. (1995) Tectonics of the Central Appalachian 

Orogen in the Vicinity of Corridor E-3; With 

Implications for Tectonics of the Southern 

Appalachians

Provides maps, cross sections, and discussion of major structures in vicinity 

of CVSZ and beyond. The authors thoroughly review paleogeography and 

associated pre-Mesozoic tectonics of central Appalachians; however, they 

provide little discussion of post-Paleozoic paleogeography or tectonics.
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

Keller et al. (1985) Seismicity, Seismic Reflection, Gravity, and 

Geology of the Central Virginia Seismic 

Zone: Part 3. Gravity

The authors use a variety of techniques to model position of thrust fault 

separating Greenville basement from overlying units in Virginia.

Kim and Chapman 

(2005)

The 9 December 2003 Central Virginia 

Earthquake Sequence: A Compound 

Earthquake in the Central Virginia Seismic 

Zone

Describes December 9, 2003, earthquake as Mw 4.3 (≈ mb 4.5) and Max MMI 

= VI, largest event recorded by seismograph in CVSZ. Predominantly thrust 

faulting with depth 10 ± 2 km (6 ± 1 mi.). Compound earthquake comprising 

two nearly identical events separated by 12 sec and 300 m (984 ft.) along an 

azimuth of ~195°). Focal mechanisms from December 9, 2003, event and 11 

other events in CSVZ inverted to obtain local stress tensor: maximum 

principal stress trends 133° and plunges 14°; least principal stress trends 25°

and plunges 52°. Indicates a broad-scale thrust-faulting stress regime in 

CSVZ. Maximum principal stress direction is rotated 68° clockwise relative to 

the average orientation of 65° for ENA. 

Klose and Seeber 

(2007)

Shallow Seismicity in Stable Continental 

Regions

The authors investigate seismicity of stable continental regions (SCRs) and 

determine that while it has a bimodal depth distribution, ~80% of SCR 

earthquakes are shallow (<7 km, or 4 mi.).

Marple and 

Talwani (2000)

Evidence for a Buried Fault System in the 

Coastal Plain of the Carolinas and 

Virginia—Implications for Neotectonics in 

the Southeastern United States

Proposes the East Coast fault system (ECFS) in Coastal Plain of Carolinas 

and Virginia. ECFS comprises three segments: southern, central, and 

northern. Northern segment located in vicinity of CVSZ. The authors provide 

data suggesting existence is strongest for southern segment, weakens 

northward. 

Marple and 

Talwani (2004)

Proposed Shenandoah Fault and East 

Coast-Stafford Fault System and Their 

Implications for Eastern U.S. Tectonics

Proposes that Shenandoah fault is a deep, NW-striking ~300 km (186 mi.) 

long basement fault that accommodates an apparent ~110 km (68 mi.) offset 

between the NE-striking Stafford and East Coast fault systems (restraining 

bend). Fault was formed by late Alleghanian indentation in Salisbury 

embayment by NW Africa. CVSZ seismicity may be related to compression at 

restraining bend. 

Munsey and 

Bollinger (1985)

Focal Mechanism Analyses for Virginia 

Earthquakes (1978-1984)

Focal mechanisms from single earthquakes located in CVSZ show no 

consistent orientation and show both reverse and strike-slip faulting. 

Hypocentral locations are scattered geographically and no surface ruptures 

are known, so no systematic sense of movement is indicated for CVSZ. 
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

Obermeier and 

McNulty (1998)

Paleoliquefaction Evidence for Seismic 

Quiescence in Central Virginia During Late 

and Middle Holocene Time

Survey of 300 km (186 mi.) of river banks for liquefaction and 

paleoliquefaction features along portions of Rapidan, Mataponi, North Anna 

(during high-water conditions with poor exposures), South Anna, Appomattox, 

and James rivers, including Rivanna, Hardware, Rockfish, Slate, and Willis 

tributaries. Moderately susceptible deposits of 2–3 ka are common; only three 

small prehistoric liquefaction features are identified.

―Near total lack of widespread liquefaction features in large search area 

strongly suggests that very strong seismic shaking cannot have occurred 

often in 2–3 ka and for past 5 ka west and north of Richmond...Paucity of 

liquefaction features in central Virginia makes it seem unlikely that any 

earthquakes in excess of ~M 7 have struck there...even if M 6–7 earthquakes 

had been relatively abundant, then many more liquefaction effects would have 

been expected.‖

Seeber and 

Armbruster (1988)

Seismicity Along the Atlantic Seaboard of 

the U.S.: Intraplate Neotectonics and 

Earthquake Hazard

The authors investigate intraplate seismicity in the eastern U.S. and compare 

it to other intraplate regions, as well as to the western U.S. They determine 

that the Appalachian front spatially controls seismicity on a large scale and 

may be boundary of a stress province for the eastern U.S.

Weems and 

Edwards (2007)

Post-Middle Miocene Origin of Modern 

Landforms in the Eastern Piedmont of 

Virginia

Recognizes intermittent Cenozoic fault motion in the NE-striking Stafford fault 

system and north-striking Dutch Gap fault. Indicates a fault-bounded trough 

filled with Coastal Plain marine sediments of late Middle Miocene age.

Recent Source Characterizations of CVSZ

Bollinger (1992) Specification of Source Zones, Recurrence 

Rates, Focal Depths, and Maximum 

Magnitudes for Earthquakes Affecting the 

Savannah River Site in South Carolina

Estimates the following parameter values for areal source zone representing 

CVSZ: a = 1.18, b = 0.64, Mmax = mb 6.4.

Chapman and 

Krimgold (1994)

Seismic Hazard Assessment for Virginia Estimates the following parameter values for areal source zone representing 

CVSZ: a = 1.18, b = 0.64, Mmax = mb 7.25.

Frankel et al. 

(1996)

National Seismic-Hazard Maps: 

Documentation

Does not designate a finite source or zone for CVSZ; modeled using a 

gridded seismicity cell network within extended margin region: Mmax = 

Mw 7.5. No source- or zone-specific b-value. Background b-value for extended 

margin region = 0.96.
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Citation Title Description and Relevance to SSC

Frankel et al. 

(2002)

Documentation for the 2002 Update of the 

National Seismic Hazard Maps

Does not designate a finite source or zone for CVSZ; modeled using a 

gridded seismicity cell network within extended margin region: Mmax = Mw

7.50. Assumes same b-value as Frankel et al. (1996), i.e., 0.96.

Petersen et al. 

(2008)

Documentation for the 2008 Update of the 

United States National Seismic Hazard 

Maps

Does not designate a finite source or zone for CVSZ; modeled using a 

gridded seismicity cell network within extended margin region: Mmax = Mw

7.50. Assumes same b-value as Frankel et al. (1996), i.e., 0.96.

Seismicity

Ammon et al.

(1998)

Faulting Parameters of the January 16, 

1994 Wyomissing Hills, Pennsylvania 

Earthquakes

The January 1994 Wyomissing Hills, Pennsylvania, earthquake sequence 

was dominated by M 4.0 foreshock and M 4.6 main shock. The sequence was 

well recorded by U.S. and Canadian national seismic networks, which 

provided data for waveform modeling. Both events exhibit thrust-fault 

geometry with a nearly horizontal compression axis oriented NE-SW, 

consistent with regional stress patterns. A preferred depth of 3–5 km (2–3 mi.) 

is estimated for these two events, which are located in the region of historical 

seismicity termed the Lancaster seismic zone by Armbruster and Seeber 

(1987).

Armbruster et al. 

(1994)

The Jan. 1994 Wyomissing Hills 

Earthquakes (mbLg = 4.0 & 4.6) in 

Southeastern Pennsylvania: A 2-km-Long 

Northwest-Striking Fault Illuminated by 

Aftershocks

Abstract describes locations and magnitudes of the instrumentally observed 

January 1994 Wyomissing Hills earthquakes in SE Pennsylvania. 

Bakun et al. (2003) Estimating Locations and Magnitudes of 

Earthquakes in Eastern North America from 

Modified Mercalli Intensities

The authors create modified Mercalli intensity model for eastern North 

America, and use that model to determine the epicenter and magnitude of 

several historical earthquakes, including 1755 Cape Ann, Massachusetts, 

earthquake. 

Bent (1995) A Complex Double-Couple Source 

Mechanism for the MS 7.2 1929 Grand 

Banks Earthquake

Analysis of additional seismographs indicates that MS 7.2 1929 Grand Banks 

earthquake is in fact an earthquake with a complex source mechanism as 

opposed to a landslide. The first and largest sub-event was a strike-slip 

double-couple event occurring on a NW-striking plane. Two later sub-events 

were probably strike-slip double couples on NE-striking planes. All appear to 

have occurred at a depth of 20 km (12 mi.). The sum of sub-event moments 

corresponds to Mw of 7.2 ± 0.3. 
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

Bollinger et al. 

(1991)

Seismicity of the Southeastern United 

States: 1698 to 1986

Seismicity within ECC is not randomly distributed, but tends to be clustered 

with intervening areas exhibiting low seismicity. Hypocenters of events in 

Coastal Plain regions are distributed throughout upper crust (~13 km, or 8 mi., 

deep), and focal-mechanism solutions indicate N-NE maximum compressive 

stress. 

The authors review the seismicity of SE United States as documented by the 

studies to date of historical and network databases. The reasons for that 

division are the differences in levels of completeness and accuracy with 

respect to earthquake size and location. A regional summary synthesizes 

historical, instrumental, and network seismicity results with respect to the 

regional host geologic/physiographic provinces. The authors note that the

feature of Coastal Plain seismicity is the apparent NW trend, perpendicular to 

northeasterly tectonic fabric of adjoining Piedmont and Appalachian 

Highlands and their associated seismicity. Although various interpretations 

have been put forth, the faults associated with Coastal Plain earthquakes 

have not been unambiguously identified. In Georgia and Alabama, the 

Coastal Plain earthquakes are spatially and temporally sparse. The 

earthquakes of Georgia Piedmont have been interpreted to represent failure 

on planes of weakness or joints within 4 km (2.5 mi.) of surface.

The largest earthquake in the SE United States during historical times 

occurred in this province in 1886 (mb 6.7, MS = 7.7, MMI = X). Epicenter was 

probably about 20–30 km (12–19 mi.) NW of Charleston in Middleton Place–

Summerville seismic zone (see Charleston Table). The hypocenters of 

Coastal Plain shocks are distributed throughout upper 13 km (8 mi.) of crust 

where focal mechanisms indicate N-NE maximum compressive stress.

Bollinger and 

Wheeler (1988)

The Giles County, Virginia, Seismic Zone—

Seismological Results and Geological 

Interpretations

The authors define Giles County seismic zone from a three-year study of 

microseismicity and interpret results in the context of the greater tectonic 

forces that formed Appalachians.
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Citation Title Description and Relevance to SSC

Dawers and 

Seeber (1991)

Intraplate Faults Revealed in Crystalline 

Bedrock in the 1983 Goodnow and 1985 

Ardsley Epicentral Areas, New York

Presents argument that bedrock geologic studies in epicentral areas of 1983 

Goodnow (Mw = 5.1) and 1985 Ardsley (mL = 4.0) earthquakes in New York 

State suggest that seismogenic intraplate faults have subtle, but recognizable, 

expressions in crystalline bedrock along surface extrapolations of these welldefined earthquake ruptures. The 1983 Goodnow and 1985 Ardsley ruptures

are correlated with Caitlin Lake fault zone (CLFZ) and Dobbs Ferry fault zone 

(DFFZ), respectively. The authors base these correlations on (1) spatial 

correlation of rupture plane, as defined by aftershock hypocenters, with a 

prominent fracture-controlled topographic lineament, and (2) observations of 

mesoscopic brittle structures along the lineaments that reflect larger-scale 

structures and, more importantly, that are consistent with both rupture 

orientation and sense of slip determined from seismic data.

The authors point out that there is considerable uncertainty as to age of 

formation of both CLFZ and DFFZ, and some fault surfaces along DFFZ 

record evidence of reactivation in the form of superimposed slickensides. It is 

difficult to argue that the fault zones formed entirely in intraplate environment, 

instead; some of deformation could be Mesozoic in age. The authors 

speculate that the fault zones were activated as extensional structures during 

the Mesozoic and, being weaker than surrounding rock, remained active in 

the present intraplate regime. The authors state that the issue of small 

displacements on active structures that are relatively large and possibly old 

remains problematic. 

Ebel (2000) A Reanalysis of the 1727 Earthquake at 

Newbury, Massachusetts

Uses analysis of felt reports, aftershocks, and recent instrumental seismicity 

near Amesbury, Massachusetts, to infer main-shock source parameters for 

the 1727 Newburyport, Massachusetts, earthquake. Data suggest that 1727 

earthquake was shallow, located NW of Newbury, Massachusetts, and had 

mb about 5.6. 

Ebel and Hart

(2001)

Observational Evidence for Amplification of 

Earthquake Ground Motions in Boston and 

Vicinity

Uses analysis of felt reports, aftershocks, and recent instrumental seismicity 

near Amesbury, Massachusetts, to infer main-shock source parameters for 

the 1727 Newburyport, Massachusetts, earthquake. Data suggest that 1727 

earthquake was shallow, located NW of Newbury, Massachusetts, and had 

mb about 5.6.

Ebel (2006a) The Cape Ann, Massachusetts Earthquake 

of 1755: A 250th Anniversary Perspective

The earthquake of November 18, 1755, is likely located about 40 km (25 mi.) 

ENE of Cape Ann, Massachusetts. Based on attenuation of MMI with 

epicentral distance, the magnitude was estimated as mbLg 6.2 or M 5.9. 
Table D-7.3.7 Data Summary 

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D-207 

Citation Title Description and Relevance to SSC

Hough and Seeber 

(1991)

Seismological Constraints on Source 

Properties of the mb = 4.0, 1985 Ardsley, 

New York, Earthquake: A Characteristic 

Rupture?

Analyzes October 19, 1985, magnitude 4.0 earthquake that occurred in 

southern Westchester County, New York, approximately 30 km (19 mi.) north 

of central Manhattan. The earthquake was part of sequence of six events (mb

1.8 to 4.0) that occurred along NW-trending Dobbs Ferry fault zone that cuts 

across Manhattan Prong. Hypocenters fall within 1 km (0.6 mi.) of each other, 

indicating rupture on a relatively small segment of Dobbs Ferry fault, which is 

at least 10 km (6 mi.) long. Aftershocks delineate a subvertical plane striking 

roughly 300° and define a rupture area roughly 700 m (2,300 ft.) across and

between 4.5 and 5.5 km (3–3.5 mi.) deep. First-motion data indicate that leftlateral strike-slip motion predominates. The 500–1,000 m (1,640–3,281 ft.) 

wide rupture inferred from the hypocenter distribution corresponds to 1 km 

(0.6 mi.) long structurally defined segment of Dobbs Ferry fault zone.

Kafka et al. (1985) Earthquake Activity in the Greater New 

York City Area: Magnitudes, Seismicity, 

and Geologic Structures

Describes locations and magnitudes of instrumentally observed seismicity in 

greater New York City area. Roughly half the earthquakes are located near 

Ramapo fault system, and many other earthquakes located near Newark 

basin. Despite these spatial associations, the cause of earthquakes in this 

area remains unknown.

Klose and Seeber 

(2007)

Shallow Seismicity in Stable Continental 

Regions

Presents a worldwide compilation of well-constrained fault ruptures and focal 

depths of earthquakes for stable continental regions (SCRs). Depth 

distributions of fault ruptures and earthquakes in well-monitored SCRs 

worldwide indicate the following features:

Many earthquakes and fault ruptures are bimodally distributed with depth 

modes in upper third of crust (<10 km, or 6 mi.) and lower third of crust 

(>20 km, or 12 mi.).

Depth and strength of contrasting modes vary regionally and indicate less 

stable intracrustal boundaries that may be located by seismic profiling.

Many medium-to-large earthquakes (4.5 < M < 8.0) tend to nucleate at 

very shallow depths (<7 km, or 4 mi.) and ruptures often reach surface.

Almost 80% of seismic moment density for shallow ruptures is released in 

uppermost 7 km (4 mi.) of crust.

Hypocentral depths of earthquakes are on average overestimated by 88%

± 30% (standard mean ± standard mean error).
Table D-7.3.7 Data Summary 

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D-208 

Citation Title Description and Relevance to SSC

Seborowski et al. 

(1982)

Tectonic Implications of Recent 

Earthquakes near Annsville, New York

The authors analyze a sequence of microearthquakes that occurred in 

January 1980 near Annsville, New York. The events yielded a composite focal 

mechanism solution indicating E-NE compression, resulting in thrust motion 

on N-NW-striking fault plane, with main shock having strike of N34°W and dip 

of 26°NE. A major structural feature of epicentral area is Annsville fault, a fault 

of Paleozoic age that strikes to NE and dips SE. The authors indicate that

epicentral alignments and focal mechanism solutions for earthquakes near 

Annsville do not permit interpretation that movement occurred on this or other 

subparallel structures. Instead, the fault structure inferred to be associated 

with these earthquakes is transverse to Annsville fault. The active structure 

has no apparent surface expression and is possibly limited in spatial extent. 

Focal mechanisms reported for Annsville events suggest that major geologic 

structures may not be involved directly in current seismic activity of region. 

But the authors note that the structures may serve as zones of weakness that 

focus strain along less significant or less apparent structures within crust.

Seeber and 

Armbruster (1988)

Seismicity Along the Atlantic Seaboard of

the U.S.: Intraplate Neotectonics and 

Earthquake Hazard

The authors discuss the potential for damaging earthquakes along Atlantic 

Seaboard and observe the following:

Seismicity along Atlantic Seaboard moderately high for an intraplate region 

and includes large, damaging earthquakes. These tend to be distributed 

among many faults with small ruptures about 1–2 km (0.6–1.2 mi.) across 

for ~M 5 earthquakes and may be characterized by high stress drops.

Damaging earthquakes in east can be generated by small faults that do not 

reach surface and that may not be detected by geological and geophysical 

investigations.

The Appalachian Front, defined as NW limit of allochthonous crystalline 

slab above the master detachment, appears to control spatial distribution 

of seismicity on a large scale. Further, stress indicators are ambiguous 

about a distinct stress province along Appalachians/Atlantic Seaboard. 

At an intermediate scale, seismicity is also often controlled by preexisting 

structure. Newark basin is an example in that it is aseismic but is bounded 

by concentrations of seismicity. 

The apparent lack of one-to-one correlation between seismicity and 

preexisting structural features may be the result of changes in patterns of 

seismicity that occur over periods longer than the available historical 

record. 
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

Seeber and 

Armbruster (1989)

Low-Displacement Seismogenic Faults and 

Nonstationary Seismicity in the Eastern 

United States

Historical seismicity record shows that distribution of seismicity is nonrandom 

and that generally the pattern of seismicity derived from short-term 

instrumental data resembles that derived from long-term samples of historical

data. The authors note that earthquake data associated with 1886 Charleston, 

South Caroline, earthquake suggests that hazard analysis based on 

assumption of stationarity may be appropriate for small- and intermediatemagnitude events, but may be misleading for large events.

Seeber and 

Dawers (1989)

Characterization of an Intraplate 

Seismogenic Fault in the Manhattan Prong, 

Westchester Co., N.Y.

The authors argue that there is close correlation in location, orientation, and 

sense of slip between Dobbs Ferry fault zone (DFFZ) and 1985 Ardsley 

earthquake rupture (mb = 4.0) in southern Westchester County, New York. 

The DFFZ is a tabular zone of discontinuous faults and fractures rather than a 

single through-going fault, and cumulative offset across it is very small, 

considering size and Paleozoic age of structure. Mesoscopic structural data 

argue for predominantly left-lateral motion on DFFZ, while accumulated 

displacement on the fault zone shown by offset Paleozoic-age markers is 

right-lateral (20–30 m, or 66–98 ft.). While DFFZ is at least 8 km (5 mi.) long 

(later found to be at least 10 km, or 6 mi., long by Hough and Seeber [1991]), 

there is little evidence in surface outcrops of a single through-going fault; in 

addition, there is no evidence for Quaternary surface displacement. The 

authors consider that, given the small total accumulated displacement, 

Quaternary surface offset seems unlikely. They argue that segmented 

geometry of DFFZ suggests that structural data may provide criteria to 

constrain the largest possible ruptures on intraplate faults, as opposed to 

analyzing length of entire fault. Therefore, the concept of characteristic 

earthquake and characteristic rupture may be applicable to intraplate regions.

Wise and Faill 

(1998)

Lancaster County Seismic Zone (Penna.): 

Reactivation of a Taconic Structural 

Feature?

Abstract describes instrumentally observed seismicity in Lancaster County 

seismic zone of Pennsylvania. Suggests that if short, shallow faults of 

Lancaster seismic zone do not slip seismically, faults and earthquakes 

together might reflect some other, deeper geologic control on seismicity.

Zoback (1992) Stress Field Constraints on Intraplate 

Seismicity in Eastern North America

Uses focal mechanisms from 32 midplate earthquakes in North America to 

determine how maximum horizontal compressive stress changes from the 

central eastern United States (strike-slip faulting stress regime) to SE Canada 

(thrust faulting stress regime).
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

Geologic Structures Interpreted from Geologic, Geomorphic, Geophysical, and Seismic-Profile Data

Cook and Oliver 

(1981)

The Late Precambrian–Early Paleozoic 

Continental Edge in the Appalachian

Orogen

Integration of geological and geophysical data indicates that eastern edge of 

the late Precambrian–early Paleozoic North American continent is buried 

beneath crystalline rocks of southern Appalachian orogen. The transition 

appears to be essentially coincident with strong gravity gradient that is 

continuous throughout much of the length of the orogen. COCORP seismicreflection data in southern Appalachians indicate that most of near-surface 

crystalline rocks of Blue Ridge and Inner Piedmont are allochthonous and that 

reflection character in the crust changes near Inner Piedmont–Charlotte belt 

boundary. Layered reflectors beneath Kings Mountain belt, Charlotte belt, and 

Carolina slate belt in Georgia are interpreted as sedimentary (or 

metasedimentary) strata, and associated gravity change is interpreted as an 

edge effect corresponding to boundary between continental and former 

oceanic or attenuated continental crust. 

Cook and 

Vasudevan (2003)

Are There Relict Crustal Fragments 

Beneath the Moho?

Images of upper mantle structure from lithoprobe seismic-reflection profile 

suggests that a relict Mesoproterozoic subduction zone lies beneath Moho in 

NW Canada. 

Cook and 

Vasudevan (2006)

Reprocessing and Enhanced Interpretation 

of the Initial COCORP Southern

Appalachians Traverse

The authors present results of reprocessed 1978–1980 COCORP Southern 

Appalachian seismic-reflection data that has produced improved images of 

structures related to emplacement of Blue Ridge–Inner Piedmont allochthon. 

Results enhance and extend the interpretation presented previously (Cook et 

al., 1979) that Blue Ridge and Inner Piedmont are allochthonous above a 

shallow and shallow-dipping detachment that can be followed from outcrop at 

the Blue Ridge/Valley and Ridge transition to at least beneath Carolina 

terrane. Continuity of reflections in the new images supports interpretation 

that southern Appalachian detachment is not rooted on east side of Inner 

Piedmont, but rather projects as a low-angle detachment (or zone of 

decoupling) to beneath Coastal Plain. An implication of this geometry is that 

terranes, such as Carolina terrane, between autochthonous North America 

and the Alleghanian suture beneath Coastal Plain are detached, thin flakes. 

Some key structures, such as layered supracrustal rocks beneath 

Appalachian detachment, were visible previously but are considerably 

improved. Other features (e.g., continuity of subhorizontal reflections beneath 

Carolina terrane and the shallowing of the Moho) that either were only 

marginally visible or were surmised based on ancillary information (e.g.,
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

palinspastic reconstructions) are now apparent. Still others, such as a 

prominent west-dipping midcrustal reflection beneath the Inner Piedmont 

ramp are visible for first time. These new results, combined with 

interpretations of regional reflection data recorded during 1980s south and 

west of the initial survey, have been incorporated into a schematic threedimensional interpretation of crustal structure of the region. According to this 

interpretation, terranes (e.g., Carolina terrane) that were caught between 

ancient North American (Laurentian) lithosphere and African lithosphere are 

represented today as thin flakes that were juxtaposed with and emplaced 

above SE margin of Grenvillian basement.

Cook et al. (1979) Thin-Skinned Tectonics in the Crystalline 

Southern Appalachians: COCORP Seismic 

Reflection Profiling of the Blue Ridge and 

Piedmont

COCORP seismic-reflection profiling in Georgia, North Carolina, and 

Tennessee and related geological data indicate that crystalline Precambrian 

and Paleozoic rocks of Blue Ridge, Inner Piedmont, Charlotte belt, and 

Carolina slate belt constitute an allochthonous sheet, generally 6–15 km (4–9 

mi.) thick, which overlies relatively flat-lying autochthonous lower Paleozoic 

sedimentary rocks, 1–5 km (0.6–3 mi.) thick, of proto-Atlantic continental 

margin. Thus crystalline rocks of southern Appalachians appear to have been 

thrust at least 260 km (162 mi.) to west, and they overlie sedimentary rocks 

that cover an extensive area of central and southern Appalachians. The data 

show that Brevard fault is surface expression of an eastward-dipping splay of 

the main sole thrust, and the authors indicate that other major faults of this 

region have similar origins. The data support view that large-scale, thin 

crystalline thrust sheets may be significant features of orogenic zones.

Cook et al. (1980) The Brevard Fault: A Subsidiary Thrust 

Fault to the Southern Appalachian Sole 

Thrust

COCORP seismic-reflection profiling data suggest that Brevard fault is a 

subsidiary thrust fault related to southern Appalachian detachment.

Cook et al. (1981) COCORP Seismic Profiling of the 

Appalachian Orogen Beneath the Coastal 

Plain of Georgia

A southeastward extension onto Coastal Plain of an earlier COCORP traverse 

yielded the following results:

Confirmation of east-dipping layers beneath Charlotte belt and 

subhorizontal layers east of these. Such midcrustal layers are apparently 

extensive beneath Eastern Piedmont and are most easily interpreted as 

late Precambrian–early Paleozoic metasediments and metavolcanics. 

Lateral correlation of these reflectors implies that a major detachment 

extends eastward beneath crystalline rocks of Eastern Piedmont and 

Coastal Plain.
Table D-7.3.7 Data Summary 

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Citation Title Description and Relevance to SSC

Recognition of a major SE-dipping reflector in crystalline basement that

projects to surface location of Augusta fault and is thus interpreted as its 

subsurface extension. This feature extends 80 km (50 mi.) or more SE of 

surface trace of Augusta fault and is apparently a major lithologic and 

tectonic boundary in this area.

Recognition of upwardly concave reflectors that are listric into Augusta 

fault. These may be late Paleozoic thrust faults, Mesozoic listric normal 

faults, or both.

Observation of a significant thickness (up to 6.0 sec) of layered reflections 

beneath Augusta fault. One interpretation of these events is that they are 

late Precambrian–early Paleozoic basinal strata that have been thickened 

by repeated thrusting. 

Discovery of an anticlinal feature in crystalline rocks beneath eastern 

Coastal Plain. Tectonic evolutionary models must now incorporate 

compressional deformation in North America at least as far east as eastern 

limit of Augusta fault (about 80 km, or 50 mi., east of its surface trace).

Gates and Costa 

(1998)

Multiple Reactivations of Rigid Basement 

Block Margins: Examples in the Northern 

Reading Prong, USA

Suggests that zones of crustal weakness in northern Reading Prong that 

formed during Grenville orogenesis were reactivated during subsequent 

tectonic events. As many as seven phases of reactivation are identified within 

Morgan Hill, Ramapo, and Reservoir faults. 

Kean and Long 

(1981)

A Seismic Refraction Line Along the Axis of 

the Southern Piedmont and Crustal 

Thicknesses in the Southeastern United 

States

Describes COCORP seismic-reflection profiling data from southern Piedmont 

and estimates of crustal thickness.

Nelson et al. 

(1987)

Results of Recent COCORP Profiling in the 

Southeastern United States

The authors describe COCORP seismic-reflection profiling data from SE

United States. They interpret reflections associated with Appalachian 

detachment, Alleghanian suture, South Georgia rift basin, and other features. 

Talwani et al. 

(1995)

The Edge Experiment and the U.S. East 

Coast Magnetic Anomaly

The East Coast magnetic anomaly is spatially correlated with a zone of 

transitional igneous crust that extends along entire Atlantic margin. The 

authors suggest that basalts and underlying intrusives source the anomaly. 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-213 

Citation Title Description and Relevance to SSC

Faults with Cenozoic Activity

Behrendt et al. 

(1981)

Cenozoic Faulting in the Vicinity of the 

Charleston, South Carolina, 1886 

Earthquake

Data from onshore multichannel seismic-reflection profiles in 1886 

meizoseismal area show evidence of Cenozoic faulting, including the reverse 

(?) Cooke fault. Data suggest that most recent slip on the Cooke fault is 

Eocene or later. Data from offshore multichannel seismic-reflection profiles 

and single-channel high-resolution data show Helena Banks fault as a 30+ km 

(19 mi.) long structure with most recent movement in post-Miocene or 

Pliocene time. 

Behrendt et al. 

(1983)

Marine Multichannel Seismic-Reflection 

Evidence for Cenozoic Faulting and Deep 

Crustal Structure near Charleston, South 

Carolina

Seismic-reflection data collected offshore from Charleston show Helena

Banks fault as NE-striking, west-dipping reverse fault that extends upward to 

about 10 km (6 mi.) from sea bottom. The authors interpret it as Mesozoic 

extensional fault reactivated as reverse-oblique fault at least as young as 

Miocene or Pliocene. They also interpret it as a subhorizontal detachment at 

11.4 ± 1.5 km (7 ± 1 mi.) depth. They suggest that Charleston seismicity is 

primarily caused by movement along the detachment, and that movement on 

high-angle reverse faults (e.g., the Helena Banks fault and others) may also 

cause earthquakes. 

Bramlett et al. 

(1982)

The Belair Fault: A Cenozoic Reactivation 

Structure in the Eastern Piedmont

The authors determined that Belair fault zone (near Augusta, Georgia) 

represents a tear fault in upper plate of Augusta fault and that most of the ~23 

km (14 mi.) of lateral displacement estimated by Prowell and O’Conner (1978) 

occurred during Paleozoic Alleghanian orogeny and not post-Cretaceous 

time. During Late Cretaceous and Cenozoic, the Belair fault was reactivated

as an oblique-slip reverse fault displacing Middendorf and Barnwell 

formations of Atlantic Coastal Plain. Prowell et al. (1975) and Prowell and 

O’Connor (1978) document Cenozoic brittle reverse slip on Belair fault. 

Quaternary slip on Belair fault is allowed but not demonstrated by the 

available data (i.e., Crone and Wheeler, 2000).

Darton (1950) Configuration of the Bedrock Surface of the 

District of Columbia and Vicinity

Geologic mapping of extension of Stafford fault system at Fredricksburg, 

Virginia, suggests possible faulted fluvial terraces that may indicate postPliocene movement.

Faye and Prowell 

(1982)

Effects of Late Cretaceous and Cenozoic 

Faulting on the Geology and Hydrology of 

the Coastal Plain near the Savannah River, 

Georgia and South Carolina

Geologic and hydrologic studies in Coastal Plain of Georgia and South 

Carolina suggest faulted upper Cretaceous to lower Tertiary rocks near Millet, 

South Carolina. The postulated Statesboro fault strikes NE and shows 

apparent down-to-the-NW motion. 
Table D-7.3.7 Data Summary 

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D-214 

Citation Title Description and Relevance to SSC

Jacobeen (1972) Seismic Evidence for High Angle Reverse 

Faulting in the Coastal Plain of Prince 

Georges and Charles County, Maryland

Recognizes subsurface high-angle reverse Brandywine fault system in 

Cenozoic sediments of SW Maryland, based on seismic-reflection profiling. 

Mayer and 

Wentworth (1983)

Geomorphic Differences East and West of 

the Stafford Fault System, Northeastern 

Virginia

Geomorphic relationships of fluvial terraces near Stafford fault system. Where 

faults are found to displace Cenozoic sediments of Coastal Plain, inferred 

cumulative rates tend to be less than 1 m (3 ft.) per million years (from Seeber 

and Armbruster, 1988).

Mixon and Newell 

(1978)

The Faulted Coastal Plain Margin at 

Fredericksburg, Virginia

The authors identify four en echelon NE-trending structures, including SEdipping monoclines and NW-dipping high-angle reverse faults, along inner 

edge of Coastal Plain in NE Virginia termed the Stafford fault system. The 

structures affect the present distribution of Coastal Plain sediments with 

estimated displacements of 15–60 m (49–197 ft.). The fault system extends at 

least 56 km (35 mi.) parallel to Fall Line and NE-trending reach of the 

Potomac estuary where the authors hypothesize that the Fall Line and major 

river deflections along it have been tectonically influenced. The authors 

suggest possible relationship between Coastal Plain deformational belts and 

zones of weakness in crystalline basement rocks characterized by normal 

faulting in Triassic. The speculative relationship of Stafford fault system to 

Triassic or older basement structures is based on alignment of Stafford fault 

with Farmville basin Triassic fault trend and Brandywine fault system that 

could potentially mark a major zone of deformation in basement rocks that 

records recurrent movement in pre-Mesozoic, Mesozoic, and Cenozoic time.

Newell (1985) Architecture of the Rappahannock 

Estuary—Neotectonics in Virginia

The authors describe Stafford fault system as zone of NW-dipping, en 

echelon reverse faults near the Fall Line in NE Virginia.

Pavich et al. (1989) Investigations of the Characteristics, Origin, 

and Residence Time of the Upland 

Residual Mantle of the Piedmont of Fairfax 

County, VA

This study suggests that regolith of Piedmont most likely represents Pliocene 

and Quaternary weathering system that is product of interaction of bedrock 

and ground water in an actively eroding landscape. Variation in saprolite 

thickness, and therefore regolith thickness, is a function of distribution of 

minerals in the rock, grain contact relations, and structural fabric. 

Pavlides (1994) Continental Margin Deposits and the 

Mountain Run Fault Zone of Virginia—

Stratigraphy and Tectonics

Provides descriptions and geologic mapping of NE-striking reverse Everona–

Mountain Run fault zone in Virginia. From offset late Cenozoic gravels and 

rugged topography of scarps along Everona fault, the author infers possible 

Quaternary reactivation of Everona fault or some part of Mountain Run fault 

zone.
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-215 

Citation Title Description and Relevance to SSC

Pavlides et al. 

(1983)

Late Cenozoic Faulting Along the Mountain 

Run Fault Zone, Central Virginia Piedmont

The authors investigate faulting along Everona–Mountain Run fault zone near 

Everona, Virginia, including late Cenozoic stream gravels apparently offset 

vertically ~1.5 m (5 ft.). 

Prowell (1983) Index of Faults of Cretaceous and 

Cenozoic Age in the Eastern United States

Many investigators have recognized and documented post-rift faulting of 

Cretaceous and Cenozoic ages in Atlantic Coastal Plain. The author compiled 

information and describes evidence for possible Cretaceous and Cenozoic 

faults in the eastern U.S. Faults, fractures, and joints in eastern New York 

State generally trend N-NE, but none of these structures have been shown to 

displace Holocene deposits. Within the ECC, the geometry of the Coharie 

unconformity on adjacent sides of the Hares Crossroads fault plane suggests 

that significant lateral offset may have occurred on fault. It is considered to be 

a reverse fault that has a strike of N7°E and a dip of 63° to the SE. Basement 

rock affected by faulting includes Paleozoic Piedmont schist, slate, and 

phyllite. Sedimentary rocks (or sediments) affected by faulting include 

unconsolidated clayey sand of Coharie Formation (Pliocene-Pleistocene). 

Greatest vertical displacement is 2.8 m (9 ft.) and greatest horizontal 

displacement is 2 m (>6 ft.). 

Prowell (1988) Cretaceous and Cenozoic Tectonism on 

the Atlantic Coastal Margin

The author indicates that the predominant orientation of mapped Cretaceous 

and younger faults within ECC is N-S to NE-SW. Further, post-Cretaceous 

movement on these faults is reverse slip, with limited evidence for strike-slip 

movement. Within the ECC source zone, several NE-trending reverse fault 

zones in fault systems up to 100 km (62 mi.) long have experienced Cenozoic 

activity. These faults typically strike N-NE, dip steeply, and displace 

sedimentary rocks of Late Cretaceous to Miocene (100–5.3 Ma) age. 

Observed displacements are dip-slip, but some strike-slip may have occurred. 

Individual fault zone displacements are generally tens of meters, with a 

maximum cumulative offset of as much as 80 m (262 ft.). The available 

stratigraphic data generally show greater displacement on older units, 

indicating progressive displacement through time. The author describes

vertical slip rates as ranging from 0.0003 to 0.00015 meters per thousand 

years (m/kyr) during the past 110 Ma, averaging 0.0005 m/kyr.
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-216 

Citation Title Description and Relevance to SSC

Prowell and 

O’Connor (1978)

Belair Fault Zone: Evidence of Tertiary 

Fault Displacement in Eastern Georgia

The authors describe Belair fault zone as comprising NE-striking oblique-slip 

reverse faults with as much as 30 m (98 ft.) of apparent vertical offset since 

deposition of Late Cretaceous–middle Tertiary Coastal Plain sediments. In 

contrast with Prowell et al. (1975), the authors indicate that no fault movement 

has occurred in past 2,000 years, but that movement may have occurred in 

late Tertiary time.

Prowell et al. 

(1975)

Preliminary Evidence for Holocene 

Movement Along the Belair Fault Zone near 

Augusta, Georgia

Describes results of paleoseismic trenching across Belair fault near Augusta, 

Georgia. Lenses of organic material are interpreted as faulted and deformed. 

A composite sample of this material yielded mid- to late Holocene ages. 

Sykes et al. (2008) Observations and Tectonic Setting of 

Historic and Instrumentally Located 

Earthquakes in the Greater New York City–

Philadelphia Area

The authors compiled a catalog of 383 earthquakes (from historical and 

instrumental data) in SE New York, SW Connecticut, northern New Jersey, 

and eastern Pennsylvania. Observations from this study are as follows:

Most hypocenters are concentrated in older terranes bordering Mesozoic 

Newark basin in Reading, Manhattan, and Trenton prongs and in similar 

rocks found at shallow depth beneath Coastal Plain from south of New 

York City across central New Jersey. Historical shocks of mbLg 3 and larger 

were more numerous in latter zone.

Most earthquakes are shallow (94% are ≤10 km, or 6 mi., deep).

Many earthquakes have occurred beneath 12 km (7.5 mi.) wide Ramapo 

seismic zone (RSZ) in eastern part of Reading Prong, where station 

coverage has been the most extensive since 1974.

The SE boundary of the RSZ, which is nearly vertical, extends from near 

the surface trace of Mesozoic Ramapo fault to depths of 12–15 km (7.5–9 

mi.). Mesozoic border fault dips about 50°–60°SE; therefore, earthquakes 

are occurring within middle Proterozoic through early Paleozoic rocks. 

Causative faults and their orientations within RSZ in eastern part of 

Reading Prong are uncertain.

Seismicity is nearly absent in Mesozoic sedimentary rocks of Newark basin 

and in Cambro-Ordovician rocks inferred beneath them. This is attributed 

to either those rocks being relatively weak, in the velocity-strengthening 

rheological regime, being decoupled from the basement beneath them by 

thrust and/or detachment faults along weak layers, or a lack of preexisting 

brittle faults that are suitably oriented with respect to contemporary 

stresses. 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-217 

Citation Title Description and Relevance to SSC

A newly identified feature—NW-trending Peekskill-Stamford seismic 

boundary—is nearly vertical, extends from near surface to depths of about 

12–15 km (7.5–9 mi.), and is subparallel to brittle faults farther south in 

Manhattan Prong.

These brittle faults may have formed between Mesozoic basins to 

accommodate Mesozoic extension.

The Great Valley in NW part of study region is nearly devoid of known 

earthquakes.

Maximum compressive stress is nearly horizontal and is oriented about 

N64°E.

Extrapolation of the frequency-magnitude relationship indicates that an 

event of mbLg – 6.0 is expected about once every 670 years.

Which faults are active in this intraplate region has been a subject of 

ongoing debate. Several faults displace Mesozoic sedimentary and 

igneous rocks, but evidence of faulting in younger sediments of Coastal 

Plain and in postglacial sediments is either missing or debatable.

Wentworth and 

Mergner-Keefer 

(1983)

Regenerate Faults of Small Cenozoic 

Offset—Probable Earthquake Sources of 

the Southeastern United States

Proposes that Mesozoic normal faults in Piedmont and Coastal Plain have 

been reactivated as reverse and reverse-oblique faults.

Postulated Faults

Crone and 

Wheeler (2000)

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic Features 

in the Central and Eastern United States, 

East of the Rocky Mountain Front

The authors provide a compilation and evaluation of Quaternary faults, 

liquefaction features, and possible tectonic features in CEUS. They assigned

faults to three classes, which they define by features as follows. Class A 

features are those for which geologic evidence demonstrates existence of a 

Quaternary fault of tectonic origin. Class B features are those for which the 

fault may not extend deeply enough to be a potential source of significant 

earthquakes, or for which currently available geologic evidence is not 

definitive enough to assign the feature to either Class C or Class A. Class C 

features are those for which geologic evidence is insufficient to demonstrate 

existence of a tectonic fault, Quaternary slip, or deformation associated with 

the feature. 

Class A structures or seismic zones within the ECC include the following:

Central Virginia seismic zone, Virginia—Zone of elevated seismicity.
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-218 

Citation Title Description and Relevance to SSC

Charleston-Bluffton-Georgetown liquefaction features (see Charleston

Data Summary Table D-6.1.2)

Newbury, Massachusetts, liquefaction features.

Class B—There are no Class B faults in the ECC.

Class C structures and features within the ECC and explanation of Class C 

assignment are as follows:

Belair fault zone, Georgia—Two trenches record pre-Quaternary age.

Cacoosing Valley earthquake, Pennsylvania—No surface rupture from 

earthquake correlated to this fault.

Cape Fear arch, North Carolina–South Carolina—Lack of evidence for 

Quaternary faulting.

Catlin Lake–Goodnow Pond lineament, New York—No evidence of 

continuous fault zone and lacks paleoseismological evidence of 

Quaternary motion. 

Champlain lowlands normal faults, New York–Vermont—No evidence for 

Quaternary motion.

Clarendon-Linden fault zone, New York—No paleoseismological evidence 

for Quaternary motion.

Cooke fault, South Carolina—Lack of evidence of faulting younger than 

Eocene.

Cornwall-Massena earthquake, New York–Ontario—No 

paleoseismological evidence for Quaternary motion.

Dobbs Ferry fault zone, New York—Earthquakes were too deep to produce 

any recognized surface cracking along trace of fault zone; no 

paleoseismologic evidence for Quaternary motion.

Everona fault–Mountain Run fault zone, Virginia—No detailed 

paleoseismologic or other investigations. 

Hares Crossroads fault, North Carolina—Faulting is not demonstrably of 

Quaternary age.

Helena Banks fault zone, offshore South Carolina—No reported evidence 

for slip younger than Miocene.

Kingston fault, New Jersey—Faulting is not demonstrably of Quaternary 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-219 

Citation Title Description and Relevance to SSC

age. 

Lancaster seismic zone, Pennsylvania—No structural, stratigraphic, or 

paleoseismological evidence for Quaternary faulting.

Lebanon Church fault, Virginia—Faulting is not demonstrably of 

Quaternary age.

Moodus seismic zone, Connecticut—Causes and causative faults of the 

earthquakes remain enigmatic.

Mosholu fault, New York—Faulting is not demonstrably of Quaternary age.

New York Bight fault, offshore New York—Fault lacks documented 

Quaternary offset.

Offset glaciated surfaces, Maine–Massachusetts–New Hampshire–New 

York–Vermont—Their most likely origin is in frost heaving, not tectonics. 

Old Hickory faults, Virginia—Faulting was probably of Pliocene age.

Pen Branch fault, South Carolina—Lack of evidence for post-Eocene slip.

Ramapo fault system, New Jersey–New York—Lack of evidence for 

Quaternary slip on fault.

Upper Marlboro faults, Maryland—Surficial structures do not extend to 

hypocentral depths.

Dominion Nuclear 

North Anna LLC 

(2004)

North Anna Early Site Permit Application 

Response to Request for Additional 

Information No.3.

The key observations and conclusions from the Dominion assessment 

regarding the East Coast fault system (ECFS-N segment) are summarized as 

follows:

No consistent co-occurrence of two or more anomalies along each of the 

drainages was observed, as may be expected if they have developed in 

response to uplift of northern zone of river anomalies (ZRA-N).

There is no consistent pattern of anomalies along trend of ZRA-N, as 

expected if structure was active along its entire length.

It was not possible to verify or duplicate geomorphic observations, such as 

channel incision.

The ―upward displaced fluvial surfaces‖ are inferred only from qualitative 

analysis of convexities of river profiles, and therefore, this type of 

―anomaly‖ does not provide evidence for tectonic uplift and is inconsistent 

with other geomorphic observations. These features in most cases are 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-220 

Citation Title Description and Relevance to SSC

more objectively characterized as convexities, or local increases in 

gradient of longitudinal profiles of floodplains due to intersection of 

concave profiles at river confluences.

Direct stratigraphic evidence for no Quaternary deformation was 

documented in vicinity of a large meander of Nottoway River that Marple 

and Talwani (2000) interpreted to have formed in response to systematic 

folding and northeastward tiling.

The fluvial geomorphic features cited by Marple and Talwani (2000) are 

likely produced by nontectonic fluvial processes and are not anomalous, 

which does not support Marple and Talwani’s interpretation of the 

presence and activity of ZRA-N (ECFS-N).

Marple and 

Talwani (2000)

Evidence for a Buried Fault System in the 

Coastal Plain of the Carolinas and

Virginia—Implications for Neotectonics in 

the Southeastern United States

The authors postulate a N-NE-/S-SW-striking buried fault system in Coastal 

Plain of Carolinas and Virginia, named East Coast fault system (ECFS). 

Geomorphic analyses of Coastal Plain rivers led to differentiation of three 

nearly collinear, approximately 200 km (125 mi.) long segments (ECFS-S, 

ECFS-C, and ECFS-N) that were initially referred to as southern, central, and 

northern zones of river anomalies (ZRA-S, ZRA-C, and ZRA-N). Southern 

segment is located primarily in South Carolina; central segment is located 

primarily in North Carolina; and northern segment extends from NE North 

Carolina through Virginia. Identification of postulated fault system is based on 

alignment of geomorphic changes along streams, areas of uplift, and local 

evidence of faulting. The authors concluded that (1) ZRAs were produced by 

gentle late Quaternary uplift along an approximately 600 km (370 mi.) long

buried fault system, and (2) because most of the river anomalies occur in 

unconsolidated floodplain sediments of upper Pleistocene (<130 ka) or 

younger age, deformation occurred during this period and may be ongoing.

Marple and 

Talwani (2004)

Proposed Shenandoah Fault and East 

Coast–Stafford Fault System and Their 

Implications for Eastern U.S. Tectonics

Comparison of Shenandoah igneous province, Central Virginia seismic zone, 

a NW-trending linear magnetic anomaly offshore Virginia, and other tectonic 

features in Virginia suggests presence of a deep crustal NW-striking

basement fault, named Shenandoah fault. Along Shenandoah fault, the 

Central Virginia seismic zone coincides with an apparent –110 km (–68 mi.) 

offset between NE-striking Stafford fault zone and East Coast fault system 

(ECFS). The authors postulate that the following series of events likely 

occurred in the formation of the fault system:

Stafford fault zone and ECFS formed a continuous ~1,100 km (684 mi.) 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-221 

Citation Title Description and Relevance to SSC

long East Coast–Stafford fault system (EC-SFS) extending from South 

Carolina to New Jersey before the Alleghanian orogeny. 

During Alleghanian or an earlier orogeny, EC-SFS was beheaded by NWvergent thrusting of allochthonous terranes, concealing it beneath those 

terranes. 

Late Alleghanian indentation in Salisbury embayment by Reguibat uplift of 

NW Africa produced Shenandoah fault and offset EC-SFS left-laterally—

110 km (–68 mi.) beneath allochthonous terranes in central Virginia.

Late Jurassic to Cenozoic dextral reactivation of ECFS and Stafford fault at 

depth fractured overlying terranes and may have produced N-NE-oriented 

linking faults that reconnected EC-SFS along a large left-step restraining 

bend. 

The cause of seismicity in central Virginia may be from compression at the 

bend, which is causing displacements on a variety of faults in the area, 

including linking faults, Shenandoah fault, and older Paleozoic faults. 

Late Jurassic and Middle Eocene dextral deformation along the large 

restraining bend along EC-SFS in central Virginia produced tension across 

Shenandoah fault to the NW. This tension caused normal sense 

reactivation of the fault beneath the allochthonous terranes of Blue Ridge 

and Valley and Ridge provinces. 

Consequently, magma migrated up Shenandoah fault and then along 

bedding planes and NW joints within Valley and Ridge strata to form 

Shenandoah igneous province.

Progress Energy 

Carolinas, Inc. 

(2008)

Shearon Harris Nuclear Power Plants Units 

2 and 3, Docket Nos. 52-022 and 52-023, 

Supplement 1 to Response to Requests for 

Additional Information Letter 030 Related to 

Basic Geologic and Seismic Information

The key observations and conclusions from the Progress Energy assessment 

of East Coast fault system (ECFS) are summarized as follows:

There is supporting geological, geophysical, and seismological information 

to suggest that geomorphic anomalies identified along southern half of 

ECFS-S segment may be associated with Quaternary displacement on 

Woodstock fault and that this fault may be source of Charleston 

earthquake (see Charleston Data Summary Table D-6.1.2).

There is no similar evidence to suggest that northern part of ECFS-S, 

ECFS-C, and ECFS-N segments are capable tectonic structures as 

defined by the U.S. Nuclear Regulatory Commission (Regulatory Guide 

1.208).
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-222 

Citation Title Description and Relevance to SSC

Observations and lines of evidence presented by Marple and Talwani 

(2000) do not provide convincing arguments in support of a buried N-NEstriking strike-slip fault (postulated ECFS-C) through North Carolina 

Coastal Plain region.

Evidence of neotectonic deformation (i.e., differential uplift of the Piedmont 

relative to the Coastal Plain regions, regional tilting, and broad zones of 

tilting or flexure) can be explained by lithospheric flexure 

(i.e., long-wavelength bending or warping of lithosphere) related to regional 

patterns of erosion and Cenozoic deposition.

Localized Cenozoic faulting observed near Piedmont–Coastal Plain 

boundary may be related to stresses in the region of greatest flexure 

(Pazzaglia, 1999).

The possibility cannot be precluded given the available data that some 

local structures along general trend of ECFS may be present and may be 

favorably oriented for reactivation in the present tectonic setting.

There are no geological data, however, to demonstrate Quaternary surface 

faulting.

There is no associated seismicity or reported evidence of paleoliquefaction 

to indicate activity along ECFS-C segment.

The implication that the postulated central and northern segments of ECFS 

if they exist may produce earthquakes of a similar size to the 1886 

Charleston earthquake, as inferred by Marple and Talwani, is not 

demonstrated.

Wheeler (2005) Known or Suggested Quaternary Tectonic 

Faulting, Central and Eastern United 

States-New and Updated Assessments for 

2005

Provides 13 assessments, 12 of which are new; the 13th incorporates 

significant new information. The new assessments describe faults, fields of 

paleoliquefaction features, seismic zones, and geomorphic features for which 

too little geologic information was available to write an assessment before 

now. The following features are located within ECC and are all assigned to 

Class C for their respective reasons.

Class C updated structures:

Eastern Border fault, Connecticut—No faulting demonstrated in Quaternary 

sediments.

East Coast fault system, North Carolina–South Carolina–Virginia—The 

1886 and prehistoric liquefying earthquakes in coastal South Carolina 
Table D-7.3.7 Data Summary 

Extended Continental Crust Zone—Atlantic Margin 

D-223 

Citation Title Description and Relevance to SSC

demonstrates occurrence of repeated Quaternary tectonic faulting, but the 

link between these earthquakes and East Coast fault system or Woodstock 

fault remains speculative.

Fall Lines of Weems, North Carolina, Virginia, and Tennessee—Fall zones 

are not demonstrably reproducible. Tectonic faulting is not yet 

demonstrated.

Hopewell fault, Virginia—No observed offsets of Pleistocene terrace 

deposits.

New Castle County faults, Delaware—Subsurface studies showed no 

evidence of Quaternary faulting. 

Stafford fault system, Virginia—None of the strands of Stafford fault system 

are known to have moved during Quaternary.

Paleoseismic Investigations

Amick (1990) Paleoliquefaction Investigations Along the 

Atlantic Seaboard with Emphasis on the 

Prehistoric Earthquake Chronology of 

Coastal South Carolina

Search for paleoliquefaction features along U.S. East Coast at over 1,000 

sites from southern Georgia to New Jersey. Features found only in coastal 

Carolinas. Includes rough maps of areas searched in which no features 

found, as well as sketches and photographs of selected features. Includes 

discussion of criteria by which to distinguish seismically induced liquefaction 

features from ―pseudoliquefaction‖ features.

Amick, Gelinas, et 

al. (1990)

Paleoliquefaction Features Along the 

Atlantic Seaboard

Search for paleoliquefaction features along U.S. East Coast at over 1,000 

sites from southern Georgia to New Jersey. Features found only in coastal 

Carolinas. Includes discussion of criteria by which to distinguish seismically 

induced liquefaction features from ―pseudoliquefaction‖ features. 

Amick and Gelinas 

(1991)

The Search for Evidence of Large 

Prehistoric Earthquakes Along the Atlantic 

Seaboard

Search for paleoliquefaction features along U.S. East Coast at over 1,000 

sites from southern Georgia to New Jersey. Features found only in coastal 

Carolinas. 

Obermeier and 

McNulty (1998)

Paleoliquefaction Evidence for Seismic 

Quiescence in Central Virginia During Late 

and Middle Holocene Time

Survey of 300 km (186 mi.) of river banks for liquefaction and 

paleoliquefaction features along portions of Rapidan, Mataponi, North Anna 

(high water with poor exposures), South Anna, Appomattox, and James 

rivers, including Rivanna, Hardware, Rockfish, Slate, and Willis tributaries. 

Moderately susceptible deposits of 2–3 ka common; only three small 

prehistoric liquefaction features identified.

―Near total lack of widespread liquefaction features in large search area 
Table D-7.3.7 Data Summary 

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D-224 

Citation Title Description and Relevance to SSC

strongly suggests that very strong seismic shaking cannot have occurred 

often in 2–3 ka and for past 5 ka west and north of Richmond...Paucity of 

liquefaction features in central Virginia makes it seem unlikely that any 

earthquakes in excess of ~M 7 have struck there...even if M 6–7 earthquakes 

had been relatively abundant, then many more liquefaction effects would have 

been expected.‖

Tuttle (2007) Re-evaluation of Earthquake Potential and 

Source in the Vicinity of Newburyport, 

Massachusetts

Recent searches for earthquake-induced liquefaction features in 

Newburyport, Massachusetts, area yielded only one small sand dike. 

Tuttle (2009) Re-evaluation of Earthquake Potential and 

Source in the Vicinity of Newburyport, 

Massachusetts

Searches for earthquake-induced liquefaction features along several rivers 

south of Newburyport, in vicinity of Hampton Falls, and west of Hampton Falls 

in New Hampshire yielded only one liquefaction feature: a small sand dike 

along Hampton Falls River in New Hampshire.

Tuttle and Seeber 

(1991)

Historic and Prehistoric EarthquakeInduced Ground Liquefaction in Newbury, 

Massachusetts

The authors found both historical and prehistoric liquefaction features (sand 

dikes). The historical features were attributed to 1727 earthquake, and the 

prehistoric features were estimated to have formed during past 4,000 years.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-225 

Citation Title Description and Relevance to SSC

Seismicity

Angell and 

Hitchcock (2007)

A Geohazard Perspective of 

Recent Seismic Activity in the 

Northern Gulf of Mexico

Describes seismotectonic setting of northern Gulf of Mexico with specific reference to 

the 2006 earthquakes. Presents detailed information regarding seismic source 

characteristics of the 2006 earthquakes. Also addresses seismogenic capability of 

growth faults. Discusses implications to seismic hazard assessment in Gulf of Mexico. 

Presents a possible two-layer source model for Gulf of Mexico.

Davis et al. (1989) A Compendium of Earthquake 

Activity in Texas

Comprehensive review and database of historical earthquake activity in Texas 1847–

1986. Largest earthquakes have occurred in W Texas and are interpreted as resulting 

from either tectonic stresses or oil and gas field operations. Helps to constrain 

estimates of the minimum maximum earthquake magnitude for Gulf of Mexico coastal 

plain.

Dellinger and 

Nettles (2006)

Dellinger, Dewey 

et al. (2007)

Dellinger, Ehlers et 

al. (2007)

The 10 February 2006, Magnitude 

5.2 Gulf of Mexico Earthquake: 

Insights and Implications

Relocating and Characterizing the 

10 Feb 2006 ―Green Canyon‖ Gulf 

of Mexico Earthquake Using OilIndustry Data

The Green Canyon Event as

Recorded by the Atlantis OBS 

Node Survey

Detailed analysis of the earthquake with focus on the relative amount and timing 

energy release during the event. Focuses on determining a location and magnitude for 

the event, and hypothesizes that the event is most consistent with a slow, nontectonic 

event (e.g., large-scale slump, landslide).

Dewey and 

Dellinger (2008)

Location of the Green Canyon 

(Offshore Southern Louisiana) 

Seismic Event of February 10, 

2006

Presents analysis constraining location and depth of February 10, 2006, earthquake. 

Provides information on the seismotectonic setting of the earthquake, and minor 

discussion of potential causes of the event (i.e., nontectonic event).

Frohlich (1982) Seismicity in the Central Gulf of 

Mexico

Provides general overview of the sparse seismicity in Gulf of Mexico and a more 

detailed discussion of July 24, 1978, M 5.0 earthquake. Interprets the location and 

reverse mechanism for the event to possibly indicate that the event is related to crustal 

subsidence and downwarping of Gulf of Mexico basin.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-226 

Citation Title Description and Relevance to SSC

Frohlich and Davis 

(2002)

Texas Earthquakes Provides catalog of earthquakes in Texas 1847–2001. Helps constrain minimum 

maximum magnitude estimate for the Gulf of Mexico coastal plain region. Provides only 

minor discussions of potential earthquake mechanisms for the region.

Gangopadhyay 

and Sen (2008)

A Possible Mechanism for the 

Spatial Distribution of Seismicity in 

Northern Gulf of Mexico

Modeling of regional stress concentrations and the mechanical properties of salt and 

surrounding sediments to investigate the possible mechanism for the 2006 Gulf of 

Mexico earthquakes. Results show that locations of high shear stress in the Gulf of 

Mexico correlate well with the spatial distribution of seismicity in the northern Gulf of 

Mexico, suggesting a possible causal association between mechanical differences 

between salt and surrounding sediment and regional shear stresses. 

Gomberg and Wolf 

(1999)

Possible Cause for an Improbable 

Earthquake: The 1997 Mw 4.9 

Southern Alabama Earthquake 

and Hydrocarbon Recovery

An investigation into possible causes of 1997 Alabama earthquake. Concludes that 

hydrocarbon recovery is likely cause, but that tectonic mechanisms or influence cannot 

be ruled out.

Nettles (2006) Two Unusual Seismic Events in 

the Gulf of Mexico

Seismological analysis of the February 10, 2006, mb 5.2 and April 18, 2006, MS 4.8 

earthquakes in the northern Gulf of Mexico. Concludes from waveforms and energy 

release that the two events are best modeled as gravity-driven ―landslide‖ 

mechanisms.

Nettles (2007) Analysis of the 10 February 2006 

Gulf of Mexico Earthquake from 

Global and Regional Seismic Data

Describes analysis of February 10, 2006, mb 5.2 earthquake and the conclusion that 

earthquake was gravity-driven and did not have a tectonic source.

Nunn (1985) State of Stress in the Northern Gulf 

Coast

Addresses state of stress in Gulf of Mexico coastal plain region as related to 

Quaternary fault activity. Concludes that activity is consistent with lithospheric flexure 

caused by sediment loading in Gulf of Mexico. Also concludes that lack of seismicity 

may be due to relaxation of these stresses over time.

Peel (2007) The Setting and Possible 

Mechanism of the 2006 Green 

Canyon Seismic Event

Describes geologic setting of February 10, 2006, mb 5.2 earthquake. Presents an 

interpretation of the ocean-continent boundary as interpreted from industry seismic and 

nonseismic potential field geophysical data. Concludes that earthquake was restricted 

to growth sedimentary section in shallow upper crust.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-227 

Citation Title Description and Relevance to SSC

Stevenson and 

McCulloh (2001)

Earthquakes in Louisiana General description of earthquakes and fault activity in Louisiana with earthquake 

database. Concludes that most active faulting is associated with creeping growth 

faults.

Todd and Ammon 

(2007)

Characteristics of Recent Seismic 

Activity in the Gulf of Mexico

Presents information on depth and source characteristics of September 10 and 

February 10, 2006, earthquakes in Gulf of Mexico. Concludes that they occur within a 

―stable cratonic region‖ of North America and there are no well-known fault systems in 

the vicinity of the earthquakes, and therefore earthquakes of similar size may occur 

elsewhere in Gulf of Mexico. Provides constraints on the estimate of a minimum 

maximum earthquake magnitude for northern Gulf of Mexico.

Crustal Structure

Anderson and 

Schmidt (1983)

The Evolution of Middle America 

and the Gulf of Mexico-Caribbean 

Sea Region During Mesozoic Time

Provides plate reconstruction model for the Gulf of Mexico and Caribbean region. 

Focuses on structures accommodating microplate motions in Mexico (e.g., MojaveSonora megashear).

Baksi (1997) The Timing of Late Cretaceous 

Alkalic Igneous Activity in the 

Northern Gulf of Mexico Basin, 

Southeastern USA

Discusses distribution and age of Cretaceous igneous rocks in northern Gulf of Mexico. 

In particular, discusses Magnet Cove rocks of southern Arkansas that provide evidence 

of Mesozoic igneous activity in southern Arkansas.

Bird (2001) Shear Margins: Continent-Ocean 

Transform and Fracture Zone 

Boundaries

Presents compilation of interpretations of plate tectonic continental shear margins 

worldwide. Compares plate tectonic models of Pindell (2000) to those of Buffler and 

Thomas (1994), and the implications of a Gulf Coast–parallel shear margin (Buffler and 

Thomas, 1994) to a shear margin along eastern coast of Mexico (Pindell, 2000).

Bird et al. (2005) Gulf of Mexico Tectonic History: 

Hotspot tracks, Crustal 

Boundaries, and Early Salt 

Distribution

Provides constraints on location of ocean-continent crust boundary in northern Gulf of 

Mexico based on seismic-reflection and potential field geophysical data. Includes a 

comparison of the ocean-continent boundary as interpreted by multiple authors. 

Buffler and Sawyer 

(1985)

Distribution of Crust and Early 

History, Gulf of Mexico Basin

Provides general overview of geologic and tectonic evolution of Gulf of Mexico. The 

tectonic reconstruction model is compared with previous models. Provides constraints 

on the locations of continental and oceanic crust in Gulf of Mexico.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-228 

Citation Title Description and Relevance to SSC

Buffler and 

Thomas (1994)

Crustal Structure and Evolution of 

the Southwestern Margin of North 

America and the Gulf of Mexico 

Basin

Presents interpretations of E-W-trending tectonic elements in south-central U.S. 

(Alabama-Arkansas fault system and Suwanee-Wiggins suture) as major structural 

features associated with development of Gulf of Mexico. These E-W structures are 

important with respect to crosscutting relationships with NW-trending fracture zones in 

eastern Gulf of Mexico.

Byerly (1991) Igneous Activity Presents a synthesis of the igneous activity throughout Gulf of Mexico during the 

Mesozoic and Cenozoic.

Christenson 

(1990)

The Florida Lineament Provides interpretations of location and geometry of a major NW-trending fracture zone 

(the Florida lineament) based on borehole, regional gravity, and regional magnetic 

data. Describes a major structure in eastern Gulf of Mexico located near September 

10, 2006, M 5.8 earthquake. 

Collins (2004) Summary of the Balcones Fault 

Zone, Central Texas: A Prominent 

Zone of Tertiary Normal Faults 

Marking the Western Margin of the 

Texas Coastal Plain

Discusses tectonic history of Balcones fault zone.

Cook et al. (1979) Crustal Structure and Evolution of 

the Southern Rio Grande Rift

Discusses southern extent of Rio Grande rift in New Mexico using geophysical data 

(gravity, heat flow, seismic reflection).

Cox et al. (2000) Quaternary Faulting in the 

Southern Mississippi Embayment 

and Implications for Tectonics and 

Seismicity in an Intraplate Setting

Proposes existence of a Quaternary active Saline River fault zone in southern 

Arkansas based on equivocal observations of deformed Eocene and potentially 

Pliocene to Pleistocene deposits in natural exposures and shallow trenches.

Daniels et al. 

(1983)

Distribution of Subsurface Lower 

Mesozoic Rocks in the 

Southeastern United States, as 

Interpreted from Regional 

Aeromagnetic and Gravity Maps

Discusses extent of Mesozoic rocks in northwestern Gulf of Mexico, in particular, in 

Florida and Georgia. Presents figures showing extent of Bahamas fracture zone and 

South Georgia rift.

Dickerson and 

Muehlberger 

(1994)

Basins of the Big Bend Segment of 

the Rio Grande Rift, Trans-Pecos 

Texas

Discusses southern extent of Rio Grande rift in western Texas and northern Mexico. 

Presents maps of faults in Big Bend region of Texas and neighboring Mexico. 
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-229 

Citation Title Description and Relevance to SSC

Dunbar and 

Sawyer (1987)

Implications of Continental Crust 

Extension for Plate 

Reconstruction: An Example from 

the Gulf of Mexico

Presents kinematic model for the opening of Gulf of Mexico.

Ewing and Lopez 

(1991)

Principal Structural Features of the 

Gulf of Mexico Basin

Map of geologic and structural features of Gulf of Mexico region.

Gordon et al. 

(1997)

Cenozoic Tectonic History of the 

North America-Caribbean Plate 

Boundary Zone in Western Cuba

Summarizes tectonic history of Cuba. 

Gray et al. (2001) Thermal and Chronological Record 

of Syn- to Post-Laramide Burial 

and Exhumation, Sierra Madre 

Oriental, Mexico

Presents thermo-chronological data constraining development of the Sierra Madre 

Oriental in western Gulf of Mexico.

Hall et al. (1982) The Rotational Origin of the Gulf of 

Mexico Based on Regional Gravity 

Data

Presents interpretations of regional gravity data to constrain first-order tectonic 

elements in northern Gulf of Mexico. Provides review of previous interpretations of 

location and extent of oceanic crust.

Hall and 

Najmuddin (1994)

Constraints on the Tectonic 

Development of the Eastern Gulf 

of Mexico Provided by Magnetic 

Anomaly Data

Provides constraints on location of ocean-continent crust boundary in northern Gulf of 

Mexico. Also provides constraints on depth of oceanic crust.

Hatcher et al. 

(2007)

Tectonic Map of the Southern and 

Central Appalachians: A Tale of 

Three Orogens and a Complete 

Wilson Cycle

Comprehensive review of formation of Appalachians.

Hendricks (1988) Bouguer Gravity Anomaly of 

Arkansas 

Presents map of Arkansas. Discusses gravity anomalies of Arkansas and evidence of 

Cretaceous igneous activity.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-230 

Citation Title Description and Relevance to SSC

Hildenbrand and 

Hendricks (1995)

Geophysical Setting of the 

Reelfoot Rift and Relations 

Between Rift Structures and the 

New Madrid Seismic Zone

Discusses geophysical signature of Reelfoot rift. Presents summary of Cretaceous 

igneous intrusions in southern Arkansas thought to indicate southernmost extent of rift.

Jacques et al. 

(2004)

Digital Integration of Potential 

Fields and Geologic Datasets for 

Plate Tectonic and Basin Dynamic 

Modeling—The First Step Towards 

Identifying New Play Concepts in 

the Gulf of Mexico Basin

Presents plate tectonic reconstructions of Gulf of Mexico showing major tectonic 

elements. Principal features are the location and extent of oceanic crust, major 

transform faults within oceanic crust, major NW-trending fracture zones in eastern Gulf 

of Mexico–related Atlantic rifting, and N- and NW-trending deep structural trends within 

transitional and thinned continental crust.

Kanter (1994) Tectonic Interpretation of Stable 

Continental Crust

Presents locations of continental crust, extended crust, and oceanic crust in Gulf of 

Mexico region.

Klitgord et al. 

(1984)

Florida: A Jurassic Transform 

Plate Boundary

Discusses existence of Bahamas fracture zone that was active in the Jurassic during 

the opening of Gulf of Mexico. Presents maps of Florida delineating extent of Mesozoic 

rift basins and pre-Mesozoic crust.

Marton and Buffler 

(1994)

Jurassic Reconstruction of the Gulf 

of Mexico Basin

Presents detailed discussion of Gulf of Mexico structure and a model for the opening of 

Gulf of Mexico. Includes interpretation of extent of oceanic crust in Gulf of Mexico.

McBride and 

Nelson (1988)

Integration of COCORP Deep 

Reflection and Magnetic Anomaly 

Analysis in the Southeastern 

United States: Implications for 

Origin of the Brunswick and East

Coast Magnetic Anomalies

Suggests three possible sources for the Brunswick magnetic anomaly (BMA): 

subducted root nappes of the Inner Piedmont, obducted upper mantle, or Mesozoic 

rifting. Authors do not strongly support a particular solution, but go on to suggest that 

the BMA and East Coast magnetic anomaly may have a continuous, related source.

McBride et al. 

(2005)

Integrating Seismic Reflection and 

Geological Data and 

Interpretations Across an Internal 

Basement Massif: The Southern 

Appalachian Pine Mountain 

Window, USA

Traces master Appalachian decollement from the Inner Piedmont to Coastal Plain. 

Authors find that beneath the Carolina terrane, the decollement roots to the Moho, 

indicating location of Acadian-Alleghanian suture.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-231 

Citation Title Description and Relevance to SSC

McHuron and Rice 

(1974)

Tectonic Evolution of the Gulf 

Coast: Relation to Nuclear Power 

Plant Site Selection and Design 

Criteria

Delineates different crustal types in Gulf of Mexico and describes characteristics such 

as crustal type, relative stability, and history of stress application represented by 

tectonic fabrics. Directly addresses application of crustal characterization to seismic 

hazard and the siting of nuclear power plants in Gulf of Mexico coastal plain region.

Nagihara and 

Jones (2005)

Geothermal Heat Flow in the 

Northeast Margin of the Gulf of 

Mexico

Presents heat flow data for NE Gulf of Mexico and uses the data to revise estimates of 

location of oceanic crust within Gulf of Mexico.

Pindell and Dewey 

(1982)

Permo-Triassic Reconstruction of 

Western Pangea and the Evolution 

of the Gulf of Mexico/Caribbean 

Region

Presents a detailed reconstruction of Gulf of Mexico and Caribbean region. Outlines 

extent of oceanic crust within Gulf of Mexico.

Pindell and 

Kennan (2001)

Kinematic Evolution of the Gulf of 

Mexico and Caribbean

Presents plate tectonic reconstructions of Gulf of Mexico and Caribbean region. Helps 

to constrain location of oceanic crust in Gulf of Mexico.

Pindell et al. 

(2000)

Putting It All Together Again Presents interpretations of location and geometry of oceanic crust beneath Gulf of 

Mexico basin. Northern margin agrees well with Peel (2007).

Russo (2006) Earthquakes in the Gulf of Mexico Presents possible mechanism for producing the September 10, 2006, M 5.8 

earthquake. Influx of sediment into deep portions of Gulf of Mexico basin loads the 

underlying Mesozoic oceanic crust, causing flexure and buckling. Reverse earthquakes 

are produced by bending moment faults caused by buckling.

Salvador (1991) Origin and Development of the 

Gulf of Mexico Basin

Presents comprehensive overview of geologic development of Gulf of Mexico. Provides 

information regarding distribution of crustal types and relationship to overlying growthfault systems. 

Sarwar (2002) Northern Gulf of Mexico:

A Passive or Passive Active 

Margin?

Presents alternative model for the modern tectonic setting of northern Gulf of Mexico 

that includes the region in a right-lateral mega-shear extending eastward from the 

Pacific–North America Plate margin.

Sawyer et al. 

(1991)

The Crust Under the Gulf of 

Mexico Basin

Presents interpretations of the deep crustal structure of Gulf of Mexico based on 

compilation of regional seismic-reflection, seismic-refraction, gravity, magnetic, and 

subsidence techniques. Presents a map and cross sections constraining the depth to 

basement and locations of different types of crust.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-232 

Citation Title Description and Relevance to SSC

Thomas (1988) Early Mesozoic Faults of the 

Northern Gulf Coastal Plain in the 

Context of Opening of the Atlantic 

Ocean

Discusses role of Mesozoic faults in the opening of Gulf of Mexico and the coincidence 

of some of those faults (e.g., Alabama-Arkansas transform) to transform faults 

associated with the Paleozoic rifting that opened the Iapetan ocean.

Thomas (2006) Tectonic Inheritance at a 

Continental Margin

Presents interpretations of NW-trending transform faults in eastern Gulf of Mexico. 

Provides information on possible crustal source of September 10, 2006, M 5.8 

earthquake.

Wheeler and 

Frankel (2000)

Geology in the 1996 USGS 

Seismic-Hazard Maps, Central and 

Eastern United States

Discusses the geologic data used in development of USGS National Seismic Hazard 

Map source model (e.g., source geometries).

White (1980) Permian−Triassic Continental 

Reconstruction of the Gulf of 

Mexico−Caribbean Area

Presents kinematic model for the opening of Gulf of Mexico.

Growth Faults

Bradshaw and 

Watkins (1994)

Growth-Fault Evolution in Offshore 

Texas

Presents line drawing of seismic data across major growth-fault systems in northern 

Gulf of Mexico. Presents conceptual model for evolution of the growth-fault systems. 

Provides important constraints on the depth distribution, kinematic style, and origin. 

These characteristics contribute to the understanding of seismic potential of growth 

faults.

Dokka et al. (2006) Tectonic Control of Subsidence 

and Southward Displacement of 

Louisiana with Respect to Stable 

North America

Description of southern coastal Louisiana as part of a 7–10 km (4.3–6.2 mi.) thick 

allocthonous region detached from cratonic North America based on GPS data 

collected between 1995 and 2006. Describes a spatial association of post-1978 

earthquakes with the allocthonous region. Concludes that earthquakes result from 

internal deformation of the allocthon. Cites subsidence rate of ~7 mm/yr relative to 

mean sea level.

DuBar et al. (1991) Quaternary Geology of the Gulf of 

Mexico Coastal Plain

Provides description of Quaternary geology of Gulf of Mexico coastal plain of the U.S. 

Includes general discussion of fault activity due to movement on growth faults and 

man-induced seismicity associated with subsurface mineral withdrawal (oil, gas, and 

water).
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-233 

Citation Title Description and Relevance to SSC

Gagliano (2005) Effects of Earthquakes, Fault 

Movements, and Subsidence on 

the South Louisiana Landscape

Describes growth faulting on Louisiana coast and its possible relationship to 

earthquake activity. No firm conclusions regarding source of earthquakes in the region, 

but suggests that movement on growth faults is the causative mechanism. Does not 

include a discussion of creep vs. strike-slip behavior, and the implications to 

earthquake generation potential of growth faults.

Jackson (1982) Fault Tectonics of the East Texas 

Basin

Discussion of distribution, geometry, displacement history, and origin of Quaternary 

faulting in the East Texas basin, and implications to the siting of hypothetical high-level 

nuclear waste repositories. Concludes that none of the faults pose a seismic threat.

Karlo and Shoup 

(2000)

Classifications of Syndepositional 

Systems and Tectonic Provinces 

of the Northern Gulf of Mexico

Presents detailed overview of growth-fault systems in northern Gulf of Mexico, showing 

the style and relative ages of deformation. Provides important constraints on geometry 

and evolution of growth-fault systems.

Morton et al. 

(2001)

Shallow Stratigraphic Evidence of 

Subsidence and Faulting Induced 

by Hydrocarbon Production in 

Coastal Southeast Texas

Describes effects of growth faulting in coastal Texas and its relationship to 

hydrocarbon production. Concludes that fault activity is related to hydrocarbon 

withdrawal.

Peel et al. (1995) Genetic Structural Provinces and 

Salt Tectonics of the Cenozoic 

Offshore U.S. Gulf of Mexico: A 

Preliminary Analysis

Provides overview of Gulf of Mexico growth-fault domain and provinces. Emphasizes 

the linked structural system of updip extension and downdip compression, and 

illustrates the development of the Sigsbee salt nappe.

Rowan et al. 

(1999)

Salt-Related Fault Families and 

Fault Welds in the Northern Gulf of 

Mexico

Presents a classification of different types of salt-related growth faults in northern Gulf 

of Mexico. Provides information on kinematics and origin of growth faults. 

Watkins and 

Buffler (1996)

Gulf of Mexico Deepwater Frontier 

Exploration Potential

Describes deepwater environments of entire Gulf of Mexico that may contain significant 

hydrocarbon reserves. Shows cross section across Florida escarpment in the vicinity of 

September 10, 2006, M 5.8 earthquake. Provides information on the geologic 

environment of the earthquake.

Watkins et al. 

(1996)

Bipolar Simple-Shear Rifting 

Responsible for Distribution of 

Mega-salt Basins in Gulf of 

Mexico?

Describes relationship between basement structure (basins and fracture zones) and 

the setting of Louann ―mother‖ salt in Gulf of Mexico. Shows a diagram emphasizing 

importance of NW-trending fracture zones in compartmentalizing salt accumulation and 

the development of salt basins.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-234 

Citation Title Description and Relevance to SSC

Watkins et al. 

(1996)

Structure and Distribution of 

Growth Faults in the Northern Gulf 

of Mexico OCS

Overall description with seismic data examples of growth-fault systems of the Gulf of 

Mexico and Gulf coastal plain. Provides constraints on the map and cross-sectional 

geometry and location of growth faults, their depth extent and their relationship to 

underlying salt.

Wheeler (1999b) Fault Number 924, Gulf-Margin 

Normal Faults, Texas, Quaternary 

Fault and Fold Database of the 

United States

Provides description of evidence and characteristics of Quaternary faulting in the 

coastal plain region of Texas, Louisiana, and Alabama. Concludes that fault activity is 

due to three driving forces: movement over mobile salt and shale, mineral extraction, 

and flexure of continental margin due to sediment loading in Gulf of Mexico.

Wu et al. (1990) Allochthonous Salt, Structure and 

Stratigraphy of the North-Eastern 

Gulf of Mexico. Part II: Structure

Presents line drawing of seismic data across major growth-fault systems in northern 

Gulf of Mexico. Presents a conceptual model for evolution of growth-fault systems. 

Provides important constraints on depth distribution, kinematic style, and origin. These 

characteristics contribute to the understanding of the seismic potential of growth faults.

Seismic Source Models

American 

Petroleum Institute 

(2000)

Recommended Practice for 

Planning, Designing and 

Constructing Fixed Offshore 

Platforms—Working Stress Design 

(API RP 2A-WSD)

Provides guidance for seismic engineering design criteria for fixed structures in 

northern offshore Gulf of Mexico. Places the region in ―Zone 0,‖ reflecting a design 

acceleration of 0.2 g.

Frankel et al.

(2002)

Documentation for the 2002 

Update of the National Seismic 

Hazard Maps

Presents seismic hazard model and seismic source characterization for the U.S. The 

northern Gulf of Mexico background source is assigned a maximum earthquake 

magnitude of M 7.5.

Johnston and 

Nava (1990)

Seismic-Hazard Assessment in the 

Central United States

Presents a seismic source zonation for Central U.S., including northern Gulf of Mexico 

coastal region. Characterizes Gulf coastal plain and northern offshore Gulf of Mexico 

as aseismic.

Johnston et al. 

(1994)

The Earthquakes of Stable 

Continental Regions

Presents maps and information constraining ages and types of crustal domains (e.g., 

extended vs. non-extended continental crust, oceanic vs. continental crust, etc.) in 

northern Gulf of Mexico and in Gulf coastal plain. These domains and seismotectonic 

characteristics provide some precedence for characteristics of an updated seismic 

source model for the region.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-235 

Citation Title Description and Relevance to SSC

Petersen et al. 

(2008)

Documentation for the 2008 

Update of the United States 

National Seismic Hazard Maps

Presents boundary of Mesozoic/Paleozoic crust in southern CEUS.

Potential ALM Source Zone

Ambraseys (1988) Engineering Seismology Presents magnitude-bound relation for liquefaction.

Calais et al. (2006) Deformation of the North American 

Plate Interior from a Decade of 

Continuous GPS Measurements

Uses regionally extensive continuous GPS stations throughout CEUS to determine the 

deformation field within the CEUS. No anomalies are present within the project study 

region, but it should be noted that there are very few stations within this region.

Cox (1994) Analysis of Drainage-Basin 

Symmetry as a Rapid Technique 

to Identify Areas of Possible 

Quaternary Tilt-Block Tectonics: 

An Example from the Mississippi 

Embayment

Uses spatial distribution of drainage basin asymmetry to hypothesize existence of 

active faults and block tilting in Saline, Ouachita, and Arkansas River area. 

Cox (2002) Investigation of SeismicallyInduced Liquefaction in the 

Southern Mississippi Embayment

NEHRP final report presenting results of paleoliquefaction trenching in Ashley and 

Desha Counties, Arkansas.

Cox (2009) Investigations of SeismicallyInduced Liquefaction in Northeast 

Louisiana

NEHRP technical report documenting preliminary results for the Louisiana liquefaction 

fields investigated by Cox. Identifies two sand blows in one field and one sand blow in 

another. Radiocarbon dating can only loosely constrain minimum ages, essentially 

providing no constraints on timing of sand blows. Cox notes that some of the blow-like 

features observed in aerial photos in Louisiana are eolian deposits. 

Cox and Gordon 

(2008)

Sand Blows on Late Quaternary 

Surfaces in Northeast Louisiana

Abstract presenting preliminary results of paleoliquefaction investigations identifying 

sand blows in NE Louisiana.

Cox and Larsen 

(2004)

Investigation of SeismicallyInduced Liquefaction in the 

Southern Mississippi Embayment

NEHRP final report presenting results of paleoliquefaction trenching in Ashley and 

Desha Counties, Arkansas.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-236 

Citation Title Description and Relevance to SSC

Cox and Van 

Arsdale (1997)

Hotspot Origin of the Mississippi 

Embayment and Its Possible 

Impact on Contemporary 

Seismicity

Hypothesizes role of the Bermuda hotspot in the formation of Mississippi embayment 

and suggests that the hotspot may have significantly weakened the lithosphere. Also 

notes correlation between hotspot tracks and the Charleston, South Carolina and the 

St. Lawrence rift system, regions of moderate to large earthquakes. 

Cox et al. (2000) Quaternary Faulting in the 

Southern Mississippi Embayment 

and Implications for Tectonics and 

Seismicity in an Intraplate Setting

Hypothesizes existence of a Quaternary-active Saline River fault zone based on a 

concentration of historical seismicity and the apparent deformation of PliocenePleistocene deposits in road cuts. 

Cox, Forman, et 

al. (2002)

New Data of Holocene Tectonism 

in the Southern Mississippi 

Embayment

Abstract presenting preliminary results of paleoliquefaction trenching in Ashley County, 

Arkansas.

Cox, Harris, et al. 

(2004)

More Evidence for Young 

Tectonism Along the Saline River 

Fault Zone, Southern Mississippi 

Embayment

Abstract presenting preliminary results and interpretation of S-wave reflection profiles 

of Saline River fault zone and the relation of these structures to preliminary sand-blow 

dates.

Cox, Larsen, and 

Hill (2004)

More Paleoliquefaction Data from 

Southeastern Arkansas: 

Implications for Seismic Hazards

Abstract presenting preliminary results of paleoliquefaction trenching in Ashley and 

Desha Counties, Arkansas.

Cox, Larsen, 

Forman, et al. 

(2004)

Preliminary Assessment of Sand 

Blows in the Southern Mississippi 

Embayment

Presents compilation of all paleoliquefaction trenching and dating done through 2004 

within the Saline River area. Hypothesizes a correlation between source of liquefaction 

and Cox’s proposed Quaternary deformation features within Saline River area.

Cox et al. (2007) Seismotectonic Implications of 

Sand Blows in the Southern 

Mississippi Embayment

Presents compilation of paleoliquefaction trenching and dating done from 2004 through 

2007 within Saline River area. Also presents results of geotechnical studies of sandblow host deposits and the implications for that data with respect to the amount of 

ground shaking required to cause liquefaction. Hypothesizes a correlation between 

source of liquefaction and Cox’s proposed Quaternary deformation features within 

Saline River area.

Cushing et al. 

(1964)

General Geology of the Mississippi 

Embayment

Provides general discussion of geology and structure of Mississippi embayment.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-237 

Citation Title Description and Relevance to SSC

Ewing (1991) Structural Framework Provides general discussion of tectonic and geologic structures of Gulf of Mexico 

region. 

Garrote et al. 

(2006)

Tectonic Geomorphology of the 

Southeastern Mississippi 

Embayment in Northern 

Mississippi, USA

Uses the spatial distribution of drainage basin asymmetry to hypothesize the existence 

of active faults.

Gordon and Cox 

(2008)

Recurrent Mesozoic and Cenozoic 

Faulting along the Southern 

Margin of the North American 

Craton

Abstract hypothesizing that the Alabama-Oklahoma transform and related structures 

may be the tectonic feature that is source of strong ground shaking that caused the 

Arkansas liquefaction features and the deformed Saline River fault zone deposits.

Green et al. (2005) Engineering Geologic and 

Geotechnical Analysis of 

Paleoseismic Shaking Using

Liquefaction Effects: Field 

Examples

Presents examples of how to back-calculate ground motions (e.g., earthquake 

magnitudes) from paleoliquefaction data.

Harry and 

Londono (2004)

Structure and Evolution of the 

Central Gulf of Mexico Continental 

Margin and Coastal Plain, 

Southeast United States

Identifies location of the potential Precambrian, passive-margin, transform plate 

boundary that trends from Alabama to Oklahoma. Uses gravity modeling, industry 

seismic data, and well data to construct transects across the transform.

Hosman (1996) Regional Stratigraphy and 

Subsurface Geology of Cenozoic 

Deposits, Gulf Coastal Plain, 

South-Central United States

Provides general discussion of structure and geology of Gulf coastal plain and 

Mississippi embayment from the perspective of an aquifer analysis.

Liang and 

Langston (2009)

Three-Dimensional Crustal 

Structure of Eastern North America 

Extracted from Ambient Noise

Maps three-dimensional shear-wave velocity throughout CEUS and discusses 

presence of rifting episodes apparent in the data.

Mickus and Keller 

(1992)

Lithospheric Structure of the 

South-Central United States

Constructs a N-S cross section from Gulf of Mexico to Missouri along the TexasLouisiana border using primarily gravity data but qualitatively including seismicreflection, well log, and geologic data.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-238 

Citation Title Description and Relevance to SSC

Murray (1961) Geology of the Atlantic and Gulf 

Coastal Province of North America

Provides general discussion of structure and geology of Gulf of Mexico region.

Obermeier and 

Pond (1999)

Issues in Using Liquefaction 

Features for Paleoseismic Analysis

Summary paper describes concerns about the use of paleoliquefaction data as 

evidence of strong ground shaking.

Olson et al.

(2005a)

Geotechnical Analysis of 

Paleoseismic Shaking Using 

Liquefaction Features: A Major 

Updating

Presents methodology for how to back-calculate ground motions (e.g., earthquake 

magnitudes) from paleoliquefaction data.

Olson et al. 

(2005b)

Revised Magnitude Bound 

Relation for the Wabash Valley 

Seismic Zone of the Central United 

States

Presents an updated magnitude-bound relationship for paleoliquefaction in CEUS.

Salvador (1991) Origin and Development of the 

Gulf of Mexico Basin

Provides general discussion of the structure of Gulf of Mexico region, as well as the 

tectonic history of the Gulf. Identifies location of Alabama-Oklahoma transform.

Saucier and Smith 

(1986)

Geomorphic Mapping and 

Landscape Classification of the 

Ouachita and Saline River Valleys, 

Arkansas

Presents detailed mapping of terraces within the Ouachita and Saline River valleys. 

Dating and terrace classification presented in this report was used by others (e.g., Cox, 

1994) to correlate terraces in the basins.

Al-Shukri et al. 

(2005)

Spatial and Temporal 

Characteristics of Paleoseismic 

Features in the Southern Terminus 

of the New Madrid Seismic Zone in 

Eastern Arkansas

Presents preliminary results of investigation of liquefaction features further discussed 

by Tuttle et al. (2006).

Tuttle (2001) The Use of Liquefaction Features 

in Paleoseismology: Lessons 

Learned in the New Madrid 

Seismic Zone, Central United 

States

Summary paper describing use of paleoliquefaction data within New Madrid seismic 

zone to constrain paleo-earthquakes within the zone.
Table D-7.3.9 Data Summary 

Extended Continental Crust Zone—Gulf Coast 

D-239 

Citation Title Description and Relevance to SSC

Tuttle, Schweig, et 

al. (2002)

The Earthquake Potential of the 

New Madrid Seismic Zone

Presents summary of paleoseismic history of New Madrid seismic zone and the areas 

of liquefaction associated with New Madrid earthquakes.

Tuttle et al. (2006) Very Large Earthquakes Centered 

Southwest of the New Madrid 

Seismic Zone 5,000–7,000 Years 

Ago

Presents results of paleoliquefaction trenching and dating in central-eastern Arkansas. 

Identifies at least two different sets of sand blows at ~5,500 and 6,800 yr BP.

Wheeler (2005) Known or Suggested Quaternary 

Tectonic Faulting, Central and 

Eastern United States—New and 

Updated Assessments for 2005

Presents summary discussion of the Arkansas paleoliquefaction features discovered 

by Cox, and Cox’s hypothesized Saline River fault zone.

Zhang et al. 

(2009b)

Tomographic Pn Velocity and 

Anisotropy Structure in the Central 

and Eastern United States

Maps Pn (upper mantle) velocity structure throughout CEUS and hypothesizes at a 

potential correlation between edges of high-velocity zones and the locations of 

intraplate seismic zones. 
Table D-7.3.12 Data Summary 

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D-240 

Citation Title Description and Relevance to SSC

General for Region

Atekwana (1996) Precambrian Basement Beneath the 

Central Midcontinent United States as 

Interpreted from Potential Field Data

References previous geologic and geophysical investigations (Hinze et al., 

1975; Klasner et al., 1982; Bickford et al., 1986; Van Schmus, 1992) that 

reveal that Precambrian basement within the Midcontinent region consists of 

several provinces that formed before 900 million years ago (Ma), including 

the Superior province (2.7 billion years ago [Ga]); Penokean province (1.83–

1.88 Ga); Central Plains province (1.63–1.7 Ga); Eastern Granite-Rhyolite 

province (1.42–1.5 Ga); Midcontinent rift system (1.1–1.0 Ga); and Grenville 

province (0.8–1.1 Ga). 

Li et al. (2009) Spatiotemporal Complexity of 

Continental Intraplate Seismicity:

Insights from Geodynamic Modeling

and Implications for Seismic Hazard 

Estimation

This paper explores the complex spatiotemporal patterns of intraplate 

seismicity using a 3-D viscoelasto-plastic finite-element model. The model 

simulates tectonic loading, crustal failure in earthquakes, and coseismic and 

postseismic stress evolution. For a laterally homogeneous lithosphere with 

randomly prespecified perturbations of crustal strength, the model predicts 

various spatiotemporal patterns of seismicity at different time scales: spatial 

clustering in narrow belts and scattering across large regions over hundreds 

of years, connected seismic belts over thousands of years, and widely 

scattered seismicity over tens of thousands of years.

The orientation of seismic belts coincides with the optimal failure directions 

associated with the assumed tectonic loading. Stress triggering and migration 

cause spatiotemporal clustering of earthquakes. Fault weakening can lead to 

repeated earthquakes on intraplate faults. The predicted patterns vary with 

the weakening history. Clusters of large intraplate earthquakes can result 

from fault weakening and healing, and the clusters can be separated by long 

periods of quiescence. The complex spatiotemporal patterns of intraplate 

seismicity predicted in this simple model suggest that assessment of 

earthquake hazard based on the limited historical record may be biased 

toward overestimating the hazard in regions of recent large earthquakes and 

underestimating the hazard where seismicity has been low during the 

historical record.
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-241 

Citation Title Description and Relevance to SSC

Liang and 

Langstrom (2009)

Three-Dimensional Crustal Structure of 

Eastern North America Extracted from 

Ambient Noise

Group velocity dispersion curves of surface waves extracted from ambient 

seismic noise are inverted to find 3-D shear-wave structure of the crust 

beneath eastern North America. The 3-D model consists of one sediment 

layer and another six layers with fixed depths of 5, 7.5, 10, 15, 25, and 43 km

(3, 4.7, 6.2, 9.3, 15.5, and 26.7 mi.). Almost all failed ancient rifting 

earthquakes (e.g., the Reelfoot rift, Ouachita triple junction, and Midcontinent 

rift) and rifting-related earthquakes (e.g., the Ozark uplift and Nashville dome) 

are associated with high-velocity bodies in the middle and lower crust. 

Results suggest the existence of a triple-junction-like high-velocity body 

centered around the New Madrid and Wabash Valley seismic zones (NMSZ 

and WVSZ), with the Reelfoot rift, the Ozark uplift, and the Nashville dome 

being on its SW, NW, and SE arms, respectively. The Appalachian 

Mountains are characterized by high-velocity upper crust underlain with 

relatively low-velocity middle and lower crust. All major seismic zones are 

associated with either divergent or convergent events. The NMSZ and WVSZ 

are clearly associated with the failed Reelfoot rift. Both the eastern 

Tennessee seismic zone and the Ouachita orogen are located along 

convergent boundaries.

Marshak and 

Paulsen (1997)

Structural Style, Regional Distribution, 

and Seismic Implications of Midcontinent 

Fault-and-Fold Zones, United States

Paleozoic/Mesozoic strata of the U.S. continental interior contain arrays of 

steeply dipping faults and associated monoclinal forced folds. This paper 

hypothesizes that these structures were initiated during episodes of 

Proterozoic extensional tectonism. Two sets identified: one trending N-NE 

and the other trending W-NW. These sets break upper crust into blocks that 

cause slight movements in response to changes in stress state. Many 

W-NW-trending fault and fold zones link along strike to define 

semicontinuous NW-trending deformation corridors. One of these, the 200 

km (124 mi.) wide Transamerican tectonic zone, traces over 2,500 km (1,553 

mi.) from Idaho to South Carolina. Seismicity most frequently occurs where 

N-NE-trending fault and fold zones cross the Transamerican tectonic zone, 

suggesting that intracratonic strain in the U.S. currently concentrates at or 

near intersecting fault zones within this corridor.
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-242 

Citation Title Description and Relevance to SSC

NICE Working 

Group (2007)

Reinterpretation of Paleoproterozoic 

Accretionary Boundaries of the NorthCentral United States Based on a New 

Aeromagnetic-Geologic Compilation

Presents a new tectonic province map, based on interpretation of a new 

aeromagnetic compilation, published geologic maps, and geochronologic 

data. The map shows a progressive accretion of juvenile arc terranes from 

ca. 1,900–1,600 Ma. The Spirit Lake tectonic zone, characterized by a sharp 

magnetic discontinuity that marks the southern limit of Archean and 

Penokean-interval rocks, is interpreted to represent an eastern analog of the 

Cheyenne belt suture zone in southern Wyoming. The data reveal a 

progressive tectonic younging to the south as the Laurentian craton grew 

southward and stabilized during the Proterozoic. Late Mesoproterozoic rift 

magmatism produced pronounced geophysical anomalies, indicating strong 

but localized crustal modification. Little tectonism has occurred here in the 

last billion years, providing a preserved record of the Precambrian evolution 

of the continental U.S. lithosphere.

Sims et al. (2005) Preliminary Precambrian Basement 

Structure Map of the Continental United 

States—An Interpretation of Geologic 

and Aeromagnetic Data

The systematics of major regional post-assembly Precambrian basement 

structures throughout the continental U.S. point to a common causal 

mechanism for their development. The model presented accords with 

geodynamic models for North and South American Plate motions, based on 

seismic anisotropy beneath the continents that invoke mechanical coupling 

and subsequent shear between the lithosphere and asthenosphere such that 

a major driving force for plate movement is deep-mantle flow.

Two orthogonal sets of shear zones and faults are predominant in the 

continent: (1) NE-striking, partitioned ductile shear zones, and (2) NWtrending strike-slip ductile-brittle faults. The NE-striking shear zones are 

interpreted as resulting from NW-SE shortening, apparently formed during 

the interval 1.76–1.70 Ga. The NW-trending (1.7–1.5 Ga) transcurrent fault 

system consists of W-NW to NW synthetic faults and northerly trending 

antithetic transfer faults; it is attributed to transpressional-transtensional 

deformation, i.e., strike-slip deformation that deviates from simple shear 

because of a component of shortening or extension orthogonal to the 

deformation zone. The NE- and NW-oriented shears and faults mimic 

orthogonal teleseismic images of the upper mantle. These structures were 

reactivated during the Mesoproterozoic and later times.

The kinematics of regional basement structures within the continental U.S.

suggest that deformation since at least early Proterozoic time has been 

predominantly transpressional. Transcurrent lithospheric structures formed 
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-243 

Citation Title Description and Relevance to SSC

during Proterozoic mantle deformation are oriented obliquely to the SW 

(absolute) motion of the North American Plate. Stress caused by traction 

between the asthenosphere and lithosphere during the SW drift focused on 

preexisting block boundaries repeatedly have reactivated basement zones of 

weakness, thus localizing sedimentation, magmatism, and generation of ore

deposits.

Whitmeyer and 

Karlstrom (2007)

Tectonic Model for the Proterozoic 

Growth of North America

Presents a plate-scale model for the Precambrian growth and evolution of the 

North American continent. The core of the North American continent 

(Canadian shield) came together in the Paleoproterozoic (2.0–1.8 Ga) by 

plate collisions. The thick, buoyant, and compositionally depleted mantle 

lithosphere that now underlies North America, although dominantly of 

Archean age, took its present shape by processes of collisional orogenesis 

and likely has a scale of mantle heterogeneity similar to that exhibited in the 

overlying crust.

In marked contrast, lithosphere of southern North America (much of the 

continental U.S.) was built by progressive addition of a series of dominantly 

juvenile volcanic arcs and oceanic terranes accreted along a long-lived 

southern (present coordinates) plate margin. The lithospheric collage that 

formed from dominantly juvenile terrane accretion and stabilization (1.8–1.0 

Ga) makes up about half of the present-day North American continent. 

Throughout (and as a result of) this long-lived convergent cycle, mantle 

lithosphere below the accretionary provinces was more hydrous, fertile, and 

relatively weak compared to mantle lithosphere under the Archean core.

Zhang et al. 

(2009b)

Tomographic Pn Velocity and 

Anisotrophy Structure in the Central and 

Eastern United States

Inversion of tomographic data to map the velocity and anisotropy structure of 

the lithospheric mantle in the CEUS. The Pn tomographic model shows a 

broad region of very fast velocity under the North American craton (northern 

CEUS) and significant lateral variation within the rest of the CEUS. The 

surface locations of the major intraplate seismic zones are near the edges of 

high-velocity anomalies, which is consistent with the notion that stress 

accumulation—and hence focused deformation—is likely to occur at the 

rheological boundaries around the rigid lithospheric root. Ancient rifts show 

no clear correlation to the low-velocity anomalies in the lithospheric mantle. 
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-244 

Citation Title Description and Relevance to SSC

Geophysical Anomalies

Commerce Geophysical Lineament (CGL)

Hildenbrand and 

Hendricks (1995) 

Langenheim and 

Hildenbrand (1997)

Geophysical Setting of the Reelfoot Rift 

and Relations Between Rift Structures 

and the New Madrid Seismic Zone

Commerce Geophysical Lineament—Its 

Source, Geometry, and Relation to the 

Reelfoot Rift and New Madrid Seismic 

Zone

The Commerce geophysical lineament (CGL) is a NE-trending feature that 

extends from NE Arkansas to at least Vincennes, Indiana. This lineament 

comprises a series of linear, NE-trending magnetic and gravity anomalies 

traceable for more than 384 km (239 mi.). This feature has been interpreted 

to consist of en echelon faults and igneous intrusions in the basement that 

are related to the Neoproterozoic to early Paleozoic Reelfoot rift; however, it

is postulated to have an even older ancestry.

Hildenbrand et al. 

(2002)

The Commerce Geophysical Lineament 

and Its Possible Relation to 

Mesoproterozoic Igneous Complexes 

and Large Earthquakes in the Central 

Illinois Basin

New inversions of existing magnetic and gravity data provide information on 

upper-crustal structures in the central Illinois basin. Results of 2-D and 3-D 

inversion techniques suggest that the source of the CGL follows the SE 

boundary of a dense and magnetic NE-trending igneous center named the 

Vincennes igneous center. The buried Vincennes igneous center is 

suggested to be the source of inferred volcanic units of the Centralia 

sequence and is related to a rifted margin or a Proterozoic plate boundary.

Comparing gravity and magnetic fields of the Vincennes igneous center with 

those of the St. Francois Mountains igneous center in SE Missouri suggests 

that the associated sources in each region are similar in composition and 

perhaps origin. The CGL that is defined in this region by a 5–10 km (3–6 mi.) 

wide deformation zone appears to have influenced the structural 

development of the Vincennes igneous center. The Commerce deformation 

zone evolved in the Mesoproterozoic (1.1–1.5 Ga) as a major cratonic 

rheological boundary and has been the focus of episodic reactivation related 

to varying stress regimes throughout its history.
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-245 

Citation Title Description and Relevance to SSC

South-Central Magnetic Lineament (SCML)

Hildenbrand et al. 

(1983)

Digital Magnetic-Anomaly Map of Central 

United States: Description of Major 

Features

Describes a regional W-NW-trending lineament characterized by a band of 

steep magnetic gradients that coincides with a prominent Bouguer anomaly 

and the general position of the Cottage Grove fault system, Ste. Genevieve 

fault zone, and Hicks dome.

Kolata and 

Hildenbrand (1997)

Structural Underpinnings and 

Neotectonics of the Southern Illinois 

Basin: An Overview

Seismic-reflection profiles show that a layered Precambrian sequence in the 

upper crust in the southern Illinois basin terminates abruptly at this boundary.

St. Charles Lineament (SCL)

Harrison and 

Schultz (2002)

Tectonic Framework of the Southwestern 

Margin of the Illinois Basin and Its 

Influence on Neotectonism and 

Seismicity

The St. Charles lineament (SCL) is the informal name given to an alignment 

of geochemical and geophysical features that extends from SW Ontario to SE 

Oklahoma. A paleotectonic history of the SCL is difficult to decipher because 

many structural features related to the lineament lie beneath the alluvial plain 

of the Missouri River. There is no apparent stratigraphic offset of Paleozoic 

strata across the SCL, but a zone of conjugate strike-slip faults of probable 

late Mississippian to early Pennsylvanian age is exposed along the SCL near 

Acton, Illinois. These faults do not displace overlying Pleistocene loess. 

Harrison and Schultz postulate two lines of weak and nondefinitive evidence 

for neotectonic activity along the SCL: (1) the Missouri River bends to a NE 

course upon encountering the SCL, suggesting a tectonic control on the river, 

which alternatively could reflect the influence of an older deformational fabric; 

and (2) the postdepositional tilting of Miocene (?) Grover Gravel may be due 

to faulting along the SCL. 

Hildenbrand and 

Kucks (1992) 

Hildenbrand and 

Hendricks (1995)

Filtered Magnetic Anomaly Maps of 

Missouri

Geophysical Setting of the Reelfoot Rift 

and Relations Between Rift Structures 

and the New Madrid Seismic Zone

This lineament is defined by a regional neodymium (Nd) isotopic boundary 

that coincides with linear geophysical trends along most of its length. 
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-246 

Citation Title Description and Relevance to SSC

Mateker et al. 

(1966)

Geophysical Evidence for a Northeast 

Crustal Lineament near St. Louis

Notes that the SCL is parallel to the Reelfoot rift and the New Madrid seismic 

zone as well as to a trend of minor earthquake activity in the St. Louis–St. 

Charles area. 

Sims (1990) 

Sims and Peterman 

(1986)

Precambrian Basement Map of the 

Northern Midcontinent, U.S.A.

Early Proterozoic Central Plains Orogen: 

A Major Buried Structure in the NorthCentral United States

These publications map the boundary between Paleoproterozoic 

metamorphic/granitoid rocks and Mesoproterozoic rhyolitic/granitic rocks 

along the SCL, which they interpret as the margin of a Paleoproterozoic 

Central Plains orogen. 

Sims et al. (1987) Geology and Metallogeny of Archean 

and Proterozoic Basement Terranes in 

the Northern Midcontinent, U.S.A.—An 

Overview

Suggests that the margin coincident with the SCL is an ancient suture zone.

Van Schmus et al. 

(1996)

Proterozoic Geology of the East-Central 

Midcontinent Basement

Interprets the Nd isotopic boundary as a Paleoproterozoic crustal margin that 

separates late Paleoproterozoic lower-crustal rocks to the NW from early 

Mesoproterozoic lower-crustal rocks to the SE.

Seismicity

(Note: The Anna, Ohio, and Northeast Ohio seismicity zones are both discussed in the section on Paleoliquefaction Studies.)

Bakun and Hopper 

(2004a)

Catalog of Significant Historical 

Earthquakes in the Central United States

Modified Mercalli intensity assignments are used to estimate source locations 

and moment magnitude, M, for 18 nineteenth-century and 20 early twentiethcentury earthquakes in the central U.S. for which estimates of M are 

otherwise not available. Four M > 5.0 central U.S. historical earthquakes 

have occurred: in Kansas in 1867, Nebraska in 1877, Oklahoma in 1882, and 

Kentucky in 1980.

Hinze and 

Hildenbrand (1988)

The Utility of Geopotential Field Data in 

Seismotectonic Studies in the Eastern 

United States

The Sharpsburg earthquake of July 27, 1980 (mb = 5.1) originated at a depth 

of 15 km (9.3 mi.), in the vicinity of a prominent gravity gradient and complex 

magnetic anomalies caused by mafic Grenvillian (Precambrian) basement 

rocks, suggesting that this moderate-sized earthquake originated in the 

reactivation of a Precambrian zone of weakness.
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

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Citation Title Description and Relevance to SSC

Joeckel et al. 

(2003)

Earthquake History, Seismicity, and 

Related Tectonics in Nebraska

Nebraska experienced two significant earthquakes in 2002: a June 20, M 3.5 

earthquake and a November 3, M 4.3 earthquake. About 50 earlier 

earthquakes, almost all M < 4, have occurred in Nebraska since 1867. A 

cluster of microearthquakes reported in 1979 in Red Willow County in SW 

Nebraska may have been related to petroleum production. Other 

earthquakes occurred at about the same time in SE Nebraska along the 

Nemaha uplift, a major N-S structure extending into basement rocks. Larger 

earthquakes seem to be related to the periodic release of accumulated 

regional stresses in major structures (Nemaha uplift, Midcontinent rift) and 

around proposed sutures resulting from the Proterozoic (1.8–1.6 Ga) 

accretion of island arcs across the region. 

Structures

Anton Escarpment, Colorado

Wheeler (2005) Known or Suggested Quaternary 

Tectonic Faulting, Central and Eastern 

United States—New and Updated 

Assessments for 2005

Classifies the Anton escarpment as a Class C feature. The NE-facing 

topographic escarpment is 20–30 m high. A trench excavated across the 

escarpment in 2004 did not expose any faults associated with the 

topographic feature; no significant vertical offset exists across the 

escarpment, as indicated by stratigraphy correlated between the trench and 

nearby boreholes. If the feature is a fault-line scarp, displacement has not 

occurred for a long time. The lack of a demonstrated fault-related origin for 

the escarpment justifies the Class C classification. 

Brockton-Froid Fault Zone, Montana

Crone and Wheeler 

(2000)

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic

Features in the Central and Eastern 

United States, East of the Rocky 

Mountain Front

Classifies the Brockton-Froid fault zone as Class B. 
Table D-7.3.12 Data Summary 

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D-248 

Citation Title Description and Relevance to SSC

Wheeler (1999a) Fault Number 707, Brockton-Froid Fault 

Zone, Quaternary Fault and Fold 

Database of the United States

Classified as a Class B fault, this feature is located in the glaciated plains of 

NE Montana. The fault zone contains Quaternary deformation; the 

deformation may not have occurred by faulting, but it also may indicate a 

basement fault that was reactivated during glacial or postglacial time. The 

linear fault zone is about 54 km (33.5 mi.) long and does not have an obvious 

fluvial, glacial, or glaciotectonic origin. The origin of the feature is enigmatic.

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

The Brockton-Froid fault needs further study to determine whether it is a 

Quaternary tectonic fault. Late Wisconsinan outwash and Quaternary 

sheetwash alluvium and colluvium occupy a straight zone a few hundred 

meters wide and at least 53 km (33 mi.) long along the trace of the inferred 

fault zone. The narrow zone is bounded by till on both sides. Data from lines 

of auger holes show that the Quaternary deposits inside the zone are thicker 

than the adjacent deposits. The 1:24,000-scale topographic maps along the 

zone show its geomorphic expression as alignments of straight stream 

segments and valleys, elongated hills and ridges, and large, closed 

depressions; the zone descends to cross streams and rises to cross 

interfluves without obvious deflection. The authors reference Colton (1963a, 

1963b), who interpreted the zone as a fault-bounded feature—yet nowhere 

are faults exposed that juxtapose outwash and till. Structure-contour and 

isopach maps of Paleocene lignites at depths of 240 m and less do not show 

detectable offset across the zone (Hardie and Arndt, 1988; Biewick et al., 

1990). If the straight zone is bounded by faults, it is unclear whether the faults 

penetrate deeply enough into bedrock to pose a seismic threat.

Wong et al. (2005) Probabilistic Earthquake Hazard Maps 

for the State of Montana

The Brockton-Froid fault zone was characterized as a possible fault source 

(probability of activity of 0.5) in a statewide seismic hazard study conducted 

for the State of Montana. The map data and length were from M. Stickney of 

the Montana Bureau of Mines and Geology (digital shape-files, May 1, 2002, 

to S. Olig, URS) after recent mapping by Bergantino and Wilde (1998a, 

1998b), which includes a possible NE extension near Medicine Lake. 

Subsurface data is ambiguous with regard to the depth extent of this 

enigmatic structure and its sense of slip (Crone and Wheeler, 2000). 

Additionally, slip may have been related to postglacial relaxation and, if so, it 

may no longer be as active; thus the authors assigned a lower probability of 

activity. Slip rates are based on one or two possible post–late Wisconsinan

(<40 ka) earthquakes (Crone and Wheeler, 2000).
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Cape Girardeau Fault System, Missouri

Harrison and 

Schultz (2002)

Tectonic Framework of the Southwestern 

Margin of the Illinois Basin and Its 

Influence on Neotectonism and 

Seismicity

The Cape Girardeau fault system, which is a continuation of the Simms 

Mountain fault system, consists of numerous branching and anastomosing, 

dominantly NW-striking, near-vertical faults. Although NE- and N-NW-striking

faults are less common, they appear to show evidence for the most recent 

deformation. There are rhomb-shaped pull-apart graben related to strike-slip 

faulting that can be divided into three groups: (1) those that contain only 

Paleozoic rocks, (2) those that contain upper Cretaceous and lower Tertiary 

formations, and (3) those that contain Quaternary strata. 

Unequivocal evidence of faulting of Quaternary gravel has been observed in 

a quarry and roadcut at the SE end of the fault system near its intersection 

with the Commerce geophysical lineament. Results of recent trenching show 

evidence of Quaternary faulting, possibly post-Sangamon in age. Unfaulted 

Peoria Loess (late Wisconsinan in age) and possibly Roxana Silt overlie the 

fault and graben fill. The authors interpret the Quaternary deformation to 

have formed under E-NE horizontal maximum principal stress. They favor 

erosion and fill as an alternative to the finding by Tuttle, Chester, et al. (1999) 

of a source of possible faulting in Quaternary gravel discovered on part of the 

Cape Girardeau fault system approximately 14.5 km (9 mi.) to the NW.

Wheeler (2005) Known or Suggested Quaternary 

Tectonic Faulting, Central and Eastern 

United States—New and Updated 

Assessments for 2005

Classifies the Slinkard quarry graben in Missouri as a Class A feature, noting 

that faults that bound the graben or are near it have undergone multiple 

periods of movement, including pre-Cenozoic, Paleocene, and at least two 

periods in the Quaternary, with the youngest being post-Sangamon Geosol 

(< 130 ka) and pre-Wisconsinan loess. The NW margin of the graben 

juxtaposes Quaternary gravel against late Tertiary Mounds Gravel. The fault 

on the NW margin strikes N35°–40°E and dips approximately 74°SE. Mounds 

Gravel in the footwall has been rotated to dip 54°–85°E, with strike parallel to 

the fault. The faults are assigned to a slip-rate category of less than 0.2 

mm/yr. The sense of movement is normal dextral; the graben is interpreted to 

be a pull-apart graben in a dextral strike-slip system. The length of the 

Slinkard quarry graben is unknown, but the NW margin fault is at least 180 m 

long.
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Citation Title Description and Relevance to SSC

Criner Fault, Oklahoma

Hanson et al. 

(1997)

Quaternary Deformation Along the Criner 

Fault, Oklahoma: A Case Study for 

Evaluating Tectonic Versus Landslide 

Faulting

This study summarizes field investigations at a locality (a natural stream 

exposure) along the Criner fault where deformation of late Pleistocene 

alluvium had been suggested as evidence for Quaternary faulting on the 

Criner fault, which is part of the 310 km (193 mi.) long Meers-Duncan-Criner 

fault system. Excavation and detailed mapping of the exposure, in which a 

steep shear zone juxtaposes Quaternary alluvium against bedrock, provided 

evidence to indicate that the deformation was due to landsliding. 

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Summarizes studies that evaluated possible evidence for Quaternary 

deformation on the Criner fault. A topographic and vegetation lineament, a 

linear hill, and scarps 0.3–1.0 m high along the hill front and across gullies 

suggested possible Quaternary movement. This study cites the results of 

Hanson et al. (1997) that the preferred interpretation of the only locality 

where Quaternary deformation was clearly documented is that the faulting is 

due to landsliding rather than tectonic faulting.

Crooked Creek Fault 

Crone (1998b) Fault Number 1032, Crooked Creek 

Fault, in Quaternary Fault and Fold 

Database of the United States

Classified in the USGS Quaternary Fault and Fold Database as a Class B 

feature because of the uncertainty concerning the cause of subsurface 

deformation. Deformation may be solely the result of dissolution of soluble 

subsurface strata or deep-seated tectonic movements. The postulated fault is 

defined largely on the basis of drillhole data and anomalous geomorphic 

features above the subsurface structure. No exposures of the fault are 

known. Deformation associated with the feature has resulted in a structural 

depression in the subsurface and an elongate topographic trough. 

Due to the absence of any clear surface expression, the postulated structure 

is poorly located and defined; the length is unknown. The sense of movement 

and dip are not well known; data suggest significant vertical movement, but 

no information exists to determine if the offset would be reverse or normal.

Pleistocene and Holocene (sinkholes) deformation is associated with the 

postulated structure. Due to uncertainty related to the origin of this postulated 

structure, it is not possible to assign a time of the most recent paleoearthquake or recurrence interval.
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

East Continent Rift Basin (ECRB)

Drahovzal et al. 

(1992)

The East Continent Rift Basin:

A New Discovery

Integration of lithologic, stratigraphic, geochemical, gravity, magnetic, 

structural, and seismic data resulted in recognition of an eastern arm of the 

Midcontinent rift system named the East Continent rift basin (ECRB). An 

elongate N-S-trending Precambrian rift basin is present from SE Michigan 

through Ohio and Indiana, into central Kentucky. The ECRB is filled with red 

continental lithic arenites, minor red siltstones and shales, and volcanics. 

Gravity, magnetic, and seismic data indicate that the basin is composed of 

several subbasins. The basin is bounded by the Grenville Front to the east 

and by normal block faults to the west. The basin narrows to the north; the 

southern boundary is not well constrained. The basin is interpreted to be 

Keweenawan in age and associated with the middle Proterozoic Midcontinent 

rift system. The ECRB predates the Grenville orogeny, which resulted in 

folding and faulting of the rift-fill sequence. Post-Grenville erosion, Paleozoic 

inversion, and wrench faulting resulted in the present configuration of the 

basin.

Farmington Anticline, Missouri

Harrison and 

Schultz (2002)

Tectonic Framework of the Southwestern 

Margin of the Illinois Basin and Its 

Influence on Neotectonism and 

Seismicity

The Farmington anticline–Avon block is a broad (as much as 19.3 km, or 12 

mi., wide) NW-trending low-relief structural feature that lies between the Ste. 

Genevieve and Simms Mountain faults. Weak to moderate seismicity is 

clustered around this structure, which has been interpreted to occur above 

buried faults cutting middle Proterozoic basement rock. A zone of NWtrending horsts and graben with subsidiary and contemporaneous NE-striking

oblique-slip faults coincides with the axis of the fold.

Goodpasture Fault, Colorado

Widmann (1997c) Complete Report for Goodpasture Fault 

(Class A) No. 2329

The Goodpasture fault forms a fairly prominent escarpment and vegetation 

lineation that trends NW to the east of Hogback Mountain in the Wet 

Mountains in Colorado. The most recent fault displacement may have 

occurred in the early to middle Quaternary. Geomorphic features on 

Quaternary deposits indicative of youthful faulting have not been observed in 

aerial reconnaissance. The fault is 5 km (3 mi.) long.
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Great Lakes Tectonic Zone (GLTZ), Minnesota

Atekwana (1996) Precambrian Basement Beneath the 

Central Midcontinent United States as 

Interpreted from Potential Field Data

Major E-NE Archean crustal boundary, which is observed on gravity and 

magnetic anomaly maps, separates greenstone-granite terranes (~2,700 Ma) 

on the north from gneiss terrane (3,600 Ma) on the south. The feature is a 

locus of repeated reactivation.

Sims et al. (1980) The Great Lakes Tectonic Zone—A 

Major Crustal Structure in Central North 

America

The Great Lakes tectonic zone is a major Precambrian crustal feature more 

than 1,200 km (746 mi.) long extending eastward from Minnesota into 

Ontario, Canada. It is a zone of distinctive tectonism, affecting both Archean 

and early Proterozoic rocks along the northern margin of the early 

Proterozoic Penokean fold belt adjacent to the Archean Superior province. 

The zone coincides with the boundary between two Archean crustal 

segments recognized in the region: a greenstone-granite terrane (~2,700 Ma)

to the north (Superior province) and an older (in part 3,500 Ma) gneiss 

terrane to the south. Tectonism along the zone began in the late Archean, 

during the joining together of the two terranes into a single continental mass, 

and culminated in the early Proterozoic, when steep or northward-facing 

overturned folds were formed in the supracrustal rocks, and intense 

cataclasis and a penetrative cleavage developed in subjacent basement 

rocks of the greenstone-granite terrane. The Proterozoic deformation took 

place under low to intermediate pressures.

In the early Proterozoic, crustal foundering, which was parallel to the zone 

and was diachronous, initiated the structural basins in which the early 

Proterozoic sequences of the Lake Superior and Lake Huron regions were 

deposited. Later, during the Penokean orogeny (~1,850–1,900 Ma), 

compression deformed the sequences in both regions. Still later (~1,850–

1,100 Ma), intermittent crustal extension provided sites for emplacement of 

abundant mafic igneous rocks. There is no definite evidence that any of the 

extensional events progressed to the stage of development of oceanic crust; 

probably the zone has been wholly intracratonal since its inception in late 

Archean time. 

During the Phanerozoic, minor differential movements occurred locally in the 

Great Lakes tectonic zone, as recorded by the thinning of Cretaceous strata 

and their subsequent tilting and by historical earthquakes in Minnesota.
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Kentucky River Fault System, Kentucky

Van Arsdale (1986) Quaternary Displacement on Faults 

Within the Kentucky River Fault System 

of East-Central Kentucky

The Kentucky River fault system (KRFS) is the north-bounding fault system 

of the Rome Trough (a Paleozoic aulacogen). Recurrent Paleozoic 

movement is documented, but recognition of Mesozoic and lower Tertiary 

displacement is complicated by the absence of preserved post-Paleozoic 

stratigraphy. Numerous faults of the KRFS are partially overlain by PliocenePleistocene terrace sediments. Preliminary drilling and electrical-resistivity 

surveys suggest that a number of the faults have been active since 

deposition of the terraces. The folding and faulting is interpreted to be 

tectonic in origin, indicating that the KRFS has been active within the past 

five million years and probably within the past million years. 

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Notes that the seismic hazard associated with the Lexington and Kentucky 

River fault systems remains uncertain. A personal communication from R. 

Van Arsdale to the authors in 2000 indicates that although Van Arsdale 

favored the deformation as tectonic faulting, solution collapse cannot be ruled 

out as a cause of Quaternary deformation.

Midcontinent Rift Basin–Midcontinent Rift System (MRS)

Behrendt et al. 

(1988)

Crustal Structure of the Midcontinent Rift 

System: Results from GLIMPCE Deep 

Seismic Reflection Profiles

Interpretation of Great Lakes International Multidisciplinary Program on 

Crustal Evolution (GLIMPCE) seismic-reflection profiles indicates that the 

1,100 Ma Midcontinent rift system (MRS), or Keweenawan rift, of volcanic 

rocks and postvolcanic and interbedded sedimentary rocks extends to depths 

as great as 32 km (20 mi.; about 10.5 s reflection time) along profiles 

crossing western, central, and eastern Lake Superior and the northern end of 

Lake Michigan. The area may overlie the greatest thickness of intracratonic 

rift deposits on earth. Times to Moho reflections vary along strike from about 

37–46 km (23–29 mi.) depth in the western portion, 55 km (34 mi.) in the 

central portion, and 42–49 km (26–29 mi.) depth in the eastern portion of 

Lake Superior. The prerift crust, however, was thinned 25–30 km (15.5–18.5 

mi.) beneath the central rift (compared with its flanks), providing evidence for 

crustal extension by factors of about 3–4. The MRS differs from Phanerozoic 

rifts in having total crustal thicknesses equal to or greater than the 

surrounding (presumably unextended) regions.
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Citation Title Description and Relevance to SSC

Cannon (1994) Closing of the Midcontinent Rift—A FarField Effect of Grenvillian CompressionThe Midcontinent rift formed in the Laurentian supercontinent between 1,109 

and 1,094 Ma. Soon after rifting, stresses changed from extensional to 

compressional, and the central graben of the rift was partly inverted by 

thrusting on original extensional faults. Thrusting culminated at about 1,060 

Ma but may have begun as early as 1,080 Ma. On the SW-trending arm of 

the rift, the crust was shortened about 30 km (18.5 mi.); on the SE-trending

arm, strike-slip motion was dominant. The rapid evolution from an extensional 

to a compressional feature was coincident with renewal of NW-directed 

thrusting in the Grenville, probably caused by continent-continent collision. 

Stresses transmitted from the Grenville province utilized the zone of weak 

lithosphere to close and invert the rift.

Cannon et al. 

(1989)

The North American Midcontinent Rift 

Beneath Lake Superior from GLIMPCE 

Seismic Reflection Profiling

The Midcontinent rift is a 1.1 Ga structure, generally buried beneath 

Paleozoic rocks but traceable by its strong gravity and magnetic anomalies. 

Seismic-reflection surveys by GLIMPCE imaged the deep structure of the rift 

beneath Lake Superior. Major observations are as follows:

Presence of a deep, asymmetrical central graben.

In addition to crustal sagging, normal faulting played a major role in 

subsidence of the axial region of the rift.

A sequence of volcanic and sedimentary rocks, in places >30 km (18.5 

mi.) thick, fills the graben.

Thinner volcanic and sedimentary units lie on broad flanks of the rift 

outside of the graben.

Near the axis, the prerift crust is thinned to about one-fourth of its original 

thickness, by a combination of low-angle extensional faulting and ductile 

stretching or distributed shear.

The sense of asymmetry of the central graben changes along the trend of 

the rift, documenting the segmented nature of the structure and 

suggesting the existence of accommodation zones between the segments.

The location of the accommodation zones is inferred from abrupt 

disruptions in the Bouguer gravity signature.

Uplift of the central graben occurred when the original graben-bounding 

normal faults were reactivated as high-angle reverse faults with throws of 

5 km (3 mi.) or more in places.
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Cannon et al. 

(1991)

Deep Crustal Structure of the 

Precambrian Basement Beneath 

Northern Lake Michigan, Midcontinent 

North America

The Midcontinent rift is expressed by a northward-thickening wedge of 

strong, continuous reflections as deep as 7 s (921 km) that are interpreted as 

basalt flows. The very high gravity values in this region cannot be accounted 

for solely by the thick basalt section, but also require an unusually high 

density for the lower crust, which may be due to large volumes of rift-related 

mafic rocks intruded into the lower crust or upper mantle. The unusual 

thickness of the crust in this region may be caused, in part, by underplating of 

mafic rocks, as is suggested for comparably thick crust beneath Lake 

Superior.

Keller (2010) An Integrated Geophysical Analysis of 

the Mid-Continent Rift System

Discusses the possible extension of the MRS through Oklahoma to at least 

the Wichita uplift. The structural grain of the Precambrian basement provides 

a basis to differentiate between features related to the MRS and older ones. 

It is noted that a major zone of seismicity in Oklahoma and Kansas follows

the Nemaha fault zone/ridge and gravity and magnetic anomalies that are 

likely related to the MRS.

Rose diagrams from processed potential maps delineate basement features 

that are parallel to the NW and NE-strike direction of lineaments identified 

from the seismic-reflection data. Basement structure lineaments were found 

to be parallel in orientation with the trend of lineaments seen within the 

Mississippian and Arbuckle Group. NW-striking lineaments are interpreted to 

be related to the late-Paleozoic tectonism that affected both the Precambrian 

and Paleozoic section in Osage County to the south. The NE lineaments are 

interpreted to be primarily related to features associated with the 

MRS/Nemaha fault zone.

Based on the gravity maps, the MRS is interpreted to likely extend across 

Oklahoma, abutting against the Southern Oklahoma aulacogen. This cannot 

be substantiated at this time given available geochronologic ages. It is 

suggested that the relatively young MRS structures are the ones most likely

to be tectonically reactivated, and that this assertion is supported by trends in 

historical seismicity.
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Nyquist and Wang 

(1988)

Flexural Modeling of the Midcontinent 

Rift

A 2-D flexural model of basin formation for the Midcontinent rift at a latitude of

45°25′N is constrained from a seismic-reflection profile. Based on seismic 

refraction data and comparison with other rifts, this paper hypothesizes that a 

magmatic ―rift pillow‖ intruded into the lower crust. The basaltic pillow 

subsequently solidified to produce a large, high-velocity region in the lower 

crust, centered under the rift axis, as determined from deep seismic 

refraction. This crystallization and cooling may be responsible for the ―sag‖ 

phase of rift evolution, as evidenced by laterally widespread occurrence of 

postvolcanic sediments.

Trehu et al. (1991) Imaging the Midcontinent Rift Beneath 

Lake Superior Using Large Aperture 

Seismic Data

Presents a detailed velocity model across the Midcontinent rift system (MRS) 

in central Lake Superior derived primarily from onshore-offshore largeaperture seismic and gravity data. Total crustal thickness decreases rapidly 

from 55 to 60 km (34 to 37 mi.) beneath the axis of the rift to about 40 km (25 

mi.) beneath the south shore of the lake, and decreases more gradually to 

the north. Above the Moho is a high-velocity lower crust interpreted to result 

from syn-rift basaltic intrusion into and/or underplating beneath the Archean 

lower crust. Lower crust is thickest beneath the axis of the main rift half 

graben. A second region of thick lower crust is found ~100 km (62 mi.) north 

of the axis of the rift beneath a smaller half graben that is interpreted to 

reflect an earlier stage of rifting.

The model resembles recent models of some passive continental margins 

and is in marked contrast to many models of both active and extinct 

Phanerozoic continental rift zones. In the absence of major tectonic activity, 

the Moho is very stable, since the large, abrupt variations in crustal thickness 

beneath the MRS have been preserved for at least a billion years.
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-257 

Citation Title Description and Relevance to SSC

Nemaha Ridge and Humboldt Fault Zone (NRHF)

Bakun and Hopper 

(2004a)

Catalog of Significant Historical 

Earthquakes in the Central United States 

See below

Associates a 4.9 (4.5–5.2) magnitude earthquake on April 9, 1952, with the 

Nemaha fault in Oklahoma.

Gay (2003a, 

2003b)

The Nemaha Trend—A System of 

Compressional Thrust-Fold, Strike-Slip 

Structural Features in Kansas and 

Oklahoma, Part 1; and Part 2 

(Conclusion)

Association with seismicity:

References Koff (1978, unpublished MS thesis, University of Oklahoma),

which shows possible association of seismicity with Oklahoma City fault.

Crustal extent/bedrock deformation:

The Nemaha ridge/uplift was generated by thrusting in three regional 

compressional events that were contemporaneous with Appalachian (and 

probably Rocky Mountain) orogenic events. The main bounding thrust 

(generally on the east side) is steeply dipping or vertical (frequently 

mistaken for a normal fault). Based on well data, the fault has reverse 

displacement and dips steeply west. It appears to decrease in dip with 

depth in basement (becoming listric).

Considerable left-lateral (6 km) strike-slip movement occurred on the 

Nemaha system during later phases of thrusting. ―Relaxation‖ normal 

faulting occurred in response to isostatic adjustments after the 

compressive phase ceased in Late Permian or post-Permian time.

An apparent misconception regarding the origin of the Nemaha system is 

that it is somehow related to the 1.1 Ga Proterozoic Midcontinent rift 

system (MRS). The MRS lies 40–60 km (25–40 mi.) to the west and is not 

parallel to the Nemaha trend, and it is more than 600 Myr older and was 

formed under a distinctly different structural regime. These may be relict 

weakness zones that were later reactivated, but author is not aware of 

them and has not seen this on magnetic data.

Niemi et al. (2004) Investigation of Microearthquakes, 

Macroseismic Data, and Liquefaction 

Associated with the 1867 Wamego 

Earthquake in Eastern Kansas

Association with seismicity: 

Historical felt earthquakes and instrumentally recorded microseismicity 

loosely associated with basement structures (Humboldt fault and subparallel 

Nemaha uplift). Seismicity is somewhat dispersed and does not follow a 

single, well-defined fault feature. Joint inversion with 3-D seismic velocity 
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-258 

Citation Title Description and Relevance to SSC

variations.

Crustal extent/bedrock deformation:

Possible association with 1867 M 5.2 Wamego earthquake basement 

Nemaha Ridge–Humboldt fault (NRHF) structures. The NRHF lies to the east 

and is roughly parallel to the Proterozoic MRS, which extends from Kansas 

NE to Lake Superior.

Nemaha Ridge (NR) is a N-NE-trending anticlinal structure of folded 

Paleozoic rocks overlying an uplifted Precambrian granitic rock core. 

Tectonic motion has been accommodated along the steeply dipping 

Humboldt fault that lies along the eastern boundary of the NR. The Abilene 

anticline structure overlies basement faults along the western boundary of the 

NR uplift. NR is complexly broken into a series of horsts and graben by cross 

faults and folds. The Humboldt fault (HF) is buried along most of its length, 

but is at the surface in NE Kansas where both right-lateral strike-slip and 

reverse motion are observed on surface faults offsetting late Paleozoic rocks.

Major uplift of the Nemaha structure occurred during the Pennsylvanian 

but the structure has been reactivated by post-Permian deformation. 

Precambrian offset as much as 1,000 m across the HF. Post-Permian throw 

of 75 m on high-angle faults (down to the east).

Quaternary deformation-paleoseismicity:

Quaternary-age sediments overlie the HF. Field investigations confirm that 

sedimentary deposits with moderate liquefaction susceptibility are present in 

the vicinity of Wamego and Wabaunsee, Kansas, the preferred source 

location of the 1867 Wamego earthquake. Soft-sediment deformation 

features, including flame and dish structures, are present in late Holocene 

floodplain deposits of the Kansas River and appear to be concentrated in the 

horseshoe bend region of the Kansas River near Wamego and Wabaunsee, 

Kansas.

Initial results suggest that liquefaction features (e.g., clastic dikes), which 

may be attributed to seismically induced liquefaction, are present but may not 

be pervasive in this region. These data suggest that the 1867 M 5.2 Wamego 

earthquake may characterize the seismic source in this region.
Table D-7.3.12 Data Summary 

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D-259 

Citation Title Description and Relevance to SSC

Serpa et al. (1984) Structure of the Southern Keweenawan 

Rift from COCORP Surveys Across the 

Midcontinent Geophysical Anomaly in 

Northeastern Kansas

Crustal extent/bedrock deformation observations:

COCORP profiling reveals structural basins and other features of the 

Precambrian Keweenawan rift buried beneath the Phanerozoic cover. 

The main basin, which is asymmetric, is 40 km (25 mi.) wide and has a 

maximum depth of 3 km (2 mi.) on the east and 8 km (5 mi.) on the west.

Basin fill is characterized by a lower layered sequence of strong, westdipping reflectors interpreted to be middle Keweenawan interbedded 

volcanic and clastic rocks exposed along the MGA in the Lake Superior 

region. Upper fill is correlated to upper Keweenawan sequence. 

A shallower, tilted basin lies to the east of the main rift basin.

Mafic intrusions are interpreted to lie beneath the main rift basin.

Normal faults that are associated with the rift dip at moderate angles to the 

east.

The data for reactivation of preexisting structures is inconclusive.

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Summarizes the following observations from previous studies, concluding

that the potential for large-magnitude earthquakes in the area remains 

uncertain:

Two damaging earthquakes occurred in the vicinity of the Humboldt fault 

zone on the Nemaha uplift: a M 5.5 in eastern Kansas in 1867 and a M 5.7

in central Oklahoma in 1952.

Felt historical earthquakes and microearthquakes located by a regional 

seismograph network tend to concentrate near the fault zone and uplift.

Historical accounts report possible liquefaction during the 1867 Kansas 

earthquake, but a search for these liquefaction features and for prehistoric 

liquefaction features was unsuccessful (see Niemi et al., 2004, results 

above).
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Niagara Fault Zone

Atekwana (1996) Precambrian Basement Beneath the 

Central Midcontinent United States as 

Interpreted from Potential Field Data

Interpreted suture between a northern and southern zone: the northern

consisting of early Proterozoic epicratonic rocks and associated Archean 

basement gneiss, and the southern consisting of volcanic and granitoid rocks 

(the Wisconsinan magmatic terrane). 

Cannon et al. 

(1991)

Deep Crustal Structure of the 

Precambrian Basement Beneath 

Northern Lake Michigan, Midcontinent 

North America

Deep seismic-reflection profile in northern Lake Michigan provides a cross 

section of the crust across the 1,850 Ma Penokean orogen, in which an early 

Proterozoic island arc complex was deformed between two converging 

Archean continental masses. The Niagara fault zone is interpreted as a sharp 

inflection in the gravity profile; no strong reflectors can be ascribed to the fault 

surface, which is interpreted to dip steeply (80° to south), similar to an 

exposed section to the west.

Plum River Fault, Illinois

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Summarizes previous studies that suggested there might be Quaternary 

deformation along the Plum River fault, an E-W-trending fault that offsets 

Paleozoic rocks in Iowa and Illinois. Late Quaternary loess-covered terraces 

along an ancient south-flowing channel of the Mississippi River have 

northward dips where the terraces cross the Plum River fault, but they could 

also be explained by terrace erosion and subsequent burial beneath a 

blanket of loess. No paleoseismic work has been done to evaluate the 

hypothesis of Quaternary tectonic faulting.

Potter County Fault, Texas

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

An apparent offset of a lithologic escarpment by the Potter Creek fault in the 

Texas panhandle that was considered possible evidence of Quaternary 

faulting was investigated through interpretation of aerial photographs and

aerial and field reconnaissance studies. This paper summarizes the 

conclusions from studies by other researchers that showed no evidence of

Quaternary faulting along the fault trace. Field studies showed that at two 

localities, the base of Miocene rocks is unfaulted at both sides of the fault.
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Rampart Range Fault, Colorado

Widmann (1997b) Complete Report for Rampart Range 

Fault (Class A) No. 2328

This fault trends N-S along the eastern margin of the Front Range, north of 

Colorado Springs, for about 46 km (29 mi.). The fault is marked by 

topographic breaks and vegetation lineaments. It is a range-front fault that 

had reverse movement during the Laramide, but normal movement during 

the late Cenozoic. Approximately 8 m (26 ft.) of down-to-the-west Quaternary 

displacement has been reported. Trenching investigations indicated that the 

most recent displacement occurred between 600 ka and 30–50 ka.

Ste. Genevieve Fault Zone (SGFZ), Missouri and Illinois

Harrison and 

Schultz (2002)

Tectonic Framework of the Southwestern 

Margin of the Illinois Basin and Its 

Influence on Neotectonism and 

Seismicity

Detailed studies of this fault zone document contractional, extensional, and

strike-slip movement along high-angle faults, as well as multiple periods of 

movement.

The zone dies out near both the St. Charles and Commerce lineaments (see 

the Geophysical Anomalies section of this table), suggesting a genetic link 

and demonstrating the influence of these structural features on tectonism in 

the region. 

Deformation along this structure is correlative to the late Mississippian to 

middle Pennsylvanian tectonic episode identified elsewhere in the 

Midcontinent. The paper provides evidence for a period of extension probably 

of late Pennsylvanian to Permian age.

Detailed and reconnaissance mapping along the Ste. Genevieve fault zone 

for more than 75 years has revealed no evidence of Tertiary or Quaternary 

faulting. 

Heigold and Kolata 

(1993)

Proterozoic Crustal Boundary in the 

Southern Part of the Illinois Basin

The fault may have originated as a crustal plate boundary or suture zone 

during the Proterozoic. 
Table D-7.3.12 Data Summary 

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Citation Title Description and Relevance to SSC

Nelson (1995) 

Nelson et al. (1997)

Structural Features in Illinois

Tertiary and Quaternary Tectonic 

Faulting in Southernmost Illinois

The SGFZ is mapped for approximately 193 km (120 mi.) along strike from 

SE Missouri into SW Illinois. It consists of numerous en echelon strands and 

braided segments having variable deformation styles and a complex history 

of reactivation. Displacement across the zone ranges from less than 198 m 

(650 ft.) to as much as 1,189 m (3,900 ft.). Detailed studies of this fault zone 

document contractional, extensional, and strike-slip movement along highangle faults, as well as multiple periods of movement. 

In Illinois, compressional deformation is documented along the Ste. 

Genevieve fault in early Pennsylvanian rocks (Nelson, 1995). The later 

report, Nelson et al. (1997), however, indicates that some faults along the SE 

part of the SGFZ in Illinois displace Cretaceous and Tertiary sediments, but 

Quaternary deposits are not faulted. 

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest of the 

New Madrid Seismic Zone

Identifies soft-sediment deformation that could be related to low levels of 

ground shaking at one location along a strand of the fault. Diffuse seismicity 

occurs in the block between the SGFZ and Simms Mountain fault system. 

However, no evidence has been documented of any tectonic deformation of 

Quaternary deposits, nor has convincing evidence for paleoliquefaction been 

observed in this area.

Simms Mountain Fault System, Missouri 

Harrison and 

Schultz (2002)

Tectonic Framework of the Southwestern 

Margin of the Illinois Basin and Its 

Influence on Neotectonism and 

Seismicity

The Simms Mountain fault system in SE Missouri consists of numerous 

braided and en echelon fault strands that are continuous southward into the 

Cape Girardeau fault system. Together these fault systems extend more than 

106 km (66 mi.), and in places reach as wide as 79 km (24 mi.). Left-lateral 

strike-slip movement occurred on the fault system, primarily before formation 

of Mississippi Valley–type ore deposits of Permian age, although some are 

later or of unknown age (Harrison and Schultz, 2002).
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Ute Pass Fault Zone

Widmann (1997a) Complete Report for Ute Pass Fault 

Zone (Class A) No. 2327

This fault zone consists of five generally NW-trending faults that define the 

west and SW margins of the Rampart Range west of Colorado Springs. 

There is evidence of late Cenozoic movement along most of the fault. 

Quaternary deposits do not appear to be offset across the north end of the 

fault zone; on the south end of the fault zone, scarps developed on 

Quaternary rockfall deposits may indicate Quaternary fault activity. No 

evidence of offset in late Pleistocene to Holocene deposits has been found. 

The length of the fault zone is about 71 km (44 mi.).

Vaughn Fault, New Mexico

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Summarizes information regarding an escarpment along the north-striking 

Vaughn fault that impounds Quaternary sediments on its west side and 

blocks most local streams. Based on geologic mapping, an inferred 150–300

m of west-side-down subsurface offset is present along the fault. Although 

the evidence is suggestive of Quaternary faulting, such faulting has not been 

demonstrated, and the fault might be a near-surface effect of subsurface 

solution.

Valmont Fault, Colorado

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Summarizes reported information on the Valmont fault that was inferred from 

a single road cut that exposes a 13 m wide zone of disrupted and shingled 

stones in Quaternary alluvium. The alluvium is offset 1.5 m across the zone. 

The fault lacks geomorphic expression. The faulting has been explained by 

both tectonic faulting and intrusion of a nearby dike. 

Washita Valley Fault, Oklahoma

Van Arsdale et al. 

(1989)

Post-Pennsylvanian Reactivation Along 

the Washita Valley Fault, Southern 

Oklahoma

This study searched for geomorphic, structural, and other geologic evidence 

of young faulting at sites along the Washita Valley fault. Two trenches at 

site A exposed unfaulted Holocene alluvium dated at 1,910 ± 80 yr BP. One 

trench and a natural exposure at site B contained unfaulted 12–15 ka terrace 

alluvium. Seven trenches and two natural exposures at site E revealed 

faulted Cretaceous strata overlain by unfaulted Wisconsinan terrace alluvium. 
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Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

This paper summarizes work by Van Arsdale et al. (1989) that found no 

evidence of Quaternary faulting along the Washita Valley fault.

Nontectonic Faults

Wheeler and Crone 

(2001)

Known and Suggested Quaternary 

Faulting in the Midcontinent United 

States

Summarizes field studies that have shown that six previously inferred 

Quaternary faults have nontectonic origins: Barrera and Carlsbad faults, New 

Mexico; Fowler fault, Colorado; Harlan County fault, Nebraska; Ord 

escarpment, Nebraska; and two small faults west of Pierre, South Dakota.

Paleoliquefaction Studies

Tuttle, Chester, et 

al. (1999)

Paleoseismology Study Northwest of the 

New Madrid Seismic Zone

Based on the spatial distribution of prehistoric liquefaction features, the paper 

indicates that the Waterloo-Dupo anticline, Valmeyer anticline, and St. Louis 

fault are possible sources for paleoearthquake features observed in eastern

Missouri, but also emphasizes that other scenarios relying on sources farther 

east are equally possible (i.e., on the DuQuoin monocline–Centralia fault). 

(For further discussion of these structures, see the Illinois Basin-Wabash 

Valley Data Summary Table [Appendix Table D-6.1.9)

Tuttle (2005b) Paleoseismological Study in the St. Louis 

Region: Collaborative Research

This paper summarizes and updates observations reported by Tuttle, 

Chester, et al. (1999). At least two generations of Holocene earthquakeinduced liquefaction features, including sand and silt dikes and sills, and only 

two sand blows, are identified in the St. Louis region. Some features probably 

formed during the 1811-1812 or earlier New Madrid earthquakes, and others 

formed during a middle Holocene earthquake in 4520 BC ± 160 yr. Late 

Holocene sand dikes, up to 26 cm in width, occur along the Kaskaskia River 

and its tributaries, Crooked, Shoal, and Silver creeks, as well as along 

Cahokia and Piasa creeks and the Cache, Castor, Marys, and Meramec 

rivers. The 4250 BC earthquake may or may not have been responsible for 

all of the middle Holocene features. The relatively large size of features 

identified near Germantown, Illinois, suggests that the earthquake source 

may be located east of St. Louis. Alternative sizes and locations are 

suggested. The Meramec River features could have formed as a result of a 

moderate-to-large earthquake centered in the St. Louis area or a very large 

earthquake centered 80–100 km (50–62 mi.) east of St. Louis.
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Anna Seismic Zone

Atekwana (1996) Precambrian Basement Beneath the 

Central Midcontinent United States as 

Interpreted from Potential Field Data

Portions of the NW-trending anomalies of the East Continent gravity high

have been called the Fort Wayne rift (FWR) and are interpreted to be older 

than N-S-trending anomalies in central Ohio to Kentucky and the Grenville 

Front, further suggesting that the Grenville Front truncates the FWR. The 

author attributes the formation of the FWR to processes occurring in the 

formation of the Granite-Rhyolite province or later reactivation of preexisting 

basement structures. A whole-rock rubidium-strontium date of 1.325 Ga is 

older than dates reported for the Midcontinent rift system, suggesting that 

Fort Wayne rifting formed during an earlier rifting event.

Baranoski et al. 

(2009)

Unconformity-Bounded Seismic 

Reflection Sequences Define GrenvilleAge Rift System and Foreland Basins 

Beneath the Phanerozoic in Ohio

Interprets four sequences of layered reflectors (A, B, C, and D) below the 

Phanerozoic deposits and above basement of the Granite-Rhyolite and 

Grenville provinces from reprocessed data of COCORP Line OH-1. Episodic 

deposition of these sequences records rifting and a westward shift of the 

major axis of depositional thickening that began as a series of half graben 

and culminated in a highly deformed foreland basin at the end of the 

Grenville orogeny. The unconformities at the top of sequences A, B, and C 

represent the end of an episode of crustal extension in the west and 

rejuvenation of crustal shortening in the east, recording a westward 

progression of thrusting and crustal loading during the Grenville orogeny. 

Sequences A and B are more localized and may contain volcaniclastic and 

alluvial sediments deposited above a NW-trending gravity low in a rapidly 

subsiding fault bounding the FWR.

Each sequence becomes more widespread due to continued subsidence. 

The more widespread sequences C and D are correlated with the Middle Run

Formation of the East Continent rift basin. The deposition of discontinuous, 

intertonguing clastic sediments of sequence D marks the end of subsiding rift 

basins in response to late Grenville collision, culiminating in a widespread 

regional foreland basin marking the end of the Grenville orogeny. Without 

datable drill core samples, the authors are unable to establish, on the basis of 

sequence stratigraphy, structural relationships, and geopotential field data, 

whether the FWR is coeval with the SE arm of the Midcontinent rift in 

Michigan. 
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Crone and Wheeler 

(2000)

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic 

Features in the Central and Eastern 

United States, East of the Rocky 

Mountain Front

Assigns the Anna seismic zone to Class C. (Geologic evidence is insufficient 

to demonstrate Quaternary fault displacement for features assigned to 

Class C.) Earthquakes associated with the seismic zone span approximately 

80 km (50 mi.), with most of the seismicity concentrated within an area 30–35 

km (18.6–21.7 mi.) across. Most epicenters cluster along the NW-striking

Anna-Champaign fault, which has been mapped in the basement beneath 

Paleozoic platform strata. The largest earthquakes recorded in the zone were 

two that occurred in March 1937 and had intensities of VII and VIII and M 4.9 

and 5.1. Focal mechanisms indicate strike-slip faulting.

Selected stream banks and sand and gravel pits in the Anna area were 

examined by Obermeier (1995) for evidence of prehistoric liquefaction 

features; none were found. Based on the spacing of potentially liquefiable 

materials, he concluded that an earthquake larger than M 7 has not occurred 

in the past several thousand years, although smaller ones cannot be 

excluded. 

Drahovzal et al. 

(1992) 

The East Continent Rift Basin:

A New Discovery

Identified the East Continent rift basin (ECRB) based on the following 

evidence:

presence of Middle Run Formation (a pre-Mt. Simon lithic arenite 

interbedded with basalt representative of continental flood basalts);

association with the East Continent gravity high, a NW-trending positive 

gravity anomaly from NE Indiana, SW Michigan, and central-western Ohio, 

crossing the Grenville Front tectonic zone into Kentucky and coincident 

with the Fort Wayne rift (FWR) in Indiana and Ohio; and

magnetic anomalies coincident with gravity anomalies, suggesting deeprooted bodies of mafic composition, possibly emplaced during rifting.

The ECRB and FWR have uncertain Proterozoic ages based on a few age 

dates from drill core. Less distinct magnetic anomalies east of the Grenville 

Front and east-dipping thrust sheets overlying Middle Run Formation in 

Kentucky indicate that the ECRB cannot be as young as Cambrian. The 

overthrust relationship between the Grenville and ECRB is not clear on data 

from COCORP line OH-1. Rifting associated with the ECRB may be 

contemporaneous with Keweenawan rifting in Michigan. The thickness of the 

basin-fill sequence exceeds 20,000 feet at several locations along the 

Grenville Front tectonic zone in central Kentucky and central Ohio and 
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northern Ohio. The basin-fill sequence thins on an uplifted block in SE 

Indiana and along the trend of the FWR in the vicinity of COCORP line OH-1. 

The trend of the FWR defines a NW-trending basement high that separates 

deeper portions of the basin. 

Hansen (1987) July 1986 Auglaize County Earthquake The July 12, 1986, ML 4.5 earthquake in western Auglaize County, near St. 

Marys township, occurred on the Anna-Champaign fault, a NW-SE-trending

structure that extends into Shelby, Auglaize, and Mercer counties. The 

ancient Teays River followed the trace of the Anna-Champaign fault before

Pleistocene glaciations. The deep alluvial valley was thought to amplify 

ground motions during earthquakes, which was not observed during the July 

12, 1986, earthquake.

This observation suggests that relocating the March 2 and March 9, 1937, 

earthquakes to the vicinity of the July 12, 1986, earthquake and adjusting 

their magnitudes downward is not warranted. Review of a seismic record 

made of these 1937 earthquakes by a Jesuit priest suggests they occurred at 

or SE of Anna, Ohio. Such a location would be more consistent with the felt 

reports of the 1937 earthquakes and the isoseismal map of the 1986 

earthquake. The July 12, 1986, earthquake had no associated foreshocks or 

aftershocks and produced MMI VI shaking confined to a small area 

surrounding the epicenter. 

Hansen (1993) Earthquakes and Seismic Risk in Ohio The Anna seismic zone, also called the Western Ohio seismic zone, 

coincides with NW-SE-trending basement faults associated with the FWR in 

Shelby, Auglaize, and nearby counties. This zone has produced at least 40 

felt earthquakes since 1875, including earthquakes in 1875, 1930, 1931, 

1937, 1977, and 1986 that caused minor to moderate damage. The July 12, 

1986, earthquake near the town of St. Marys in Auglaize County was the 

largest earthquake to occur in the zone since 1937. The author concludes 

that the historical record indicates a maximum magnitude of 5, but suggests 

that this zone was capable of producing a magnitude 6.0–7.0 earthquake. 

Hauser (1993) Grenville Foreland Thrust Belt Hidden 

Beneath the Eastern U.S. Midcontinent

Interprets the Middle Run Formation as forming in a Grenville foreland basin 

or, alternatively, as a constituent of the Granite-Rhyolite province. Does not 

recognize a rift origin. 
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McPhee (1983) Regional Gravity Analysis of the Anna, 

Ohio, Seismogenic Region

Generated regional and local gravity and magnetic models to evaluate the 

relationship of seismicity and basement geology in the Anna seismic zone. 

The models require a large source of positive density contrast extending 

upward from the Moho into the lower crust beneath the FWR, interpreted as a 

deep crustal mafic source. Seismicity appears to be concentrated at the 

boundary between the rift-type mafic volcanic rocks of the FWR and the 

granitic body to the NE. This pattern of seismicity can be attributed to either 

reactivation of graben-type faults, activation of a zone of weakness at the 

contrasting lithologies, or extension of the Bowling Green fault in the 

basement. 

Obermeier (1995) Paleoseismic Liquefaction Studies—

Central U.S. and Pacific Northwestern 

U.S.

Investigated stream banks in the vicinity of Anna, Ohio, and portions of the 

Auglaize, Great Miami, Stillwater, and St. Marys rivers and found no evidence 

of paleoliquefaction features indicative of a M 7 earthquake in the past 

several thousand years. 

Ruff et al. (1994) Geophysical Investigations of the 

Western Ohio–Indiana Region: Final 

Report 1986–September 1992

Describes earthquake activity in the western Ohio–Indiana region that was 

monitored with a regional seismograph network between 1977 and 1992. A 

total of 78 local and regional earthquakes were recorded by the network 

during this time period. The largest earthquake recorded was the July 12, 

1986, St. Marys earthquake (mb 4.5) within the Anna seismic zone. The focal 

mechanism indicated a strike-slip earthquake with an E-NE-striking

compressional axis.

The history of felt earthquakes in the Anna zone dates back to the late 1700s 

and includes several earthquakes of about magnitude 5. Attributes seismicity 

to the Anna-Champaign, Logan, and Auglaize faults. 

Schwartz and 

Christensen (1988)

The 12 July 1986 St. Marys, Ohio 

Earthquake and Recent Seismicity in the 

Anna, Ohio Seismogenic Zone

Determined hypocenter of 3 mi. (5 km) for the magnitude (mb) 4.5 earthquake 

and a focal mechanism (strike = 25°, dip = 90°, rake = 175°) representing 

mostly strike-slip, with a small oblique component approximately parallel to 

Anna-Champaign fault and a nearly horizontal P axis oriented E-NE. 
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Stark (1997) The East Continent Rift Complex: 

Evidence and Conclusions

Informed with the work of Drahovzal et al. (1992), Stark extends the concept 

of the East Continent rift basin (ECRB) to a major multiphase rift complex in 

the eastern Midcontinent: the East Continent rift complex. This interpretation 

involves four phases:

1. Keweenawan extension (1.05–1.3 Ga) rifted the Granite-Rhyolite province 

along the ECRB/FWR, the English Graben/Flatrock subbasin, and the 

Southern Indiana graben into an internally complex half graben along rift 

margins containing considerable thickness of rift fill sediments and 

volcanic rocks.

2. Grenvillian contraction (880–990 Ma) resulted in overthrusting the eastern 

margin of the East Continent rift complex, emplacement of an allochthon of 

metamorphic strata above and adjacent to the rift strata, remobilization of 

NW-SE-trending transtensive wrench systems as transpressive 

detachment zones, and formation of a foreland basin with concomitant fold 

systems. 

3. Pre-Eocambrian uplift and erosion (650–550 Ma) resulted in substantial 

syn- and/or postdepositional deformation before the Sauk unconformity, 

which may have removed most or all of the Grenvillian foreland basin.

4. Eocambrian extension (650–560 Ma) associated with the opening of the 

Iapetus Ocean initiated rifting of Reelfoot rift, Rough Creek graben, and 

Rome trough; and reactivation of Rough Creek graben/Shawneetown fault 

system, Kentucky River fault system, Lexington fault system, Bowling 

Green fault zone, and Warfield fault system. Middle Cambrian thermal 

subsidence downwarped these rifts, leading to widespread deposition of 

the Sauk Sequence carbonates. 

Deep wells along the FWR at the Anna seismic zone encountered mafic 

basalt fill sequence, whereas wells to the north and south encountered 

Middle Run Formation. This observation implies that structures associated 

with the Anna seismic zone were uplifted before the late Proterozoic erosion 

and therefore must have remobilized through geologic time, further 

suggesting that the Anna seismic zone is associated with an accommodation 

structure within the ECRB/FWR. 
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Northeast Ohio Seismic Zone

Crone and Wheeler 

(2000)

Data for Quaternary Faults, Liquefaction 

Features, and Possible Tectonic 

Features in the Central and Eastern 

United States, East of the Rocky 

Mountain Front

Assigns Northeast Ohio seismic zone to Class C. (Geologic evidence is 

insufficient to demonstrate Quaternary fault displacement for features 

assigned to Class C.) Earthquakes associated with this zone form a diffuse 

cluster aligned NE-SW and about 80 km (50 mi.) long and 40 km (25 mi.)

wide. The 11 largest epicenters lie along and NW of Akron magnetic 

lineament. Obermeier (1995) examined selected stream banks in this area for 

evidence of prehistoric liquefaction, but found none. Exposures that could 

provide definitive evidence of prehistoric earthquakes are scarce in region; 

still, the zone lacks paleoseismological evidence of Quaternary faulting.

Dineva et al. (2004) Seismicity of the Southern Great Lakes: 

Revised Earthquake Hypocenters and 

Possible Tectonic Controls

Describes results of analyses to establish better constraints on epicenter 

locations and focal depth estimations for 106 earthquakes that occurred from 

1990 to 2001 in southern Great Lakes region. Earthquakes within Northeast 

Ohio seismic zone, also referred to as a cluster of earthquakes south of Lake 

Erie on the Ohio-Pennsylvania border, were relocated. Earthquakes in this 

zone form a cluster that trends NE-SW and follows Lake Erie shoreline for 

about 60 km (37 mi.). Hypocenter locations are confined to the crust above 

30 km (18.6 mi.); most occur above 20 km (12.4 mi.). Seismicity appears to 

be localized where preexisting tectonic structures (e.g., the Akron magnetic 

boundary) are favorably oriented with respect to present-day stress field, and 

where water is present at surface.

Hansen et al. 

(2001)

Seismic Spotlight Shines on Ashtabula Describes the series of earthquakes in 1987 and 2001 that occurred in the 

vicinity of Ashtabula in NE Ohio. Before the 1987 earthquake, earthquakes 

had not been felt in this area since it was settled in the early 1800s. Portable 

seismographs deployed in the region and the Ohio Seismic Network 

implemented in 1999 provide detailed information on these earthquakes. An 

isoseismal map for areas of approximately equal MM intensity for the January

25, 2001, main shock at Ashtabula shows a N-S elongation for this shoreline 

earthquake; the cause of this phenomenon is reported as unknown.
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Hartline (1995) Deep Structural Analysis Related to the 

Akron Magnetic Boundary Using 

Geophysical Well Logs and Potential 

Field Data, East-Central Ohio

Reviews geophysical well logs, gravity data, magnetic data, and COCORP 

seismic data in Knox, Coshocton, Muskingum, and Licking counties, Ohio, 

and presents structure-contour and isopach maps on 16 key horizons in the 

Paleozoic cover to evaluate basement-controlled faulting associated with the 

Akron magnetic boundary. Finds no evidence of basement-controlled faulting 

along the Akron magnetic boundary; however, the study area is in central 

Ohio, not along the Northeast Ohio seismic zone.

Hoehn (1991) An Integrated Geophysical Study of the 

Grenville Province in the Greater Lake 

Erie Region

Reprocesses Vibroseis seismic-reflection data from line LE-01 in Lake Erie 

and compares the results to potential field data. The reprocessed data can 

resolve reflections to a depth of 18 km (11.2 mi.). Decrease in the gravity 

profile across Akron magnetic boundary is attributed to an east-dipping lowdensity body in the upper crust. Interprets the Eastern Midcontinent magnetic 

belt as relic structures associated with a reversal of subduction polarity within 

the Proterozoic bound to the east by NW-directed thrusts of Akron magnetic 

boundary. Sedimentary units east of the Akron magnetic boundary exhibit 

extension within the Elzevir terrane. Multiple reflections within the first two 

seconds of the data obscure Akron magnetic boundary in the upper crust.

Lidiak and Hinze

(1993)

Grenville Province in the Subsurface of 

Eastern United States

Interprets Akron magnetic boundary as a major Grenville suture separating 

contrasting magnetic anomalies and seismic reflectors. To the east of the 

Akron magnetic boundary, basement is characterized by lower-amplitude 

anomalies and west-dipping reflectors that exhibit ductile deformation. Crust 

to the west exhibits high-amplitude magnetic anomalies and east-dipping 

reflectors indicative of the Grenville front and related structures. The authors 

present a mapped location trending NE through eastern Lake Erie; they 

postulate that Akron magnetic boundary separates Elzevir terrane in the east 

from their proposed Eastern Midcontinent magnetic belt to the west.
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Nicholson et al. 

(1988)

The Northeastern Ohio Earthquake of 31 

January 1986: Was It Induced?

Describes the January 31, 1986, earthquake that occurred about 40 km (25 

mi.) east of Cleveland, Ohio, with mb 5.0 and intensity VI–VII at distances of 

15 km (9.3 mi.). Focal depths for this earthquake and the aftershocks ranged 

from 2 to 6 km (1.2 to 3.7 mi.). The aftershocks occurred in a tight cluster 

about 1 km (0.6 mi.) wide and oriented to the N-NE, and focal mechanisms of 

the aftershocks represent predominantly oblique right-slip motion on nearly 

vertical planes oriented N15°–45°E, with a nearly horizontal P (maximum 

compressive stress) axis, consistent with the modern stress regime. Factors 

that suggest a natural origin for the earthquake include a history of small and 

moderate earthquakes in the region prior to the initiation of injection, and the 

lack of large numbers of small earthquakes typical of many induced 

sequences. The 1986 cluster is coincident with a N40°E-trending gravity and 

magnetic anomaly (Akron magnetic boundary). 

Nicholson and 

Wesson (1990)

Earthquake Hazard Associated with 

Deep Well Injection—A Report to the 

U.S. Environmental Protection Agency

Includes descriptions of earthquakes that occurred about 40 km (25 mi.) 

apart in NE Ohio in January 1986 and July 1987 and reviews evidence for 

possible triggering of these earthquakes. Reviews the state of knowledge 

about earthquakes related to injection of fluid into deep wells. Describes the 

probable physical mechanism for the triggering and the criteria for predicting 

whether earthquakes will be triggered that depend on the local state of stress 

in the earth’s crust, the injection pressure, and the physical and hydrologic 

properties of rocks into which the fluid is being injected. Concludes that the 

January 1986 earthquake had a natural origin, although triggering by well 

activities of at least a few small aftershock earthquakes could not be 

precluded, and that the July 1987 earthquakes were most likely induced.

Obermeier (1996a) Summary of 1995 Paleoliquefaction Field 

Search in the Vicinity of Perry, Ohio

Letter report summarizing a paleoliquefaction investigation performed in the 

vicinity of the Perry Nuclear Power Plant along the Grand River, Trumbull 

Creek, and Cuyahoga River and near a tributary to Phelps Creek of NE Ohio. 

Based on observations along these streams, Obermeier made the following 

conclusions:

The lack of suitable exposures within 20 km (12.5 mi.) of the nuclear 

power plant at Perry, Ohio, precludes definitive statements as to whether 

there has been strong seismic shaking for most of Holocene time. 

The lack of exposures with liquefiable sediment more than a few thousand 

years old and within 20–25 km (12.5–25 mi.) of the plant precludes any 
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statement concerning whether there could have been strong shaking at 

the plant locale from even moderate-sized earthquakes (M ~ 6) occurring 

more than a few thousand years ago. 

The lack of liquefaction features in latest Pleistocene sediment (moderate 

to high liquefaction susceptibility through time) in the locality of a large 

sand and gravel pit (―Pit-CL‖) does not provide sufficient data to make a 

statement on seismic shaking at a distance of 32 km (20 mi.) from the 

Perry Nuclear Power Plant.

Obermeier noted in the letter report that perennial streams flowing subparallel 

and through a beach ridge/sand dune complex within 2–6 km (1.2–3.7 mi.) 

inland from the shore (identified from examination of the Soil Survey Report 

of Lake County) might offer the possibility of a field setting where liquefaction 

features could have developed for much of Holocene time. 

Seeber and 

Armbruster (1993)

Natural and Induced Seismicity in the 

Lake Erie-Lake Ontario Region: 

Reactivation of Ancient Faults with Little 

Neotectonic Displacement

Defines the Northeast Ohio seismic zone on the basis of a 50+ km (31+ mi.) 

long belt of seismicity striking NE near the shoreline of Lake Erie. Proposes 

that the belt of seismicity may be associated with a major fault and related 

secondary faults. The Northeast Ohio seismic zone correlates spatially with 

the Akron magnetic lineament and a portion of the Akron magnetic boundary. 

The authors speculate that the Akron magnetic boundary may be associated 

with the Niagara-Pickering magnetic lineament/Central Metasedimentary Belt 

boundary zone as a continental scale Grenville-age structure. 

Evaluates the hypothesis that the July 13, 1987, mbLg 3.8 Ashtabula 

earthquake and sequence of 36 aftershocks were triggered by fluid injection 

into a deep waste disposal well penetrating the basal Mt. Simon sandstone. 

The well had been in operation since July 1986. Well-located earthquakes of 

the Ashtabula sequence cluster in a narrow, east-trending vertical zone about 

1.5 km (1 mi.) long and between 1.7 and 3.5 km (1.1 and 2.2 mi.) deep,

located as close as 0.7 km (0.4 mi.) to the injection well. The depth to 

basement in this area is approximately 1.8 km (1.1 mi.), indicating that this 

cluster of seismicity is concentrated below the Mt. Simon–Grenville 

unconformity.

The authors interpret this narrow zone as an active fault, referred to as the 

Ashtabula fault. Subsequent seismicity from 1987 to 1992 suggests a 

westward migration by 5–10 km (3.1–6.2 mi.), possibly along the proposed 
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fault. However, because the temporary seismic network used to locate the 

aftershocks of the 1987 main shock was no longer in operation, the locations 

of the 1992 earthquakes are not as well constrained as the aftershocks of the 

main 1987 earthquake.

Based on the assumption that the 1992 seismicity and the 1987 earthquakes 

defined a single rupture plane, the authors estimate that the postulated 

Ashtabula fault could produce a magnitude 5–6 earthquake.

Seeber et al. 

(2004)

A Fluid-Injection-Triggered Earthquake 

Sequence in Ashtabula, Ohio: 

Implications for Seismogenesis in Stable 

Continental Regions

Describes an earthquake sequence near Ashtabula in NE Ohio that is 

believed to have been triggered by fluid injection. The sequence began in 

1987 with a mblg 3.8 main shock; the largest earthquake recorded was a mblg

4.3 earthquake in 2001. Well-located aftershocks of the June 3, 2001, mbLg

3.0 and the July 17, 2003, mbLg 2.5 earthquakes define a 7 km (4.3 mi.) long 

plane striking 96° and dipping 65° south. The authors interpret this plane as 

the source fault for the 2001 seismicity, which resembles the postulated E-Wstriking fault with left-lateral slip defined by the 1987 seismicity (Seeber and 

Armbruster, 1993). These subparallel faults are 4.5 and 0.7 km (2.9 and 0.4 

mi.) south of the injection well, respectively.

Seeber et al. revise the previous interpretation of Seeber and Armbruster 

(1993) regarding the tectonic implications of the 1987 earthquake sequence 

and subsequent earthquakes in 1992 to conclude that the linear patch of 

1987 earthquakes is a portion of a basement fault activated by high pore 

pressure rather than evidence of a single rupture. This conclusion was based 

in part on the observation that these earthquakes are scattered over the 

patch as opposed to clustering at the edges.

Seeber et al. attribute the quiescence from 1995 to 2000 to a lack of 

favorably oriented structures between these two fault planes. They speculate 

that seismicity initiates when and where a significant pore-pressure rise 

intersects preexisting faults close to failure, and is turned off when pressure 

starts dropping back. They conclude that these faults are preexisting faults 

located in the uppermost portion of the Grenville basement reactivated by a 

high pore-pressure anomaly spreading from the injection site.
Table D-7.3.12 Data Summary 

MidContinent-Craton Zone 

D-275 

Citation Title Description and Relevance to SSC

Wesson and 

Nicholson (eds.) 

(1986)

Studies of the January 31, 1986, 

Northeastern Ohio Earthquake—A 

Report to the U.S. Nuclear Regulatory 

Commission

This earthquake occurred about 17 km (10.5 mi.) south of the Perry Nuclear 

Power Plant and generated accelerations of 0.18 g of short duration at the 

plant. Analysis of the main shock and aftershocks indicated no obvious 

structure or fault with which the earthquakes could be associated. The 

earthquakes were located within 15 km (9.3 mi.) of three deep waste-disposal 

injection wells and could have been due to fluid injection that reactivated 

favorably oriented, preexisting fractures. Available information indicated that 

although triggering was a possibility, the probability that injection played a 

significant role should be regarded as low. It was reported that there was 

nothing to suggest the occurrence of an earthquake larger than expected for 

the region, or the activation of a major structure close to the wells or near the 

power plant.

NUREG-2115 DOE/NE-0140 EPRI 1021097

APPENDIX E 

CEUS Paleoliquefaction Database, Uncertainties Associated with 

Paleoliquefaction Data, and Guidance for Seismic Source Characterization 

E 

APPENDIX 

CEUS Paleoliquefaction Database, Uncertainties Associated with 

Paleoliquefaction Data, and Guidance for Seismic Source Characterization 
E-ii

DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES 

THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN 

ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH 

INSTITUTE, INC. (EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE 

ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: 

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) 

WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR 

SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS 

FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR 

INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL 

PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'S 

CIRCUMSTANCE; OR 

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER 

(INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE 

HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR 

SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, 

PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT. 

ORGANIZATIONS THAT PREPARED THIS DOCUMENT 

M. Tuttle & Associates 

Fugro William Lettis & Associates 
CITATIONS 

This report was prepared by 

M. Tuttle & Associates 

128 Tibbetts Lane 

Georgetown, ME 04548 

Principal Investigator 

M.P. Tuttle 

Fugro William Lettis & Associates 

27220 Turnberry Lane Suite 110 

Valencia, CA 91355 

Principal Investigator 

R.D. Hartleb 

This report describes research sponsored by the U.S. Nuclear Regulatory Commission, U.S. 

Department of Energy (DOE), and Electric Power Research Institute (EPRI). 
E-iv

Acknowledgments 

Drs. Martin Chapman, Russell Green, and Scott Olson, specialists in seismology and 

geotechnical engineering, reviewed an outline of this document and provided comments and 

suggestions that were incorporated into the report. Laurel Bauer, Randal Cox, Hanan Mahdi, 

Stephen Obermeier, Okba Al-Qahdi, Haydar Al-Shukri, Pradeep Talwani, Martitia Tuttle, Roy 

Van Arsdale, and James Vaughn contributed data to the CEUS paleoliquefaction database. Scott 

Lindvall assisted with database design and provided overall guidance for the contents of this 

document. Tanya Broadbent, Jason Finley, Caroline Moseley, David Slayter, and Kathy Tucker 

assisted with data entry and verification, database management, map development, graphics, and 

copyright research. Lawrence Salomone, Project Manager for the CEUS SSC Project, conveyed 

the importance of this study to industry and government stakeholders, helped to coordinate our 

efforts, and facilitated communications among the Participatory Peer Review Panel (PPRP), 

CEUS SSC Project Team and Sponsors. Thanks to the reviewers whose comments and 

suggestions enhanced the depth and breadth of this report: TI Team member Stephen McDuffie, 

members of the PPRP and U.S. NRC staff, and Russell Wheeler of the U.S. Geological Survey.
E-v

CONTENTS 

1 Development of the Paleoliquefaction Database 1 

1.1 Database Structure 1 

1.2 Regional Data Sets 4 

1.2.1 New Madrid Seismic Zone and Surrounding Region 8 

 1.2.1.1 Overview 8 

 1.2.1.2 Data Description 9 

 1.2.1.3 Recommendations 9 

1.2.2 Marianna, Arkansas, Area 10

1.2.2.1 Overview 10

 1.2.2.2 Data Description 12

 1.2.2.3 Recommendations 12

1.2.3 St. Louis Region 13

1.2.3.1 Overview 13

 1.2.3.2 Data Description 14

 1.2.3.3 Recommendations 14

1.2.4 Wabash Valley Seismic Zone and Surrounding Region 15

1.2.4.1 Overview 15

 1.2.4.2 Data Description 16

 1.2.4.3 Recommendations 16

1.2.5 Arkansas-Louisiana-Mississippi Region 17

1.2.5.1 Overview 17

 1.2.5.2 Data Description 17

 1.2.5.3 Recommendations 18

1.2.6 Charleston Seismic Zone 18

1.2.6.1 Overview 18

 1.2.6.2 Data Description 18

 1.2.6.3 Recommendations 19
E-vi 

1.2.7 Atlantic Coast Region and the Central Virginia Seismic Zone 20

1.2.8 Newburyport, Massachusetts, and Surrounding Region 20

1.2.8.1 Overview 20

 1.2.8.2 Data Description 21

 1.2.8.3 Recommendations 21

1.2.9 Charlevoix Seismic Zone and Surrounding Region 22

1.2.9.1 Overview 22

 1.2.9.2 Data Description 23

 1.2.9.3 Recommendations 23

2 Uncertainties Associated with Paleoliquefaction Data 24

2.1 Collection of Paleoliquefaction Data 24

2.1.1 Identification of Earthquake-Induced Liquefaction Features 25

2.1.2 Dating Liquefaction Features 27

2.1.3 Dating Techniques 28

2.1.3.1 Dendrochronology 29

2.1.3.2 Radiocarbon Dating 29

2.1.3.3 Optically Stimulated Luminescence 31

2.1.3.4 Archeological Context 32

2.1.3.5 Stratigraphic Context 33

2.1.3.6 Soil Development 34

2.2 Uncertainties Related to Interpretation of Paleoliquefaction Data 34

2.2.1 Timing of Paleoearthquakes 35

2.2.2 Correlation of Liquefaction Features 36

2.2.3 Location of Paleoearthquakes 37

2.2.4 Magnitude of Paleoearthquakes 38

2.2.4.1 Comparative Studies 38

2.2.4.2 Empirical Relations 39

2.2.4.3 Geotechnical Analysis 40

2.2.5 Recurrence of Paleoearthquakes 41

2.2.5.1 Age Estimates of Liquefaction Features and Paleoearthquakes 41

2.2.5.2 Length and Completeness of the Paleoliquefaction Record 42
E-vii 

2.3 Recommendations for Future Research 42

3 Guidance for the Use of Paleoliquefaction Data in Seismic Source Characterization 

 44

4 Glossary 45

5 References 48

5.1 References Cited in Paleoliquefaction Database 48

5.2 References Cited in Appendix E 53
E-viii 

LIST OF FIGURES 

Figure E-1. Map of CEUS showing locations of regional data sets included in the CEUS SSC 

Project paleoliquefaction database, including New Madrid seismic zone and surrounding region; 

Marianna, Arkansas, area; St. Louis region; Wabash Valley seismic zone and surrounding 

region; Arkansas-Louisiana-Mississippi region; Charleston seismic zone; Atlantic Coastal region 

and the Central Virginia seismic zone; Newburyport, Massachusetts, and surrounding region; 

and Charlevoix seismic zone and surrounding region. 

Figure E-2. Diagram illustrating size parameters of liquefaction features, including sand blow 

thickness, width, and length; dike width; and sill thickness, as well as some of the diagnostic 

characteristics of these features. 

Figure E-3. Diagram illustrating sampling strategy for dating of liquefaction features as well as 

age data, such as 14C maximum and 14C minimum, used to calculate preferred age estimates 

and related uncertainties of liquefaction features.

Figure E-4. GIS map of New Madrid seismic zone and surrounding region showing portions of 

rivers searched for earthquake-induced liquefaction features by M. Tuttle, R. Van Arsdale, and J. 

Vaughn and collaborators (see explanation); information contributed for this report. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-5. GIS map of New Madrid seismic zone and surrounding region showing locations of 

liquefaction features for which there are and are not radiocarbon data. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-6. GIS map of New Madrid seismic zone and surrounding region showing locations of 

liquefaction features that are thought to be historical or prehistoric in age or whose ages are 

poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983. 

Figure E-7. GIS map of New Madrid seismic zone and surrounding region showing preferred 

age estimates of liquefaction features; features whose ages are poorly constrained are excluded. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-8. GIS map of New Madrid seismic zone and surrounding region showing measured 

thicknesses of sand blows. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. 

Figure E-9. GIS map of New Madrid seismic zone and surrounding region showing preferred 

age estimates and measured thicknesses of sand blows. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. 
E-ix

Figure E-10. GIS map of New Madrid seismic zone and surrounding region showing measured 

widths of sand dikes. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. 

Figure E-11. GIS map of New Madrid seismic zone and surrounding region showing preferred 

age estimates and measured widths of sand dikes. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983. 

Figure E-12. GIS map of New Madrid seismic zone and surrounding region illustrating 

preferred age estimates and measured thicknesses of sand blows as well as preferred age 

estimates and measured widths of sand dikes for sites where sand blows do not occur. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-13. GIS map of Marianna, Arkansas, area showing seismicity and locations of 

paleoliquefaction features relative to mapped traces of Eastern Reelfoot rift margin fault, White 

River fault zone, Big Creek fault zone, Marianna escarpment, and Daytona Beach lineament. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-14. (A) Trench log and (B) ground-penetrating radar profile, showing vertical sections 

of sand blows and sand dikes at Daytona Beach SE2 site along the Daytona Beach lineament

southwest of Marianna, Arkansas. Vertical scale of GPR profile is exaggerated (modified from 

Al-Shukri et al., 2009). 

Figure E-15. GIS map of Marianna, Arkansas, area showing locations of liquefaction features 

for which there are and are not radiocarbon data. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983. 

Figure E-16. GIS map of Marianna, Arkansas, area showing locations of liquefaction features 

that are thought to be historical or prehistoric in age or whose ages are poorly constrained. To 

date, no liquefaction features thought to have formed during 1811-1812 earthquakes have been 

found in area. Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983. 

Figure E-17. GIS map of Marianna, Arkansas, area showing preferred age estimates of 

liquefaction features; features whose ages are poorly constrained are excluded. Map projection is 

USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-18. GIS map of Marianna, Arkansas, area showing measured thicknesses of sand 

blows. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983. 

Figure E-19. GIS map of Marianna, Arkansas, area showing preferred age estimates and 

measured thicknesses of sand blows. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. 

Figure E-20. GIS map of Marianna, Arkansas, area showing measured widths of sand dikes. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-21. GIS map of Marianna, Arkansas, area showing preferred age estimates and 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 
E-x

Figure E-22. GIS map of St. Louis, Missouri, region showing seismicity and portions of rivers 

searched for earthquake-induced liquefaction features by Tuttle and collaborators; information 

contributed for this report. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. 

Figure E-23. GIS map of St. Louis, Missouri, region showing locations of liquefaction features, 

including several soft-sediment deformation structures, for which there are and are not 

radiocarbon data. Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983. 

Figure E-24. GIS map of St. Louis, Missouri, region showing locations of liquefaction features 

that are thought to be historical or prehistoric in age or whose ages are poorly constrained. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-25. GIS map of St. Louis, Missouri, region showing preferred age estimates of 

liquefaction features; features whose ages are poorly constrained, including several that are 

prehistoric in age, are not shown. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-26. GIS map of St. Louis, Missouri, region showing measured thicknesses of sand 

blows at similar scale as used in Figure E-8 of sand blows in New Madrid seismic zone. Note 

that few sand blows have been found in St. Louis region. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. 

Figure E-27. GIS map of St. Louis, Missouri, region showing preferred age estimates and 

measured thicknesses of sand blows. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. 

Figure E-28. GIS map of St. Louis, Missouri, region showing measured widths of sand dikes at 

similar scale as that used in Figure E-10 for sand dikes in New Madrid seismic zone. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-29. GIS map of St. Louis, Missouri, region showing measured widths of sand dikes at 

similar scale as that used in Figures E-42 and E-48 for sand dikes in the Newburyport and 

Charlevoix regions, respectively. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-30. GIS map of St. Louis, Missouri, region showing preferred age estimates and 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-31. GIS map of Wabash Valley seismic zone and surrounding region showing portions 

of rivers searched for earthquake-induced liquefaction features (digitized from McNulty and 

Obermeier, 1999). Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983. 

Figure E-32. GIS map of Wabash Valley seismic zone and surrounding region showing 

measured widths of sand dikes at similar scale as that used in Figures E-10 and E-11 for sand 

dikes in New Madrid seismic zone. Map projection is USA Contiguous Albers Equal Area 

Conic, North America Datum 1983. 
E-xi 

Figure E-33. GIS map of Wabash Valley region of Indiana and Illinois showing preferred age 

estimates and paleoearthquake interpretation. Map projection is USA Contiguous Albers Equal 

Area Conic, North America Datum 1983. 

Figure E-34. GIS map of Arkansas-Louisiana-Mississippi (ALM) region showing 

paleoliquefaction study locations. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-35. GIS map of Charleston, South Carolina, region showing locations of 

paleoliquefaction features for which there are and are not radiocarbon dates. Map projection is 

USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-36. GIS map of Charleston, South Carolina, region showing locations of historical and 

prehistoric liquefaction features. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-37. Map of Atlantic coast region showing areas searched for paleoliquefaction features 

by Gelinas et al. (1998) and Amick, Gelinas, et al. (1990). Rectangles indicate 7.5-minute 

quadrangles in which sites were investigated for presence of paleoliquefaction features. The 

number of sites investigated is shown within that quadrangle, if known. Orange and yellow 

indicate quadrangles in which paleoliquefaction features were recognized. 

Figure E-38. Map of Central Virginia seismic zone region showing portions of rivers searched 

for earthquake-induced liquefaction features by Obermeier and McNulty (1998). 

Figure E-39. GIS map of Newburyport, Massachusetts, and surrounding region showing 

seismicity and portions of rivers searched for earthquake-induced liquefaction features (Gelinas 

et al., 1998; Tuttle, 2007, 2009). Solid black line crossing map represents Massachusetts–New 

Hampshire border. Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983. 

Figure E-40. GIS map of Newburyport, Massachusetts, and surrounding region showing 

locations of liquefaction features for which there are and are not radiocarbon dates. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-41. GIS map of Newburyport, Massachusetts, and surrounding region showing 

locations of liquefaction features that are thought to be historical or prehistoric in age or whose 

ages are poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. 

Figure E-42. GIS map of Newburyport, Massachusetts, and surrounding region showing 

measured widths of sand dikes. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-43. GIS map of Newburyport, Massachusetts, and surrounding region showing 

preferred age estimates and measured widths of sand dikes. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. 

Figure E-44. Map of Charlevoix seismic zone and adjacent St. Lawrence Lowlands showing 

mapped faults and portions of rivers along which reconnaissance and searches for earthquakeinduced liquefaction features were performed. Charlevoix seismic zone is defined by 

concentration of earthquakes and locations of historical earthquakes northeast of Quebec City. 
E-xii 

Devonian impact structure in vicinity of Charlevoix seismic zone is outlined by black dashed 

line. Taconic thrust faults are indicated by solid black lines with sawteeth on upper plate; Iapetan 

rift faults are shown by solid black lines with hachure marks on downthrown side (modified from 

Tuttle and Atkinson, 2010). 

Figure E-45. GIS map of Charlevoix seismic zone and surrounding region showing locations of 

liquefaction features, including several soft-sediment deformation structures, for which there are 

and are not radiocarbon data. Note the location of 1988 M 5.9 Saguenay earthquake northwest of 

the Charlevoix seismic zone. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 

Figure E-46. GIS map of Charlevoix seismic zone and surrounding region showing locations of 

liquefaction features that are modern, historical, or prehistoric in age, or whose ages are poorly 

constrained. Map projection is USA Contiguous Albers Equal Area Conic, North America 

Datum 1983. 

Figure E-47. GIS map of Charlevoix seismic zone and surrounding region showing preferred 

age estimates of liquefaction features; features whose ages are poorly constrained are excluded. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 

Figure E-48. GIS map of Charlevoix seismic zone and surrounding region showing measured 

widths of sand dikes. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. 

Figure E-49. GIS map of Charlevoix seismic zone and surrounding region showing preferred 

age estimates and measured widths of sand dikes. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983. 

Figure E-50. Photograph of moderate-sized sand blow (12 m long, 7 m wide, and 14 cm thick) 

that formed about 40 km from epicenter of 2001 M 7.7 Bhuj, India, earthquake (from Tuttle, 

Hengesh, et al., 2002), combined with schematic vertical section illustrating structural and 

stratigraphic relations of sand blow, sand dike, and source layer (modified from Sims and 

Garvin, 1995). 

Figure E-51. Tree trunks buried and killed by sand blows, vented during 1811-1812 New 

Madrid earthquakes (from Fuller, 1912). 

Figure E-52. Large sand-blow crater that formed during 2002 M 7.7 Bhuj, India, earthquake. 

Backpack for scale. Photograph: M. Tuttle (2001). 

Figure E-53. Sand-blow crater that formed during 1886 Charleston, South Carolina, earthquake. 

Photograph: J.K. Hillers (from USGS Photograph Library). 

Figure E-54. Photograph of sand blow and related sand dikes exposed in trench wall and floor in 

New Madrid seismic zone. Buried soil horizon is displaced downward approximately 1 m across 

two dikes. Clasts of soil horizon occur within dikes and overlying sand blow. Degree of soil 

development above and within sand blow suggests that it is at least several hundred years old and 

formed prior to 1811-1812 New Madrid earthquakes. Organic sample (location marked by red 

flag) from crater fill will provide close minimum age constraint for formation of sand blow. For 

scale, each colored intervals on shovel handle represents 10 cm. Photograph: M. Tuttle. 
E-xiii 

Figure E-55. Sand dikes, ranging up to 35 cm wide, originate in pebbly sand layer and intrude 

overlying diamicton, These features were exposed in cutbank along Cahokia Creek about 25 km 

northeast of downtown St. Louis (from Tuttle, 2000). 

Figure E-56. Photograph of small diapirs of medium sand intruding base of overlying deposit of 

interbedded clayey silt and very fine sand, and clasts of clayey silt in underlying medium sand, 

observed along Ouelle River in Charlevoix seismic zone. Sand diapirs and clasts probably 

formed during basal erosion and foundering of clayey silt due to liquefaction of the underlying 

sandy deposit. Red portion of shovel handle represents 10 cm (modified from Tuttle and 

Atkinson, 2010). 

Figures E-57. (A) Load cast formed in laminated sediments of Van Norman Lake during 1952 

Kern County, California, earthquake. Photograph: J. Sims (from Sims, 1975). (B) Load cast, 

pseudonodules, and related folds formed in laminated sediment exposed along Malbaie River in 

Charlevoix seismic zone. Sand dikes crosscutting these same laminated sediments occur at a 

nearby site. For scale, each painted interval of the shovel handle represents 10 cm (modified 

from Tuttle and Atkinson, 2010). 

Figure E-58. Log of sand blow and uppermost portions of related sand dikes exposed in trench 

wall at Dodd site in New Madrid seismic zone. Sand dikes were also observed in opposite wall 

and trench floor. Sand blow buries pre-event A horizon, and a subsequent A horizon has 

developed in top of sand blow. Radiocarbon dating of samples collected above and below sand 

blow brackets its age between 490 and 660 yr BP. Artifact assemblage indicates that sand blow 

formed during late Mississippian (300–550 yr BP or AD 1400–1670) (modified from Tuttle, 

Collier, et al., 1999). 

Figures E-59. (A) Photograph of earthquake-induced liquefaction features found in association 

with cultural horizon and pit exposed in trench wall near Blytheville, Arkansas, in New Madrid 

seismic zone. Photograph: M. Tuttle. (B) Trench log of features shown in (A). Sand dike formed 

in thick Native American occupation horizon containing artifacts of early Mississippian cultural 

period (950–1,150 yr BP). Cultural pit dug into top of sand dike contains artifacts and charcoal 

used to constrain minimum age of liquefaction features (modified from Tuttle and Schweig, 

1995). 

Figure E-60. In situ tree trunks such as this one buried and killed by sand blow in New Madrid 

seismic zone offer opportunity to date paleoearthquakes to the year and season of occurrence. 

Photograph: M. Tuttle. 

Figure E-61. Portion of dendrocalibration curve illustrating conversion of radiocarbon age to 

calibrated date in calendar years. In example, 2-sigma radiocarbon age of 2,280–2,520 BP is 

converted to calibrated date of 770–380 BC (from Tuttle, 1999). 

Figure E-62. Empirical relation developed between A horizon thickness of sand blows and years 

of soil development in New Madrid region. Horizontal bars reflect uncertainties in age estimates 

of liquefaction features; diamonds mark midpoints of possible age ranges (from Tuttle et al., 

2000) 

Figure E-63. Diagram illustrating earthquake chronology for New Madrid seismic zone for past 

5,500 years based on dating and correlation of liquefaction features at sites (listed at top) across 

region from north to south. Vertical bars represent age estimates of individual sand blows, and 
E-xiv 

horizontal bars represent event times of 138 yr BP (AD 1811-1812); 500 yr BP ± 150 yr; 1,050 

yr BP ± 100 yr; and 4,300 yr BP ± 200 yr (modified from Tuttle, Schweig, et al., 2002; Tuttle et 

al., 2005). 

Figure E-64. Diagram illustrating earthquake chronology for New Madrid seismic zone for past 

2,000 years, similar to upper portion of diagram shown in Figure E-63. As in Figure E-63, 

vertical bars represent age estimates of individual sand blows, and horizontal bars represent 

event times. Analysis performed during CEUS SSC Project derived two possible uncertainty 

ranges for timing of paleoearthquakes, illustrated by the darker and lighter portions of the 

colored horizontal bars, respectively: 503 yr BP ± 8 yr or 465 yr BP ± 65 yr, and 1,110 yr BP ± 

40 yr or 1055 ± 95 yr (modified from Tuttle, Schweig, et al., 2002). 

Figure E-65. Maps showing spatial distributions and sizes of sand blows and sand dikes 

attributed to 500 and 1,050 yr BP events. Locations and sizes of liquefaction features that formed 

during AD 1811-1812 (138 yr BP) New Madrid earthquake sequence shown for comparison 

(modified from Tuttle, Schweig, et al., 2002).

Figure E-66. Liquefaction fields for 138 yr BP (AD 1811-1812); 500 yr BP (AD 1450); and 

1,050 yr BP (AD 900) events as interpreted from spatial distribution and stratigraphy of sand 

blows (modified from Tuttle, Schweig, et al., 2002). Ellipses define areas where similar-age sand 

blows have been mapped. Overlapping ellipses indicate areas where sand blows are composed of 

multiple units that formed during sequence of earthquakes. Dashed ellipse outlines area where 

historical sand blows are composed of four depositional units. Magnitudes of earthquakes in 500 

yr BP and 1,050 yr BP are inferred from comparison with 1811-1812 liquefaction fields. 

Magnitude estimates of December (D), January (J), and February (F) main shocks and large 

aftershocks taken from several sources; rupture scenario from Johnston and Schweig (1996; 

modified from Tuttle, Schweig, et al., 2002).

Figure E-67. Empirical relation between earthquake magnitude and epicentral distance to 

farthest known sand blows induced by instrumentally recorded earthquakes (modified from 

Castilla and Audemard, 2007). 

Figure E-68. Distances to farthest known liquefaction features indicate that 500 and 1,050 yr BP 

New Madrid events were at least of M 6.7 and 6.9, respectively, when plotted on Ambraseys 

(1988) relation between earthquake magnitude and epicentral distance to farthest surface 

expression of liquefaction. Similarity in size distribution of historical and prehistoric sand blows, 

however, suggests that paleoearthquakes were comparable in magnitude to 1811-1812 events or 

M ~7.6 (modified from Tuttle, 2001). 
E-xv

LIST OF TABLES 

Table E-1.2-1. Summary of Information on Liquefaction Features in Regional Data Sets 

Table E-1.2-2. Summary of Type and Prevalence of Paleoliquefaction Features 

Table E-2.1.3. Summary of Dating Techniques Used in Paleoliquefaction Studies 

Table E-2.2. Uncertainties Related to Interpretation of Paleoearthquake Parameters

E-1

E 

APPENDIX 

Over the past 30 years, paleoliquefaction studies have contributed to the understanding of the 

earthquake hazards of various regions in the Central and Eastern United States (CEUS) and 

southeastern Canada. Paleoliquefaction studies have provided estimates of ages, source areas, 

magnitudes, and recurrence times of large paleoearthquakes and uncertainties associated with 

these estimates. Given the need for this information in probabilistic seismic hazard assessment 

(PSHA), the paleoliquefaction task was undertaken to aid in the development of the seismic 

source model for the CEUS SSC Project. Under this task, a new paleoliquefaction database, 

including regional data sets, was created and this report was prepared, documenting and 

illustrating the database, discussing uncertainties associated with paleoliquefaction data, and 

providing guidance on the use of paleoliquefaction data in seismic source characterization. 

All large data sets of paleoliquefaction features are included in the CEUS paleoliquefaction 

database, including those collected in the vicinity of the Charleston seismic zone in eastern South 

Carolina, the New Madrid seismic zone in southeastern Missouri, northeastern Arkansas, western 

Tennessee, and western Kentucky, the Wabash Valley seismic zone in southern Illinois and 

southern Indiana, and the Charlevoix seismic zone in southeastern Quebec (Figure E-1). The 

paleoliquefaction data compiled for this task are used to estimate recurrence rates and 

magnitudes of paleoearthquakes, critical seismic source parameters in PSHA and in

characterization of seismic source zones for the CEUS SSC Project. 

E.1 Development of the Paleoliquefaction Database 

Building on a regional paleoliquefaction database for the New Madrid seismic zone and 

surrounding region previously developed by M. Tuttle & Associates, the Center for Earthquake 

Research and Information, and the U.S. Geological Survey, the new CEUS database includes 

readily available paleoliquefaction data gathered by a diverse group of investigators. The 

structure of the new database was designed to capture pertinent information for source 

characterization, as explained below. There are some significant differences between regional 

data sets in the types of features that have been used to identify paleoearthquakes in the geologic 

record and in the approaches used to estimate the ages and related uncertainties of 

paleoliquefaction features. These differences are discussed below for each regional data set. 

E.1.1 Database Structure 

This section describes the database structure, including definitions of column headings, units of 

measure, and other relevant information for all data entries. The database itself is available in 

digital format on the CEUS SSC Project website. For fields where no data are available or that 

do not apply, that database entry field is left blank. The following paragraphs describe each data 

field and provide information on how data was and was not tabulated. Each data field is 
E-2

described individually and in the order in which they appear in the database. Discussions of 

earthquake-induced liquefaction features as well as various approaches and dating techniques 

used to estimate the ages of liquefaction features can be found in Sections E.2.1.1, E.2.1.2, and 

E.2.1.3. Figures E-2 and E-3 are provided to illustrate size parameters of liquefaction features 

and age data used to estimate preferred ages and related uncertainties of liquefaction features. 

KEY: Unique numeric designator of study region for each entry in database. The following 

ranges are used for the specified priority study areas: 

1000–1999: Alabama-Louisiana-Mississippi region (ALM) 

2000–2999: Charleston seismic zone 

3000–3999: Wabash Valley seismic zone and surrounding region 

4000–4999: St. Louis, Missouri, region 

5000–5999: New Madrid seismic zone and surrounding region 

6000–6999: Marianna, Arkansas, area 

7000–7999: Newburyport, Massachusetts, and surrounding region 

8000–8999: Charlevoix seismic zone and surrounding region 

9000-9999: Atlantic Coast Region and the Central Virginia Seismic Zone 

SITE_NAME: Alphabetic designator of study site within study region. 

FEAT_ID: Unique alphabetic paleoliquefaction feature identifier that includes shortened version 

of site name (example: ―Bluf-2‖ indicates paleoliquefaction feature 2 from the Bluffton, South 

Carolina site). 

XCOORD: Numeric value of longitude, in decimal degrees. All values should be negative (―-‖). 

Coordinates of archeological sites rounded to 0.1 decimal degree to protect locations of sites. 

YCOORD: Numeric value of latitude, in decimal degrees. All values should be positive. 

Coordinates of archeological sites rounded to 0.1 decimal degree to protect locations of sites. 

COORD_ORIG: Alphabetic description (≤ 254 characters) of positional data for 

paleoliquefaction feature, including reference shorthand (examples: ―digitized from Talwani and 

Schaeffer (2001) Figure 1‖ or ―unpublished hand-held GPS coordinates from Tuttle‖). 

OBS_TYPE: Alphabetic description of observation type. Includes: trench, cutbank, aerial 

photograph, quarry, field mapping, and test pit / auger. 

FEAT_TYPE: Alphabetic description of feature type. Includes: sand blow, crater fill, dike, sill, 

and SSD (for soft sediment deformation structures that are likely earthquake-related). 

SSD_DESCR: Alphabetic description (≤ 254 characters) of SSD. This field is used only where 

―SSD‖ is entered in the FEAT_TYPE column. Includes description of SSD and assessment of 

likelihood that it is/is not earthquake-related. Features that are clearly non-earthquake-related are 

not included in the database. 

FEAT_REF: Alphabetic description of citation shorthand for source of FEAT_TYPE 

information and, where applicable, SSD_DESCR. 
E-3

SB_THICK, SB_WIDTH, SB_LENGTH, DK_WIDTH, and SILL_THICK: Numeric values of 

dimensions of sand blow thickness, sand blow width, sand blow length, dike width, and sill 

thickness, respectively (see Figure E-2). All dimensions are in cm. Because these dimensions 

typically are from limited trench exposures, values typically are minimum values (with a few 

exceptions). Additional descriptive information is entered into the COMMENT field(s), as 

needed. 

DIM_REF: Alphabetic description of reference shorthand for dimensional values listed in 

previous five columns. 

C14_MAX: Numeric value of lower bracketing 2-sigma radiocarbon age on feature, in yr BP 

relative to AD 1950. 

C14_MIN: Numeric value of upper bracketing 2-sigma radiocarbon age on feature, in yr BP 

relative to AD 1950. 

C14_REF: Alphabetic description of reference shorthand for radiocarbon data listed in previous 

two columns. 

OSL_MAX: Numeric value of lower bracketing 2-sigma optically stimulated luminescence 

(OSL) age on feature, in yr BP relative to AD 1950. 

OSL_MIN: Numeric value of upper bracketing 2-sigma OSL age on feature, in yr BP relative to 

AD 1950. 

OSL_REF: Alphabetic description of reference shorthand for OSL data listed in previous two 

columns. 

PREFAGEEST: Numeric value of preferred age estimate. In most cases, this will simply be the 

average or value midway between either: (1) C14_MAX and C14_MIN; and/or (2) OSL_MAX 

and OSL_MIN, in yr BP (see Figure E-3). However, in special circumstances, this value may 

represent a researcher’s preferred age estimate, taking into account specific archeological, 

stratigraphic, or other criteria. Additional descriptive information is entered into the COMMENT 

field(s), as needed. 

PREFAGEUNP: Numeric value of the upper bound of the preferred age estimate. This value 

represents the ―+‖ portion of the 2-sigma ―±‖ uncertainty value associated with the 

PREFAGEEST value. 

In most cases this value will be symmetric about the PREFAGEEST value. In other words, a 

preferred age estimate of 600 ± 200 yr BP is entered into the database as follows: ―600‖ in 

PREFAGEEST field, ―200‖ in the PREFAGEUNP field, and ―200‖ in the PREFAGEUNM 

field. 

In some cases, the uncertainty will be asymmetric about the PREFAGEEST (e.g., 600 +200/-

150 yr BP). If so, ―600‖ will appear in the PREFAGEEST field, ―200‖ in the PREFAGEUNP 

field, and ―150‖ in the PREFAGEUNM field (described below). 

PREFAGEUNM: Numeric value of the lower bound of the preferred age estimate. This value 

represents the ―-‖ portion of the 2-sigma ―±‖ uncertainty value associated with the 

PREFAGEEST value. See above. 

PREFAGEREF: Alphabetic description of reference shorthand for preferred age and preferred 

age uncertainty data listed in previous three columns. 
E-4

STRAT: Alphabetic description of qualitative age data from stratigraphic relationships, if any. 

Also includes reference shorthand information. 

ARCHEO: Alphabetic description of archaeological age data, if any. Also includes reference 

shorthand information. 

WEATHERING: Alphabetic description of degree of weathering of feature (not weathering of 

surrounding sediments), if available. Also includes reference shorthand information. 

GEOTEC: Alphabetic description of availability of geotechnical information describing 

paleoliquefaction feature. ―Local‖ or ―regional‖ indicate the type of geotechnical data available 

for the feature or site. 

GEOTEC_REF: Alphabetic description of reference shorthand for geotechnical data listed in 

previous column. 

COMMENT: Alphabetic description of other relevant data not captured in other fields. Note: if > 

254 characters required, comments continued in COMMENT2 and COMMENT3 fields, as 

needed. 

E.1.2 Regional Data Sets 

All large data sets of paleoliquefaction features in the CEUS and southeastern Canada that have 

been described in published articles are included in the project paleoliquefaction database 

(Figure E-1). Summaries of regional data sets are provided below, including overviews of 

paleoliquefaction studies, descriptions of date types and age estimates, and recommendations for 

future research. In addition, maps were generated with the geographical information system 

(GIS) ArcGIS to illustrate the regional data sets and to show geographical and geological 

features mentioned in the text. 

There are some significant differences between data sets, including the types of liquefaction 

features used to identify paleoearthquakes, information gathered about those features (e.g., their 

dimensions), basis of age estimates of the features, and overall quality of the data. A summary of 

the differences in the regional data sets is presented in Table E-1.2.-1. Additional information 

about the specific types of liquefaction features and their prevalence in the various regions is 

summarized in Table E-1.2-2. To try to maintain consistency between data sets, we adopted 

well-established criteria that features must meet to be accepted as earthquake-induced 

liquefaction features and to be used in seismic source characterization. These criteria include the 

following (Obermeier, 1996; Tuttle, 2001): 

sedimentary characteristics consistent with case histories of earthquake-induced liquefaction; 

sedimentary characteristics indicative of sudden, strong, upwardly directed hydraulic force of 

short duration; 

occurrence of more than one type of liquefaction feature and of similar features at multiple 

locations; 

occurrence in geomorphic settings where hydraulic conditions described in (2) would not 

develop under nonseismic conditions; and 

age data to support both contemporaneous and episodic formation of features over a large 

area. 
E-5

Table E-1.2-1. Summary of Information on Liquefaction Features in Regional Data Sets 

Regional 

Data Set1

Type2

Size3

Age Estimate4

Arch 

Data5

Soils

Data6

Geotech 

Data7 Quality8 SB SD SS Num Infer

NMSZ + + – + + – √ + √ 1

Marianna + + – + + + √ 2

St. Louis – + √ + √ – – + √ 2

WVSZ + – – + – – √ 3

ALM – √ 4

CSZ + – + – √ 2

AC-CVA – √ 3

NEWBURY – + √ – – 3

CxSZ √ + – + √ – + √ 2

1. NMSZ = New Madrid seismic zone and surrounding region; WVSZ = Wabash Valley seismic zone and 

surrounding region; ALM = Arkansas-Louisiana-Mississippi region; CSZ = Charleston seismic zone; AC-CVA = 

Atlantic Coast and Central Virginia reconnaissance; NEWBURY = Newburyport, Massachusetts, and surrounding 

region; CxSZ = Charlevoix seismic zone and surrounding region (includes information of features that formed 

during 1988 Saguenay earthquake). 

2. SB = sand blow; SD = sand dike; SS = other soft-sediment deformation structures (see Section E.2.1.1 and 

Glossary); + = many features; √ = some features; – = few features; blank = no features. 

3. Size = measured dimension of liquefaction features provided; + = many features; √ = some features; – = few 

features; blank = no features. 

4. Num = numerical, based on radiocarbon and or OSL dating; Infer = inferred, based on weathering characteristics 

and/or stratigraphic position. 

5. Arch Data= archeological data helps to estimate age of liquefaction features. 

6. Soils Data = information on soil and/or weathering characteristics of liquefaction features. 

7. Geotech Data = geotechnical data used to assess liquefaction susceptibility of sediments and/or to estimate 

magnitude of paleoearthquake. 

8. Quality = overall quality of data set based on feature type meeting identification criteria, availability of information 

on feature size, and age estimates based primarily on numerical minimum and maximum constraints; 1 = high 

quality; 2 = good quality; 3 = fair quality; 4 = low quality. 

In addition, we identified sedimentary characteristics consistent with these criteria to facilitate 

the evaluation of regional data sets. These characteristics are based on studies of modern and 

historical earthquake-induced liquefaction features and are discussed in more detail in Section 

E.2 of this appendix (see Figure E-2). Sedimentary characteristics of earthquake-induced 

liquefaction features include the following: 

Sand blows or sand-blow craters (with feeder dikes) 

o Typically elliptical or linear, sometimes circular, in plan view 

o Connected to feeder dikes below

o Often characterized by ―cut-and-fill‖ structure and flow structures, and/or lineations, 

above the feeder dike 
E-6

o Vented sediment typically fine to coarse sand, may include some silt and clay 

o Often becomes finer-grained upsection and laterally away from feeder dike/vent 

o Usually thins laterally away from feeder dike/vent 

o May comprise multiple fining-up depositional units related to a sequence of earthquakes; 

seismites may be separated by layers of fines such as silty clay or clay that accumulated 

between earthquakes 

o May contain clasts of host deposit, especially near feeder dike, clast size generally 

decreases with distance from vent 

o Volume of vented deposit should ―make sense‖ relative to size and number of sand dikes

o Subsidence structures may be seen near vent, including localized downwarping of surface 

soil and host strata and possible vertical displacement across feeder dikes 

o Sand-blow craters often form in organic-rich soils or clay-rich host deposits 

o Sand-blow craters contain vented sand deposits and clasts of host material; overlain by 

crater fill deposits and/or reworked material 

Sand dikes 

o Dike sidewalls typically subparallel, usually widen downward; also may broaden upward 

into vent structure at the ground surface (event horizon) 

o Typically a few meters to tens of meters long (in plan view); therefore, often, but not 

always, exposed in both walls of a trench 

o Sand within dikes often fines upward 

o Often characterized by flow structure or lineations 

o Often contain clasts of host deposit(s) 

o Near-vertical dikes may exhibit grading, with finer material along dike margins; inclined 

dikes may exhibit bedding 

o May be characterized by subsidiary dikes and/or sills 

o Source layer often lacks original sedimentary structure where fluidized, may exhibit flow 

structure or lineations as well as soft-sediment deformation structures such as ball-andpillow structures and dish structures (see Glossary and Section E.2.1.1)

There also are significant differences between data sets in the approaches used to estimate the 

ages of paleoliquefaction features, and in the uncertainty associated with those age estimates. To 

minimize these differences, preferred age estimates and their associated uncertainty have been 

calculated for this project from 2-sigma minimum and maximum constraining ages for individual 

liquefaction features. The preferred age estimate is the average of the minimum and maximum 

values of the constraining age ranges (see Figure E-3). The uncertainty is the difference between 

the average and the minimum and maximum values of the constraining age ranges. Since they 

more closely reflect the ages of the liquefaction features, close minimum and close maximum 

constraining ages, as well as contemporary ages, are preferred over minimum and maximum 

constraining ages in calculating age estimates. In some cases, additional information provided by 
E-7

archeological or stratigraphic context or by soil development in the liquefaction feature itself is 

used to help to estimate feature age. Differences in feature types and approaches used to estimate 

ages of paleoliquefaction features are discussed below in the summaries for each regional data 

set.

Table E-1.2-2 

Summary of Type and Prevalence of Paleoliquefaction Features 

Feature 

Type1

Prevalence2of Paleoliquefaction Features in Regions3

Selected 

References4

NMSZ MAR STL WVSZ ALM CSZ

ACCVA NBY CxSZ

Sand blow + + - √ - √ (a) (b) (c) (d) 

(e) (f) (g) (h) 

(i) (j) (k) (l) 

(m) 

Sand-blow 

crater

√ + - (a) (n) (o) (p) 

(q) 

Sand dike + + + + - √ - √ + (b) (e) (g) (n) 

(p) (r) (s) (t) 

(u) (v) (w) (x) 

(y) (z) 

Sand sill √ - √ - - (d) (e) (f) (g) 

(j) (r) 

Ball-andpillow 

structure

- (f) (g) 

Basal erosion 

and sand 

diapirs

- - - - (f) (g) (z) 

Dish 

structure

- - (f) (g) 

Load casts - - (f) (g) (z) 

Pseudonodules- - - (f) (g) (z) 

1. See Section E.2.1.1 and Glossary. 

2. Prevalence of liquefaction features: + = many features; √ = some features; - = few features; blank = no features. 

3. NMSZ = New Madrid seismic zone and surrounding region; MAR = Marianna Area; STL = St. Louis and 

surrounding region; WVSZ = Wabash Valley seismic zone and surrounding region; ALM = Arkansas-LouisianaMississippi region; CSZ = Charleston seismic zone; AC-CVA = Atlantic Coast and Central Virginia 

reconnaissance; NBY = Newburyport, Massachusetts, and surrounding region; CxSZ = Charlevoix seismic zone 

and surrounding region. 

4. Selected references shown here (also see paleoliquefaction database and reference lists at the end of this report). 

(a) Amick, 1990; (b) Tuttle et al., 1990; (c) Saucier, 1991; (d) Hajic et al., 1995; (e) Munson and Munson, 1996; (f) 

Tuttle, 1999; (g) Tuttle, Chester, et al., 1999; (h) Tuttle, Schweig, et al., 2002; (i) Tuttle et al., 2005; (j) Al-Shukri et 

al., 2005; (k) Tuttle et al., 2006; (l) Wolf et al., 2006; (m) Talwani et al., 2008; (n) Tuttle et al., 1992; (o) Talwani et 

al., 1993; (p) Noller and Forman, 1998; (q) Talwani and Schaeffer, 2001; (r) Tuttle and Seeber, 1991; (s) 

Obermeier et al., 1991; (t) Obermeier et al., 1993; (u) Munson et al., 1995; (v) McNulty and Obermeier, 1999; (w) 

Broughton et al., 2001; (x) Cox, Larsen, et al., 2004; (y) Exelon, 2003, 2004; (z) Tuttle and Atkinson, 2010. 
E-8

E.1.2.1 New Madrid Seismic Zone and Surrounding Region 

E.1.2.1.1 Overview 

In 1811-1812, a major earthquake sequence including three main shocks with moment 

magnitudes, M 7 to 8, and several large aftershocks, struck the central United States (Figures E-4

through E-12; e.g., Johnston, 1996c; Hough et al., 2000; Bakun and Hooper, 2004). These 

earthquakes are inferred to have been centered in the New Madrid seismic zone (NMSZ) and to 

include some of the largest known intraplate earthquakes in the world (Johnston and Kanter, 

1990). The large liquefaction field produced by the 1811-1812 main shocks, including 

liquefaction more than 240 km from their inferred epicenters, supports the interpretation that 

they were very large-magnitude earthquakes (Fuller, 1912; Ambraseys, 1988; Johnston and 

Schweig, 1996; Tuttle, Schweig, et al., 2002; Castilla and Audemard, 2007). 

During the past 20 years, various investigators have searched for and studied earthquake-induced 

liquefaction features in the NMSZ and surrounding region (Figures E-4 through E-12). Initially, 

most liquefaction features were assumed to have formed in 1811-1812; but attention to soil 

development and relations with cultural horizons and features at archeological sites led to the 

discovery of pre-1811 sand blows and related sand dikes (Saucier, 1991; Tuttle and Schweig, 

1995; Tuttle, Lafferty, Guccione, et al., 1996). Since then, paleoseismic studies have focused on 

finding and dating paleoliquefaction features, constraining their ages, comparing their internal 

stratigraphy, size, and spatial distribution to features that formed during the 1811-1812 

earthquakes, and estimating the locations, magnitudes, and recurrence times of their causative 

paleoearthquakes (e.g., Saucier, 1989; Tuttle, Schweig, et al., 2002; Figures E-5 through E-12). 

Some studies involved investigations of sand blows at archeological sites in the New Madrid 

seismic zone (e.g., Craven, 1995b; Tuttle et al., 1998, 2000, and 2005), whereas others involved 

searching for liquefaction features along drainage ditches and river cutbanks across the 

Mississippi River floodplain and along tributary valleys (Figure E-4; e.g., Vaughn, 1994; Li et 

al., 1998; Tuttle, 1999; Broughton et al., 2001). 

The age estimates of liquefaction features across the region cluster around AD 1810 ± 130 years, 

AD 900 ± 100 years, AD 1450 ± 150 years, and 2350 BC ± 200 yr and were interpreted to be the 

dates of causative earthquakes (Figure E-7; Tuttle, Schweig, et al., 2002; Tuttle et al., 2005; 

Guccione, 2005). Other Holocene paleoliquefaction features have been documented across the 

region, suggesting additional paleoearthquakes, but the ages of these features are poorly 

constrained or do not correlate temporally with one another making interpretation difficult. One 

of these sand blows is similar in age to a ―channel straightening‖ event of the Mississippi River 

attributed to reverse faulting on the Reelfoot thrust between 2,750 and 3,250 yr BP (Holbrook et 

al., 2006). In addition, several Late Wisconsin sand blows and dikes have been found in the 

Western Lowlands (Vaughn, 1994) and in western Kentucky (Tuttle, 2005a; see Figure E-7). 

The size, compound nature, and spatial distributions of sand blows that formed circa AD 900 ± 

100 years and AD 1450 ± 150 years were found to be strikingly similar to those that formed in 

1811-1812 (Figures E-9 and E-12; Tuttle, 1999; Tuttle, Schweig, et al., 2002). The similarity 

between the historical and prehistoric liquefaction fields suggested that the paleoearthquakes 

were generated by the same source and had similar magnitudes, M 7 to 8, to the main shocks of 

the 1811-1812 sequence. These magnitude estimates were supported by several studies that 

conducted liquefaction potential analysis of geotechnical data collected in different parts of the 

region (e.g., Schneider and Mayne, 2000; Schneider et al., 2001; Liao et al., 2002; Stark, 2002; 
E-9

Tuttle and Schweig, 2004). Taken together, the paleoliquefaction findings suggested that the 

NMSZ generated earthquake sequences including very large, M 7 to 8, main shocks every 500 

years on average during the past 1,200 years (Tuttle, 1999; Tuttle, Schweig, et al., 2002). 

E.1.2.1.2 Data Description 

Paleoliquefaction data sets were contributed by the foremost researchers in the New Madrid 

region including M. Tuttle, J. Vaughn, R. Van Arsdale, R. Cox, and their collaborators and 

compiled in the CEUS SSC Project paleoliquefaction database. Additional paleoliquefaction data 

are drawn from journal articles, technical reports, and graduate student theses. All the data were 

previously published as indicated in the paleoliquefaction database. For this project, Tuttle, 

Vaughn, and Van Arsdale identified river sections searched by them and their collaborators, 

which allowed us to produce Figure E-4. All data were reviewed, 2-sigma minimum and 

maximum constraining ages entered, and preferred age estimates reassessed. Most of the 

radiocarbon ages were determined by Beta Analytic Radiocarbon Laboratory and calibrated 

using the Pretoria procedure (Talma and Vogel, 1993; Vogel et al., 1993). High precision 

radiocarbon ages were determined for several subsamples by the University of Washington 

Quaternary Isotope Laboratory. The results compared favorably to those of Beta Analytic. In 

addition, several calibrated dates provided by Beta Analytic were checked with the calibration 

program CALIB (Stuiver and Reimer, 1993; Stuiver et al., 2005). This exercise also produced 

similar results. 

For most liquefaction features, preferred age estimates and related uncertainties are calculated 

from minimum and maximum constraining ages (Figure E-3). The constraining ages are usually 

2-sigma calibrated radiocarbon dates, but in a few cases they are optically simulated 

luminescence (OSL) dates. For a few liquefaction features with only minimum or maximum age 

constraints and with other information that can help assess the feature’s age (e.g., archeological 

horizons and features, soil development, and stratigraphic position), preferred age estimates have 

been assigned. In a few other cases, preferred age estimates and uncertainties have been 

calculated from close maximum radiocarbon dates. In these instances, the preferred age estimate 

is the average of the range of the 2-sigma calibrated date and the uncertainty is the difference 

between the average and the maximum and minimum values of the range. For features with 

neither minimum nor maximum constraining ages, no preferred age estimate is assigned, unless 

there are constraining ages for a similar feature in the same stratigraphic position at a nearby site. 

The paleoliquefaction data in this data set form the basis of the CEUS SSC Project analyses of 

the timing, location, and magnitude of paleoearthquakes that induced liquefaction in the NMSZ. 

E.1.2.1.3 Recommendations 

Although a great effort was made between 1995 and 2005 to understand paleoseismicity in the 

NMSZ and surrounding region, several important issues remain to be resolved that would 

improve understanding of the earthquake potential of the most hazardous region on the North 

American continent east of the Rocky Mountains. These issues include the uncertainty in 

recurrence times of large earthquakes, sources other than the NMSZ that may be capable of large 

earthquakes such as the Commerce and Eastern Reelfoot Rift Margin faults (e.g., Baldwin et al., 

2006; Cox et al., 2006; Magnani and McIntosh, 2009), and migration of seismicity from one part 

of the Reelfoot Rift fault system to another (e.g., McBride et al., 2002; Tuttle et al., 2006; Al-
E-10

Shukri et al., 2009). Therefore, we recommend the following research to help resolve these 

issues: 

Additional paleoseismic studies in the NMSZ and surrounding region to improve 

completeness of the paleoearthquake record for the period 1–4 ka and to extend the 

earthquake chronology back to 10–20 ka. It would be advantageous to investigate sand blows 

at archeological sites where there would be a high probability of finding suitable organic 

material for narrowly constraining the ages of the sand blows and thus their causative 

earthquakes. At sites where in situ tree stumps are found buried beneath sand blows, 

dendrochronology may help to precisely date paleoearthquakes with uncertainty of a few 

months to a few years. In addition, it would be advisable to search for sand blows in Late 

Wisconsin deposits where there may be a longer and older record of paleoearthquakes. It 

may be advantageous to use OSL dating of sediments at sites of older liquefaction features 

where organic samples may not be available for radiocarbon dating. Information gained 

through these efforts would help to reduce uncertainties related to recurrence of large 

earthquakes.

Additional paleoseismic studies in the vicinity and along other proposed active faults such as 

the Eastern rift margin and Commerce faults. Evaluate whether or not the ages and sizes of 

liquefaction features in close proximity to these faults support the hypothesis that the Eastern 

rift margin and Commerce faults generated repeated large earthquakes during the Late 

Wisconsin and Holocene. Additional information is needed to constrain the sizes and 

recurrence of paleoearthquakes produced by these seismic sources. 

Study of the spatial and temporal characteristics of paleoearthquakes across the region to 

determine if seismicity migrates from one part of the Reelfoot Rift fault system to another, 

and if so, if it migrates in a systematic way or with a certain periodicity. The results could 

help to characterize long-term deformation in the Reelfoot Rift region and may have 

implications for other aulacogens in intraplate settings. 

E.1.2.2 Marianna, Arkansas, Area 

E.1.2.2.1 Overview 

The Marianna area is located at the southwestern end of the Reelfoot Rift and characterized by 

little to no seismic activity during the instrumental period (Al-Shukri et al., 2005; Figures E-12 

and E-13). In the early 2000s, light-colored patches that appeared to represent large sand blows 

were identified on satellite images and aerial photographs of the Marianna area about 80 km 

southwest of the southern end of the NMSZ (Al-Shukri et al., 2005; Figure E-12). Several of 

these features southwest of Marianna were located on the ground, surveyed with groundpenetrating radar (GPR), and excavated (Figures E-13 and E-14). Trench exposures revealed 

large sand blows and related feeder dikes. No suitable organic samples were collected for 

radiocarbon dating, but their high degree of weathering suggested that the sand blows were 

prehistoric in age. 

Subsequently, several other sand blows were excavated, including an exceptionally large 

(approximately 2.45 m thick, 70 m wide, and 230 m long) sand blow that occurred along a 

northwest-oriented lineament, referred to as the Daytona Beach lineament (Figures E-13 and 

E-15 through E-21; Al-Shukri et al., 2006; Tuttle et al., 2006). Radiocarbon and OSL dating of 
E-11

the buried soil immediately below the sand blow provided a close maximum age constraint of 

about 5,500 years for the formation of the sand blow (Figures E-17 and E-19; Tuttle et al., 2006). 

The sand blow’s large feeder dike had a strike similar to the lineament. Noting that other large 

sand blows and sand dikes occurred along the Daytona Beach lineament, the researchers 

proposed that the lineament is the surface expression of an active fault (Figure E-13; Al-Shukri 

et al., 2006; Tuttle et al., 2006). In addition, a compound sand blow with the uppermost sand 

blow interbedded with the basal layers of a backswamp deposit was discovered northeast of 

Marianna during reconnaissance of the St. Francis Ditch. Radiocarbon and OSL dating of the 

backswamp deposit immediately above the sand blow provided close minimum age constraint of 

about 6,800 years (Figures E-17 and E-19; Tuttle et al., 2006). 

During the past 5 years, numerous sand blows identified on satellite images and aerial 

photographs of the Marianna area were confirmed in soil pits, trenches, and with GPR surveys 

that imaged sand dikes below the sand blows (Figures E-14 through E-21; Al-Shukri et al., 2009; 

Al-Qadhi, 2010). Many of these sand blows occur along the Daytona Beach lineament that was 

traced for a total of 17 km by conducting GPR surveys (Figure E-13). One of the trenched sand 

blows along the lineament is composed of two stratigraphically stacked sand blows and several 

large feeder dikes. A possible fault, similar in strike to the Daytona Beach lineament, crosscuts 

one of the large feeder dikes and extends into the upper sand blow (Figure E-14, sand blow 2 on 

trench log). Layering and layer thickness within the upper sand blow varies across the possible 

fault suggesting lateral displacement. Both sand blows exposed in the trench were weathered, but 

the lower, smaller sand blow was especially so (Figure E-14, sand blow 1 on trench log). 

Radiocarbon and OSL dating of the buried soil immediately below the upper sand blow provided 

close maximum age constraints of about 10 ka and 12 ka, respectively (Al-Shukri et al., 2009). 

OSL dating of a sample collected from the soil immediately below the smaller lower sand blow 

indicates that it formed less than 38 ka. The researchers have concluded that there is a 12 k.y., 

and possibly 38 k.y., long history of strong ground shaking in the vicinity of the Daytona Beach 

lineament. The length and linear morphology of the Daytona Beach lineament, as well as the 

observation of a possible fault crosscutting a large sand blow that formed along the lineament, 

support the interpretation that the lineament is the surface expression of an active fault. 

The sand blows in the Marianna area have been attributed to large paleoearthquakes generated by 

a source in the Marianna area, possibly the southwestern extension of the Eastern rift margin 

fault, or the northwest-oriented White River fault zone (WRFZ), or both (Figure E-13; Tuttle et 

al., 2006; Al-Shukri et al., 2009). As observed in the NMSZ, compound sand blows are 

indicative of sequences of large earthquakes resulting from complex fault interaction (Saucier, 

1989; Tuttle, 1999). As discussed above, the Daytona Beach lineament, subparallel to the nearby 

WRFZ, may be the surface expression of an active fault (Tuttle et al., 2006; Al-Shukri et al., 

2009). The large size of the Marianna sand blows and their spatial association with local faults 

suggest that the causative earthquakes were centered near Marianna (Figures E-13 and E-18 

through E-21). The sand blows are thought not to be distant liquefaction features produced by a 

large New Madrid earthquake. The ages of the Marianna sand blows do not correlate with events 

in the New Madrid paleoearthquake chronology and no sand blow has yet been found in the 

Marianna area that is less than 5,000 years old and could have formed during the historical or 

prehistoric New Madrid earthquakes. 

The investigators noted that a few liquefaction features have been found elsewhere in the 

Mississippi embayment that are similar in age (approximately 5,500 years) but smaller in size 
E-12

than some of the Marianna sand blows (Tuttle et al., 2006; Tuttle, 2010). These include a sand 

blow and related feeder dikes near Marked Tree, Arkansas, about 80 km northeast of Marianna 

(Figure E-12). According to empirical relations between earthquake magnitude and distance to 

surface manifestation of liquefaction (i.e., sand blows; Ambraseys, 1988; Castilla and Audemard, 

2007), a M ~6.6 earthquake could produce sand blows up to 80 km from its epicenter. Therefore, 

a large earthquake centered near Marianna might be responsible for the 5,500-year-old 

liquefaction features near Marked Tree (Tuttle, 2010). 

E.1.2.2.2 Data Description 

Paleoliquefaction data were contributed by H. Mahdi, O. Al-Qahdi, H. Al-Shukri, and M. Tuttle 

for the Marianna, Arkansas, area and compiled in the CEUS SSC Project paleoliquefaction 

database. Most of the data were previously published in journal articles, technical reports, and 

graduate student theses as indicated in the paleoliquefaction database. For this project, all the 

data were reviewed, 2-sigma minimum and maximum constraining ages entered, and preferred 

age estimates calculated. All of the radiocarbon ages were determined by Beta Analytic 

Radiocarbon Laboratory and calibrated using the Pretoria procedure (Talma and Vogel, 1993; 

Vogel et al., 1993). 

In the Marianna area, most of the samples used in radiocarbon and OSL dating were collected 

from buried soil immediately below sand blows and provide close maximum age constraint (see 

Figure E-3). A few samples were collected above sand blows and provide close minimum age 

constraint. Constraining ages are derived from 2-sigma calibrated radiocarbon dates and from a 

few OSL dates. In calculating preferred age estimates, radiocarbon dates are given preference 

over OSL dates since the radiocarbon dates have smaller uncertainties. In most cases, preferred 

age estimates and related uncertainties of liquefaction features have been calculated from either 

close maximum or close minimum radiocarbon dates, not both. The preferred age estimate is the 

average of the range of the 2-sigma calibrated date and the uncertainty is the difference between 

the average and the end members of the range. No preferred age estimate is assigned to features 

that have neither close minimum nor close maximum constraining ages. The paleoliquefaction 

data in this data set form the basis of the CEUS SSC Project analyses of the timing, location, and 

magnitude of paleoearthquakes that induced liquefaction in the Marianna area. 

E.1.2.2.3 Recommendations 

Paleoseismic studies have been conducted in the Marianna area over the past 10 years but have 

been limited in scope. Most of the work has been concentrated along the northwest-oriented 

Daytona Beach lineament (Figure E-13). The compound nature of some of the sand blows 

suggests that multiple faults may rupture in a short period of time to produce earthquake 

sequences much like the NMSZ. Clearly, there is still much more to be learned in the Marianna 

area regarding the timing, location, and magnitude of paleoearthquakes that would help to 

improve the earthquake source model at the southern end of the Reelfoot Rift. To these ends, we 

recommend the following research: 

Additional paleoseismic investigations of sand blows in the Marianna area including those 

spatially associated with the northwest-oriented lineament and the northeast-oriented 

extension of the Eastern Rift fault and other sand blows not associated with any lineament or 

fault trend. It may be necessary to use OSL dating of sediments buried by sand blows at sites 

of older liquefaction features where organic samples are not available for radiocarbon dating. 
E-13

Additional reconnaissance for and investigation of liquefaction features in the region 

surrounding Marianna. More information on the ages, size, and spatial distribution of sand 

blows will help to constrain the timing, locations, and magnitudes of the paleoearthquakes in 

the region. 

Liquefaction potential analysis of geotechnical data already collected by the USGS and the 

Arkansas State Highway and Transportation Department to help assess the magnitudes of the 

paleoearthquakes in the Marianna area. 

Further development of an earthquake chronology for the Marianna area and comparison of 

the chronology with that for the NMSZ and with the fault displacement history of the Eastern 

rift margin fault in western Tennessee.

Geophysical investigations to determine if the Daytona Beach lineament is underlain by a 

fault and to help assess its long-term displacement history.

E.1.2.3 St. Louis Region 

E.1.2.3.1 Overview 

In contrast to the NMSZ about 200 km to the south-southeast, the St. Louis region is 

characterized by low to moderate seismic activity (Figures E-4 and E-22; Nuttli and Brill, 1981; 

Johnston and Schweig, 1996). A diffuse concentration of seismicity extends northwest from the 

NMSZ to St. Louis. Seismicity in this region often is attributed to reactivation of old basement 

faults and earthquake epicenters are spatially associated with the St. Louis fault (Harrison, 1997) 

and the Centralia fault zone (Mitchell et al., 1991). Over the last 20 years, however, seismicity 

has not been directly related to any mapped basement structures. 

Since the initial discovery of sand dikes along the Kaskaskia River east of St. Louis, 

paleoseismology studies have documented scores of liquefaction features along rivers in 

southwestern Illinois and southeastern Missouri (Figures E-22 through E-30; Hajic et al., 1995; 

McNulty and Obermeier, 1997, 1999; Tuttle, Lafferty, Chester, et al., 1996; Tuttle, Chester, et 

al., 1999; Tuttle et al., 2004; see also Figures E-31 through 33 and Section E.1.2.4). There are at 

least two generations of liquefaction features that are Holocene in age. Some of the features are 

young and probably formed during the 1811-1812 New Madrid earthquakes, known to have 

induced liquefaction near Cahokia, Illinois. Other features are middle Holocene in age and 

probably formed during an earthquake about 6,470 yr BP ± 160 yr (Figures E-24, E-25, E-27, 

and E-30; Tuttle, Lafferty, Chester, et al., 1999). 

McNulty and Obermeier (1997, 1999) attributed the middle Holocene liquefaction features in the 

Shoal Creek-Kaskaskia River area to a M > 6 earthquake located near the lower portion of Shoal 

Creek (Figure E-33). The earthquake source area was inferred from the distribution and widths 

of sand dikes. The magnitude of the earthquake was derived from the relation between 

earthquake magnitude and maximum epicentral distance to surface evidence of liquefaction (e.g., 

Ambraseys, 1988). Tuttle et al. (Tuttle, Lafferty, Chester, et al., 1996; Tuttle, Chester, et al., 

1999; Tuttle et al., 2004) found liquefaction features, mostly sand dikes and one sand blow, in 

the St. Louis region along the Big Muddy, Kakaskia, and Marys rivers and Cahokia, Crooked, 

Mud, Piasa, Shoal, and Silver creeks in Illinois and along the Big and Meramec rivers and Saline 

Creek in Missouri (Figures E-23 through E-30). The largest dikes occur along Shoal Creek, but 
E-14

fairly large dikes also occur along Cahokia Creek and the Meramec River (Figures E-26 through 

E-29). The age estimates of many of the sand dikes are poorly constrained and regional 

correlation problematic (Figure E-30). Various locations and magnitudes of scenario earthquakes 

were evaluated using liquefaction potential analysis that could explain the observed distribution 

of liquefaction features (Tuttle, Lafferty, Chester, et al., 1999). 

E.1.2.3.2 Data Description 

Paleoliquefaction data were contributed by M. Tuttle and collaborators in the St. Louis region 

and compiled in the CEUS SSC Project paleoliquefaction database. Most of the data were 

published in technical reports to the U.S. NRC and U.S. Geological Survey as indicated in the 

database. Tuttle identified river sections searched by her and collaborators that allowed us to 

produce Figure E-22. All the data were reviewed, 2-sigma minimum and maximum constraining 

ages entered, and preferred age estimates calculated. All of the radiocarbon ages were 

determined by Beta Analytic Radiocarbon Laboratory and calibrated using the Pretoria 

procedure (Talma and Vogel, 1993; Vogel et al., 1993). Paleoliquefaction data gathered in this 

region by E. Hajic, S. Obermeier, and collaborators are included in the data set for the Wabash 

Valley seismic zone (see discussion below). 

Paleoseismic data in the St. Louis regional data set are from reconnaissance-level studies. Most 

of the liquefaction features found in the area are sand dikes (Tables E-1.2-1 and E-1.2-2). The 

ages of the liquefaction features are poorly constrained, except for a few features that formed 

during the historic period and about 6,470 yr BP (Figure E-25). Some of the sand dikes are 

greater than 30 cm in width, suggesting that the paleoearthquake responsible for their formation 

was located in the St. Louis region (Figures E-19 and E-30). However, given that the 1811-1812 

New Madrid earthquakes induced liquefaction near St. Louis and several historical sand dikes 

have been found in the region, it raises the question whether some of the paleoliquefaction 

features could have formed during paleoearthquakes generated by the NMSZ. To date, no known 

New Madrid paleoearthquake occurred circa 6,470 yr BP (Figure E-12). The paleoliquefaction 

data in this data set contributed to the CEUS SSC Project analyses of the timing, location, and 

magnitude of paleoearthquakes that induced liquefaction in the St. Louis region. 

E.1.2.3.3 Recommendations 

Additional study and dating of liquefaction features in the St. Louis region is needed to better 

constrain the number and timing of paleoearthquakes and to make regional correlations of 

similar-age liquefaction features. A more complete picture of the size and spatial distributions of 

liquefaction features would help to reduce the uncertainty of the location and magnitudes of 

paleoearthquakes, including the 6,470 yr BP event. Therefore, the following research is 

recommended: 

Add overlapping portion of Wabash Valley data set to St. Louis data set, reviewing each site 

to avoid duplication. 

Resurvey portions of the Meramec and Kaskaskia rivers and Shoal and Cahokia creeks, 

where the largest have been found (Figures E-26, E-28, and E-29), in the hopes of finding 

additional sand blows and collecting samples above and below the sand blows for 

radiocarbon and OSL dating. At the same time, try to relocate documented liquefaction sites 

and collect samples for radiocarbon and OSL dating that would improve age estimates of 
E-15

liquefaction features. These efforts would likely improve estimates of the timing, locations, 

and magnitudes of paleoearthquakes. 

Study whether the liquefaction features in the Shoal Creek–Kaskaskia River area (Figures 

E-26, E-28, and E-29) could be due to earthquake characteristics such as directivity of 

ground motions, Moho bounce, or site amplification of ground motions generated by large 

New Madrid earthquakes. This effort would likely reduce uncertainties related to the 

locations and magnitudes of paleoearthquakes. 

E.1.2.4 Wabash Valley Seismic Zone and Surrounding Region 

E.1.2.4.1 Overview 

Numerous small- to moderate-magnitude earthquakes have occurred in the Wabash Valley 

region of southeastern Illinois and southwestern Indiana in historical time. Paleoliquefaction 

features identified in the region provide evidence for multiple older, moderate- to largemagnitude earthquakes (e.g., Obermeier et al., 1991, 1993; Hajic et al., 1995; Munson et al., 

1995, 1997; Munson and Munson, 1996; Obermeier, 1996, 1998, 2009; and McNulty and 

Obermeier, 1999; Figures E-31 through E-33). The causative fault or faults for the Wabash 

Valley paleoearthquakes are not known. The great majority of the paleoliquefaction features in 

the Wabash Valley region are sand dikes found along actively eroding stream banks, but 

researchers also have identified sand blows and sand sills. Figure E-31 shows river sections 

searched for liquefaction features and was produced by digitizing published maps from Munson 

et al. (1997) and McNulty and Obermeier (1999). 

The identification of paleoearthquakes in the Wabash Valley region primarily is based on age 

estimates of paleoliquefaction features, the regional pattern of paleoliquefaction features 

(especially dike widths), and geotechnical analyses of liquefaction potential. Researchers 

interpret from six (Munson and Munson, 1996) to eight (McNulty and Obermeier, 1999) 

Holocene earthquakes, with at least one more during latest Pleistocene time. Based on 

overlapping radiocarbon ages and the spatial distribution and widths of dikes, McNulty and 

Obermeier (1999) correlate paleoliquefaction features between sites to estimate the timing, 

location, and magnitude of paleoearthquakes in the Wabash Valley region (Figure E-33). 

Magnitude estimates for the paleoearthquakes range from M 6 to ~7.8 (Pond and Martin, 1997; 

Obermeier, 1998; McNulty and Obermeier, 1999; Green et al., 2005; Olson et al., 2005b).

Section 6.1.9 of the main report provides detailed discussion of magnitude estimates for the 

interpreted paleoearthquakes in the Wabash Valley region. The two largest earthquakes inferred 

from paleoliquefaction data are the Vincennes-Bridgeport and Skelton–Mt. Carmel 

paleoearthquakes. The M ~7 to 7.8 Vincennes paleoearthquake occurred at approximately 6,100 

200 yr BP (Hajic et al., 1995; Munson and Munson, 1996; Munson et al., 1997). The M ~6.3 to 

7.3 Skelton paleoearthquake occurred at approximately 12 k.y. 1,000 yr BP (Munson and 

Munson, 1996; Munson et al., 1997). The energy centers for these two earthquakes are inferred 

to be located within 25–40 km (15.5–25 mi.) of Vincennes, Indiana (Munson et al., 1997; 

McNulty and Obermeier, 1999).
E-16

E.1.2.4.2 Data Description 

Paleoliquefaction data are drawn from published journal articles and reports by the foremost 

researchers in the Wabash Valley region, including S. Obermeier, P. Munson, and E. Hajic 

(Hajic et al., 1995; Munson et al., 1995; Munson and Munson, 1996; Obermeier, 1998; McNulty 

and Obermeier, 1999), as well as from a technical report to the Exelon Generation Company’s 

Clinton site in central Illinois (Exelon, 2003, 2004). Most of the liquefaction features found in 

the Wabash Valley area are planar, sand-filled dikes (Tables E-1.2-1 and E-1.2-2) that are 

vertically to steeply dipping and that widen downward and connect to a sediment source at depth 

(Obermeier et al., 1991). Apparent widths of these sand dikes were measured in the field, the 

largest of which is 2.5 m wide (Munson and Munson, 1996). Ages of some of these dikes are 

estimated from radiocarbon dating of organic-rich materials collected from the sediment crosscut 

by the sand dikes, with supporting evidence from archeological and stratigraphic context, and the 

relative degree of soil profile development (Hajic et al., 1995; Munson et al., 1995; Munson and 

Munson, 1996; Obermeier, 1998; McNulty and Obermeier, 1999). For this regional data set, we 

did not estimate preferred age estimates of liquefaction features because we did not have the 

necessary information to do so (e.g., C14 or OSL sample location relative to sand dikes and sand 

blows). Instead, we entered the investigators’ assigned ages into the database. 

E.1.2.4.3 Recommendations 

Numerous researchers have studied paleoliquefaction in the Wabash Valley region during the 

past 20 years, and this research is ongoing. As a result, the Wabash Valley data set is relatively 

mature. However, we recommend the following as useful topics for future paleoliquefaction 

research in the Wabash Valley region: 

Re-evaluation of previously collected age data and estimation of preferred age estimates of 

liquefaction features. 

Additional sampling and age analyses to further refine and reduce uncertainties of age 

estimates and correlation of paleoliquefaction features between sites, if possible. 

Additional geotechnical testing to provide better estimates for the locations and magnitudes 

of paleoearthquakes, as recommended by McNulty and Obermeier (1999). 

Additional reconnaissance in the northern part of the Illinois basin where moderate–sized 

earthquakes are recorded in the instrumental record. Documenting the presence or absence of 

paleoearthquakes in the northern part of the basin in an area with similar susceptible deposits 

would help to better evaluate the apparent spatial stationarity of earthquakes in the southern 

part of the Illinois basin. 

E.1.2.5 Arkansas-Louisiana-Mississippi Region 

E.1.2.5.1 Overview 

Cox and collaborators have conducted studies in southeastern Arkansas, northeastern Louisiana, 

and western Mississippi areas (ALM) investigating what they interpret to be paleoliquefaction 

features related to moderate- to large-magnitude earthquakes possibly produced by the Saline 

River fault zone in southeastern Arkansas (Cox, 2002, 2009; Cox, Harris, et al., 2004; Cox, 

Larsen, et al., 2004; Cox, Larsen, and Hill, 2004; Cox and Larsen, 2004; Cox and Gordon, 2008; 
E-17

Figure E-34). Many of the features interpreted as earthquake-induced liquefaction features were 

not reviewed in the field by other geologists with prior experience with such features. The ALM 

observations and interpretations can be summarized as follows: 

On aerial photographs, Cox and collaborators observed roughly circular light-colored patches 

throughout the Arkansas and Mississippi River valleys between southeastern Arkansas and 

northeastern Louisiana and interpreted the patches to be seismically induced sand blows. 

In trenches excavated at seven locations, sandy deposits and crosscutting features were 

observed and interpreted as sand blows and sand dikes, respectively, and attributed to several 

episodes of earthquake-induced liquefaction. 

On the basis of similar sedimentary stratigraphy as well as radiocarbon and OSL dating of 

deposits, Cox and collaborators attributed the features they interpreted as sand blows and 

sand dikes to several moderate- to large-magnitude earthquakes centered near the Saline 

River fault zone. 

As part of the CEUS SSC Project, the results of the investigations by Cox and collaborators in 

the ALM were evaluated to determine if there is either (1) paleoseismic evidence of repeated 

large-magnitude earthquakes; or (2) evidence for a single large-magnitude Quaternary event that 

might affect seismic source characterization. As described in Section 7.3.9 (Extended 

Continental Crust-Gulf Coast, or ECC-GC) of the main CEUS SCC Project report, no evidence 

was found for repeated large-magnitude earthquakes and little to no evidence was found for large 

(M > 6) earthquakes during a review of published papers as well as original photographs and 

logs. 

In general, the ALM features did not exhibit sedimentary characteristics typical of earthquakeinduced liquefaction features and therefore did not meet the criteria adopted for this project and 

described above in Section E.1.2. More specifically, the sandy deposits interpreted as sand blows 

often lacked a clear connection to sand dikes below and rarely appeared to thin and fine laterally 

away from the main feeder dike. Many of the features interpreted as sand dikes lacked clear 

margins and lateral continuity and rarely broadened downward. The best candidate for a 

paleoliquefaction feature comes from the west wall of the Portland, Arkansas, trench, where a 

possible small (<6 cm wide) dike is shown in logs and photographs at approximately meter 4.5 

(Cox, Larsen, et al., 2004). It remains unclear whether this relatively small dike is the result of 

(1) a moderate-magnitude local earthquake; (2) a larger, more distant earthquake; or (3) nonearthquake processes. Other small sand dikes may occur in other trenches. Please see Section 

7.3.9 of the main CEUS SCC Project report for a thorough discussion of the evaluation of the 

ALM features. 

E.1.2.5.2 Data Description 

Paleoliquefaction data for the ALM region were contributed by R. Cox and drawn from journal 

articles and technical reports by Cox and his collaborators. We reviewed the paleoliquefaction 

data from the ALM region and consider them highly uncertain and the data set relatively 

immature. These data do not provide evidence for a source of repeated large-magnitude 

earthquakes in the ALM region. The CEUS paleoliquefaction database includes the locations of 

seven paleoseismic trenches in the ALM region (Cox, Harris, et al., 2004; Cox, Larsen, et al., 
E-18

2004; Cox et al., 2007; Figure E-34), with a brief description of the researchers’ interpreted 

results provided in the COMMENT data field. 

E.1.2.5.3 Recommendations 

As determined for the CEUS SSC Project (see Section 7.3.9 of the main report), the 

paleoliquefaction data from the ALM region are considered highly uncertain and do not provide 

evidence for a source of repeated large-magnitude earthquakes in the ALM area. We recommend 

the following as topics for future paleoliquefaction research in the ALM region: 

Additional field work and trenching to evaluate the interpretation that the roughly circular 

sandy deposits observed in aerial photographs are earthquake-induced sand blows (e.g., Cox, 

Harris, et al., 2004; Cox, Larsen, et al., 2004; Cox et al., 2007; Cox, 2009) or if they formed 

by some other means. 

Additional sampling and age analyses to further refine the timing and correlation of any 

paleoliquefaction features between trench sites and with other areas of paleoliquefaction such 

as the Marianna area, if possible. 

E.1.2.6 Charleston Seismic Zone 

E.1.2.6.1 Overview 

Strong ground shaking during the 1886 Charleston, South Carolina, earthquake produced 

extensive liquefaction expressed primarily as sand-blow craters at the ground surface (Dutton, 

1889). Liquefaction features from the 1886 event are preserved in geologic deposits at numerous 

locations in the South Carolina coastal region (e.g., Talwani and Cox, 1985; Amick, 1990; 

Amick, Gelinas, et al., 1990; Amick, Maurath, and Gelinas, 1990; Amick and Gelinas, 1991; 

Obermeier et al., 1989, 1990; and Talwani and Schaeffer, 2001; Figures E-35 and E-36). 

Documentation of sand-blow craters and other paleoliquefaction features throughout coastal 

South Carolina provides evidence for prior strong ground motions during prehistoric large 

earthquakes (e.g., Obermeier et al., 1989, 1990; Weems and Obermeier, 1990; Amick, Gelinas, 

et al., 1990; Amick, Maurath, and Gelinas, 1990; Talwani and Schaeffer, 2001; Talwani et al., 

2008; Figures E-35 and E-36). Talwani and Schaeffer (2001) interpret between three and four 

large-magnitude earthquakes in the past approximately 2,000 years, and between five and seven 

large-magnitude earthquakes in the past approximately 5,800 years. 

As described in more detail in Section E.1.2.7, reconnaissance-level searches for 

paleoliquefaction features have been conducted along the eastern seaboard (e.g., Amick, Gelinas, 

et al., 1990; Gelinas et al., 1998; Figure E-37). These studies did not find paleoliquefaction 

features beyond the Charleston region and suggest a stationary source of repeated, largemagnitude earthquakes located near Charleston. 

E.1.2.6.2 Data Description 

Data for the Charleston region in the CEUS SSC study paleoliquefaction database primarily are 

taken from Talwani and Schaeffer’s (2001) compilation, with additional data from other studies 

(e.g., Noller and Forman, 1998; Talwani et al., 2008). Most of the age estimates of 

paleoliquefaction features in coastal South Carolina are based on radiocarbon dating. Noller and 

Forman (1998) present luminescence age estimates for five samples collected from sand-blow 
E-19

craters exposed at Gapway, South Carolina. However, they emphasize that their reported age 

estimates are preliminary and ―should be used with caution‖ (Noller and Forman, 1998, pp. 

4-56). Therefore, the age estimates of paleoliquefaction features used by the CEUS SSC Project 

to constrain the timing of prehistoric earthquakes in the Charleston region are based on 

radiocarbon analyses. Talwani and Schaeffer (2001) combine radiocarbon ages from previously 

published sources with their own studies of paleoliquefaction features in the South Carolina 

coastal region. Their compilation forms the basis of the CEUS SSC Project analyses of 

Charleston paleoliquefaction. These data include ages that provide contemporary, minimum, and 

maximum limiting ages for the formation of paleoliquefaction features. 

Talwani and Schaeffer (2001) identify individual earthquake episodes based on samples with a 

―contemporary‖ age constraint that have overlapping calibrated radiocarbon ages at 

approximately 1-sigma confidence interval. The standard in paleoseismology, however, is to use 

calibrated ages with 2-sigma (95.4 percent confidence interval) error bands (Grant and Sieh, 

1994). Likewise, in paleoliquefaction studies, to more accurately reflect the uncertainties in 

radiocarbon dating and age estimates of paleoliquefaction features, Tuttle (2001) advises the use 

of calibrated radiocarbon dates with 2-sigma error bands (as opposed to narrower 1-sigma error 

bands). In recognition of this, the conventional radiocarbon ages presented in Talwani and 

Schaeffer (2001) are recalibrated and reported with 2-sigma error bands for use in the CEUS 

SSC Project. This recalibration was performed with the radiocarbon calibration program OxCal 

version 4.1 (Bronk Ramsey, 2009) using the calibration curve of Stuiver et al. (1998). The 

recalibrated 2-sigma radiocarbon ages form the basis of the CEUS SSC Project analyses of the 

timing, location, and magnitude of paleoearthquakes that induced liquefaction in the vicinity of 

Charleston, South Carolina. Section 6.1.2 of the main report provides additional discussion of the 

earthquake chronology for the Charleston seismic zone, including space-time diagrams and 

tabulated results. 

E.1.2.6.3 Recommendations 

Numerous researchers have studied paleoliquefaction in the Charleston region during the past 

30+ years, and this research is ongoing. As such, the Charleston data set is relatively mature. 

However, we recommend the following as useful topics for future paleoliquefaction research in 

the Charleston region: 

Additional and more detailed documentation of feature size (e.g., dike width, sand-blow 

deposit thickness). This additional information could be used to further refine locations and 

magnitude estimates of paleoearthquakes. 

More detailed documentation of areas searched. This additional information could be used to 

assess the uncertainties associated with paleoearthquake locations and design future studies 

to improve those locations. 

Additional site-specific and regional geotechnical characterizations, including liquefaction 

susceptibility and liquefaction potential. This additional information could be used to further 

refine locations and magnitude estimates of paleoearthquakes. 
E-20

E.1.2.7 Atlantic Coast Region and the Central Virginia Seismic Zone 

Reconnaissance-level searches for paleoliquefaction features were conducted along the eastern 

seaboard from southernmost Georgia to New Jersey (Amick, Gelinas, et al., 1990) and as far 

north as New England (e.g., Gelinas et al., 1998; Figure E-37). These studies did not find 

paleoliquefaction features beyond the Charleston region and suggest a stationary source of 

repeated, large-magnitude earthquakes located near Charleston. 

The Central Virginia seismic zone is an area of persistent, low-level earthquake activity that 

extends about 120 km in a north-south direction and about 145 km in an east-west direction from 

Richmond to Lynchburg, Virginia (Bollinger and Sibol, 1985). Seismicity in the Central Virginia 

seismic zone ranges in depth from about 3 to 13 km (Wheeler and Johnston, 1992). The largest 

historical earthquake that has occurred in the Central Virginia seismic zone is the December 23, 

1875, mb 5.0 Goochland County earthquake (Bollinger and Sibol, 1985). It is difficult to attribute 

the seismicity to any known geologic structure, and it appears that the seismicity extends both 

above and below the Appalachian detachment. 

Searches for paleoliquefaction features were conducted along several rivers in the vicinity of the 

Central Virginia seismic zone (Obermeier and McNulty, 1998; Dominion, 2004) (Figure E-38). 

They identified possible small sand dikes at three sites and interpreted them as paleoliquefaction 

features resulting from at least one, and possibly as many as three, moderate-magnitude 

earthquakes during the Holocene. Obermeier and McNulty (1998) conclude that ―the paucity of 

liquefaction features in central Virginia makes it seem unlikely that any earthquake in excess of 

M ~7 has struck there.‖

We recommend that any additional searches for liquefaction features in the Atlantic Coast region 

and Central Virginia seismic zone include documentation of rivers searched, of the liquefaction 

features including their sedimentological characteristics and stratigraphic context, and field 

conditions such as quality of exposures and water levels at the time of reconnaissance. 

E.1.2.8 Newburyport, Massachusetts, and the Surrounding Region 

E.1.2.8.1 Overview 

Northeastern Massachusetts, southeastern New Hampshire, and southernmost Maine have 

experienced many small, and several moderate to large, earthquakes during the past 400 years 

(Figure E-39). The two most notable earthquakes, the 1727 felt-area magnitude (Mfa) 5.5 

Newburyport and 1755 Mfa 6 Cape Ann events, induced liquefaction and caused damage to 

buildings (Ebel, 2000, 2001). During a paleoseismology study in the late 1980s, both historical 

and prehistoric liquefaction features were found in the Newburyport area (Tuttle et al., 1987; 

Tuttle and Seeber, 1991; Figures E-40 through E-43). This initial study involved interpreting 

aerial photographs, excavating trenches at locations described in historical accounts of 

liquefaction, and searching for liquefaction features in exposures provided by sand and gravel 

pits and excavations for new building foundations. 

The historical features were attributed to the 1727 earthquake and the prehistoric features were 

estimated to have formed during the past 4,000 years. Because the ages of the prehistoric 

liquefaction features were poorly constrained, the number and timing of paleoearthquakes were 

not estimated. In addition, the area over which the prehistoric earthquake(s) induced liquefaction 
E-21

was not determined, limiting interpretations of earthquake source area and magnitude. During a 

subsequent paleoseismic study, searches for earthquake-induced liquefaction features were 

conducted in marshes, rivers, and bays in northeastern Massachusetts and southeastern New 

Hampshire (Gelinas et al., 1998; Figure E-39). No additional liquefaction features were found, 

but sedimentary conditions suitable for the formation of liquefaction features were notably sparse 

in many of the areas searched. The failure to find additional liquefaction features was interpreted 

as a lack of evidence for a M 6 earthquake in the region during the late Holocene (Gelinas et 

al., 1998). 

More recently, searches for earthquake-induced liquefaction features have been conducted along 

several rivers south of Newburyport, Massachusetts, as well as in the vicinity of Hampton Falls 

and west of Hampton Falls in New Hampshire (Figure E-39; Tuttle, 2007, 2009). 

Reconnaissance was performed in areas where ground failure indicative of liquefaction was 

reported for the 1727 earthquake (Brown, 1990; Coffin, 1845). Surveys were conducted when 

river levels and tides were low and cutbank exposures were at a maximum. During the surveys, 

only one liquefaction feature, a small sand dike, was found along the Hampton Falls River in 

New Hampshire (Figures E-42 and E-43). The upper portion of the sand dike had been eroded 

and any relation to an overlying sand lens (possibly a sand blow or sand sill) could not be 

determined. Radiocarbon dating of organics collected adjacent to the uppermost intact portion of 

the dike provides a maximum constraining age of 2,750 yr BP In addition, a distinctive 2,200-

year-old sand layer, that exhibits some characteristics of tsunami deposits, was observed in 

several marshes along the Massachusetts–New Hampshire coast (Tuttle, 2007, 2009). 

E.1.2.8.2 Data Description 

Paleoliquefaction data were contributed by M. Tuttle and collaborators for the Newburyport, 

Massachusetts, region and compiled in the CEUS SSC Project paleoliquefaction database. Most 

of the data were published previously in journal articles and technical reports. Sections of rivers 

searched by Tuttle and collaborators as well as by Gelinas et al. (1998) are shown in Figure 

E-39. The Newburyport paleoliquefaction data were reviewed, 2-sigma minimum and maximum 

constraining ages entered, and preferred age estimates calculated. All of the radiocarbon ages 

were determined by Beta Analytic Radiocarbon Laboratory and calibrated using the Pretoria 

procedure (Talma and Vogel, 1993; Vogel et al., 1993). All of the liquefaction features dated in 

the Newburyport region are sand dikes (Tables E-1.2-1 and E-1.2-2). Relations with possible 

sand blows could not be confirmed. Only maximum constraining ages are available for some of 

the dikes. Crosscutting relations and weathering characteristics suggest two generations of 

features, one of which is historical in age. The paleoliquefaction data in this data set contributed 

to the CEUS SSC Project analyses of the timing, location, and magnitude of paleoearthquakes in 

this part of New England. 

E.1.2.8.3 Recommendations 

Newburyport, Massachusetts, and the surrounding region is a seismically active area relative to 

the rest of New England. Historically, the largest earthquake to have occurred in the region was 

the 1775 Mfa ~6 earthquake. Paleoseismic studies have found several liquefaction features in the 

Newburyport-Hampton Falls area attributed to the 1727 Mfa ~5.5 earthquake and to a 

paleoearthquake sometime during the past 4,000 years (Figure E-43). The scarcity of liquefaction 

features may be due to the limited distribution of sandy sediments susceptible to liquefaction at 
E-22

relatively low levels of ground shaking. Also, the lateral and vertical variability of Late 

Wisconsin deposits in the region makes searching for liquefaction features especially challenging 

(Tuttle and Seeber, 1991). Significant uncertainties remain regarding the maximum magnitude 

earthquake and the recurrence rates of earthquakes in this region. Therefore, despite the 

challenges of working in this region, the following research is recommended to help reduce these 

uncertainties: 

Broader search for liquefaction features targeting areas where sediments susceptible to 

liquefaction are present and where exposures are available along river cutbanks. 

Re-excavation of some of the paleoliquefaction sites in Newburyport to better constrain their 

ages and to re-evaluate their relationships to possible sand blows. 

E.1.2.9 Charlevoix Seismic Zone and the Surrounding Region 

E.1.2.9.1 Overview 

The Charlevoix seismic zone in Quebec Province of southeastern Canada is one of the most 

seismically active areas in eastern North America and is spatially associated with Iapetan faults 

and the Charlevoix impact crater (Figure E-44; e.g., Adams and Basham, 1989; Lamontagne et 

al., 2000). Charlevoix was the source of three historical earthquakes of M > 6 dating back to the 

1660s (e.g., Bent, 1992; Lamontagne et al., 2007; Lamontagne, 2009). Accounts of ground 

failure during the 1870 and 1925 Charlevoix earthquakes are indicative of liquefaction in the 

Gouffre River valley (Smith, 1966). 

Recently, a paleoseismic study was conducted in the Charlevoix seismic zone and the St. 

Lawrence Lowlands to the southwest in the Quebec City–Trois Rivières region (Figure E-44; 

Tuttle and Atkinson, 2010). During the study, river cutbanks were searched for earthquakeinduced liquefaction features, including 40 km in the Charlevoix region and 100 km in the 

Quebec City–Trois Rivières region. In the Charlevoix region, three generations of earthquakeinduced liquefaction features that formed during the past 10.2 k.y. were found in Late Wisconsin 

and Holocene deposits, whereas no liquefaction features were found in the Quebec City–Trois 

Rivières region despite searching more than twice the river length in similar deposits (Figures 

E-44 through E-49). 

The Charlevoix liquefaction features included sand dikes and soft-sediment deformation 

structures such as basal erosion and sand diapirs, load casts, pseudonodules, and related folds 

(Tables E-1.2-1 and E-1.2-2; see Section E.2.1.1). The authors suggested that the liquefaction 

record of paleoearthquakes is likely to be incomplete for the Holocene due to fluctuating 

hydrologic conditions related to changes in relative sea level in the St. Lawrence estuary (Tuttle 

and Atkinson, 2010). Thus three earthquakes large enough to induce liquefaction during the past 

10.2 k.y. should be viewed as a minimum. During the study, various magnitudes and locations of 

earthquakes were evaluated using liquefaction potential analysis. The results indicated that the 

distribution of liquefaction features could be explained by M > 6.2 earthquake located in the 

Charlevoix seismic zone (Tuttle and Atkinson, 2010). 

In 1988, the M 5.9 Saguenay earthquake occurred north of the Charlevoix seismic zone in the 

Laurentide Mountains, an area that had been thought to have a low seismic hazard. The 1988 

Saguenay earthquake (Somerville et al., 1990; Du Berger et al., 1991) triggered rock falls and 
E-23

landslides and induced liquefaction in Holocene fluvial and Late Wisconsin glaciofluvial and 

glaciolacustrine deposits (Tuttle et al., 1989, 1990). Liquefaction occurred in the epicentral area 

and up to 30 km from its epicenter in the Ferland-Boilleau valley (Figures E-45 through E-49). 

During excavation and documentation of modern sand blows in Ferland, the researchers found 

evidence for a prior earthquake (Tuttle et al., 1992; Tuttle, 1994). Radiocarbon dating of the 

paleoliquefaction features indicated that a large earthquake occurred in the region in AD 1420 ± 

200 yr. Given the relative size of the two generations of features, the previous event may have 

been larger or located closer to the Ferland-Boilleau valley than the 1988 earthquake.

E.1.2.9.2 Data Description 

Paleoliquefaction data from the Charlevoix seismic zone and the Saguenay region, as well as 

liquefaction data related to the 1988 Saguenay earthquake, were contributed by M. Tuttle and 

collaborators to the CEUS SSC Project paleoliquefaction database. The paleoliquefaction data 

and information about river sections searched in the Charlevoix seismic zone and the Quebec 

City–Trois Rivières region were previously published in journal articles and/or technical reports. 

For this project, a new map was created of the Charlevoix seismic zone and the Quebec City–

Trois Rivières region showing mapped structures and river sections along which reconnaissance 

and systematic searched for liquefaction features were performed (Figure E-44). All Quebec 

paleoliquefaction data were reviewed, 2-sigma minimum and maximum constraining ages 

entered, and preferred age estimates calculated. All age estimates of liquefaction features are 

based on radiocarbon dating, and all radiocarbon ages were determined by Beta Analytic 

Radiocarbon Laboratory and calibrated using the Pretoria procedure (Talma and Vogel, 1993; 

Vogel et al., 1993). 

In the Charlevoix region, most of the samples used in radiocarbon dating were collected from 

deposits cut by sand dikes, from animal burrows or root casts that crosscut sand dikes, or from 

deposits in which soft-sediment deformation structures had formed (Tables E-1.2-1 and E-1.2-2). 

In the Saguenay region, there was no need to date the sand blows that formed during the 1988 

Saguenay earthquake, but paleoliquefaction features, including sand-blow craters, sand blows, 

and sand dikes were dated with samples that pre- and post-dated them. Constraining ages were 

derived from 2-sigma calibrated radiocarbon dates, and preferred age estimates and uncertainties 

were calculated from minimum and maximum constraining ages. In one case, a preferred age 

estimate and related uncertainty is calculated from a close minimum constraining age. In this 

case, the preferred age estimate is the mean of the 2-sigma calibrated age range and the 

uncertainty is the difference between the average and the end values of the range. The 

paleoliquefaction data in this data set contributed to the CEUS SSC Project analyses of the 

timing, location, and magnitude of paleoearthquakes in the Charlevoix seismic zone and 

surrounding region. 

E.1.2.9.3 Recommendations 

The Charlevoix paleoseismic study suggests that seismicity may be stationary and localized in 

the Charlevoix seismic zone. However, the search for paleoliquefaction features outside the 

Charlevoix seismic zone only extended toward the southwest (Figure E-44). The largest 

historical earthquake in the region, the 1663 M ~7 earthquake, has been thought to have occurred 

in the Charlevoix seismic zone but there are new results from studies of terrestrial and 

subaqueous mass movements that suggest that the 1663 event may have been centered in the 
E-24

Saguenay region instead (e.g., Levesque et al., 2006; Locat, 2008). The Saguenay liquefaction 

study found evidence for a paleoearthquake about AD 1420 that was larger or located closer to 

the Ferland-Boilleau valley than the 1988 M 5.9 earthquake, suggesting that an earthquake 

source capable of large earthquakes may occur in the Saguenay region (Figure E-49). There are 

large uncertainties regarding the maximum magnitude and recurrence rates of earthquakes in the 

Charlevoix seismic zone and the Saguenay region. Both may be capable of future large 

earthquakes that could affect southeastern Canada and northeastern United States. To help 

address these issues, the following research topics are recommended: 

Additional searches for paleoliquefaction features in the Charlevoix region that might help to 

improve age estimates and recurrence times of paleoearthquakes. Employ OSL dating to help 

date liquefaction features at sites where organic material is not available for radiocarbon 

dating. 

Additional searches for paleoliquefaction features along tributaries of the St. Lawrence River 

both southwest of Trois Rivières and northeast of the Charlevoix seismic zone to further test 

the hypothesis that seismicity in the Charlevoix seismic zone is stationary and that its rate of 

seismicity is higher than other locations along the Iapetan rift margin. 

Additional searches for paleoliquefaction features in the Saguenay region to determine the 

timing, location, and magnitude of the paleoearthquake about AD 1420 and to test the 

hypothesis that the 1663 M ~7 earthquake was located in the Saguenay region. 

E.2 Uncertainties Associated with Paleoliquefaction Data 

E.2.1 Collection of Paleoliquefaction Data 

It is advisable that experienced, qualified investigators be involved in planning and execution of 

paleoliquefaction studies. Lacking familiarity with earthquake-induced liquefaction features and 

the conditions under which they form, inexperienced investigators can squander time and 

resources searching for features in the wrong settings, misidentify features in the geologic 

record, and misinterpret the presence and absence of features. 

For the results of a paleoliquefaction study to be most useful in assessing seismic hazards, search 

areas must be selected where sedimentological and hydrological conditions are conducive for the 

formation and preservation of liquefaction features. These conditions include (1) the presence of 

loose to moderately dense sandy sediments that occur below the water table or are otherwise 

saturated at the time of an earthquake; (2) an overlying layer of less permeable clay or clayey silt 

to promote the increase in pore-water pressure in and liquefaction of saturated sandy sediment 

during ground shaking; and (3) an environment of sediment accumulation or relative stability 

that is not undergoing denudation (Sims, 1975; Obermeier, 1996; Tuttle, 2001). 

Utmost care must be taken to correctly identify earthquake-induced liquefaction features and not 

to confuse them with features that formed as the result of other processes. Deposits and features 

that have been misidentified as earthquake-induced liquefaction feature include fluvial deposits, 

chemical weathering, tree-throw, and cultural features. Liquefaction features have certain 

characteristics, described below and summarized in Section E.1.2, that help to distinguish them 

from other deposits and features (Figure E-50). For example, the presence of feeder dikes helps 

to distinguish earthquake-related sand blows from fluvial deposits and deformation related to tree 
E-25

throw. With close examination of deposits and features by an experienced eye, earthquakeinduced liquefaction features can be identified with confidence. 

Exposure of sediments must be adequate to reveal liquefaction features, if they are present. 

Dense forests and other vegetation can obscure surficial sand blows, making it difficult to 

identify them on aerial photographs and satellite images. Agricultural practices such as plowing 

and grading can disturb and destroy them. Exposures can be created to verify interpretations 

from aerial photographs and satellite images by excavating trenches in sand blows. Geophysical 

techniques such as electrical resistivity and ground-penetrating radar can be used to map sand 

blows and locate sand dikes (Figure E-14; Wolf et al., 1998, 2006; Al-Shukri et al., 2006; 

Al-Qadhi, 2010). Fieldwork should be conducted at times of the year, and even the time of day in 

coastal areas, when exposure is optimal in order to minimize chances that liquefaction features 

are missed due to high water, heavy vegetation, or snow cover. Exposures along actively eroding 

river cutbanks and recently excavated drainage ditches can be used to search for liquefaction 

features and to examine their sedimentary characteristics and structural relations. 

Field studies should be designed to try to fully characterize the size and spatial distribution of 

paleoliquefaction features. As the size and frequency of liquefaction features decrease, the more 

cutbank exposure must be examined to find and characterize them. If liquefaction features are 

not found, it is important to verify that the search areas are underlain by sediments that are 

susceptible to liquefaction. 

E.2.1.1 Identification of Earthquake-Induced Liquefaction Features 

Liquefaction is the phenomenon by which saturated sandy sediments, when subjected to strong 

ground shaking, lose shear strength as pore-water pressure in the sediments increases, leading to 

ground failure, injection of sand dikes and sills, ejection of sand volcanoes or sand blows, and 

formation of sand-blow craters (Figures E-2 and E-50; Seed and Idriss, 1982; Youd, 1984). Sand 

dikes, sand blows, and sand-blow craters are considered diagnostic of earthquake-induced 

liquefaction, and their characteristics have been documented following historical (e.g., Dutton, 

1889; Fuller, 1912) and modern earthquakes (e.g., Tuttle et al., 1990: Tuttle, Schweig, et al., 

2002; Sims and Garvin, 1995). Several notable studies in the Charleston seismic zone (e.g., 

Amick, Gelinas, et al., 1990; Amick, Maurath, and Gelinas, 1990; Obermeier et al., 1989; and 

Talwani and Schaeffer, 2001); the New Madrid seismic zone (e.g., Russ, 1982; Saucier, 1991; 

Tuttle, Schweig, et al., 2002; and Tuttle et al., 2005); and the Wabash Valley seismic zone (e.g., 

Obermeier et al., 1993; Munson et al., 1997; and Obermeier, 1998) have used paleoliquefaction 

features to reconstruct the earthquake history from the geologic record (Table E-1.2-2).

The following general criteria have been advanced for identifying earthquake-induced 

liquefaction features: (1) sedimentary characteristics consistent with case histories of earthquakeinduced liquefaction; (2) sedimentary characteristics indicative of sudden, strong, upwardly 

directed hydraulic force of short duration; (3) occurrence of more than one type of liquefaction 

feature and of similar features at multiple locations; (4) occurrence in geomorphic settings where 

hydraulic conditions described in (2) would not develop under nonseismic conditions; and (5) 

age data to support both contemporaneous and episodic formation of features over a large area 

(Obermeier, 1996; Tuttle, 2001). 

Sand blows are sand deposits that result from liquefaction of loose, saturated, sandy sediment, 

usually within 15–20 m of the ground surface, and venting of the slurry of pressurized pore-
E-26

water and entrained sediment through fissures, cracks, and other voids to the surface (Figures 

E-2, E-50, and E-51). In the case of sand-blow craters, a crater forms at the ground surface and 

the sand blow is deposited around the rim of the crater (Figures E-51 through E-53). In plan 

view, the shape of the sand blows and sand-blow craters is related to the void through which the 

slurry vented. Most sand blows and sand-blow craters are elliptical in shape because the slurry 

vented through fissures (Tuttle and Barstow, 1996). Sand blows and sand-blow craters that are 

circular in shape result from venting through tubular-shaped voids such as decomposed tree roots 

and trunks and animal burrows (Audemard and de Santis, 1991; Tuttle, 1999). 

In cross section, sand blows usually bury soil horizons and are connected at their bases to one or 

more feeder dikes or tubular conduits, which are the sand-filled voids through which the 

fluidized sediment vented (Figures E-2, E-50, and E-54). Sand blows are thickest and coarsestgrained immediately above the feeder dikes or tubular conduits and thin and fine away from the 

vent. Sand blows often contain clasts of the underlying deposits through which water and sand 

vented. The clasts tend to be larger and more concentrated above the vent. In cases of ground 

subsidence related to venting of subsurface sediment or to lateral spreading, the buried soil may 

dip toward or be displaced across the sand-filled vent structures such as sand dikes. Sand blows 

and sand-blow craters should exhibit most if not all of these characteristics including a structural 

connection with feeder dikes (Section E.1.2) and should not be confused with fluvial deposits 

such as overbank sediments or crevasse splays that bury soils and may be limited in extent. 

As mentioned above, sand dikes and tubes are the sand-filled voids resulting from liquefaction of 

sediment at depth and intrusion of overlying deposits by the pressurized slurry of water and 

entrained sediment (Figures E-50, E-54, and E-55). Sand dikes usually have well-defined 

margins and can be differentiated from the host deposit by differences in grain-size and 

weathering characteristics. Sand dikes originate in a layer of sandy sediment, often referred to as 

the source bed, that has undergone liquefaction and fluidization. The source beds of sand dikes 

may lack original sedimentary structure and may exhibit soft-sediment deformation structures 

such as ball-and-pillow structures and dish structures as well as flow structure or lineations (see 

Glossary). The sand dikes intrude overlying deposits and crosscut bedding. They often narrow, 

branch, and become finer-grained upward, are characterized by flow structure, and contain clasts 

of the deposits that they intrude (Section E.1.2; Obermeier, 1996; Tuttle, 2001). In cases where 

the slurry of water and sand did not make it to the surface, sand dikes pinch out or terminate 

within the stratigraphic section (Figure E-2). Extensions of sand dikes, sand sills sometimes form 

along the base of less permeable layers. Sand-filled root casts and dessication cracks that branch 

and pinch downward should not be confused with sand dikes resulting from earthquake-induced 

liquefaction. 

Soft-sediment deformation structures, including sand diapirs, basal erosion, convolute bedding, 

pseudonodules, load casts and related folds, have been attributed to earthquake-induced 

liquefaction on the basis of laboratory experiments (Kuenen, 1958) and field studies (Sims, 1973 

and 1975; Obermeier, 1996; Tuttle, 1999). During field studies of earthquake-induced 

liquefaction features, sand diapirs and basal erosion have been found to form where fine-grained 

deposits overlie coarse-grained deposits (Figures E-2 and E-56). Pieces of the overlying finegrained sediment founder into the coarse-grained sediment due to loss of its bearing strength 

during liquefaction. Simultaneously, coarse-grained sediment moves upward to replace the 

foundered material forming sand diapirs. Sand diapirs and basal erosion may form when ground 
E-27

motions are capable of inducing liquefaction in susceptible sediments but not capable of 

generating the pore-water pressures required for hydraulic fracturing of the overlying deposits. 

Load casts, pseudonodules, and related folds typically form in interbedded fine- and coarsegrained deposits when fine-grained sediment sinks into coarse-grained sediment due to loss of 

bearing strength (Figure E-57). In cases where layer integrity is maintained, the resulting features 

are called load casts. In cases where layer integrity is not maintained and coarse-grained 

sediment separates into domains or irregular masses, the features are called pseudonodules. 

Pseudonodules, load casts, and related folds typically form close to the sediment-water interface 

at the time of deposition. It is important to note that the soft-sediment deformation structures 

mentioned above also can form by non-earthquake processes (e.g., Lowe and LoPicollo, 1974; 

Lowe, 1975; Allen, 1982; and Owen, 1987). Criteria have been proposed for distinguishing 

seismic from nonseismic soft-sediment deformation structures. These criteria are similar to those 

advanced for identifying earthquake-induced sand blows and sand dikes and include the 

following (Wheeler, 2002): 

evidence for sudden formation, 

synchroneity and zoned map distribution over many exposures, 

size of the structures, and 

tectonic and depositional settings. 

Soft-sediment deformation structures that meet these criteria and are used with caution in 

combination with sand blows and sand dikes may aid in mapping areas of liquefaction and 

defining the limits of liquefaction fields (e.g., Tuttle and Atkinson, 2010). 

E.2.1.2 Dating Liquefaction Features 

By dating liquefaction features, it is possible to estimate the ages of the paleoearthquakes that 

were responsible for their formation. It is important to constrain the ages of liquefaction features 

as narrowly as possible to help correlate similar-age features across a region and differentiate 

closely timed events. The dating strategy depends on the type of liquefaction features 

encountered, as does the likelihood of narrowly constraining their ages. Because it is often 

possible to determine both maximum and minimum age constraints and thus bracket their ages, 

sand blows usually provide the best opportunity for estimating the ages of paleoearthquakes with 

relatively small uncertainties (Figure E-3; Tuttle, 2001). Close maximum age constraint can be 

determined by dating plant material, such as twigs and leaves, and sediments that were at or near 

the ground surface and buried by the sand blows at the time of the event (Figure E-58). 

Similarly, plant material derived from surface soils and incorporated in the vented deposits of 

sand blows and sand-blow craters also provides close maximum age constraint. For those cases 

in which samples are reworked, there is more uncertainty regarding their origin and thus their 

age relation to the liquefaction features. 

In addition, minimum age constraint, and sometimes, close minimum age constraint, can be 

determined for sand blows and sand-blow craters. For example, close minimum age constraint 

can be achieved by dating plant material and sediment that accumulated in craterlets in the upper 

surface of sand blows soon after they formed. More commonly, minimum age constraints come 
E-28

from dating plant material in soils that developed in the sand blows over time and from tree roots 

and cultural pits that extend down into sand blows from above (Figure E-59). 

Estimating the age of sand dikes and sand sills usually involves greater uncertainty than for sand 

blows and sand-blow craters (Tuttle, 2001). This is because dikes and sills may terminate several 

meters below the ground surface at the time of the paleoearthquake (Figure E-2). Maximum age 

constraints can be determined by dating the uppermost stratigraphic units that they crosscut or 

overlie, but these ages may be hundreds to thousands of years older than the liquefaction feature 

(Figure E-3; Tuttle, Chester, et al., 1999). Minimum age constraints of dikes and sills can be 

determined by dating roots, animal burrows, and cultural pits that clearly intrude and postdate the 

liquefaction features or by dating deposits that overlie unconformities that truncate the 

liquefaction features. However, it is fairly uncommon to find circumstances such as these that 

help to constrain the minimum age of dikes and sills (Tuttle, 2001). Therefore, age estimates of 

sand dikes and sills often have large uncertainties. Some investigators will make educated 

guesses as to the ages of these types of liquefaction features based on weathering characteristics 

of the features themselves or the approximate age of the deposits in which they occur. There can 

be large uncertainties in these estimates on the order of thousands of years. 

Pseudonodules, load casts, and related folds typically form close to the sediment-water interface 

at the time of sediment deposition (Figure E-57; Sims, 1973, 1975). Age estimates and related 

uncertainties for causative earthquakes can be derived by dating the deformed sediments 

themselves or by dating plant material above and below the deformed sediment. There often are 

much larger uncertainties in estimating the ages of sand diapirs and basal erosion. This type of 

soft-sediment deformation may have formed anytime following deposition of the stratigraphic 

units involved. Maximum age constraint can be established by dating the deformed deposits but 

the deformation may be hundreds or thousands of years younger than the deposits. 

E.2.1.3 Dating Techniques 

This section provides discussion of dating techniques used in paleoliquefaction studies, including 

dendrochronology, radiocarbon dating, optically stimulated luminescence, archaeological and 

stratigraphic context, and soil development. Table E-2.1.3 provides a summary of these dating 

techniques. 

E.2.1.3.1 Dendrochronology 

Dendrochronology is the dating of past events through the study of the tree ring record and has 

the potential to date events to the year and even the season (Table E-2.1.3; Pierce, 1986; Stahle et 

al., 2004). For example, trees killed by coseismic subsidence along the coast of Washington State 

helped to provide exact dates of megathrust earthquakes along the Cascadia subduction zone 

(Atwater et al., 2004). Abrupt changes in soil-moisture conditions due to liquefaction-related 

subsidence of the ground surface and/or burial by thick sand blows as well as disruption of tree 

root systems by lateral spreading, may affect tree ring growth and even lead to tree death 

(Figures E-51 and E-60; Tuttle, 1999). Therefore, trees buried and preserved below sand blows 

may provide precise dates of paleoearthquakes. Before dendrochronology can be used, however, 

regional chronologies for affected tree species must be developed. Long-lived tree species 

provide the best dendrochronology records. In the New Madrid region, a regional chronology has 

been developed only for baldcypress and only for the past 1,000 years (Stahle et al., 1985). So 
E-29

far, dendrochronology has been used very little in paleoliquefaction studies but has the potential 

to better constrain age estimates of paleoearthquakes, especially in regions where liquefactionrelated ground failures were severe (Table E-2.1.3). 
E-30

Table E-2.1.3. Summary of Dating Techniques Used in Paleoliquefaction Studies 

Dating 

Technique

Applicable 

Time Period 

(Years BP)

Dating 

Precision 

(Years)

Applied in 

CEUS Regions1Selected References2

Dendrochronology1–1,000’s Annual, 

possibly 

seasonal

(1) NMSZ (1) Stahle et al., 1985; Tuttle, 1999

Radiocarbon 1–50,000 10’s–100’s (1) NMSZ

(2) MAR

(3) STL

(4) WVSZ

(5) ALM

(6) CSZ

(7) AC-CVA

(8) NEWBURY

(9) CxSZ

(1) Tuttle et al., 2005

(2) Tuttle et al., 2006

(3) Tuttle, Chester, et al., 1999

(4) Munson and Munson, 1996

(5) Cox, Larsen, et al., 2004

(6) Talwani and Schaeffer, 2001

(7) Obermeier and McNulty, 1998

(8) Tuttle and Seeber, 1991

(9) Tuttle and Atkinson, 2010

Optically 

stimulated 

luminescence

100–100,000 10’s–1,000’s (1) NMSZ

(2) MAR

(3) WVSZ

(4) ALM

(1) Mahan et al., 2009

(2) Tuttle et al., 2006 

(3) Mahan and Crone, 2006 

(4) Cox, Larsen, et al., 2004

Archeological 

context

1–12,000 10’s–1,000’s (1) NMSZ

(2) STL

(3) WVSZ

(1) Tuttle et al., 1998, 2000

(2) Tuttle, Chester, et al., 1999

(3) Munson and Munson, 1996

Stratigraphic 

context

1–100,000+ 100’s–

1,000’s

(1) NMSZ

(2) WVSZ

(1) Tuttle, 1999

(2) Hajic et al., 1995; Munson and 

Munson, 1996

Soil 

development

1–100,000+ Varies with 

soil property

(1) NMSZ (1) Tuttle et al., 2000

1. NMSZ = New Madrid seismic zone and surrounding region; MAR = Marianna Area; STL = St. Louis and 

surrounding region; WVSZ = Wabash Valley seismic zone and surrounding region; ALM = Arkansas-LouisianaMississippi region; CSZ = Charleston seismic zone; AC-CVA = Atlantic Coast and Central Virginia 

reconnaissance; NEWBURY = Newburyport, Massachusetts, and surrounding region; CxSZ = Charlevoix seismic 

zone and surrounding region. 

2. Selected references shown here. Also see paleoliquefaction database and reference lists at the end of this report. 

E.2.1.3.2 Radiocarbon Dating 

Radiocarbon dating or 14C dating is the most common dating technique used in paleoliquefaction 

studies (Table E-2.1.3). Although reliable for only the past 50,000 years, radiocarbon dating is 

useful for the time period of interest for most paleoseismic studies. Uncertainties in the results 

are related to the dating techniques, to conversion of radiocarbon ages to calibrated ages, and to 

sampling of materials that are used in dating liquefaction features. 

Two different radiocarbon dating techniques are used, depending on the size of the sample 

(Aiken, 1990). The radiometric technique is used for larger samples (e.g., charcoal ≥ 15 grams, 

wood ≥ 25 grams, and soil ≥ 200 grams). The accelerator mass spectrometry (AMS) technique is 

used for smaller samples (charcoal ≥ 20 milligrams, wood ≥ 20 milligrams, and soil ≥ 2 grams). 
E-31

The radiometric technique involves converting carbon to benzene, measuring the sample’s beta 

activity in a liquid scintillator, and calculating the radiocarbon age (Aiken, 1990). A precision of 

better than ± 1%, corresponding to ± 80 radiocarbon years, can usually be achieved for samples 

that are less than 10 k.y. High-precision measurements can be made on wood samples of ≥ 1 

kilogram by measuring the beta activity of the sample in a proportional gas counter (Stuiver et 

al., 1998). For these very large samples, a precision ± 0.25%, corresponding to ± 20 radiocarbon 

years, can be obtained. 

The AMS technique involves reducing the sample to graphite and then measuring carbon ions in 

an accelerator mass spectrometer (Aiken, 1990). A precision of about ± 0.5%, corresponding to ± 

40 radiocarbon years, can be achieved with the AMS technique. Isotopic fractionation may occur 

during sample preparation and can affect the radiocarbon age. This effect can be taken into 

account by measuring the 13C/12C ratio for each sample and making the appropriate correction. 

Other experimental uncertainties are related to contamination during sample preparation, lack of 

constancy of counter background and counter efficiency, residual 14C within the accelerator, and 

human error (Aiken, 1990). These uncertainties are taken into account by applying a laboratory 

error multiplier (1.3 to 2). The error multiplier is a measure of the laboratory reproducibility and 

is usually derived from repeated dating of a standard of known or consensus age (Stuiver and 

Pearson, 1993). Because of its higher precision, the AMS technique is now preferred by many 

investigators despite its greater cost. 

Radiocarbon dating results are reported as both measured and conventional 14C ages. 

Conventional ages are derived from measured ages by normalizing them to the modern standard 

through the use of 13C/12C ratios. Because 14C in the atmosphere has fluctuated over time due to 

variations in cosmic radiation and, recently, to burning of fossil fuels and testing of nuclear 

devices (Stuiver et al., 1993), it is desirable to convert conventional ages to actual or calendar 

years by using the radiocarbon calibration curve (Figure E-61; Tuttle, 1999). Although the recent 

part of the curve (12 k.y.) based on tree-ring records is the most secure and reliable, the 

calibration curve now extends to 50 k.y. BP (Walker, 2005; Reimer et al., 2009). Several 

calibration procedures have been developed that are commonly used and yield similar results. 

These procedures include CALIB (Stuiver and Reimer, 1993; Stuiver et al., 2005), OxCal (Bronk 

Ramsey, 1995, 2001), and Pretoria (Talma and Vogel, 1993; Vogel et al., 1993). It is preferable 

to use 2-sigma calibrated dates to either bracket or approximate the ages of the liquefaction 

features. This assures with a high probability that the actual ages of the liquefaction features fall 

within the estimated age range. Calibrated ages rarely have 2-sigma ranges of less than 100 

years, more often have 2-sigma ranges of about 200–300 years, and sometimes have two or three 

ranges depending on the number of intercepts of the conventional radiocarbon age with the 

calibration curve (Table E-2.1.3). 

The type and location of samples collected for radiocarbon dating affect the uncertainty of the 

age estimate of the liquefaction features. Plant remains that occur in close stratigraphic position 

to a sand blow will fairly closely reflect its age. For example, leaves or burned wood that occur 

at the contact of a buried soil horizon and an overlying sand blow would provide close maximum 

age constraint for the sand blow (Figures E-3 and E-58). Similarly, maize kernels, leaves, or 

burned wood incorporated into the top of a sand blow would provide close minimum age 

constraint. In contrast, a piece of charcoal within the buried soil or underlying sediment would 

provide maximum age constraint, but could be hundreds or even thousands of years older than 

the sand blow. Unless associated with in situ cultural or biological features such as fire pits and 
E-32

tree trunks, a charcoal sample could be reworked, in which case its age relation to the sand blow 

would be even more uncertain. Bulk samples of soils buried by or developed in sand blows can 

also be dated. However, radiocarbon dates of soils reflect the mean residence time of carbon in 

those samples (Trumbore, 1989; Walker, 2005). Also, contamination by young (e.g., modern 

humic acids) and old (e.g., lignite and calcium carbonate) carbon can be a significant problem in 

soils. Therefore, dating soils is usually a last resort and requires a sampling strategy to help 

minimize the uncertainties (Tuttle, 1999). 

E.2.1.3.3 Optically Stimulated Luminescence 

Luminescence techniques, including optically stimulated luminescence (OSL), provide an 

estimate of the time since quartz and feldspar grains were last exposed to light (which zeros the 

luminescence signal). After burial, the luminescence signal grows with exposure to radiation in 

the surrounding sediments (K, U, Th, Rb). The luminescence signal can be measured in the 

laboratory and related to the duration of burial and in situ and cosmic radiation environment 

(Murray and Olley, 2002). In other words, OSL is a numerical method used to determine the 

amount of time that has passed since sediment was last exposed to light (e.g., Wintle and 

Murray, 1997; Aitken, 1998; Forman et al., 2000; McKeever, 2001) and therefore holds promise 

for estimating the ages of paleoearthquakes by dating sediment buried by sand blows and that 

buries sand blows (Mahan and Crone, 2006; Tuttle et al., 2006; Mahan et al., 2009). The 

preponderance of age estimates in the CEUS SSC Project paleoliquefaction database are based 

on radiocarbon dating conducted over the past 20 years. However, OSL dating of sand blows is 

being increasingly used and results for several features in the New Madrid (e.g., Clarke River 

site) and Marianna (e.g., Daytona Beach and St. Francis 500 sites) regions are included in the 

database. 

OSL geochronology is a useful tool that can be used in a variety of terrestrial stratigraphic 

settings, particularly for sediments that receive brief exposure to sunlight prior to deposition. In 

general, the technique is most useful for sediments approximately 100 years to more than 100 

k.y. old (Forman et al., 2000; Lepper, 2007; LDRL, 2010). As such, OSL dating is useful even 

further back in time than radiocarbon techniques. The primary difference between radiocarbon 

dating and OSL dating is that the former is used to date organic materials, whereas the latter is 

used to date the timing of exposure of certain minerals to light. 

The preferred sediment for OSL dating is coarse silt to medium sand (quartz or feldspar) that has 

had at least one hour of sunlight exposure. Feldspar is both structurally and chemically more 

variable than quartz and requires longer exposure to sunlight to zero the luminescence signal 

(i.e., bleach). Accordingly, quartz often results in more reliable dates than feldspar. It is preferred 

if samples come from a relatively homogeneous stratigraphic unit that is at least 30 cm thick, and 

has not undergone significant water-content variations or diagenetic changes during burial 

(LDRL, 2010). OSL analysis of a sample collected from, for example, the sediment immediately 

below the base of a sand-blow deposit can yield an estimate of the time of the causative 

earthquake. 

Studies have compared the results of OSL and radiocarbon dating of sand blows in the central 

United States. This was done by dating co-located samples collected above and below sand 

blows (Mahan and Crone, 2006; Tuttle et al., 2006; Mahan et al., 2009). Correlation of OSL and 

radiocarbon dates was best for samples collected immediately below sand blows and for samples 

collected in association with sand blows buried several meters beneath fluvial deposits. 
E-33

Correlation was poor for samples collected in soils developed in surface sand blows and in 

sediment buried beneath sand blows that had been subjected to bioturbation. 

There are a number of possible uncertainties and errors that can limit the precision and accuracy 

of OSL dating. The most common complication is that the sediment has not received enough 

sunlight exposure prior to burial in order to rid the sample of previously acquired luminescence 

(i.e., ―partial‖ vs. ―full‖ bleaching; Forman et al., 2000). Partial bleaching is very unlikely in 

eolian and coastal marine sands, but is more likely in Holocene fluvial deposits. This is because 

light attenuates significantly in water. Additionally, silt and sand grains that are coated with clay 

may be shielded from the bleaching effects of sunlight. 

The accuracy of OSL dating may also be limited in pure quartz deposits because the naturally 

occurring background radiation in surrounding sediments often is low. As a result, cosmic 

radiation becomes the main source of ionizing radiation that ejects electrons from atoms in the 

crystal lattice (which are ultimately the source of the luminescence signal). Because cosmic 

radiation often fluctuates and attenuates quickly with depth below grade, uncertainty in 

depositional history has a bigger influence on the overall uncertainty of the resulting OSL age 

estimates. 

Water content of the soil also influences the rate of attenuation of ionizing radiation in situ. As a 

result, uncertainties in the average water content of the sediment since deposition influences the 

overall uncertainty of the resulting OSL age estimates. Additional complications include 

bioturbation, diagenesis and postdepositional weathering, and accumulation of secondary 

minerals (silica, calcium carbonate, and clay). Therefore, careful selection and sampling of 

sediment is crucial. Uncertainties in OSL dates increase with sediment age from a few tens to a 

few hundreds of years for the past 1–10 k.y. and to several thousands of years for the past 10–

100 k.y. (Table E-2.1.3). 

E.2.1.3.4 Archeological Context 

Archeological chronologies have been developed for many regions. These chronologies are 

developed primarily on the basis of the following: (1) seriation, or the sequence of artifact and 

ceramic types particularly within cultural horizons; and (2) radiocarbon dating of organic 

material associated with artifacts and cultural horizons (Aiken, 1990; O’Brien and Lyman, 

1999). Referring to the regional archeological chronologies, artifacts found at liquefaction sites 

can help to estimate the ages of the liquefaction features (Saucier, 1991; Tuttle, Lafferty, 

Guccione, et al., 1996; Munson et al., 1997). Some artifact types are well-constrained to specific 

cultural periods while others are not. Age estimates of liquefaction features based on their 

archeological context will have uncertainties at least as great as those based on radiocarbon 

dating (Table E-2.1.3). 

Cultural artifacts found in, or associated with, liquefaction features during reconnaissance can 

provide a preliminary estimate of the ages of the features. The stratigraphic relations of 

liquefaction features and cultural horizons and features as well as the assemblage of artifacts, 

especially if diagnostic artifact types are present, can help to further constrain the ages of the 

liquefaction features (e.g., Tuttle, 2001; Tuttle et al., 2005). For example, the assemblage of 

artifacts within an A horizon buried by a sand blow can provide an estimate of the maximum age 

of the liquefaction feature. The assemblage of artifacts within an occupation horizon developed 

in a sand blow or cultural features such as a storage pit or wall trench dug into a sand blow can 
E-34

provide an estimate of its minimum age (Figures E-58 and E-59). It is important to study 

assemblages of artifacts since there are still many uncertainties regarding the temporal and 

geographical ranges of artifact types. 

Due to their abundance of organic-rich material, archeological sites often provide good 

opportunities for finding samples suitable for radiocarbon dating and constraining the age(s) of 

any liquefaction feature that is present (Tuttle and Schweig, 1995). In these cases, it is desirable 

to conduct both archeological analyses and radiocarbon dating of organic samples because they 

provide a means of cross-checking results and add confidence to the age estimates of liquefaction 

features. 

E.2.1.3.5 Stratigraphic Context 

Stratigraphic context and relationships can be used as a means to estimate the relative ages of 

buried sand blows and sand dikes, and to correlate paleoliquefaction features between exposures. 

The law of superposition, crosscutting relationships, and identification of paleosurface indicators 

preserved in the stratigraphic record can be used to help determine the relative ages of 

paleoliquefaction features. Moreover, in an area with laterally continuous stratigraphy or 

prominent marker beds, age equivalence can be established between different exposures or sites. 

If the ages of some or all of these strata are determined by numerical or other means at one site, 

these ages can be extrapolated to other nearby sites. However, correlation of paleoliquefaction 

features identified in similar-age sediments is potentially problematic. For example, most of the 

mid- to late-Holocene sand-blow craters identified in the Charleston, South Carolina region are 

found in beach ridge deposits that are 100 ka and older (McCartan et al., 1984). If only the host 

deposits had been used to correlate and date paleoliquefaction features, the timing of the events 

may have been overestimated and the number of paleoearthquakes underestimated. Ages derived 

through other methods reveal earthquakes separated by significant periods have caused 

paleoliquefaction features within correlative stratigraphic units. 

In addition, stratigraphic context and relationships can be used to place maximum ages on, for 

example, sand dikes that terminate upward at a stratigraphic level that may be lower than the 

paleo-ground surface at the time of the causative earthquake Figure E-2). Sand dikes that 

terminate below the event horizon commonly are encountered outside of the most active seismic 

zones and at greater distances from the seismic source than sand blows. By numerical or relative 

dating of the host deposits, it is possible to place at least a maximum age constraint on the timing 

of dike formation (Figure E-3). 

As described above, stratigraphic context can be used to estimate the relative ages of 

paleoliquefacion features. However, these methods typically are less precise and less accurate 

than numerical dating techniques and therefore should be calibrated using, for example, 

radiocarbon or OSL numerical dating methods where possible. Even so, uncertainties in age 

estimates of paleoliquefaction features based on their stratigraphic context are likely to be on the 

order of several hundreds to several thousands of years at best (Table E-2.1.3). 

E.2.1.3.6 Soil Development 

The state of a soil system is defined as a function of five soil-forming factors: climate, biological 

activity, topography, parent material, and time (Jenny, 1941, 1961; Birkeland, 1999). In 

genetically related suites of soils in which all soil forming factors except for time are about 
E-35

equal, soil profiles, as well as certain soil properties, develop systematically with age (Harden, 

1982; Harden and Taylor, 1983). These soil properties include rubification (reddening and 

brightening of soil colors), clay accumulation, soil structure, consistence, and pH. Therefore, soil 

profiles and properties can be used to estimate the age of a soil if they are calibrated with 

numerical techniques, such as radiocarbon dating and OSL dating (Table E-2.1.3). 

In most paleoliquefaction studies, soil development is used as a relative dating technique to 

distinguish young, unweathered features from significantly older, more weathered features. In 

the New Madrid seismic zone, the thickness of A horizons developed in sand blows has been 

used to derive preliminary age estimates of sand blows and to aid in the selection of sand blows 

for detailed investigations (Tuttle et al., 2000). The estimates were based on a rate of A horizon 

development derived by studying soil characteristics of sand blows of known ages. The age 

estimates had uncertainties on the order of 100 years, similar to the uncertainties of radiocarbon 

dating on which the rate of A horizon development was based (Figure E-62). 

In a few regions where sand dikes have terminated within the stratigraphic section and organic 

material and cultural artifacts have not been available for constraining the ages of the features, 

soil characteristics such as iron staining and accumulation of fine-grained sediment have been 

used to correlate features over large distances. This practice is not recommended unless the soil 

characteristics have been calibrated and the uncertainties associated with their rates of 

development quantified. Otherwise, the spatial correlation of features and the interpretations 

related to the spatial distribution of those features may be erroneous (Tuttle, 2001). 

E.2.2 Uncertainties Related to Interpretation of Paleoliquefaction Data 

This section provides discussion of uncertainties related to the interpretation of paleoearthquake 

parameters from paleoliquefaction data, including the timing, magnitude, and location of 

paleoearthquakes. Table E-2.2 provides a summary of these uncertainties. 

E.2.2.1 Timing of Paleoearthquakes 

Uncertainty in the timing of paleoearthquakes is largely a function of age constraints of multiple 

liquefaction features correlated across a region (Table E-2.2). If ages of liquefaction features 

cannot be constrained within a few hundred years, it may not be possible to correlate features 

chronologically, to resolve the timing of paleoearthquakes with confidence, or to estimate 

recurrence rates for sources with earthquake cycles of less than 1,000 years. Preferably, 2-sigma 

calibrated radiocarbon dates are used to either bracket or approximate the ages of the liquefaction 

features. Clustering of age estimates of liquefaction features reflects the timing of 

paleoearthquakes (Figure E-63). For a particular cluster, the union of well-constrained age 

estimates of liquefaction features represents the time period during which the paleoearthquake is 

likely to have occurred. It is not uncommon for this time period to have a range of 100 to 1,000 

years. The timing of the event can be expressed as the average of the range plus and minus the 

difference between the average and the endpoints of the range. A few well-constrained age 

estimates of liquefaction features can lead to a more narrowly defined range of tens to hundreds 

of years and thus smaller uncertainties in the timing of the paleoearthquakes (Table E-2.2). For 

the CEUS SSC Project, uncertainty ranges of tens to hundreds of years were derived for the 

timing of paleoearthquakes in the New Madrid and Charleston seismic zones by using subsets of 
E-36

the better-constrained age estimates of liquefaction features (Figure E-64; see Section 6.1.5.4 of 

the main report). 

Table E-2.2. Uncertainties Related to Interpretation of Paleoearthquake Parameters 

Earthquake 

Parameter

Range in 

Uncertainty

Factors that Contribute to 

Uncertainty

Observations and Analyses that 

Reduce Uncertainty

Timing 10’s–1,000’s 

of years

(1) Dating of liquefaction features

(2) Use of sand dikes in absence 

of sand blows

(1) Well-constrained age 

estimates of liquefaction features

(2) Space-time diagrams

(3) Statistical analysis of 

uncertainty range of age 

estimates of multiple liquefaction 

features

Location Few–100’s of 

km

(1) above

(2) Correlation of features across 

region

(3) Size and spatial distribution of 

contemporaneous features

a. Style of faulting

b. Earthquake source 

characteristics

c. Directivity of seismic energy

d. Attenuation and amplification 

of ground motion

e. Relative density of sediment

f. Distribution of liquefiable 

sediments

g. Water table depth

(4) Field sampling and exposure

(1) through (3) above

(4) Size distribution of features

(5) Information regarding 

uncertainty factors (3a) through 

(3g).

(6) Field studies conducted where 

sedimentary and hydrologic 

conditions suitable for formation 

and preservation of liquefaction 

features, and when adequate 

exposure available to find 

features, if present

(7) Comparative study with 

calibration event in same region

(8) Relationship to active fault

Magnitude 0.25–1 unit (1) through (4) above

(5) Epicentral distance to farthest 

sand blow unlikely to be known

(6) Changes in source sediments 

due to liquefaction or to 

postliquefaction effects such as 

cementation and compaction

(1) through (8) above

(9) Empirical relations based on 

global database of earthquakes 

that induced liquefaction

(10) Evaluation of scenario 

earthquakes using liquefaction 

potential analysis 

Recurrence 

time

10’s–1,000’s

of years

(1) Uncertainty in timing of 

paleoearthquakes 

(2) Completeness of 

paleoearthquake record in space 

and time

(1) Well-constrained age 

estimates of paleoearthquakes 

(2) Space-time diagrams

(3) Consideration of history of 

sedimentation and erosion as well 

as of changes in water table 

E.2.2.2 Correlation of Liquefaction Features 

The correlation of liquefaction features between sites is necessary for interpretation of the 

timing, location, and magnitude of paleoearthquakes. This correlation is based on available 

information, including one or more of the following: 
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Chronological control: Paleoearthquakes are distinguished based on grouping 

paleoliquefaction features that have overlapping age estimates. As described above, sand 

blows typically are best to use due to more straightforward identification of the event horizon 

and their typically better-constrained age estimates, whereas the event horizon and age 

estimates associated with sand dikes often are relatively poorly constrained. 

Size distribution: Paleoearthquakes are distinguished based on the assumption that feature 

size diminishes with ground shaking and therefore with magnitude of, and distance from, the 

causative earthquake. The size distribution of liquefaction features is important for 

interpreting whether similar-age features formed during single large earthquake or multiple 

smaller earthquakes. 

Stratigraphic control: Paleoearthquakes are distinguished based on grouping 

paleoliquefaction features found in similar-age sediments (see caveats described in Section 

E.2.1.3.5 of this appendix). 

Pedologic or weathering characteristics: Paleoearthquakes are distinguished based on 

grouping paleoliquefaction features with similar soil or weathering characteristics (see 

caveats described in E. 2.1.3.6 of this appendix). 

If the information described above provides conflicting correlations for a specific field study, it 

is incumbent upon the researcher to assess the relative qualities of the different sources of 

information, and to thereby define a preferred interpretation of the available data. 

Earthquake ages are defined by selecting the age range common to multiple sand blows in a 

region. For example, an earthquake age can be defined by the union or the intersection of 

overlapping 2-sigma radiocarbon age estimates of sand blows. Using the union of overlapping 

age estimates may be overly conservative since they may include poorly constrained age 

estimates. Using the intersection of overlapping age estimates may provide the best estimate of 

the earthquake age, so long as there is a high degree of confidence in the accuracy of the age 

estimates. 

E.2.2.3 Location of Paleoearthquakes 

Once they have been correlated across a region on the basis of one or more of the criteria 

described above (e.g., chronological or stratigraphic control), liquefaction features, particularly 

sand blows and sand dikes, can be used to infer the approximate locations of paleoearthquakes. 

The regional distribution of contemporaneous liquefaction features, sometimes referred to as the 

liquefaction field, is thought to reflect the meizoseismal (strong shaking) area or source area of a 

particular paleoearthquake, and the area with the concentration of the largest liquefaction 

features is interpreted as the epicentral area (Tuttle, 2001; Castilla and Audemard, 2007) or 

energy center (Obermeier et al., 2001). As mentioned above in Section E.2.1.1, soft-sediment 

deformation structures such as basal erosion and related sand diapirs may be useful in delineating 

the outer limits of liquefaction fields so long as they meet certain criteria and are used in 

combination with sand blows and sand dikes. Lone occurrences of liquefaction features may be 

indicators of unique site conditions and should be interpreted with care. 

As demonstrated by modern earthquakes, sand blows generally decrease in size and frequency 

with increasing distance from the epicenter (e.g., Ambraseys, 1988; Castilla and Audemard, 

2007). Nevertheless, the size and spatial distribution of sand blows can be influenced by a 
E-38

variety of factors including style of faulting, earthquake characteristics, directivity of seismic 

energy, attenuation and amplification of ground motion, relative density of sediments, 

distribution of liquefiable sediments, and water table depth as demonstrated by recent 

earthquakes such as the 1988 M 5.9 Saguenay, Quebec; 1989 M 6.9 Loma Prieta, California; and 

2001 M 7.7 Bhuj, India, earthquakes. The complexity of processes and conditions influencing 

sand-blow formation contribute to uncertainties in interpreting paleoliquefaction data. 

Accounting for various seismological, geological, and hydrological factors may help to reduce 

uncertainties to some degree. In addition, the sampling strategy and sediment exposure will 

affect uncertainties related to the spatial distribution of paleoliquefaction features. If sampling, or 

searching, for liquefaction features is not performed where conditions are suitable for the 

formation and preservation of liquefaction features and at times when exposure is adequate to 

find features, information gained during paleoliquefaction studies may be skewed spatially 

and/or temporally, which can lead to erroneous interpretations. 

Taking together the possible factors affecting the occurrence and observation of 

paleoliquefaction features, uncertainty in interpreting the locations of paleoearthquakes from 

paleoliquefaction data is probably on the order of tens to hundreds of kilometers (Table E-2.2). 

Modern earthquakes that induced liquefaction, such as the 1988 M 5.9 Saguenay, Quebec, and 

2001 M 7.7 Bhuj, India, earthquakes, whose locations and magnitudes are fairly well known, can 

be used to demonstrate the uncertainty in interpreting locations of earthquakes from liquefaction 

data. If the concentration of liquefaction features that formed near Ferland, Quebec, in 1988 was 

interpreted as the earthquake’s epicentral area, the inferred location would be off by 25–30 km 

(Figure E-46). Similarly, if large sand-blow craters that formed along the Allah Bund during the 

2001 Bhuj earthquake were interpreted as the epicentral area, the inferred earthquake location 

would be in error by 100–130 km. 

Modern and historical earthquakes that induced liquefaction can serve as calibration events for 

interpreting paleoliquefaction features. If the size and spatial distribution of liquefaction features 

generated by a paleoearthquake are similar to those for a modern or historical earthquake in the 

same region, the paleoearthquake can be inferred to have a similar source area to that of the 

modern or historical earthquake. For example, the source area of the 1886 Charleston, South 

Carolina, earthquake is thought to have produced several large paleoearthquakes in the past 

5,500 years, judging from similar spatial distributions of historical and prehistoric sand-blow 

craters (Talwani and Schaeffer, 2001). 

Similarly, the New Madrid seismic zone is thought to be the source of several sequences of large 

paleoearthquakes like the 1811-1812 earthquake sequence, judging from the size, internal 

stratigraphy, and spatial distributions of historical and prehistoric sand blows (Figures E-65 and 

E-66; Tuttle, Schweig, et al., 2002; Tuttle et al., 2005). In comparative studies, however, the 

accuracy of the inferred locations of the paleoearthquakes is less than that for the modern or 

historical earthquakes, usually a few kilometers to a few tens of kilometers, respectively. For 

example, the location of the 1886 Charleston, South Carolina, earthquake has an uncertainty of 

about ± 25 km (e.g., Johnston, 1996c). Therefore, an estimated location of a paleoearthquake 

based on a comparison of its liquefaction field with that of the 1886 earthquakes will have an 

uncertainty of at least 25 km. If paleoliquefaction features can be directly related to a fault, such 

as has been done with the Reelfoot fault in the New Madrid seismic zone, uncertainty in the 

location of the paleoearthquake may be reduced to just a few kilometers (e.g., Kelson et al., 

1996; Tuttle, Schweig, et al., 2002; Table E-2.2). 
E-39

E.2.2.4 Magnitude of Paleoearthquakes 

As demonstrated by case studies of instrumentally recorded earthquakes that induced 

liquefaction, the size of sand blows, as well as the epicentral distance of sand blows, increases 

with earthquake magnitude (e.g., Ambraseys, 1988; Castilla and Audemard, 2007). Therefore, 

the size and spatial distribution of paleoliquefaction features can help to estimate the magnitudes 

of paleoearthquakes (e.g., Obermeier, 1996; Tuttle, 2001). Due to the many factors affecting the 

occurrence, distribution, and observation of liquefaction features as described above in Section 

E.2.2.3, however, uncertainty in magnitudes of paleoearthquakes estimated from 

paleoliquefaction data can be fairly large, perhaps ranging up to 1 magnitude unit. The 

uncertainty can be reduced by conducting comparative studies, using empirical relations, and 

performing geotechnical analysis to better constrain the magnitudes of paleoearthquakes (Table 

E-2.2; Tuttle, 2001). 

E.2.2.4.1 Comparative Studies 

In comparative studies, the size and spatial distribution of sand blows generated by a 

paleoearthquake are compared to those induced by a local modern or historical earthquake, 

whose magnitude is fairly well known. For example, paleoearthquakes centered in the New 

Madrid seismic zone about AD 1450 (500 yr BP) and AD 900 (1,050 yr BP) are thought to be on 

the order of M 7 to 8 based on the similarity in the size and spatial distribution of sand blows 

with those that formed during the 1811-1812 New Madrid earthquakes (Figures E-65 and E-66; 

Tuttle, Schweig, et al., 2002). A similar approach was used in the southeastern U.S. comparing 

the spatial distribution of paleoliquefaction features to those that formed during the 1886 M ~7

Charleston, South Carolina, earthquake (Talwani and Schaeffer, 2001). In studies such as these, 

the uncertainty related to the inferred magnitudes of the paleoearthquakes is greater than that for 

the modern and historical earthquakes, usually 0.25 to 0.75 of a magnitude unit, respectively. For 

example, magnitude estimates of the main shocks of the 1811-1812 New Madrid earthquake 

sequence have uncertainties of 0.5 to 0.7 of a magnitude unit (see Figure E-66). 

E.2.2.4.2 Empirical Relations 

Empirical relations have been developed between earthquake magnitude and epicentral distance 

of sand blows as well as distance of sand blows from the seismic energy source or fault rupture 

(e.g., Kuribayashi and Tatsuoka, 1975; Ambraseys, 1988). These relations were derived using 

regional and worldwide databases of instrumentally recorded earthquakes that induced 

liquefaction. The worldwide database included earthquakes in areas of low as well as high 

ground motion attenuation and differentiated between shallow- and intermediate-depth events. 

Subsequently, the worldwide database of earthquakes that induced liquefaction and the empirical 

relation between earthquake magnitude and epicentral distance of sand blows were updated 

(Figure E-67; Castilla and Audemard, 2007). In addition, the effects of various earthquake 

characteristics on liquefaction were studied. The style of faulting was found to influence both 

size and epicentral distance of liquefaction features, with thrust or reverse faulting causing the 

largest and farthest sand blows. Directivity of seismic energy along fault planes also appears to 

be an important factor (Tuttle, Hengesh, et al., 2002; Castilla and Audemard, 2007). Despite 

these effects, the relation between earthquake magnitude and epicentral distance of sand blows 

was found to be a useful estimator of approximate magnitudes of pre-instrumental earthquakes 

(Castilla and Audemard, 2007). 
E-40

The earthquake magnitude-liquefaction distance relations have been used in paleoliquefaction 

studies to estimate magnitudes of paleoearthquakes from their farthest observed sand blows. This 

method is sometimes referred to as the magnitude-bound procedure (Obermeier, 1996). 

Magnitude estimates derived from these relations are considered minimum values since the 

actual epicentral distance to farthest sand blow is unlikely to be known (Tuttle, 2001; Castilla 

and Audemard, 2007). A great deal of reconnaissance by an experienced investigator is often 

required to find and recognize distal sand blows since they become smaller, less frequent, and 

may occur in areas underlain by sediments that are especially susceptible to liquefaction. The 

distance to the farthest observed sand dikes should not be used to estimate magnitudes of 

paleoearthquakes. To do so could lead to overestimation of paleoearthquake magnitudes since 

sand dikes can form at greater distances than sand blows, and the magnitude-distance relations 

were based on ―surface manifestations‖ of liquefaction. 

The magnitude-distance relations have been used to estimate magnitudes of paleoearthquakes in 

the New Madrid and Wabash Valley seismic zones. For New Madrid, minimum magnitudes of 

M 6.7 and 6.9 were estimated for the paleoearthquakes of AD 1450 (500 yr BP) and AD 900 

(1,050 yr BP), respectively, from the distance of observed sand blows (Figure E-68; Tuttle, 

2001). Even though more than 1,000 km of river cutbanks have been searched, the limits of 

liquefaction have not yet been defined for these earthquakes. To improve the magnitude 

estimates of paleoearthquakes centered in the Wabash Valley seismic zone, the magnitude-bound 

relation was calibrated using one modern and several historical cases of earthquake-induced 

liquefaction in the Central and Eastern United States and southeastern Canada (Olson et al., 

2005b). This was done in an attempt to account for regional differences in earthquake source 

characteristics, ground motion attenuation, local site effects, and liquefaction susceptibility of 

sediments. The magnitude estimates based on the calibrated relation differed little (0 to 0.1 

magnitude unit) from those using the worldwide relation developed by Ambraseys (1988), 

suggesting that historical earthquakes, with poorly constrained locations and magnitudes, are 

unlikely to significantly improve the worldwide relation based on instrumental earthquakes. 

Calibration of the magnitude-bound relation may be most fruitful for regions that have 

experienced instrumental earthquakes that induced liquefaction. 

There are several obvious factors that contribute to uncertainties in magnitude estimates for 

paleoearthquakes based on the magnitude-bound method. The epicentral location may be poorly 

defined and the farthest sand blow is unlikely to be known. In addition, the magnitude-distance 

relation itself has some inherent uncertainties since the epicentral distance to the farthest sand 

blow may not be known even for instrumental earthquakes. The relation is poorly constrained for 

earthquakes greater than magnitude 7.2 (Figure E-67). 

Given the various unknowns, uncertainties associated with magnitude estimates determined with 

the magnitude-bound method are likely to range from 0.25 to 0.6 magnitude unit (Table E-2.2). 

The 2001 M 7.7 Bhuj, India, earthquakes can be used to demonstrate the uncertainty in 

magnitude estimates derived using the magnitude-bound method. If the small sand blows that 

formed near Ahmedabad (approximately 240 km from the epicenter of the Bhuj earthquake) 

were not found and those along the Allah Bund (about 130 km from the epicenter of the Bhuj 

earthquake) were thought to be the farthest sand blows induced by a paleoearthquake centered 

near Bhuj, a magnitude estimate of 7.1 would be derived using the method (Figure E-46). In this 

example, the magnitude-bound method would have underestimated the magnitudes of the 

hypothetical paleoearthquakes by 0.6 magnitude unit. 
E-41

E.2.2.4.3 Geotechnical Analysis 

In addition to the methods described above, the magnitudes of liquefaction-inducing 

paleoearthquakes also can be estimated using geotechnical characterizations of in situ soil 

properties and liquefaction potential analysis (e.g., Olson et al., 2001, 2005b; Green et al., 2005). 

The cyclic-stress (e.g., Seed and Idriss, 1982; Youd, 2001; Cetin et al., 2004) and seismic energy 

(e.g., Pond, 1996) methods of liquefaction potential analysis have been applied in 

paleoearthquake studies. Typically, these back-calculations are based on the identification of the 

soil layers that may have liquefied during paleoearthquakes, the measurement of geotechnical 

properties of these layers (penetration resistance, soil density, effective confining or overburden 

stress, etc.), and the relation between the geotechnical properties and the ground motions 

necessary to trigger liquefaction. The geotechnical approach to back-calculating magnitudes of 

paleoearthquakes has been used widely in the Charleston seismic zone (e.g., Hu et al., 2002a, 

2002b; Leon, 2003; Leon et al., 2005; Gassman et al., 2009) and the Wabash Valley seismic 

zones (e.g., Obermeier et al., 1993; Olson et al., 2001). It has also been used to a more limited 

extent in the New Madrid seismic zone (e.g., Schneider and Mayne, 2000; Schneider et al., 2001; 

Liao et al., 2002; Stark, 2002; Tuttle and Schweig, 2004) and the Charlevoix seismic zone (e.g., 

Tuttle and Atkinson, 2010; Table 1.2-1). 

Green et al. (2005) identify three main sources of uncertainty associated with the backcalculation of ground motion characteristics from paleoliquefaction data: 

Uncertainty due to changes in the geotechnical properties of the source sediments of 

liquefaction features, including but not limited to density changes due to liquefaction and to 

postliquefaction effects related to aging and groundwater conditions. 

The selection of appropriate geotechnical soil indices to be measured at paleoliquefaction 

sites. 

The selection of appropriate methodology for integration of back-calculated results of ground 

shaking from individual paleoliquefaction sites into a regional assessment of paleoseismic 

strength of shaking. An appropriate methodology must account for uncertainty in seismic 

parameters (e.g., amplitude, duration, frequency, and directivity), regional ground motion 

attenuation, local site effects, and site-to-source distance. 

The understanding of these sources of uncertainty remains the focus of ongoing research. At 

present, the geotechnical approach may yield a broad range of possible magnitudes for a 

given paleoearthquake, and these ranges may provide only a minimum constraint on 

magnitude. For example, Leon et al. (2005) calculate magnitude estimates for each of the 

Charleston paleoearthquakes and, for each paleoearthquake, their estimates vary by 0.8 to 1.4 

magnitude units. For the CEUS SSC Project, estimates of paleoearthquake magnitude based 

on geotechnical analysis were used where available to help characterize Mmax, in 

conjunction with other indicators of magnitude such as magnitude-bound and magnitudefeature size relations (e.g., Ambraseys, 1988; Castilla and Audemard, 2007). 
E-42

E.2.2.5 Recurrence of Paleoearthquakes 

E.2.2.5.1 Age Estimates of Liquefaction Features and Paleoearthquakes 

As described above, the goal of dating seismically induced paleoliquefaction features is to 

bracket the time of the causative earthquake as tightly as possible. Typically, numerical 

constraining ages are obtained that predate and postdate paleoliquefaction features. The timing of 

paleoearthquakes is defined by selecting the age range common to multiple paleoliquefaction 

features in a region. Therefore, the precision with which recurrence can be calculated depends on 

the precision of the estimated timing of the paleoearthquakes. Once a paleoearthquake 

chronology (or alternative paleoearthquake scenarios) has been developed using methodologies 

outlined above, estimates of earthquake recurrence can be calculated for that region. Wellconstrained age estimates of paleoearthquakes contribute to well-constrained estimates of 

recurrence times (Table E-2.2). For the CEUS SSC Project, paleoliquefaction data were used to 

estimate uncertainty ranges for the timing of paleoearthquakes and to calculate rates of repeated 

large-magnitude earthquakes (see Section 6.1.5.4 of the main report). For example, wellconstrained age estimates of sand blows in the New Madrid seismic zone contributed to wellconstrained ages estimates of paleoearthquakes (10–100 years) during the past 1,200 years 

(Figure E-64). However, incompleteness of the paleoearthquake record prior to 1,200 yr BP and 

questions regarding sources outside the New Madrid seismic zone led to significant uncertainty 

in recurrence time (tens to thousands of years) of repeated large-magnitude earthquake (RLME) 

sources in the greater New Madrid region. 

E.2.2.5.2 Length and Completeness of the Paleoliquefaction Record 

The completeness of the paleoearthquake record should be considered in estimating earthquake 

recurrence. The completeness of the record will vary depending on the location of the study area 

and its geologic and hydrologic history. The longer and more continuous the history of 

sedimentation, the more complete the earthquake record is likely to be (Table E-2.2). Also, loose 

sandy sediments must be saturated in order to liquefy during earthquakes. Therefore, significant 

changes in land level and sea (or lake) level related to glacio-eustatic processes can affect the 

liquefaction susceptibility of sediments and thus the completeness of the earthquake record. 

These changes may be especially important in glaciated and coastal regions. 

Many paleoearthquake chronologies are limited by the age range, distribution, and exposure of 

the deposits that were susceptible to liquefaction during the period of interest. In the New Madrid 

region, for example, liquefiable fluvial deposits are widespread, but the deposits, in general, 

increase in age from east to west across the Lower Mississippi River valley. A large percentage 

of the liquefiable fluvial deposits in the immediate vicinity of the New Madrid seismic zone are 

only five thousand years old, so the record of paleoearthquakes is relatively short. In addition, 

older sand blows may be buried too deep in the section to be exposed in river and ditch cutbanks. 

Like many depositional environments where paleoliquefaction features form, exposure in the 

Lower Mississippi River valley is limited to times of year when the water table is low. 

Liquefaction features identified along the South Carolina coast range in age from mid-Holocene 

to historical, but it remains unclear whether the older portions of the Charleston 

paleoearthquakes record is complete. Talwani and Schaeffer (2001) suggest that the record is 

complete only for the most recent approximately 2,000 years and that it is possible that 

liquefaction events are missing from the older portions of the record, especially between about 
E-43

2,000 and 5,000 yr BP. Talwani and Schaeffer (2001) suggest that past fluctuations in sea level 

have produced time intervals of low water table conditions, and thus low liquefaction 

susceptibility, during which large earthquakes may not have induced liquefaction. Similarly, the 

Late Wisconsin–Holocene record of paleoearthquakes in the Charlevoix seismic zone and St. 

Lawrence Lowlands is thought to be incomplete due to fluctuations in sea level, especially 

during the period between 6 and 7 ka (Tuttle and Atkinson, 2010).

By evaluating the completeness of the paleoearthquake record, informed decisions can be made 

regarding which data sets or portions of data sets to use to estimate realistic recurrence times. 

Incomplete data sets can provide a minimum numbers of earthquakes for a certain time period 

and help to constrain recurrence rates. 

E.2.3 Recommendations for Future Research 

Liquefaction studies have contributed to the characterization of seismic sources by providing 

information about the timing, locations, magnitudes, and recurrence rates of paleoearthquakes. 

However, there are often large uncertainties associated with these earthquake parameters. In 

addition, there are few trained professionals to carry out this type of study. With additional 

development of the field of study and of trained personnel, it may be possible to reduce 

uncertainties associated with earthquake parameters and advance the usefulness and application 

of paleoliquefaction studies. To this end, recommendations for future research are given below. 

Development of a manual of best practice would provide guidance in conducting 

paleoliquefaction studies and would promote accuracy and completeness of paleoliquefaction 

data. The manual could be complemented by training workshops with experts in the field. During 

these workshops, professional earth scientists and the next generation of paleoseismologists 

would gain experience searching for, documenting, and interpreting liquefaction features.

Case studies of liquefaction induced by modern earthquakes, with well-constrained locations, 

magnitudes, and other earthquake parameters, are encouraged and would help to further 

characterize the size and spatial distributions of liquefaction features. Such case studies should 

be regional in scope and include detailed descriptions of liquefaction features such as size and 

sedimentary characteristics of sand blows, dikes, sills and other soft-sediment deformation 

structures (see Section E.2.1.1 and Figure E-2). These case studies would be helpful in providing 

analogue events for direct comparison as well as information that could be used to further 

improve empirical relations of earthquake and liquefaction parameters. 

To gain a better understanding of both the processes of liquefaction and the effects on the source 

beds that liquefied, instrumentation of liquefaction-prone sites is encouraged, as is pre- and postevent measurement of geotechnical properties. This information may help to reduce uncertainties 

related to back-calculating magnitudes using post-event measurements. Field experiments of 

earthquake-induced liquefaction are more likely to be conducted in interplate settings where 

large earthquakes occur more frequently. Therefore, if results of these field experiments are to be 

applied in the CEUS, it would be beneficial to better understand differences between 

characteristics of intraplate and interplate earthquakes, such as frequency content and attenuation 

of ground motion, that influence liquefaction. 

In regions where paleoearthquake records exist but have not been fully developed, paleoseismic 

studies could be designed that would improve the completeness and extend the length of the 
E-44

paleoearthquake chronologies in order to improve recurrence estimates of large earthquakes and 

to improve understanding of earthquake sources. It is also recommended that paleoliquefaction 

studies be conducted in regions of low seismicity that share geologic and tectonic characteristics 

with known seismogenic zones to better understand the earthquake potential of these regions and 

to test the hypothesis that inherited structure, particularly faults that were active during the 

Mesozoic, controls seismicity in the CEUS. 

Radiocarbon and OSL are the two most common dating techniques used in paleoliquefaction 

studies. Because they are often collected stratigraphically above and below sand blows, samples 

provide minimum and maximum constraining dates for liquefaction features and thus the 

earthquakes that caused them. Although the individual dates may have precisions of ± 20–80 

years, the age estimates of liquefaction features based on the combination of the minimum and 

maximum constraining dates will have uncertainties of about 100 years in the best of 

circumstances (see Figure E-3). Dating techniques that provide more precise results and dating 

strategies that provide more accurate results would help to improve age estimates of liquefaction 

features and thus their causative earthquakes. Dendrochronology is one technique that could 

improve precision of age estimates of liquefaction features. Therefore, we recommend that 

efforts be made to use dendrochronology to date paleoliquefaction features in regions where 

chronologies of long-lived tree species already have been developed. If those efforts are 

successful, it would be worthwhile to extend the chronologies of long-lived tree species further 

back in time and to help constrain the ages of older liquefaction features. 

E.3 Guidance for the Use of Paleoliquefaction Data in Seismic Source 

Characterization 

The following is a summary of guidance for the use of paleoliquefaction data: 

Ensure liquefaction features have an earthquake origin and are not the result of other 

processes. Potential uncertainties regarding feature identification and interpretation are 

described in Section E.2 of this appendix. 

Use liquefaction features with well-constrained calibrated (2-sigma) ages to determine timing 

of paleoearthquakes (Figure E-3). Space-time diagrams illustrating age constraints and 

estimated ages of features can help to estimate timing of paleoearthquakes. 

Correlate features that are similar in age and/or occur in similar stratigraphic context within 

the same exposure or where strata are laterally continuous. 

Compare size and distribution of paleoliquefaction features with those that formed during 

modern or historical earthquakes in the same or similar geologic and tectonic settings to help 

interpret the source areas and magnitudes of causative earthquakes. 

Use information on surficial geology, geologic and groundwater history, and geotechnical 

data and analysis, to help interpret the source areas and magnitudes of paleoearthquakes. 

Time-slice maps and animations may help to interpret earthquake source areas, and ground 

motion simulations may help to interpret earthquake magnitudes. 

Use empirical relations developed from case studies of modern earthquakes in similar 

geologic and tectonic settings to estimate magnitudes of paleoearthquakes on the basis of 

maximum distance of sand blows from the inferred epicenters. 
E-45

If sufficient data are available, incorporate the effect of ground motion parameters (e.g., 

attenuation and site response) on the size and distribution of liquefaction features when 

interpreting source areas and magnitudes of paleoearthquakes. 

Consider the completeness of the paleoearthquake record in both space and time when 

estimating source areas, magnitudes, and recurrence times of paleoearthquakes. 

If sufficient data are available, estimate recurrence times of paleoearthquakes with welldefined timing, source areas, and magnitudes of paleoearthquakes. 
E-46

E.4 Glossary 

Ball-and-pillow structures. Deformation structures that form when lobes of sediment sink into 

underlying sediment forming isolated masses that resemble balls and pillows. 

Basal erosion. Foundering of the base on a sedimentary unit due to liquefaction and loss of 

strength of the underlying sediment.

Bearing capacity. The ability of soil or sediment to carry a load without failing. 

Close maximum constraining age. Maximum possible age derived by dating material collected 

immediately below a feature of interest that nearly approximates its age.

Close minimum constraining age. Minimum possible age derived by dating material collected 

immediately above a feature of interest that nearly approximates its age.

Consistence. Term describing a soil’s ability to resist crushing and to be molded.

Contemporary age. An age that reflects the formation of the deposit from which the dated 

sample was collected.

Convolute bedding. Contorted bedding usually confined to a single sedimentary unit.

Dendrocalibration curve. Relation used to convert radiocarbon ages to calendar ages based on 

radiocarbon dating of tree rings of known ages.

Dessication crack. Crack in clayey sediment that forms by shrinkage as the result of drying.

Dish structures. Deformation structures consisting of flat to concave upward laminations caused 

by liquefaction and fluidization of sediment and commonly associated with pillars.

Earthquake recurrence. The repetition of a similar magnitude earthquake generated by the 

same fault or source zone. 

Effective stress or overburden pressure. The portion of the load or force from overlying 

material that is supported by the soil or sediment grains. 

Eustacy. Of, or pertaining to, worldwide sea level.

Flow lineation. Lineation in sediment related to liquefaction and fluidization of sediment.

Fluidization. Process by which vertical fluid flow through sediment exerts sufficient drag force 

on the grains to lift or suspend them against the force of gravity. 

Glacio-isostacy. Lithospheric adjustment in response to the weight or melting of glaciers. 
E-47

Holocene. The most recent geologic epoch, following the last glaciation, known as the 

Wisconsin in North America and beginning about 12,000 years BP. 

Liquefaction. A process by which saturated, granular sediment temporarily loses its strength and 

behaves as a viscous liquid due to earthquake ground shaking 

Liquefaction field. The area over which liquefaction features form during a particular 

earthquake.

Load structure. A deformation structure that forms when sediment sinks into underlying 

sediment that has lost its strength in some cases due to liquefaction. 

Magnitude-bound. Relation defining the lowest magnitude at which liquefaction is likely to 

occur at any given epicentral distance. 

Maximum constraining age. Maximum possible age derived by dating material collected 

stratigraphically below a feature of interest.

Minimum constraining age. Minimum possible age derived by dating material collected 

stratigraphically above a feature of interest.

Optically simulated luminescence (OSL). Dating technique used to determine the amount of 

time that has passed since sediment was last exposed to light (see Section E.2.1.3.3). 

Penetration resistance. Measure of soil or sediment density expressed as N or the number of 

hammer blows it takes to drive a split-tube sampler 12 inches. 

pH. Measure of acidity of an aqueous solution and is related to the negative logarithm of the 

concentration of hydrogen ions and their tendency to interact with other components of the 

solution. 

Pillars. Deformation structures including tubular to sheet-like zones of structureless to swirled 

sediment that form during forceful and explosive water escape.

Pleistocene. The earlier of the two geologic epochs comprising the Quaternary; characterized by 

multiple glaciations. 

Pore-water pressure. The water pressure within the voids or spaces between soil or sediment 

grains.

Pseudonodule. A deformation structure similar to a load structure except that the sediment that 

sinks into underlying sediment becomes detached to form separate bodies or domains. 

Quaternary. The youngest geologic period beginning about 2.6 million years ago; subdivided 

into Pleistocene and Holocene epochs. 
E-48

Relative density. The relation between the actual void ratio and the maximum and minimum 

void ratios of a soil or sediment.

Sand blow. Deposit resulting from liquefaction and fluidization of subsurface sandy sediment 

and expulsion of liquefied sediment onto the ground surface. 

Sand dike. Intrusive sand body, often tabular in shape, resulting from liquefaction and 

fluidization of subsurface sandy sediment and injection of liquefied sediment into overlying 

deposits.

Sand diapir. A small, sandy intrusion into overlying, usually fine-grained, sediment.

Soft-sediment deformation structures. A variety of structures, including sand diapirs, basal 

erosion, convolute bedding, pseudonodules, and load casts, that form in unconsolidated 

sediments as the result of deformation ranging from bulk transport of the sediment mass to in situ 

relative grain displacement. 

Soil structure. The arrangement of primary soil particles into secondary units known as pedons.

Space-time diagram. Diagram showing variations in some parameter over space and time. 

Void ratio. The ratio of the volume of voids, or space between grains, to the volume of solids in 

a soil or sediment.

Wisconsin. The last glacial age of the Pleistocene epoch of North America.
E-49

E.5 References 

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Features in the Meizoseismal Area of the 1811-1812 New Madrid Earthquakes, Central 

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E-50

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and accelerations of prehistoric earthquakes: Earthquake Spectra, v. 21, no. 3, pp. 737-759.

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E-51

Mayne, P. W., 2001, Cone penetration testing for seismic hazards evaluation in Memphis and 

Shelby County, Tennessee, U.S. Geological Survey, Earthquake Hazards Program, Final 

Report (00HQGR0025), 21 pp.

McNulty, W. E. and Obermeier, S. F., 1999, Liquefaction Evidence for at Least Two Strong 

Holocene Paleo-Earthquakes in Central and Southwestern Illinois, USA: Environmental and 

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Earthquakes Since 20,000 Years BP in the Wabash Valley Area of Indiana, report submitted 

to the U.S. Geological Survey in fulfillment of National Earthquake Hazards Reduction 

Program Grant No. 14-08-0001-G2117, 137 pp. 

Munson, P. J., Obermeier, S. F., Munson, C. A., and Hajic, E. R., 1997, Liquefaction evidence 

for Holocene and latest Pleistocene seismicity in the southern halves of Indiana and Illinois: 

A preliminary overview: Seismological Research Letters, v. 68, pp. 521-536. 

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and Earthquakes: Review of Quaternary Geochronology and Its Application to 

Paleoseismology: U.S. Nuclear Regulatory Commission Report, NUREG/CR-5562, pp. 4.49-

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Figure E-1 

Map of CEUS showing locations of regional data sets in the CEUS SSC Project paleoliquefaction database, including New Madrid seismic zone 

and surrounding region; Marianna, Arkansas, area; St. Louis region; Wabash Valley seismic zone and surrounding region; Arkansas-LouisianaMississippi region; Charleston seismic zone; Atlantic Coastal region and the Central Virginia seismic zone; Newburyport, Massachusetts, and 

surrounding region; and Charlevoix seismic zone and surrounding region. 
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Figure E-2 

Diagram illustrating size parameters of liquefaction features including sand blow thickness, width, and length, dike width, and sill thickness, as well 

as some of the diagnostic characteristics of these features.
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Figure E-3 

Diagram illustrating sampling strategy for dating of liquefaction features as well as age data, such as 14C maximum and 14C minimum, used to 

calculate preferred age estimates and related uncertainties of liquefaction features. 
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Figure E-4 

GIS map of New Madrid seismic zone and surrounding region showing portions of rivers searched for earthquake-induced liquefaction features by 

M. Tuttle, R. Van Arsdale, and J. Vaughn and collaborators (see explanation); information contributed for this report. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. 
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Figure E-5 

GIS map of New Madrid seismic zone and surrounding region showing locations of liquefaction features for which there are and are not 

radiocarbon data. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 
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Figure E-6 

GIS map of New Madrid seismic zone and surrounding region showing locations of liquefaction features that are thought to be historical or 

prehistoric in age or whose ages are poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
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Figure E-7 

GIS map of New Madrid seismic zone and surrounding region showing preferred age estimates of liquefaction features; features whose ages are 

poorly constrained are excluded. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
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Figure E-8 

GIS map of New Madrid seismic zone and surrounding region showing measured thicknesses of sand blows. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983.
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Figure E-9 

GIS map of New Madrid seismic zone and surrounding region showing preferred age estimates and measured thicknesses of sand blows. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
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Figure E-10 

GIS map of New Madrid seismic zone and surrounding region showing measured widths of sand dikes. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983.
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Figure E-11 

GIS map of New Madrid seismic zone and surrounding region showing preferred age estimates and measured widths of sand dikes. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
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Figure E-12 

GIS map of New Madrid seismic zone and surrounding region illustrating preferred age estimates and measured thicknesses of sand blows as 

well as preferred age estimates and measured widths of sand dikes for sites where sand blows do not occur. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983.
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Figure E-13 

GIS map of Marianna, Arkansas, area showing seismicity and locations of paleoliquefaction features relative to mapped traces of Eastern Reelfoot 

rift margin fault, White River fault zone, Big Creek fault zone, Marianna escarpment, and Daytona Beach lineament. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983.
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Figure E-14 

(A) Trench log and (B) ground-penetrating radar profile, showing vertical sections of sand blows and sand dikes at Daytona Beach SE2 site along 

the Daytona Beach lineament southwest of Marianna, Arkansas. Vertical scale of GPR profile is exaggerated (modified from Al-Shukri et al., 

2009).
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Figure E-15 

GIS map of Marianna, Arkansas, area showing locations of liquefaction features for which there are and are not radiocarbon data. Map projection 

is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-83

Figure E-16 

GIS map of Marianna, Arkansas, area showing locations of liquefaction features that are thought to be historical or prehistoric in age or whose 

ages are poorly constrained. To date, no liquefaction features thought to have formed during 1811-1812 earthquakes have been found in area. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-84

Figure E-17 

GIS map of Marianna, Arkansas, area showing preferred age estimates of liquefaction features; features whose ages are poorly constrained are 

excluded. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 
E-85

Figure E-18

GIS map of Marianna, Arkansas, area showing measured thicknesses of sand blows. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983. 
E-86

Figure E-19

GIS map of Marianna, Arkansas, area showing preferred age estimates and measured thicknesses of sand blows. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983. 
E-87

Figure E-20 

GIS map of Marianna, Arkansas, area showing measured widths of sand dikes. Map projection is USA Contiguous Albers Equal Area Conic, North 

America Datum 1983. 
E-88

Figure E-21 

GIS map of Marianna, Arkansas, area showing preferred age estimates and measured widths of sand dikes. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. 
E-89

Figure E-22 

GIS map of St. Louis, Missouri, region showing seismicity and portions of rivers searched for earthquake-induced liquefaction features by Tuttle 

and collaborators; information contributed for this report. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-90

Figure E-23

GIS map of St. Louis, Missouri, region showing locations of liquefaction features, including several soft-sediment deformation structures, for which 

there are and are not radiocarbon data. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-91

Figure E-24 

GIS map of St. Louis, Missouri, region showing locations of liquefaction features that are thought to be historical or prehistoric in age or whose 

ages are poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-92

Figure E-25 

GIS map of St. Louis, Missouri, region showing preferred age estimates of liquefaction features; features whose ages are poorly constrained, 

including several that are prehistoric in age, are not shown. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983.
E-93

Figure E-26 

GIS map of St. Louis, Missouri, region showing measured thicknesses of sand blows at similar scale as used in Figure E-8 of sand blows in New 

Madrid seismic zone. Note that few sand blows have been found in St. Louis region. Map projection is USA Contiguous Albers Equal Area Conic, 

North America Datum 1983.
E-94

Figure E-27 

GIS map of St. Louis, Missouri, region showing preferred age estimates and measured thicknesses of sand blows. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983.
E-95

Figure E-28 

GIS map of St. Louis, Missouri, region showing measured widths of sand dikes at similar scale as that used in Figure E-10 for sand dikes in New 

Madrid seismic zone. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-96

Figure E-29 

GIS map of St. Louis, Missouri, region showing measured widths of sand dikes at similar scale as that used in Figures E-42 and E-48 for sand 

dikes in the Newburyport and Charlevoix regions, respectively. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983.
E-97

Figure E-30

GIS map of St. Louis, Missouri, region showing preferred age estimates and measured widths of sand dikes. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. 
E-98

Figure E-31 

GIS map of Wabash Valley seismic zone and surrounding region showing portions of rivers searched for earthquake-induced liquefaction features 

(digitized from McNulty and Obermeier, 1999). Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-99

Figure E-32 

GIS map of Wabash Valley seismic zone and surrounding region showing measured widths of sand dikes at similar scale as that used in Figures 

E-10 and E-11 for sand dikes in New Madrid seismic zone. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 

1983.
E-100

Figure E-33

GIS map of Wabash Valley region of Indiana and Illinois showing preferred age estimates and paleoearthquake interpretation. Map projection is 

USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-101 

Figure E-34

GIS map of Arkansas-Louisiana-Mississippi (ALM) region showing paleoliquefaction study locations. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983.
E-102

Figure E-35 

GIS map of Charleston, South Carolina, region showing locations of paleoliquefaction features for which there are and are not radiocarbon dates. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-103 

Figure E-36 

GIS map of Charleston, South Carolina, region showing locations of historical and prehistoric liquefaction features. Map projection is USA 

Contiguous Albers Equal Area Conic, North America Datum 1983.
E-104

Figure E-37 

Map of Atlantic coast region showing areas searched for paleoliquefaction features by Gelinas et al. (1998) and Amick, Gelanis, et al. (1990). Rectangles 

indicate 7.5-minute quadrangles in which sites were investigated for presence of paleoliquefaction features. The number of sites investigated is 

shown within that quadrangle, if known. Orange and yellow indicate quadrangles in which paleoliquefaction features were recognized. 
E-105 

Figure E-38 

Map of Central Virginia seismic zone region showing portions of rivers searched for earthquake-induced liquefaction features by Obermeier and 

McNulty (1998).
E-106

Figure E-39

GIS map of Newburyport, Massachusetts, and surrounding region showing seismicity and portions of rivers searched for earthquake-induced 

liquefaction features (Gelinas et al., 1998; Tuttle, 2007, 2009). Solid black line crossing map represents Massachusetts–New Hampshire border. 

Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-107 

Figure E-40 

GIS map of Newburyport, Massachusetts, and surrounding region showing locations of liquefaction features for which there are and are not 

radiocarbon dates. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-108

Figure E-41 

GIS map of Newburyport, Massachusetts, and surrounding region showing locations of liquefaction features that are thought to be historical or 

prehistoric in age or whose ages are poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-109 

Figure E-42

GIS map of Newburyport, Massachusetts, and surrounding region showing measured widths of sand dikes. Map projection is USA Contiguous 

Albers Equal Area Conic, North America Datum 1983. 
E-110

Figure E-43

GIS map of Newburyport, Massachusetts, and surrounding region showing preferred age estimates and measured widths of sand dikes. Map 

projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 
E-111 

Figure E-44

Map of Charlevoix seismic zone and adjacent St. Lawrence Lowlands showing mapped faults and portions of rivers along which reconnaissance and 

searches for earthquake-induced liquefaction features were performed. Charlevoix seismic zone is defined by concentration of earthquakes and 

locations of historical earthquakes northeast of Quebec City. Devonian impact structure in vicinity of Charlevoix seismic zone is outlined by black 

dashed line. Taconic thrust faults are indicated by solid black lines with sawteeth on upper plate; Iapetan rift faults are shown by solid black lines 

with hachure marks on downthrown side (modified from Tuttle and Atkinson, 2010).
E-112

Figure E-45 

GIS map of Charlevoix seismic zone and surrounding region showing locations of liquefaction features, including several soft-sediment 

deformation structures, for which there are and are not radiocarbon data. Note the location of the 1988 M 5.9 Saguenay earthquake northwest of 

the Charlevoix seismic zone. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-113 

Figure E-46 

GIS map of Charlevoix seismic zone and surrounding region showing locations of liquefaction features that are modern, historical, or prehistoric in 

age, or whose ages are poorly constrained. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-114

Figure E-47 

GIS map of Charlevoix seismic zone and surrounding region showing preferred age estimates of liquefaction features; features whose ages are 

poorly constrained are excluded. Map projection is USA Contiguous Albers Equal Area Conic, North America Datum 1983.
E-115 

Figure E-48 

GIS map of Charlevoix seismic zone and surrounding region showing measured widths of sand dikes. Map projection is USA Contiguous Albers 

Equal Area Conic, North America Datum 1983. 
E-116

Figure E-49 

GIS map of Charlevoix seismic zone and surrounding region showing preferred age estimates and measured widths of sand dikes. Map projection 

is USA Contiguous Albers Equal Area Conic, North America Datum 1983. 
E-117 

Figure E-50 

Photograph of moderate-sized sand blow (12 m long, 7 m wide, and 14 cm thick) that formed about 40 

km from epicenter of 2001 M 7.7 Bhuj, India, earthquake (from Tuttle, Hengesh, et al., 2002), combined 

with schematic vertical section illustrating structural and stratigraphic relations of sand blow, sand dike, 

and source layer (modified from Sims and Garvin, 1995). 
E-118

Figure E-51 

Tree trunks buried and killed by sand blows, vented during 1811-1812 New Madrid earthquakes (from 

Fuller, 1912).
E-119 

Figure E-52 

Large sand-blow crater that formed during 2001 M 7.7 Bhuj, India, earthquake. Backpack for scale. Photograph: M. Tuttle (2001).
E-120

Figure E-53 

Sand-blow crater that formed during 1886 Charleston, South Carolina, earthquake. Photograph: J.K. Hillers (from USGS Photograph Library). 
E-121 

Figure E-54

Photograph of sand blow and related sand dikes exposed in trench wall and floor in New Madrid seismic zone. Buried soil horizon is displaced 

downward ~1 m across two dikes. Clasts of soil horizon occur within dikes and overlying sand blow. Degree of soil development above and within 

sand blow suggests that it is at least several hundred years old and formed prior to 1811-1812 New Madrid earthquakes. Organic sample (location 

marked by red flag) from crater fill will provide close minimum age constraint for formation of sand blow. For scale, each colored intervals on 

shovel handle represents 10 cm. Photograph: M. Tuttle.
E-122

Figure E-55 

Sand dikes, ranging up to 35 cm wide, originate in pebbly sand layer and intrude overlying diamicton, 

These features were exposed in cutbank along Cahokia Creek about 25 km northeast of downtown St. 

Louis, Missouri (from Tuttle, 2000). 
E-123 

Figure E-56 

Photograph of small diapirs of medium sand intruding base of overlying deposit of interbedded clayey silt and very fine sand, and clasts of clayey 

silt in underlying medium sand, observed along Ouelle River in Charlevoix seismic zone. Sand diapirs and clasts probably formed during basal 

erosion and foundering of clayey silt due to liquefaction of the underlying sandy deposit. Red portion of shovel handle represents 10 cm (modified 

from Tuttle and Atkinson, 2010).
E-124

Figures E-57 

(A) Load cast formed in laminated sediments of Van Norman Lake during 1952 Kern County, California, 

earthquake. Photograph: J. Sims (from Sims, 1975). (B) Load cast, pseudonodules, and related folds 

formed in laminated sediment exposed along Malbaie River in Charlevoix seismic zone. Sand dikes 

crosscutting these same laminated sediments occur at a nearby site. For scale, each painted interval of 

the shovel handle represents 10 cm (modified from Tuttle and Atkinson, 2010). 
E-125 

Figure E-58 

Log of sand blow and uppermost portions of related sand dikes exposed in trench wall at Dodd site in New Madrid seismic zone. Sand dikes also 

were observed in opposite wall and trench floor. Sand blow buries pre-event A horizon, and a subsequent A horizon has developed in top of sand 

blow. Radiocarbon dating of samples collected above and below sand blow brackets its age between 490 and 660 yr BP. Artifact assemblage 

indicates that sand blow formed during late Mississippian (300–550 yr BP or AD 1400–1670) (modified from Tuttle, Collier, et al., 1999).
E-126

Figures E-59 

(A) Photograph of earthquake-induced liquefaction features found in association with cultural horizon and pit exposed in trench wall near 

Blytheville, Arkansas, in New Madrid seismic zone. Photograph: M. Tuttle. (B) Trench log of features shown in (A). Sand dike formed in thick 

Native American occupation horizon containing artifacts of early Mississippian cultural period (950–1,150 yr BP). Cultural pit dug into top of sand 

dike contains artifacts and charcoal used to constrain minimum age of liquefaction features (modified from Tuttle and Schweig, 1995).
E-127 

Figure E-60

In situ tree trunks such as this one buried and killed by sand blow in New Madrid seismic zone offer 

opportunity to date paleoearthquakes to the year and season of occurrence. Photograph: M. Tuttle.
E-128

Figure E-61

Portion of dendrocalibration curve illustrating conversion of radiocarbon age to calibrated date in calendar years. In example, 2-sigma radiocarbon 

age of 2,280–2,520 BP is converted to calibrated date of 770–380 BC (from Tuttle, 1999).
E-129 

Figure E-62 

Empirical relation developed between A horizon thickness of sand blows and years of soil development in New Madrid region. Horizontal bars 

reflect uncertainties in age estimates of liquefaction features; diamonds mark midpoints of possible age ranges (from Tuttle et al., 2000). 
E-130

Figure E-63 

Diagram illustrating earthquake chronology for New Madrid seismic zone for past 5,500 years based on dating and correlation of liquefaction 

features at sites (listed at top) across region from north to south. Vertical bars represent age estimates of individual sand blows, and horizontal 

bars represent event times of 138 yr BP (AD 1811-1812); 500 yr BP ± 150 yr; 1,050 yr BP ± 100 yr; and 4,300 yr BP ± 200 yr (modified from 

Tuttle, Schweig, et al., 2002; Tuttle et al., 2005).
E-131 

Figure E-64 

Diagram illustrating earthquake chronology for New Madrid seismic zone for past 2,000 years, similar to upper portion of diagram shown in Figure 

E-63. As in Figure E-63, vertical bars represent age estimates of individual sand blows, and horizontal bars represent event times. Analysis 

performed during CEUS SSC Project derived two possible uncertainty ranges for timing of paleoearthquakes, illustrated by the darker and lighter 

portions of the colored horizontal bars: 503 yr BP ± 8 yr or 465 yr BP ± 65 yr, and 1,110 yr BP ± 40 yr or 1055 ± 95 yr, respectively (modified from 

Tuttle, Schweig, et al., 2002).
E-132

Figure E-65 

Maps showing spatial distributions and sizes of sand blows and sand dikes attributed to 500 and 1,050 yr BP events. Locations and sizes of 

liquefaction features that formed during AD 1811-1812 (138 yr BP) New Madrid earthquake sequence are shown for comparison (modified from 

Tuttle, Schweig, et al., 2002).
E-133 

Figure E-66 

Liquefaction fields for 138 yr BP (AD 1811-1812); 500 yr BP (AD 1450); and 1,050 yr BP (AD 900) events as interpreted from spatial distribution and

stratigraphy of sand blows (modified from Tuttle, Schweig, et al., 2002). Ellipses define areas where similar-age sand blows have been mapped.

Overlapping ellipses indicate areas where sand blows are composed of multiple units that formed during sequence of earthquakes. Dashed ellipse

outlines area where historical sand blows are composed of four depositional units. Magnitudes of earthquakes in 500 yr BP and 1,050 yr BP are inferred

from comparison with 1811-1812 liquefaction fields. Magnitude estimates of December (D), January (J), and February (F) main shocks and large 

aftershocks taken from several sources; rupture scenario from Johnston and Schweig (1996; modified from Tuttle, Schweig, et al., 2002)
E-134

Figure E-67 

Empirical relation between earthquake magnitude and epicentral distance to farthest known sand blows induced by instrumentally recorded 

earthquakes (modified from Castilla and Audemard, 2007).
E-135 

Figure E-68

Distances to farthest known liquefaction features indicate that 500 and 1,050 yr BP New Madrid events 

were at least of M 6.7 and 6.9, respectively, when plotted on Ambraseys (1988) relation between 

earthquake magnitude and epicentral distance to farthest surface expression of liquefaction. Similarity in 

size distribution of historical and prehistoric sand blows, however, suggests that paleoearthquakes were 

comparable in magnitude to 1811-1812 events or M ~7.6 (modified from Tuttle, 2001). 

NUREG-2115 DOE/NE-0140 EPRI 1021097

APPENDIX F 

Workshop Summaries 

F 

APPENDIX 

WORKSHOP SUMMARIES 

WORKSHOP 1: KEY ISSUES AND AVAILABLE DATA 

July 22–23, 2008 

Electric Power Research Institute 

3420 Hillview Ave. 

Palo Alto, California 94304 

The Workshop on Key Issues and Available Data was the first in a series of workshops jointly 

sponsored by the Electric Power Research Institute (EPRI) Advanced Nuclear Technology 

(ANT) Program and the U.S. Department of Energy (DOE) in support of the Central and Eastern 

U.S. Seismic Source Characterization for Nuclear Facilities (CEUS SSC) Project. The objective 

of the CEUS SSC is to develop a comprehensive and up-to-date SSC for a probabilistic seismic 

hazard analysis (PSHA) that is appropriate for use at any site in the CEUS. The goals of this 

workshop were to (1) introduce the various participants in the project to the goals, expectations, 

and schedule for the CEUS SSC project; (2) review the SSHAC Level 3 methodology (Budnitz 

et al., 1997) to be used for the project; (3) identify the key issues that need to be addressed in the 

course of the seismic source characterization; (4) review the available data, including data 

quality; and (5) identify the path forward for the project. 

DAY 1–TUESDAY, JULY 22 

Workshop participants were welcomed by Mr. Jeffrey Hamel, the EPRI Project Manager for the 

CEUS SSC project. He stated the importance of this project to the nuclear industry and noted 

that applications for 15 nuclear power plant units are currently pending and that 9 additional 

applications are planned to be submitted in 2009. He showed a ―prism‖ slide that indicated the 

potential roles of electric sector technologies, including the role of nuclear power, in lowering 

CO2 emissions by the year 2030. He reviewed the status of the current fleet of nuclear power 

plants in the United States and cited EPRI projections of a total of ~24 GWe by 2020 and ~64 

GWe by 2030 from the new fleet that will be deployed. 

The EPRI program for supporting new nuclear power plants, the Advanced Nuclear Technology 

(ANT) program, was described briefly. The program efforts are focused around facilitating 

standardization across the new fleet, transferring technology to new plant designs, and ensuring 

top plant performance from the start of operations. ANT program activities characterized as 

emerging, growth (including the CEUS SSC project), mature and declining activities were 

described. The program is funded by more than 25 utilities, vendors, and government agencies 

F-1
interested in promoting light water reactors. In addition, there is substantial interest from utilities 

based in Europe, which reflects the growth of this technology outside the United States as well. 

Next, Mr. Lawrence Salomone, Project Manager for the CEUS SSC project, welcomed everyone 

and expressed his appreciation for their participation in the project. He asked all workshop 

participants to introduce themselves and identify their affiliations. He began his talk by 

emphasizing that nuclear capabilities are essential as clean, safe options to achieve base load 

capacity increases, noting that 50 new units will provide 25 percent of the projected increased 

demand. To expedite the licensing of next-generation nuclear power plants, Mr. Salomone 

emphasized that we can do ―more for less to achieve stability, with reduced risk through 

standardization and partnering.‖ He described the industry and government plan to advance the 

science for nuclear technology, which includes using the CEUS SSC project to replace the 

previous EPRI-Seismicity Owners Group (EPRI-SOG, 1988) and Lawrence Livermore National 

Laboratory (LLNL; Bernreuter et al.1989) seismic hazard studies that were conducted in the 

1980s. 

Next, Mr. Salomone described the goals for the CEUS SSC project, which include developing a 

―commercially viable‖ approach for SSC model development with respect to cost and schedule 

that meets the expectations of sponsors, regulators, and oversight groups. He reviewed the 

Workshop 1 objectives, noting that a documentation package would be prepared for the 

workshop to be consistent with the objective of having a transparent project process. Next he 

reviewed the CEUS SSC project history to date and outlined industry and U.S. Department of 

Energy (DOE) expectations for the project. The primary expectations are to advance the science 

and obtain a PSHA update that is based on a stable and consistent SSC model, thereby 

expediting the licensing of the next generation of nuclear power plants. 

Mr. Salomone then noted that the number of proposed sites for next-generation plants in the 

CEUS is increasing and that existing plants in the DOE complex require an updated PSHA. Such 

studies are time-consuming and costly if each utility prepares a PSHA independently; at the same 

time, regulators want to streamline the review process and be capable of moving forward 

quickly. In addition, the EPRI-SOG (1988) and LLNL (1989) seismic hazard studies need to be 

updated using new data and interpretations; also, a void exists for an SSC model that postdates 

10CFR 100.23. Accordingly, assembling a single team of experts to develop a new and stable 

CEUS SSC model that incorporates a full range of uncertainty provides many benefits, thus 

industry and government agencies have been brought together to sponsor this project. 

Next, the organization chart for the CEUS SSC project was described. The Program Managers 

have overall responsibility for the project. The Technical Integration (TI) team, which includes 

the TI staff, has responsibility for the technical assessments made during the project. The 

Participatory Peer Review Panel (PPRP) is responsible for reviewing the process and technical 

aspects of the project. Specialty contractors are involved in database, hazard input and 

calculation, and documentation support. Participants in each of the project workshops are 

important because they have databases and alternative interpretations that are valuable to the 

project. Project milestones were described for the next two years; the final milestone will be an 

EPRI Technical Report to be published in 2010. Mr. Salomone concluded his talk by 

summarizing the benefits of the project, which include (1) supporting a research and 

development program to advance the state of practice for seismic hazard assessment; (2) 

obtaining PSHA input based on a stable and consistent SSC model vetted by a wide range of 

F-2
experts; (3) avoiding unnecessary conservatism and reduction in design margins; (4) expediting 

approvals of the seismic design basis for nuclear facilities; and (5) yielding significant economic 

benefits by reducing PSHA update costs for individual sites. 

Mr. Salomone then introduced Dr. Kevin Coppersmith (Coppersmith Consulting, Inc.), the lead 

of the TI team, to speak in more detail about the CEUS SSC project and the goals of the 

workshop. Dr. Coppersmith began by stating that 20 years have passed since the previous 

seismic hazard assessments for the CEUS were conducted (e.g., EPRI-SOG, 1988, and LLNL, 

1989). The current project will provide an unbiased seismic hazard assessment that captures 

uncertainty by following the process specifically designed to achieve this objective by the Senior 

Seismic Hazard Analysis Committee (SSHAC) (Budnitz et al., 1997). 

Dr. Coppersmith described SSC as fundamentally a scientific issue involving three questions: 

where will future earthquakes occur, how large will they be, and how frequently will they 

happen? He described some of the scientific assessments needed for SSC and stated that 

locations of observed events are based on historical and instrumental earthquakes, yet for a 

hazard analysis there is a need to assess the future pattern of seismicity. Spatial stationarity, 

seismogenic potential of geologic structures, the nature of boundaries between seismic zones, 

and other assessments needed for SSC were mentioned as he showed examples that included San 

Francisco Bay Area seismicity, the active Meers fault in Oklahoma, the New Madrid seismic 

zone, seismicity in Switzerland, and an isoseismal map of the 1356 Basel, Switzerland, 

earthquake. Scientific assessments of earthquake size, especially maximum magnitude (Mmax), 

and recurrence, were also illustrated using examples. He described how uncertainties in seismic 

hazard assessments need to be captured through the use of logic tree structures and noted that 

these were new at the time the EPRI-SOG work was conducted. 

Next, Dr. Coppersmith described the SSHAC methodology that provides a framework for 

incorporation of scientific assessments. In this methodology the views of the larger scientific 

community are captured as a ―snapshot in time‖ of our knowledge and uncertainties. He 

described elements of the SSHAC methodology, including the goal of all probabilistic hazard 

analyses to represent the center, body, and range of technical interpretations that the larger, 

informed technical community could provide. To achieve this goal, expert roles and 

responsibilities have been defined. Experts must be ―evaluators‖ who need to understand and 

evaluate information provided by ―proponents.‖ Stability and longevity are the larger goals of all 

PSHA methodologies, which are achieved in part from identifying and incorporating 

uncertainties. With these attributes a PSHA will have public and regulatory confidence that all 

hypotheses have been considered and the conclusions are not subject to significant change with 

each new scientific finding; new information can also be considered and incorporated into a 

PSHA. 

Dr. Coppersmith then reviewed the SSHAC study levels 1 thru 4, which are designed to address 

increasingly difficult and contentious problems by processes that increase complexity. The 

CEUS SSC project is a Level 3 study and includes both a TI team and the active involvement of 

a participatory peer review team, led by Drs. J. Carl Stepp and Walter Arabasz as co-chairmen. 

The CEUS SSC task schedule was reviewed next. Dr. Coppersmith emphasized that a ground 

motion assessment was not part of the current project, as new alternative models were recently 

developed for the CEUS (EPRI, 2004, 2006). He then described the goals of Workshop 1, which 

include identifying key hazard-significant SSC issues and the data sets available to address these 

F-3
issues. He reviewed the ground rules for workshops, which are designed primarily for the TI 

team to exchange data, present interpretations, challenge and defend technical hypotheses, gain 

information on the project, interact, and ask questions. Observers will be provided with 

opportunities for questions/comments. Finally, he reviewed the roles of workshop participants, 

including expert roles of proponents and evaluators, and concluded his talk by reviewing the 

agenda for 

Workshop 1. 

After a short break, the workshop session titled ―Key Hazard-Significant CEUS SSC Issues‖ 

commenced. The purpose of this session was to review and discuss the technical issues of 

importance to the CEUS SSC study in the context of preparation of a PSHA. Dr. Robin McGuire 

(Risk Engineering, Inc.) gave a talk titled ―Perspectives on Seismic Hazard Sensitivity to Input 

Assumptions.‖ He noted that the purpose of his comments was to illustrate the sensitivity of 

seismic hazard to input parameter choices, and he emphasized the importance of keeping 

aleatory and epistemic uncertainties separate. He reviewed the definitions of these types of 

uncertainties and gave an example of how they are used in characteristic magnitude distribution 

(i.e., the aleatory uncertainty is that successive characteristic earthquakes have different 

magnitudes [e.g., M 7.2-7.7] and the epistemic uncertainty is in the range of these magnitudes 

[e.g., M 7.2-7.7 or M 7.0-8.0]). He explained also that these represent a ―snapshot in time‖ and 

that uncertainty tends to migrate from aleatory to epistemic as better models are developed. 

Next Dr. McGuire showed some examples for a set of sites affected by faults that represented the 

New Madrid event by showing example parameters and uncertainties for these hypothetical 

sources from the SSHAC report (Budnitz et al., 1997). He discussed the relationships between 

earthquake magnitude and hazard, such that if beta goes down, hazard increases, especially at 

larger distances; at close distances smaller events may dominate the hazard. Also, he mentioned 

that seismic hazard may be more sensitive to changes in distance if Mmax is low. For purposes of 

sensitivity analysis, he defined a significant change as a hazard result change of more than 20 

percent, as a result of alternative parameter inputs. He illustrated this with examples from Group 

A sites and Group B sites. Most changes result in a change in hazard of less than 20 percent, and 

some have no sensitivity. The integration of hazard over many events with various parameters is 

not inconsistent with the finding that the occurrence of a particular rare event could cause lots of 

damage. Multiple interpretations of seismic sources are important; this is especially critical for 

specific sites, as hazard results could be very sensitive to the boundaries defined for a particular 

seismic source. 

Dr. McGuire showed examples of the contribution of high- and low-frequency hazard to the 

magnitudes and distances of the earthquakes that contribute to hazard at a site within the area of 

influence of the 1886 Charleston event. He showed a series of plots with increasingly larger 

ground motions, which progressively showed an increased contribution from close-by, smaller 

events. Then he showed a set of plots for low-frequency hazard and the associated events that 

contribute to hazard. He provided an example in the Eastern Tennessee seismic zone (ETSZ), 

showing Mmax distributions for the ETSZ from recently completed studies as well as a series of 

slides showing the source zones for this region defined by the six EPRI-SOG teams. These give 

multiple alternative source zone interpretations and a resulting range of a factor of 5 in hazard 

from curves produced at 10 hertz (HZ) (the individual team results were ultimately weighted 

equally to produce a single hazard curve). Some of the differences are related to different 

seismicity rates within the alternative zones, which are influenced by the approach used to 

F-4
smooth the historical seismicity. At low structural frequencies, the New Madrid seismic zone is a 

major contributor and there is a tighter hazard range across the teams. He also showed that at 

high frequencies there is low sensitivity to Mmax, whereas at low frequencies there is increased 

sensitivity to Mmax. Therefore, if Mmax is low, it can be more important to hazard than if it is 

high. 

Dr. McGuire then showed geometries of New Madrid seismic sources from a recent study, the 

earthquake magnitudes for the sources used in a cluster model, and the associated sensitivity of 1 

Hz and 10 Hz spectral acceleration hazard. He showed plots of New Madrid seismic sources 

from the EPRI-SOG teams and the resulting differences in hazard at specific locations (e.g., 

moving a site 20 km could result in a 30 percent reduction in hazard). Next he showed examples 

of updated Charleston seismic source geometry alternatives and how these were merged with the 

EPRI-SOG team Charleston sources as revised (―doughnut hole‖) sources containing the updated 

Charleston source information. As with the examples shown previously, the sensitivity of the 

mean hazard varies as a function of ground-motion structural frequency. From a distribution of 

seismic hazard curves for the 85th, mean, 50th, and 15th fractile hazard, the hazard (15th to 85th) 

is known within a factor of 20; the mean of the hazard is known more precisely. There is a high 

level of sensitivity to the characteristic earthquake (Mchar). 

Seismicity parameters used in the EPRI-SOG project were the next topic discussed by Dr. 

McGuire. The EPRI-SOG seismicity parameters were determined by statistical analysis of 

historical seismicity and the parameters were calculated for each source per degree cell using 

smoothing options specified by each team. Alternative sets of seismicity parameters were 

weighted by each team. Dr. McGuire showed examples from the Bechtel team’s source BZ5. He 

showed a visual representation of different smoothing assumptions used within the zone and 

plots of the sensitivity of hazard curves to smoothing. Next, he showed examples of the central 

Virginia seismic zone using alternative zone geometries selected by the EPRI-SOG teams and 

the range of related seismicity parameters. He looked at the effect of seismic hazard at three 

sites, and found that site location is extremely sensitive to these zones: a difference in hazard of 

more than a factor of two for two sites located about 30 km apart, which is a huge difference. His 

conclusion is that alternative zone boundaries or boundary treatments are essential, as defining 

only a single source could significantly affect the hazard results for sites located either just inside 

or outside the zone boundaries. 

Next Dr. McGuire showed a CEUS region and the geometries of faults in the New Madrid 

seismic zone as modeled in a recently conducted PSHA. The hazard results for sites at three 

different locations in the region show that at a low frequency (1 Hz), there is a large contribution 

to hazard from New Madrid sources, but at 10 Hz, there is a greater contribution (two to three 

times) from local sources at each of the sites. 

In a last set of examples, Dr. McGuire showed seismic sources defined in the Gulf of Mexico 

region by each of the EPRI-SOG teams. He stated that it will be important for the CEUS SSC 

study to consider earthquakes outside the United States. Seismicity maps for Central America 

and the Caribbean were shown; both areas have seismicity that may need to be included in 

models for sites in the southeastern United States. Also shown were EPRI-SOG seismic sources 

and hazard curves for Houston, Texas. The hazard curve for 1 Hz shows strange behavior, 

having a huge range of almost two orders of magnitude difference between the 15th and 85th

F-5
fractiles. Dr. McGuire postulated that one particular ground motion equation that was used may 

be affecting the mean hazard curve. 

Following a break for lunch, Dr. McGuire concluded his presentation. He described the 

Cumulative Absolute Velocity (CAV) model developed to calculate cumulative ground motions 

at a site. This model indicates a short-duration, high-frequency earthquake will have less effect 

on a site than a large, distant earthquake. Sites where small magnitude earthquakes contribute the 

most to the overall hazard have lower hazard as a result of application of a CAV filter. 

Dr. McGuire closed by listing his recommendations regarding the relative significance of SSC 

issues in order of priority. Assessments of seismic sources having potentially large earthquake 

magnitudes (e.g., New Madrid and Charleston regions) are the most important in terms of 

characteristic magnitude distributions and source zone locations because so many sites are 

potentially affected by these sources. These sources should be given highest priority, and the 

details of the characterization will be important to many sites. Next in importance are seismic 

sources having moderate magnitudes; and the remaining zones are background sources away 

from the more active sources. At this point, Dr. McGuire turned the session over to Dr. Gabriel 

Toro (Risk Engineering, Inc.). 

Dr. Toro began by describing the equations that allow comparisons between sensitivity products. 

These comparisons are important for focusing on situations with an important seismic source 

where high sensitivity is combined with high uncertainty. He showed an example from the 

PEGASOS study in Switzerland, in which hazard in the 10–4

 to 10–5

range is important. Input 

parameters used by the four PEGASOS SSC teams were all approximately equal in importance 

(exclusive of ground motion issues). For some sites, a specific parameter dominated over other 

parameters, but in general all parameters were equally important. 

Dr. Coppersmith opened the group discussion at the end of the session by noting that the TI team 

will interact with Risk Engineering to define and properly consider sensitivities. The group 

discussed seismic source zones with large magnitudes, especially the need to define the 

characteristics of zone boundaries (e.g., uncertainties in location, ―fuzzy‖ boundaries) and 

develop alternatives to assess the hazard for a site located near a source boundary. It may be 

useful to define generalized zones for most sources but have alternative boundaries for use with 

close-in sites. Source zone definitions and logic tree complexity were discussed. Differences 

between the PSHA approaches used for the EPRI-SOG project and what is available now for the 

CEUS SSC project were discussed, including significantly increased information on tectonic 

environments, modeling approaches such as spatial smoothing, computing power, GIS tools, and 

alternative methods for incorporating uncertainties. The TI team will review alternative 

interpretations of data at Workshop 2, planned for February 2009. 

The next session of the workshop focused on data that are available to conduct the CEUS SSC 

and that may be useful in addressing the key issues discussed in the previous session. Dr. 

William Lettis of William Lettis and Associates (WLA) began with a presentation titled 

―Database Development.‖ He stated that the group was brought together for Workshop 1 to 

identify what we do and (most importantly) do not know about seismic hazard in the CEUS, 

especially for capturing uncertainty. What data sets do we have that are needed, and can some be 

targeted for additional analysis that would be useful for this project? He noted that Dr. McGuire 

had described the parameters that are most sensitive for source zone characterization, and this 

information will help the TI team focus on what is most important. Dr. Lettis described the data 

F-6
compilation objectives, which include identifying critical data sets of geologic and geophysical 

coverage, and compiling COLA and ESP data as well as DOE PSHA and other data as available 

and relevant. A data compilation and documentation process is being established. This effort will 

include constructing a GIS platform to support TI alternative interpretations and establishing a 

data server to facilitate share of data and information. Dr. Lettis reviewed the presentation 

outline and indicated the speakers who would discuss the different aspects of database 

development. 

Dr. Frank Syms (WLA) discussed the administrative issues for the data documentation process. 

He noted that it will be important to document exactly how data are evaluated and transcribed 

into GIS. He noted that there will be some sharing restrictions, as some data have to be 

purchased. Data quality will be assessed with help from the data experts. An FTP site will be 

established to store and share data, which will include all data sets plus the metadata summary 

sheet, ArcGIS shape files, and a PDF of ArcGIS coverage, as appropriate. The earthquake 

catalog for the project will be available. COLA and ESP data from relevant sites will be 

assembled and made available, as will relevant U.S. Nuclear Regulatory Commission (NRC) 

Request for Additional Information (RAI) data. He described the status of COLA and ESP data; 

nine COLAs for sites in the CEUS are currently under review by the NRC and six additional 

COLA’s have been identified as in preparation. Additionally, relevant information is available 

for the DOE Savannah River Site, as well as for the Los Alamos National Laboratory, where 

information on the seismic source characteristics of the Rio Grande Rift will be important to the 

CEUS SSC project. 

Dr. Randy Cumbest (WLA) spoke next. He showed text from the project plan about the database 

scope and coverage. The western boundary of the study region will be the foothills of the Rocky 

Mountains (about longitude 105o W), except that it will include the Rio Grande Rift system; 

coverage will extend a minimum of 200 miles beyond the coastline and 200 miles from the U.S. 

borders with Canada and Mexico. Next he showed a series of slides with the database contents, 

which will include regional geophysics, including potential field, tectonic stress, and seismic 

reflection and refraction data; regional geology, including crystalline basement, tectonic features, 

crustal thickness, Quaternary faults, paleoliquefaction sites and dates; and the earthquake catalog 

for the project. Dr. Cumbest has already determined the availability of data sets by contacting 

many of the principal investigators. For the remainder of the talk he reviewed specific data 

sources from the list and noted for many items where coverage was currently complete or 

incomplete. 

The group considered possible gaps in the list of available data sets. Items discussed included 

GPS data, mantle velocity information, Paleozoic and Mesozoic structural information, 

earthquake intensity and focal mechanism data, and shallow seismic reflection data. It was noted 

that many of the additional data sets mentioned by workshop participants would be discussed by 

presenters during the second day of Workshop 1. 

Mr. Scott Lindvall (WLA) followed up with a list of logistical questions and issues. These 

included focus on the western boundary of the study region, defined at 105o W longitude, but 

which also includes the Rio Grande Rift, although the 200-mile buffer zone also includes the rift 

zone. It was noted that seismic sources throughout the buffer zone could affect sites within the 

study region boundaries; this is particularly the case along the western boundary. However, the 

major focus of the CEUS SSC study needs to be seismic sources within the defined boundary 

F-7
region. Using source models from other studies, especially the U.S. Bureau of Reclamation 

studies for dams in some of the western states (e.g., Colorado and Wyoming) was mentioned as a 

possible source of information for the WUS buffer zone areas. Offshore there are earthquakes 

with epicenters on the continental slope that need to be included in the analyses. Earthquakes in 

Cuba could be important for a site located in southern Florida. The appropriate way to deal with 

study area boundary questions will continue to evolve. Mr. Lindvall also discussed the USGS 

Quaternary faults and folds database that needs to be updated by adding available Wheeler 

(2005) and Crone and Wheeler (2007) information, specifically, the Class C and D features. 

Finally, data sharing and copyright limitations were discussed for both GIS data and published 

papers. 

After a break, Dr. Randy Keller (University of Oklahoma) described the on-land gravity database 

being developed by the scientific community. The initial compilation of gravity data for the 

conterminous United States is currently being expanded by merging data from many 

organizations for all of North America and including data from Canada and Mexico. The 

organizations contributing to the effort include the USGS, NASA, NSF, NOAA, and others. A 

number of corrections have been made to the database to remove duplicate points, bad points, 

and to terrain-correct the data. Dr. Keller showed maps of data available from 900,000 stations in 

1999 and from 1,282,787 station locations in December of 2003. He described the processes 

used to remove duplicate points. Data sets of this type incorporate thousands of different data 

sets and he described methods used to remove bad points. He mentioned that a significant part of 

the database development effort is the creation of new standards for gravity data reduction; these 

standards are published in a Hinze et al. (2005) article in Geophysics. Next he showed a map that 

indicates the complexity of the upper crustal structure in the CUS. Basement structures are far 

from homogeneous and thus difficult to correlate with other geologic information. Dr. Keller 

showed a series of maps and identified the location of the Meers fault in Oklahoma, as well as 

other geologic features, that have clear gravity signatures. He noted that different filters can be 

used to display the data in different ways. Magnetic data are an obvious complement to the 

gravity database. GIS-type approaches allow for many types of data to be overlain and examined. 

He closed with an example of a desalinization plant in El Paso, Texas, and the search for a brine 

disposal site, ultimately found in a basin identified as a gravity low. Following his comments the 

group discussed the use of isostatic adjustments (i.e., the effect of topography removal), the 

association of lineaments with gravity data, and terrain corrections that can be made. 

Magnetic data were discussed next by Dr. Dhananajay Ravat (University of Kentucky). He 

began by showing maps of North America displaying the magnetic anomaly databases in 1987 

and 2002, developed from hundreds of different aeromagnetic data sets. The variations between 

the different data sets resulted in significant problems when they were compiled, so he has 

undertaken the process of compiling improved data products. The National Uranium 

Reconnaissance Evaluation (NURE) data obtained in the 1970s are an important source of data. 

Dr. Ravat has used CM (the Comprehensive Model of the Near-Earth Magnetic Field) to 

improve the NURE data products. Some gaps remain where data have been lost, but his 

colleagues in Egypt inserted North American Magnetic Anomaly Group (NAMAG) data 

segments to fill gaps. To identify problems, second vertical derivatives (filters) are used; short 

wavelength data integrity problems result, which are correctable but require a time-consuming 

effort. To obtain the best full-spectrum magnetic anomaly product possible in the short term for 

his presentation, he combined NURE and NAMAG data for the conterminous United States. 

F-8
Next Dr. Ravat described interpretations of the data set using reduction-to-pole of NAMAG data, 

which is important for some applications. Most modern source interpretation techniques require 

high-quality first and second derivatives. He also briefly described methods for structural 

mapping, source edge complexity, and determining continuity of sources (e.g., the use of 

interpretive products). 

Workshop participants discussed combining geologic maps with the magnetic data maps, 

although it was noted that for some regions, geologic maps have been directly derived from 

magnetic data. The major limitations for use of the new map developed for this study were also 

discussed. Dr. Ravat knows the resolution could be improved by fixing some NURE problems, 

and he described some of the corrections that can be made using second vertical derivatives. 

Data for many areas have been collected but are not available for use at this time (e.g., U.S. 

Navy and industry data). 

Dr. Walter Mooney (USGS) gave the final presentation of the day, titled ―Global Seismic 

Refraction Catalog (GSC).‖ The USGS is interested in building a global seismic refraction 

catalog containing the most up-to-date information available about the Earth’s crust. The Global 

Seismic Refraction Catalog (GSC) is a Digital Earth crustal model derived from seismic 

refraction and other geophysical data. It is an important product for seismic hazard assessments, 

earthquake studies, and petroleum research. Dr. Mooney described key features of the GSC, 

which provides global coverage using a comprehensive set of data collected from 1939 through 

the present. Using these data, 10,200 data points have been digitized at 50 km intervals; recently, 

additional high-resolution data have become available and will be added to the database. The 

database consists of seismic refraction and other data captured from open-file and published 

scientific literature sources. Dr. Mooney’s study began with comparisons of refraction data and 

laboratory experiments; velocity data have also been compiled. Dr. Mooney showed current 

coverage of the GSC database; there is a strong correlation of survey areas with areas where 

there is interest in oil and gas resources. He described what is included in data records (location, 

structure of crust, tectonic environment and experimental details, etc.) and he showed a sample 

data record. For North America there are more than 1,400 data points, containing varying 

amounts of information. North America data have not been added consistently to the database 

since 2002; many thousands of additional points have been identified and need to be added to the 

model. 

Turning to products that can be developed using GSC data, Dr. Mooney showed various maps of 

North America that displayed sediment thickness, depth to the Moho, and shear-wave velocity 

maps. The data currently being collected by the Earthscope project will eventually provide 

additional valuable information for the catalog. Dr. Mooney gave examples of how the database 

can be queried to filter information such as maps and cross sections that indicate different layers

of the crust and the structure of the crust-mantle contact. For the workshop, a cross section 

showing variations in crustal thickness and the location of the Moho was created across the 

United States from the Pacific to Atlantic oceans at 35° N. Next Dr. Mooney showed some 

average statistics for North American crust: average thickness of continental crust of 36.72 km 

and oceanic crust of 8.39 km; average P and S velocities, and other information. He then showed 

a histogram of crustal thickness for North America (the thinnest crust is in northern California; 

the thickest in the Great Basin) and stated that thickness values are much higher in the Alps, 

Andes, and Himalayas. Heat flow data were also discussed, and he noted that assumptions need 

to be made about radioactive element contributions to heat flow. There is about a 500-degree C 

F-9
range in temperatures within the crust; in colder areas there are fewer earthquakes. Heat flow 

data can also be used to estimate thickness of the lithospheric root: as the root thickens, fewer 

earthquakes are observed, as deformation tends to be concentrated in areas of thinner lithosphere. 

Next, Dr. Mooney showed the ―Bigfoot‖ array of broadband instrument stations that is being 

moved east across the United States; these data will not be available in time for use in the CEUS 

study area. He concluded his talk with examples of maps of the upper mantle from surveys in 

southern Africa. 

Mr. Salomone opened the workshop to comments and questions from observers. Several 

workshop participants commented on the data sets that had been described or were on the agenda 

to be described the following day. The workshop was then adjourned for the day. 

DAY 2–WEDNESDAY, JULY 23 

Dr. Coppersmith welcomed the group to the second day of the workshop and reminded everyone 

that the time period of interest for the CEUS SSC study is the ~50-year period of operation 

typical for conventional nuclear power plants and that the annual hazard probabilities of interest 

will be in the 10–4

 to 10–7

range. Dr. Randy Cumbest (WLA) then resumed leading the 

presentations and discussions in the ―Available Data‖ session that began the previous day. 

The first talk of the morning was given by Dr. Robert Hatcher (University of Tennessee, 

Knoxville). Dr. Hatcher’s talk was titled ―Available Data: Geologic Domains, Tectonic Features, 

Rifts,‖ and he addressed the difficulties of understanding the origin of earthquakes within 

continental plates. He began by showing a series of geologic maps, tectonic maps, and maps of 

the assembly and dispersal of the supercontinent of Rodinia. He spoke in more detail about the 

series of geologic maps of the United States and the improvements made in the level of detail 

through time. Next he showed magnetic and residual isostatic gravity anomaly maps of North 

America and pointed out structural trends and features of interest, including accreted terrains and 

suture zones. He noted that integrating geophysical data with geologic data was essential for 

understanding the geologic domains and tectonic features of the CEUS. Interpretations of 

geologic features based on a variety of geophysical data sets, including residual isostatic gravity 

anomaly data, magnetic data, and seismic reflection data, were discussed. 

Next Dr. Hatcher discussed rifting processes. He described how Africa collided with North 

America at the end of the Paleozoic, and then showed geologic maps that provide the evidence 

for the collision sequence. He also described the New Madrid area and indicated the boundaries 

of the Reelfoot Rift; instrumentally recorded seismicity is not completely within the rift and 

therefore is not clearly associated with it. The crust-forming processes and features that began to 

form in the late Proterozoic and into the Mesozoic were described. 

Dr. Hatcher then described EUS earthquake frequency and magnitude patterns. He discussed the 

eastern Tennessee seismic zone, in which earthquakes are occurring at depths of 7 to 25 km, and 

stated that there is no apparent structure in the lower crust or apparent offset of the basement that 

could be associated with this seismicity. He postulated that the Farallon Plate may extend below 

the EUS and is a possible cause of earthquakes such as the New Madrid events. In his concluding 

remarks he stated that old structural boundaries may concentrate stress and produce earthquakes, 

but they do not provide answers about why they occur where they do. Incomplete data sets, 

F-10
especially for information about the mantle, are a major handicap in understanding the seismic 

setting of the CEUS. 

The next talk was given by Dr. W.R. Van Schmus (University of Kansas), titled ―Major Tectonic 

Features of the Precambrian Basement in the Midcontinent Region, USA.‖ Dr. Van Schmus 

reviewed available data sources, including outcrop, drillhole (core and cuttings), magnetic, and 

gravity maps, that allow interpretation of the geology of the midcontinent. He commented that 

outcrop availability is quite limited and drill cores can be useful when extended into granitic 

basement. Geologic maps can be developed from all available data. Next Dr. Van Schmus 

reviewed Archean-Proterozoic continental growth in the CEUS and showed maps of the 

accretionary belts and rock provinces that were emplaced progressively towards the south and 

southeast over a time span of about three billion years. Major boundaries between various 

terrains, the timing of their formation, and fundamental differences in the crust in various areas 

were described. Dr. Van Schmus traced the boundaries of some of the terranes and noted the 

difficulties in interpreting the associated histories, as some boundaries may be erosional and not 

tectonic in origin. Next he described the Eastern Granite-Rhyolite Province and Southern 

Granite-Rhyolite Province, both of which contain isolated plutons, juvenile basement, and 

stratified rock in older basement. He also described aspects of the Midcontinent Rift system, a 

large gravity feature that contains many faults. 

Dr. Mark Zoback (Stanford University) was the next speaker, and he presented results of work 

conducted with Dr. Mary Lou Zoback (Risk Management Solutions). His talk was titled ―In Situ 

Stress and Earthquake Focal Mechanisms in the Central and Eastern U.S.–An Update.‖ First he 

reviewed the state of stress in the CEUS as it was understood in the early 1980s. At that time, 

regional ENE-WSW compression over a large area was recognized, and detailed information 

about the New Madrid zone was starting to become available. Next he compared the state of 

understanding in the late 1980s with that of the early 1980s and noted that dramatic changes 

occurred in interpretations as a result of a great increase in data on the state of stress in the 

United States. Most significantly, data were becoming available from wellbore breakouts, which 

are the best indicators available of stress orientation because they are uniform and consistent. 

The improved database also included earthquake focal mechanisms, which indicate that faulting 

in the northern part of the EUS ranges from strike-slip to strike-slip-reverse to reverse faulting 

along a NE-trending gradient. Subsequently, structural information on faults became available 

and these data are consistent with the regional stress field. Dr. Zoback noted that the current view 

of the state of stress in the CEUS is essentially the same as that presented in 1989. 

Next Dr. Zoback noted that there are relatively uniform stress orientations across many complex 

geologic boundaries. He emphasized that intraplate earthquakes resulting from the contemporary 

stress field are acting on pre-existing faults. No evidence has been found for localized sources of 

stress in intraplate seismic zones such as New Madrid and Charleston. Dr. Zoback continued his 

talk by stating that several hypotheses considered in the mid-1980s for identifying seismic source 

zones are no longer valid. These hypotheses include reactivation of Triassic basin bounding 

faults and low-angle normal faulting in the Appalachian decollement, which appears unlikely 

because of the depths of earthquakes beneath the decollement and other factors. Faults slip in 

response to regional stress, thus the greatly improved stress orientation and relative magnitude 

databases improve the geologic bases for zonation. Dr. Zoback noted that where good data are 

available (e.g., in Japan), a remarkable correlation is apparent between maximum horizontal 

stress and strain, indicating that intraplate deformation is occurring in a coherent way. A key 

F-11
question about the New Madrid region is how to reconcile the fast Holocene rate of deformation 

with the extremely slow Cenozoic rate. Also, he stated that we now understand some of the real 

physical bounds on rates of deformation and other processes, and these data are helpful for 

defining source zone boundaries. 

Following Dr. Zoback’s talk the group discussed some of the data from studies in various regions 

of the EUS and how to explain the indicated stresses. Aspects of the data sets, including data 

quality, were discussed. The availability of industry data was discussed. The discussion 

continued about the degree to which rocks are close to being in a breaking state. Dr. Zoback 

noted that in general, rocks in the EUS are close to breaking and will respond to driving stress; 

what distinguishes an active area from a craton is not the state of stress in the brittle crust (even 

when rocks are near failure) but the strain rate. He stated that cratons are characterized by cold 

temperatures and low strain; in areas of higher heat flow, earthquakes occur more frequently. He 

also noted that when rocks in the upper crust creep, they are not at the state of brittle failure; the 

crystalline basement below, however, will likely be brittle. 

Dr. Andrew Newman (Georgia Institute of Technology) spoke next with a talk titled ―The State 

of Strain in the Eastern US: Can We See It?‖ His talk focused on strain fields in the EUS and he 

stated that GPS data is the best way to obtain strain information. He noted that because a 

significant amount of time is involved in processing GPS databases, differences can arise; 

recently, however, more stable results are being obtained. Since GPS data are derivative, he 

prefers to use the term ―velocity field‖ when discussing strain. He noted that high strain rates do 

not necessarily equal high seismic hazard, as strain may be a result of discontinuity or poor data. 

He discussed rigid body motion of a plate on a sphere, the residual GPS velocity field for North 

America when plate motions are removed, and a model for glacial unloading of North America. 

No significant strain fields are recognized in the EUS except for glacial rebound areas. 

To provide contrast Dr. Newman showed a map of the Chinese GPS field and stated that China 

has a large range of velocities and transitions across structural boundaries. He compared the 

strain rates between China and North America. He noted the strain localization indicated around 

the New Madrid seismic zone. He also stated, however, that geologic maps indicate the Eastern 

coastal plain has poor bedrock coupling, thus GPS instruments may not be firmly attached to 

bedrock and may not reflect tectonic motion. Since the New Madrid zone is very close to the 

Eastern coastal plain boundary, there could be some inaccuracies in the strain measurements. He 

noted that results of GPS campaigns in 1991, 1993, and 1997 showed no discernable motion 

(<2.4 mm/yr) in the New Madrid area. He compared velocity information with what is known 

from paleoseismic data and found that these data sets are consistent. Recently collected GPS data 

indicate rapid convergence is occurring at two sites near Reelfoot Lake. Dr. Newman checked 

and replotted these data. He believes that some New Madrid aftershocks are still occurring, and 

he identified different strain results from instruments at varying distances from the linear trend of 

seismicity. The apparent differences, however, may also be a result of instruments that are not all 

located on a homogenous medium. In his concluding remarks he stated that it is better to discuss 

bulk velocity fields rather than strain rates and that no large-scale tectonic deformation is yet 

observable in the EUS. Then he asked a final question of the workshop group: will we ever 

observe Chinese-style tectonic deformation in the EUS? 

The group discussed this question and strain information for the EUS. Plate movement in China 

was discussed; it is not clear if some blocks are rigid. The extremely low strain rates in the EUS 

F-12
(10-7/yr) were also considered. It was noted that Holocene strain rates have been very high, but 

the Cenozoic rate overall is low. It is possible that we are currently in an earthquake cluster, but 

GPS data are not adequate to resolve this question. The limited amount of information available 

on the pre-1811/1812 earthquakes in the New Madrid area was discussed. Limitations inherent in 

available data sets, including the short time period in which GPS measurements have been made 

in the New Madrid area and gathering paleoliquefaction data in the soft sediment of the 

Mississippi Basin embayment, were discussed. 

After a short break, two speakers gave presentations on paleoliquefaction in the CEUS. Before 

these speakers began, Dr. Ross Hartleb (WLA) gave a brief introduction about paleoliquefaction 

data sets, which are fundamentally important for assessing seismic hazards in the CEUS. Past 

large or moderate earthquakes can be identified by paleoliquefaction information, but we also 

need to answer questions about where, when, how often, and how large these events are. 

Paleoliquefaction data are difficult to correlate across space and time. Also, it is difficult to 

identify if these features were associated with one large event or multiple moderate events, and 

whether or not they were seismically induced. He noted that a comprehensive database of 

paleoliquefaction information is currently not available but developing such a database is a goal 

of this project. 

Mr. Steve Obermeier (USGS, retired) gave the first talk, beginning by briefly describing his 

background, which includes significant geotechnical engineering experience. He gave a short 

overview of paleoliquefaction studies, noting that it is not known what controls the abundance of 

features so it is necessary to look at many miles of exposures. When he begins a study in a new 

area, he identifies localities where the water table is shallow and susceptible deposits are present, 

then he concentrates on examining exposures. He described why paleoliquefaction studies are 

useful and gave an overview of factors involved in conducting studies. He always begins with an

air photo study to identify the features to be field-checked. Many streams are ideal for study, as 

extensive exposures are needed because features can be 1,000 feet or more apart. Mr. Obermeier 

stated that the New Madrid area is in an optimal setting for observing paleoliquefaction because 

of the high water table and a continuous Holocene sedimentary record. The Wabash Valley is a 

close second, but conditions there are more problematic. The principal questions to be answered 

in making interpretations include liquefaction susceptibility (based on factors such as grain size, 

packing, cementation, and thickness of units), density of sands as reflected by blow counts, depth 

to water table, age of sediments, and an assessment as to whether or not deformation is of 

seismic liquefaction origin. The experience level of the investigator is also important. Mr. 

Obermeier noted the optimal conditions for liquefaction, including a water table depth of 0 to a 

few meters, and then described techniques for assessing ages of sediments. Finally, he noted that 

artesian conditions, thrown trees, and chemical weathering can all result in features that look 

similar to paleoliquefaction. 

Mr. Obermeier continued by discussing assessments of magnitude and showed a map with the 

extent of liquefaction features associated with large prehistoric earthquakes in the Wabash 

Valley region. Based on the severity and areal extent of liquefaction associated with the New 

Madrid earthquakes, he believes they had magnitudes in the high 7 range. He concluded his talk 

by describing five regions in the CEUS where he has worked and suggesting areas where 

additional information could be collected. 

F-13
A second talk on paleoliquefaction was given by Dr. Martitia (Tish) Tuttle (M. Tuttle and 

Associates), who focused on data and databases. She acknowledged Dr. Kathy Tucker (CERI) 

and Dr. Buddy Schweig (USGS), who contributed to the work described in her presentation. She 

began by showing a map of locations in the CEUS where liquefaction studies have been 

conducted, identifying whether or not features were found and which sites had features that were 

equivocal. She described how she began developing a paleoliquefaction database with very 

limited experience and that the lessons learned will be of benefit to the CEUS SSC project. A 

database must be designed after considering how data will be used, queried, and displayed, both 

currently and in the future. She showed the process of converting data in an Excel spreadsheet to 

ArcGIS data and ArcMap plots. She also described work done in the New Madrid area, showing 

a map with estimates of sediment ages and the thickness of sandblows. 

Next Dr. Tuttle described an archaeological site with an associated sand blow for which a wellconstrained age could be determined using radiocarbon dating and artifact analysis. She 

described another area in which well-constrained ages of numerous large and broadly distributed 

sand blows allowed recognition of two events in 1,200 years. Next she showed example map 

queries by location, attribute, thickness, and age. She provided a list of data fields recommended 

to be included in a database. She concluded her talk with a list of lessons learned. She 

emphasized that it is important to carefully consider how to query and use data and that a 

uniform identification convention should be used for locality names. Her concluding statement 

was that paleoseismology can provide ground truth for seismic hazard assessments. 

The group discussed preservation patterns of paleoliquefaction features in the geologic record 

and uncertainties associated with interpretations. Dr. Tuttle stated that for some features, 

geologic evidence including weathering patterns and fining upwards sedimentary sequences can 

clearly indicate a hiatus in deposition and allow separate events to be resolved within a few 

months. 

Following a lunch break, Mr. Salomone asked the resource experts to send their lists of 

references to lawrence.salomone@srs.gov and syms@lettis.com . After this announcement the 

final session of the workshop, whose topic was the seismicity catalog, commenced; presentations 

and discussions in the session were led by Dr. Robert Youngs (AMEC Geomatrix). Dr. Youngs 

gave the first presentation, titled ―Development of Earthquake Catalog for Seismic Source 

Characterization.‖ He began by stating that the catalog would contain events compiled for the 

period 1600 to 2008 and that event sizes would be defined in terms of moment magnitude. 

Uncertainties in size and location will be defined for incorporation into a hazard model. The 

primary sources from which the catalog will be compiled include the EPRI-SOG (1988) catalog; 

the NCEER-91 revision of EPRI-SOG; the USGS seismic hazards mapping catalog, and the 

Canadian seismic hazard mapping catalog. Studies for ESP and COL applications in the CEUS 

will provide useful information, as will special studies of individual earthquake events or 

regions. Dr. Youngs described the catalog development process in which data from all sources 

will be summarized for earthquakes larger than magnitude ~3. The compiled information will be 

reviewed with a team of experts to select preferred values, assign uncertainties, and classify 

nontectonic events. Dr. Youngs explained the data needs for development of moment magnitude 

estimates for each event; these include moment magnitude estimates from other catalogs and 

special studies for instrumentally recorded earthquakes, plus intensity/felt area data for both 

instrumentally recorded as well as historical earthquakes. 

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Next, Dr. Youngs presented a series of slides on macroseismic data for the CEUS prepared by 

Ms. Margaret Hopper (USGS), who was unable to attend the workshop and be a presenter. Her 

slides provided information on a database of over 150 earthquakes in the CEUS for which 

intensity data are available. This database will be useful for the CEUS SSC project. 

Dr. Youngs concluded his talk by describing the processes planned to identify dependent events 

within the catalog and to assess catalog completeness. The workshop group then discussed the 

possible compilation of earthquake focal mechanisms for the project, as these are important for 

mapping stress. The TI team will discuss how to proceed with this effort. 

The next speaker was Dr. Charles Mueller (USGS), who described the approach used to develop 

the USGS catalog. He stated that a mix of published and well-documented, national-scale source 

catalogs was used, and he listed many of these catalogs. Objectives for the catalog are to have it 

be dominated by events from the well-researched NCEER-91 catalog as well as to have the 

catalog be appropriate for use for PSHA. He described the procedure followed to compile the 

catalog, including selecting a single record for each earthquake, selecting a preferred magnitude 

if more than one is reported, and declustering and removing man-made events if they pose no 

hazard (e.g., mining-related seismicity in Colorado and Utah). Next he displayed various aspects 

of the data for the portion of the catalog in the CEUS. In his concluding statements he mentioned 

that improvements were being made in the USGS catalog as a result of better source catalogs, a 

more reliable update process, and incorporation of uncertainty estimates for magnitude and 

location of some events. He stated that the catalog prepared as part of the CEUS SSC study will 

be incorporated into the USGS catalog. Mr. Mueller commented that with additional resources 

he would like to focus efforts on the incorporation of uncertainty in the catalog. 

The next talk, titled ―Revising the Earthquake History of the CEUS: Identification of New 

Events and New Sources of Information,‖ was given by Mr. Jeff Munsey (Tennessee Valley 

Authority). In his first slide, Mr. Munsey listed impacts and benefits of updating an earthquake 

catalog, including providing additional information to define seismic source boundaries; refining 

activity rates, especially at local scales; increasing temporal and spatial completeness; and 

improving location and magnitude estimates. He reviewed sources of catalog information for the 

region surrounding the Tennessee Valley that had become available since the EPRI-SOG catalog 

was completed, including his own work that resulted in identification of more than 400 events 

from 1724 to 1927, primarily using historical newspapers available online. He listed the primary 

online data sources he uses and then briefly described some of the newly identified earthquakes. 

He also described how he has tracked down felt information and made estimates about 

earthquake magnitude. He concluded his talk by listing challenges and tasks ahead. These 

include establishing and recording the basis for existing events, reconciling multiple accounts of 

dramatic events, and evaluating clues to assess event depths and distances.

The final talk of the session, titled ―Earthquake Data for Seismic Hazard Determinations in the 

Northeastern U.S.,‖ was given by Professor John E. Ebel (Boston College). He began by listing 

seismic issues and items to be addressed to update a catalog. He has studied early historic 

earthquake events (1600s) based on journal entries and accounts of city funds appropriated to 

repair earthquake-induced damage. He described updates of the Northeastern United States 

(NEUS) catalog over the past decades, noting that when the NRC eliminated regional seismic 

network funding in the early 1990s, most seismic stations in the NEUS were lost. Only in the 

past few years have significant improvements been made, in part due to equipment changes that 

F-15
have improved both detection capabilities and magnitude determinations. Dr. Ebel discussed the 

problems of overlap between U.S. and Canadian seismicity catalogs, which result in multiple 

reports as well as possibly different decisions about whether a particular event has a seismic or 

nonseismic origin. Epicenter accuracy is better with a denser network, so the NEUS catalog 

reflects data of varying quality. 

Next Dr. Ebel described regional earthquakes in the EUS in the recent past, as this pattern is 

expected to continue in the future. On average, about six small earthquakes (magnitude < 3.5) are 

felt in New England each year and this regular, persistent earthquake activity has been observed 

for more than 25 years. Temporally clustered earthquake activity can also be observed. Dr. Ebel 

showed a plot of the variations of earthquake activity with time in New England since 1979. He 

described the 2006-2007 Bar Harbor earthquake sequence that resulted in M 3.4 and M 4.2 

events.

Turning to the historical catalog, Dr. Ebel described issues concerning historical NEUS 

earthquake data, including the need to identify additional events and adequately assess event 

sizes from detailed historical research. He noted that small aftershocks can help pinpoint the 

location of a stronger earthquake in the historical record. Following a 1727 earthquake, over 150 

aftershocks were felt in two different areas (17 were magnitude > 4) and this information could 

be used to more accurately locate the epicenter of the main shock. Clusters of small earthquakes 

may be aftershocks from strong events that occurred hundreds or even thousands of years ago. 

Unlike the situation in California, there is no baseline level of earthquakes in the NEUS, so it is 

easier to identify earthquake clusters as aftershocks. Dr. Ebel has developed estimated ages and 

magnitudes for many events extending back more than 1,000 yrs. 

Dr. Ebel concluded his talk with several recommendations. These include extending the catalog 

to the northeast by acquiring additional available databases and cross-checking duplicate event 

data; conducting a research program to study magnitudes of instrumental earthquakes in the 

NEUS; and targeting selected historical events for additional research to better constrain event 

size and location. In response to discussions with the group, Dr. Ebel noted that the focal 

mechanisms for most events are consistent with a tectonic origin, although glacial unloading is a 

possible cause for some. He also stated he believes a Charleston-type earthquake is possible 

anywhere in the NEUS region, although others question whether the crust could support an event 

of this magnitude. 

Dr. Coppersmith asked for comments and questions from the workshop participants, including 

the international observers. Participants discussed different areas of seismicity and earthquake 

events in the CEUS and their relevance in defining source zones. 

Dr. Coppersmith then made final remarks about the path forward for the CEUS SSC project. He 

mentioned the SSHAC implementation project that is under way and how lessons learned from 

that effort will be implemented in the current project (several participants in the CEUS SSC 

project are also participants in the SSHAC workshops). He noted the point of contact for the 

CEUS SSC project: lawrence.salomone@srs.gov, and he showed the task schedule for the 

project, noting the February 2009 timing for Workshop 2 on Alternative Interpretations. In the 

months before Workshop 2, many of the activities discussed in Workshop 1 will be under way, 

including database development and seismicity catalog development. A preliminary SSC model 

will be developed and used to identify the key alternatives for discussion at Workshop 2. Hazard 

and sensitivity analyses will be used to evaluate the preliminary SSC model. 

F-16
Mr. Salomone thanked the international observers for taking the time to attend the workshop, and 

then he offered his parting comments. He noted that the high level of expertise of the presenters 

was clearly indicated by the content of their presentations. He expressed his appreciation to all 

who have made the project and first workshop a success, and who will continue to do so as the 

project continues. He believes that the CEUS SSC project will ultimately be viewed as a 

landmark study. He then adjourned the workshop. 

REFERENCES 

Bernreuter, D.L., J.B. Savy, R.W. Mensing, and J C. Chen. 1989. ―Seismic Hazard 

Characterization of 69 Nuclear Plant Sites East of the Rocky Mountains,‖ Report NUREG/CR5250, Vols. 1–8, prepared by Lawrence Livermore National Laboratory for the U.S. Nuclear 

Regulatory Commission. 

Budnitz, R.J.; G. Apostolakis, D.M. Boore, L.S. Cluff, K.J. Coppersmith, C.A. Cornell, and P.A. 

Morris. 1997. Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on the 

Uncertainty and Use of Experts, NUREG/CR-6372. Two volumes. U.S. Nuclear Regulatory 

Commission, Washington, D.C. 

Electric Power Research Institute and Seismicity Owners Group (EPRI-SOG), 1988. Seismic 

Hazard Methodology for the Central and Eastern United States, Technical Report NP-4726-A, 

Vols. 1–10.

Electric Power Research Institute (EPRI). 2004. CEUS Ground Motion Project Final Report, 

EPRI Report 1009684, December 2004. 

Electric Power Research Institute (EPRI). 2006. Program on Technology Innovation: Truncation 

of the Lognormal Distribution and Value of the Standard Deviation for Ground Motion Models 

in the central and Eastern United States, EPRI Report 1013105, Technical Update, February. 

F-17
WORKSHOP 2: ALTERNATIVE INTERPRETATIONS 

February 18–20, 2009 

Electric Power Research Institute 

3420 Hillview Ave. 

Palo Alto, California 94304 

The Workshop on Alternative Interpretations was the second in a series of workshops jointly 

sponsored by the Electric Power Research Institute (EPRI) Advanced Nuclear Technology 

(ANT) Program, U.S. Nuclear Regulatory Commission, and the U.S. Department of Energy 

(DOE) in support of the Central and Eastern U.S. Seismic Source Characterization (CEUS SSC) 

for Nuclear Facilities Project. The objective of the CEUS SSC is to develop a comprehensive and 

up-to-date SSC for a probabilistic seismic hazard analysis (PSHA) that is appropriate for use at 

any site in the CEUS. The Technical Integration (TI) team and TI Staff are charged with 

developing a seismic source model that captures the knowledge and uncertainties within the 

larger informed technical community. The goals of this workshop were to (1) review the project 

Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 methodology, ground rules, 

expert roles, and peer review processes; (2) provide an opportunity for the TI team and TI Staff 

to understand proponent views regarding important technical issues; (3) discuss the range of 

alternative views and uncertainties within the larger technical community; and (4) discuss the 

path forward for the CEUS SSC project. The goals were accomplished by a series of 

presentations and discussions designed to provide the TI team and TI Staff with the information 

it needs to develop a preliminary seismic source characterization model. 

DAY 1–WEDNESDAY, FEBRUARY 18 

Workshop participants were welcomed by Mr. Jeffrey Hamel, the EPRI ANT Project Manager 

for the CEUS SSC project, who also reviewed some workshop logistics. Mr. Lawrence 

Salomone, Project Manager for the CEUS SSC project, then welcomed workshop participants 

and thanked them for attending. He reviewed some of the project logistics. Next Mr. Salomone 

reviewed the project goals: (1) replace the previous EPRI Seismicity Owners Group (EPRI-SOG, 

1988) and Lawrence Livermore National Laboratory (LLNL; Bernreuter et al., 1989) seismic 

hazard studies that were conducted in the 1980s; (2) capture the knowledge and uncertainties of 

the informed scientific community using the SSHAC process, and (3) present a new CEUS SSC 

model to the Nuclear Regulatory Commission, DOE, and others for review. Transparency of the 

project process is a key goal. He reviewed the management chart for the project and showed 

samples of the data sets available for the study region. Mr. Salomone summarized the project 

milestones, including the preliminary SSC model feedback to be reviewed at Workshop 3, which 

is scheduled to be held August 25–26, 2009. In his concluding remarks he noted that the project 

is on track to meet the target completion date in 2010. 

Dr. Kevin Coppersmith, the lead of the TI team, then welcomed the workshop participants. His 

talk focused on the goals of the workshop and the ground rules. Dr. Coppersmith began by 

reviewing aspects of the SSHAC project, which is documented in NUREG/CR-6372 (Budnitz et 

al., 1997) and will be implemented in the CEUS project. He reviewed the SSHAC basic 

principles for a PSHA, key attributes of the process, and expert roles, with their application to 

the current workshop. He indicated that the focus of the workshop would be on providing 

information that the TI team can use in developing the preliminary SSC model, which will be 

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completed prior to the third workshop. As such, the workshop would be structured to allow the 

TI team maximum opportunity to have their questions answered by the resource experts making 

the presentation. He reviewed the CEUS SSC task schedule and the process to be followed for 

Workshop 2. Prior to the workshop, key questions and issues were posed to the presenters to 

address in their talks (see Table 1); the knowledge and uncertainties of these members of the 

larger informed technical community are what the TI team is charged with capturing. 

The first of the talks was given by Dr. Stephane Mazzotti of the Geological Survey of Canada. 

His talk was titled ―Strain (and Stress) Constraints on Seismicity in the St. Lawrence Valley.‖

Dr. Mazzotti began by discussing the distribution of earthquakes and the definition of seismic 

zones based on concentrations of earthquakes in regional ―hot spots,‖ in this case, the Charlevoix 

and lower St. Lawrence Seaway regions. He noted that earthquakes are concentrated along 

Iapetus rifted margins and grabens that formed about 600 million years ago (Ma). He also noted 

that seismic moment and deformation rates for eastern Canada can be based on two alternative 

models for earthquake distribution: (1) earthquake statistics in historical source zones, which 

indicate a few high-strain zones and relative motion of 0.0 to 2.5 millimeters per year (mm/yr); 

and (2) geological source zones, which have no high-strain zone and motion of only 0.0 to 0.5 

mm/yr. Dr. Mazzotti reviewed GPS (global positioning systems) observations from regional 

networks and showed the vertical and horizontal velocities obtained from this data, noting that 

there is very good agreement between continuous data (3 to 6 years) and campaign data (7 to 12 

years). Next he discussed preliminary results of GPS measurements in the Charlevoix and lower 

St. Lawrence seismic zones. This data shows very low strain rates overall, as expected, but eastwest horizontal strain rates appear to be higher in high-seismicity zones. Within these zones, the 

recurrence rates derived from the observed seismicity are in good agreement with rates derived 

from geodetic data translated into seismic moment rates. Current strain rates and seismicity are 

not steady-state on a million-year time scale, inasmuch as the rates imply cumulative 

deformation over million-year time scales that are not observed. Within a resolution of 

approximately 1 mm/yr at 95 percent, it is not possible to discriminate between alternative 

models. 

Next Dr. Mazzotti described the potential role of glacial isostatic adjustment (GIA) processes 

and models. GIA is very small and it is debatable as to whether or not it is associated with 

earthquakes. Dr. Mazzotti’s work shows there may be a significant role of GIA and local weak 

rheology in seismicity for some seismic zones, as indicated in the Charlevoix and lower St. 

Lawrence regions. In his conclusions, Dr. Mazzotti mentioned that the observed seismic strain 

signal (<1 mm/yr) is at the limit of GPS precision and that GPS data cannot yet represent 

earthquake hazard over the next 500 to 5,000 years. He believes GPS strain rates should be used 

in combination with other data sets, including rheology, geology, and historical seismicity, to 

define seismic source zones and rates, but only once a robust integrative geodynamic model has 

been developed. 

The following talk was given by Dr. John Ebel of Boston College, who addressed ―Mmax for 

Eastern North America: An Examination of the 1663 Charlevoix Earthquake.‖ Dr. Ebel began by 

stating that many of the small earthquakes in the northeastern part of North America may be 

aftershocks of strong earthquakes that took place hundreds or even thousands of years ago. To 

provide a frame of reference, he first showed examples of seismicity in California, which 

indicate that aftershock zones can be active for decades after a main shock. Next he described the 

methods he used to estimate the magnitude of the 1663 Charlevoix earthquake. This event was 

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felt strongly in Canada, with major ground deformations in what is today recognized as the 

Charlevoix seismic zone. Dr. Ebel obtained data from damage reports in Boston and Roxbury in 

Massachusetts that were possibly associated with this earthquake, and he used the data to 

estimate the intensity and magnitude of the 1663 event. (The Charlevoix seismic zone is between 

560 and 640 kilometers [km] from Boston.) He also compared the reported earthquake effects 

with isoseismal maps from the 1811–1812 New Madrid earthquakes and estimated the 

earthquake magnitude from the length of the ―aftershock‖ zone that is currently active in the 

Charlevoix region. The best estimate of the moment magnitude (Mw) of the 1663 Charlevoix 

earthquake from his study is Mw ~7.3–7.5. 

Next, Dr. Ebel began speculation on the characteristics of large earthquake events in stable 

continental regions. He believes that larger aftershocks concentrate at the edges of an earlier 

earthquake rupture due to stress concentration at the crack tip. This appears to be the pattern at 

Charlevoix, where recently occurring M 4 events have been located at the edges of the 1663 

event. Dr. Ebel also speculated on recurrence rates of M > ~7 for the CEUS and eastern North 

America. The observed rate of M > ~7 earthquakes is greater than expected from extrapolations 

from the smaller earthquakes recorded in these regions. If small events reflect aftershocks of 

larger events, then the rate of M > ~7 earthquakes during the past few thousand years may be 

approximately two to three times greater than predicted by recurrence relationships that 

extrapolate the number of large events from small events. 

The next presenter was Dr. Alan Kafka of Boston College, who spoke on ―Use of Seismicity to 

Define Seismic Sources: Application to Eastern North America.‖ Dr. Kafka discussed how 

―cellular seismology‖ can be used to delineate future seismicity based on what is known about 

past seismicity. Empirical analysis of earthquakes is based on historical and instrumental 

earthquake history, but this information does not address causes of earthquakes and whether 

analysis of what is currently observed will show persistence over long time scales. Is the 

―tendency for future earthquakes to occur near past earthquakes‖ a real, measurable, physical 

phenomenon? Dr. Kafka has investigated this question and uses a simple method of analysis 

based on separating observed seismicity data into two parts before and after some point in time. 

He then looks at the percentage of events after that time (future events) that fall within zones 

defined by various radii from earthquakes prior to that time (past events). As the radii increase, 

of course, the probability that a future event will fall within the zone for past events increases 

even for a random process. However, Dr. Kafka has found that the probability increases more 

rapidly than a random process, suggesting that future events are more likely to occur near past 

events. He has looked at many regions in the United States and worldwide for these patterns. He 

has found that future large earthquakes in the CEUS have about 86 percent probability of 

occurring within 36 km of past earthquakes. He has compared the accuracy of cellular seismicity 

to other methods, including rate-based forecasts (percentage of hits vs. percentage of defined 

mapped areas). In general, he finds that for his method, greater than 60 percent hits are obtained 

(whereas a random process would be about 30 percent). In his conclusions, Dr. Kafka noted that 

he has not found any other method of forecasting locations of future earthquakes that performs 

better than cellular seismology. 

Following a lunch break, Dr. John Adams of Natural Resources Canada discussed the Canadian 

seismic hazard models in a talk titled ―Eastern Canadian Experience with Geological Source 

Zones and Mmax.‖ He briefly reviewed aspects of the third- and fourth-generation seismic hazard 

models developed for Canada. He believes that smoothed seismicity is interesting but not 

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sufficient for assessing future hazard levels. As an example, he cited the 1988 M 5.9 Saguenay 

earthquake in an area that had no prior earthquake activity of MN > 3 for more than 50 years 

prior. He believes geological sources provide essential information, and noted that geological 

sources were proposed in Canada as early as 1983 for the passive continental margin. For the 

United States, he noted that Russell Wheeler did good work on geological sources in the early 

1990s, but these were not explicitly incorporated in USGS hazard maps. Dr. Adams described 

the association of large earthquakes (M > 7) with rifted margins, noting the 1933 Baffin Bay and 

1929 Grand Banks events, which occurred on large through-going faults that were reactivated in 

the Mesozoic. He then showed a map of seismic source zones in eastern Canada and into the 

eastern United States and described how various zones were modeled, based on both geologic 

history (ancient rifted margins and failed rift arms) and seismicity. He noted geological 

structures/source zones form a way of ―filling in‖ between historical earthquake clusters. 

The eastern Canadian experience with maximum magnitude (Mmax) was described in the next 

part of Dr. Adams’s talk. He described how the Mmax estimates in previous generations of 

seismic hazard maps had been exceeded by significant earthquakes that occurred in Canada 

between 1982 and 2001. Accordingly, Mmax estimates chosen for the fourth-generation studies 

were larger and based on continent-scale and global analogs, using methods similar to the EPRI 

Stable Continental Region (Johnston et al., 1994) study. A study of Mmax in Australia was 

described as an analog for the CEUS and Canada. Mmax choices for eastern Canada were also 

described, including weights assigned to a range of observed Mmax for different tectonic 

environments; these included Mesozoic rifted margins, Paleozoic rifted margins, and plate 

interiors. In his concluding remarks, Dr. Adams stated that earthquakes of Mmax ~Mw 7.0 could 

not be ruled out anywhere, although probabilities will be very low in many stable continental 

regions. Phanerozoic rifted crust typically contains enough long and deep faults (or fault 

systems) that Mmax ~8.0 Mw seems plausible. In his final slides, Dr. Adams showed how 

Canadian seismic source zones can be extended into the CEUS. Extensions of Canadian source 

zones could be postulated to extend into the US, such as the Atlantic Rifted Zone extended to 

Charleston, South Carolina; the Iapetan Rifted Margin extending to Giles County Virginia and 

the Eastern Tennessee seismic zone. 

Dr. Coppersmith announced that the next scheduled speaker, Dr. Leonardo (Nano) Seeber 

(Lamont-Doherty Earth Observatory) was unable to attend the workshop. A talk originally 

scheduled for Day 3 of the workshop was substituted. 

Dr. Frank Pazzaglia of Lehigh University presented a talk titled ―Approaches Used to Identify 

and Evaluate Neotectonic Features in Appalachian Piedmont/Coastal Plain Setting.‖ The focus of 

the talk was the geology and geomorphology of the passive margin in the Atlantic states. Dr. 

Pazzaglia addressed the influence of broad regional flexure of the Atlantic margin on current 

patterns of seismicity, noting that there is spatial overlap in topography, active river incision, and 

seismicity. He described how topography and rivers respond to rock uplift, rock hardness, and 

erosion. He showed maps of many of the rivers along the Atlantic coast and described different 

geographic areas and their association with seismic activity. He discussed the Fall Zone and its 

location on the classic passive margin, emphasizing that the Coastal Plain is narrow and no 

waterways are navigable, which doesn’t make logical sense for that type of setting. Coastal 

margin topography suggest that this area has been undergoing uplift, thus leading to convex 

upward longitudinal profiles for the rivers. He suggested that the Appalachians might be more 

tectonically active than previously thought. For example, New England has been uplifted since 

F-21
the Miocene, and over time, the Hudson River has moved the sediments of the former Coastal 

Plain to the south. Dr. Pazzaglia described the stratigraphy along the edges of Chesapeake Bay. 

He provided evidence for faults up and down the coastal margin that are concentrated around the 

Fall Zone. 

Dr. Pazzaglia believes that future earthquakes could occur in areas with low seismicity that also 

have apparent fault structures. He showed nick points along the Fall Zone, noting that it is clear 

that a base-level fall has occurred since the Miocene, although within this 10-million-year (m.y.) 

period we cannot tell if this occurred early or late. It is now known that the Miocene sea level 

was about the same as at present, so the Piedmont is clearly rising. Faults located coincident with 

the Fall Zone would be useful targets for detailed studies to see if river anomalies are related to 

tectonics. Dr. Pazzaglia continued by discussing flexural effects from glaciations and ice 

unloading during the Quaternary. Finally, he described the Chesapeake Bay impact structure 

emplaced approximately 35.4 Ma. Rivers drained into the low area created by the impact, and 

pulses of subsidence are apparent. Dr. Pazzaglia believes that this impact structure could be a 

causative structure for some of the seismicity in the eastern United States. 

Dr. William Thomas of the University of Kentucky gave the next talk, titled ―Ouachita SubDetachment Structures.‖ He described the geology of the CEUS at 250 Ma, showing major 

structural features based on data from wells and seismic reflection lines. He indicated the leading 

edge of aulacogen (tectonic trough) locations for the Alabama-Oklahoma transform and 

Ouachita thrust sheets. He discussed the stratigraphy and timing of activity of faults at about 308 

Ma, showing the Mississippi embayment and other major structural features in palinspastic 

restorations. He also noted that episodes of movement were coincident with Iapetan rifting and 

then thrusting. He showed several seismic reflection profiles and cross sections that indicated 

stratigraphy and structure. The Ouachita thrust belt was compared with the Appalachian thrust 

belt, and different styles of deformation were described. The Ouachita accretionary prism was 

emplaced about 310 to 307 Ma, and to the east, the Suwannee terrane was emplaced about 306 to 

300 Ma. Reconstructions give information about the timing of faulting. Dr. Thomas next 

discussed the Southern Oklahoma fault system, including the Wichita uplift, which is located 

above a leaky transform fault. In his conclusion, he noted that major structures were formed in 

the CEUS about 550 to 530 Ma and 310 to 300 Ma (late Paleozoic); some structures were 

reactivated in 245 Ma. 

After a short break, Dr. James Drahovzal of the University of Kentucky gave a talk titled ―Rifts 

in the Midcontinent: East Continent Rift Basin, Rough Creek Graben and the Rome Trough.‖ In 

his talk he discussed these structures and the associated Grenville and Hoosier thrust belts, along 

with the Fort Wayne rift, which is coincident with the Anna seismic zone. Dr. Drahovzal began 

by showing the classic CEUS ―basement‖ bedrock geology and then noted that more complex 

stratigraphy and structure have been constructed from well data. Sedimentary and volcanic rocks 

underlie many areas of granite and other igneous rocks in the midcontinent. Dr. Drahovzal 

described drillhole and seismic data for portions of Ohio, Kentucky, and Indiana; seismic data 

indicates layered reflectors within sequences of as much as 20,000 to 25,000 feet of 

Mesoproterozoic rocks that are folded and faulted. He provided a preliminary Proterozoic 

chronology that indicates alternating episodes of extension and compression in the midcontinent. 

Next he described the sequence of geologic events that formed structures within the East 

Continent rift basin, including the aseismic Rough Creek graben and Rome trough. Both of the 

latter structures are likely to have experienced Mesozoic reactivation but are currently aseismic. 

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The Rome trough is a symmetrical Cambrian rift basin that contains three major fault zone 

boundaries. Several reactivations since the Paleozoic are recognized for this structure. The 

Rough Creek graben in western Kentucky also shows evidence of Mesozoic reactivation, with 

Precambrian rock offsets of up to 17,000 feet. Dr. Drahovzal described the east continent gravity 

high and the relationship of this structure to the Rome trough and East Tennessee seismic zone. 

The 1980 M 5.2 Sharpsburg earthquake was located close to the East Continent gravity high. 

The next talk was by Dr. John McBride of Brigham Young University, who discussed 

―Geophysical Characterization of Faulting and Folding in the Illinois Basin and Relation to 

Seismicity.‖ Seismic reflection data is used to understand fault deformation and seismicity in an 

area of the midcontinent centered on the Illinois Basin and the New Madrid seismic zone 

(NMSZ). Dr. McBride noted that reactivation of faults is not always clear, even in a wellconstrained area like California, so fault reactivation is even more difficult to recognize in the 

Midwest. However, a large amount of geophysical data is available for the Illinois basin, 

particularly seismic profile data, because of oil production in the state that peaked in 1937. Dr. 

McBride showed a map displaying a CEUS earthquake catalog and questioned if an area 

showing little seismicity is real or an artifact of limited instrumental coverage. Next he showed a 

map of major structures in the southern Illinois basin and described some of these, including the 

La Salle deformation belt. He reviewed information for recent earthquakes in the region and 

showed a seismic reflection profile of the La Salle anticline. A 1987 earthquake and aftershocks 

associated with a frontal thrust, plus evidence of paleoliquefaction in the region, provide 

evidence of this anticline as a possible seismic source zone. 

Next Dr. McBride described several possibly seismogenic structural features in the Illinois basin. 

The Fairfield subbasin (a deep part of the Illinois basin) includes a zone of locally more intense 

faulting, in which three fault zones can be mapped from seismic reflection profiles. Earthquakes 

that occurred in 1974 and 1987 were within the interpreted zone of rifting beneath the Fairfield 

subbasin. Dr. McBride showed the Wabash Valley fault system as imaged on a seismic profile. A 

1968 earthquake event occurred in this region and may possibly have originated on a blind thrust 

fault. The Commerce geophysical lineament corresponds locally to disrupted geologic structures 

that may be seismogenic. The Du Quoin monocline complex was described. This monocline and 

the overlying Centralia fault zone may be an overlooked possible seismic source. Folds in this 

area provide some evidence for reactivation along an older reverse fault. The Cottage Grove fault 

system corresponds to a major crustal boundary, although the seismicity rate in the area appears 

to be low. The Fluorspar Area fault complex trends towards the New Madrid seismic zone; there 

is complexity in Fluorspar Area structures and evidence for Tertiary displacements. In his 

conclusions, Dr. McBride noted that the area where the La Salle anticline and Wabash Valley 

fault systems meet may have a high potential for fault reactivation. 

After this talk, Dr. Coppersmith invited comments from observers. The participants discussed 

improvements in data available for smaller earthquakes, including better-constrained focal 

mechanisms. The group listed Paleozoic rifts that have not been reactivated. These include the 

Birmingham graben and the southern part of the Mississippi graben; the Ouachita graben also 

may not have been reactivated, but the underlying rocks are too old to indicate this history. At 

the conclusion of the discussions, the meeting was adjourned for the day. 

F-23
DAY 2–THURSDAY, FEBRUARY 19 

Dr. Coppersmith welcomed the group to the second day of the workshop. The first talk was 

given by Dr. Roy Van Arsdale (University of Memphis) on ―Quaternary Deformation within the 

Reelfoot Rift, Rome Trough, and Wabash Valley Fault System.‖ Dr. Van Arsdale began by 

showing the location of the Mississippi embayment and its relationship to the New Madrid 

seismic zone (NMSZ); earthquakes in the NMSZ define faults in the region. He showed a cross 

section of the Reelfoot fault with ―kink bands‖ or back thrusts, as well as photos of trenches on 

the Reelfoot scarp trench. The recurrence interval for earthquakes is estimated to be 

approximately 500 years. He noted that the trench data is in good agreement with the regional 

earthquake chronology developed from paleoliquefaction features. 

Dr. Van Arsdale described displacement history and slip rate on the Reelfoot fault from the late 

Cretaceous to the present. The slip rate increased dramatically in the Holocene, indicating an 

active period of fault history, but the end of this period may be near. Seismic reflection lines 

indicate deep basement faults with as much as 3 km displacement. Trenches opened above the 

seismic reflection lines show faults with transpressive right-lateral strike-slip movement. 

Right-lateral shear across the Reelfoot rift is responsible for the NMSZ earthquakes at the 

northern end of the rift. Rift margin faults are ―big players‖ in the picture. Dr. Van Arsdale 

described features in the Shelby County and Memphis region, where liquefaction deposits (sand 

blows) and a broad fold forming an anticline are present. The anticline appears to be a tectonic 

feature formed about 400 a.d. 

Dr. Van Arsdale then described work he did many years ago in the Rome trough near the area of 

the 1980 Sharpsburg earthquake, where he focused on the Kentucky River fault system. He 

showed the log of a trench excavated in a terrace that exhibited folding and an apparent shear 

zone. He estimated the timing of fault movement as within the past 5 m.y. Next he described the 

Hovey Lake fault in the Wabash Valley fault system and the Stull trench site in Union County, 

Kentucky. He concluded his talk by showing a schematic of fault scarp evolution based on the 

information obtained from the trench. 

Mr. Robert Givler of William Lettis & Associates, Inc., gave the next talk, which was coauthored with Mr. John Baldwin. The title of the talk was ―Commerce Geophysical Lineament 

and Northwestern Margin of the New Madrid Seismic Zone.‖ The Commerce geophysical 

lineament (CGL) is a 400- to 600-km-long feature that exhibits Quaternary strike-slip and 

normal faulting along a 75 to 120 km portion of its length in the New Madrid region. Mr. Givler 

described the regional geologic setting for the CGL and the detailed studies conducted at Qulin 

Ridge. This locality contains Late Wisconsin glacial outwash deposits; seismic profiles show 

Quaternary offset along a fault, and four paleoliquefaction events have been identified. Next Mr. 

Givler described the Holly Ridge locality associated with the Idalia Hills fault. Seismic reflection 

profiles show displacement of Quaternary deposits that project upwards and correlate with 

surface geomorphic features. Trench data from the Bloomfield Hills locality on the Idalia Hills 

fault indicate two poorly constrained faulting events. Mr. Givler described trench studies for 

localities on the Commerce fault and the Penitentiary fault. The Benton Hills locality is on the 

Commerce fault, where strike-slip faulting is recognized for four late Quaternary events. The 

Quaternary-active Penitentiary fault is located in the Cache River valley. The Penitentiary fault is 

a step-over from the Commerce fault and has a prominent east-facing scarp. Seismic lines in the 

area were used to further test the hypothesis that the Penitentiary fault is a seismic source; these 

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data indicate multiple faults disrupting Pleistocene and possible early Holocene deposits. A fault 

segment 75 to 120 km in length is recognized in southeast Missouri and southern Illinois along 

the Commerce fault. A weak alignment of microseismicity is associated with this fault. Based on 

all of this data, the CGL appears to have been active into the early Holocene. The fault has long 

earthquake recurrence intervals of 5 to 10 thousand years and possibly episodic activity. 

Next, Dr. Randy Cox of the University of Memphis gave a talk titled ―Some Mississippi Valley 

Holocene Faulting and Liquefaction beyond the New Madrid Seismic Zone.‖ He began by 

discussing southeast Reelfoot rift margin surface faulting. He showed a map of the topographic 

lineament of the southeast rift margin and the locations of trenches excavated to study this 

feature. He described the Porter Gap trench site where a late Holocene earthquake was 

recognized, showing the trench logs and a shallow seismic reflection line. Structural relief and 

topographic relief are consistent with faulting. Evidence of faulting in the trenches indicated an 

event with >4 meters (m) vertical displacement and horizontal (strike-slip event) displacement of 

about 8 to 15 m. Earlier events of approximately equal magnitude were also observed in early 

Holocene deposits. Next Dr. Cox described a newly recognized sand blow field in the southern 

Mississippi embayment area of northeastern Louisiana, south of the New Madrid area, which 

was identified from an aerial photo survey. He has delineated five separate fields containing 

clusters of sand blows. A trench log across an area of sand blows, and photographs of sand blows 

were shown. The earthquakes that caused the liquefaction are estimated to be M > 6 on the basis 

of the minimum radii of the fields and on cone penetration tests in the region. Multiple events are 

indicated, and based on limited data, the earthquake recurrence rate is roughly 1,000 to 2,000 

years. The earthquake events that Dr. Cox recognizes can be correlated with multiple regional 

events that affected more than one of his five zones, or they could be related to local earthquakes 

that are separate for each zone. 

He concluded his talk by describing his studies of the Saline River fault system in the craton 

margin area of the Alabama-Oklahoma transform. Seismicity data is sparse in this region but he 

has examined many exposures containing features that suggest deformation. Seismic lines show 

Triassic grabens and flower structures that extend upward into Cenozoic deposits. The trenches 

that have been excavated show faulting in mid-Pleistocene deposits; overlying Holocene deposits 

may be warped. Paleoliquefaction features of dense sand blows have been recognized in the area, 

indicating multiple earthquake events in the late Pleistocene through the late Holocene. Dr. Cox 

believes the paleoliquefaction features were caused by local earthquakes and are not related to 

far-field events such as those in the New Madrid area to the north. 

After a break, Dr. Russell Green of Virginia Polytechnic Institute gave a talk titled 

―Paleoliquefaction Interpretation of the Vincennes Earthquake, Wabash Valley Seismic Zone.‖

Dr. Green began his talk by reviewing liquefaction phenomena. He showed photographs of 

classic liquefaction phenomena as well as video footage of liquefaction phenomena resulting 

from the 1964 Niigata, Japan, earthquake. He described a ―simplified‖ liquefaction evaluation 

procedure to assess cyclic resistance or the capacity of a soil to resist liquefaction. He described 

combinations of conditions that can be used to assess when liquefaction will or will not occur, 

related to peak ground acceleration and other factors. His work has been focused on the Wabash 

Valley seismic zone and specifically, the effects of the Vincennes earthquake that occurred 

approximately 6,100 years BP. Dr. Green has estimated the probable Mmax of this earthquake 

by using plots of the severity of liquefaction with distance from the epicenter. The method he has 

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developed to assess magnitude from data at various field sites incorporates an assessment of 

overall uncertainty. 

Dr. Green discussed constraints on seismic sources, noting that the dimensions of a source can be 

estimated by contouring maximum dike width. Distinguishing between a small local earthquake 

event vs. a large distant earthquake event is difficult. Next he discussed sources of uncertainty, 

including ground-motion predictive relationships and field interpretations. To properly assess the 

uncertainties and their influence on a back-calculated Mmax, input is needed from geologists, 

geotechnical engineers, and seismologists, depending on the information to be evaluated. Dr. 

Green then reviewed ground-motion attenuation relationship information for the CEUS and 

described alternative presentations of site amplification data. Based on his analyses, the 

Vincennes earthquake may have been an M 7.3–7.5 event, with the epicenter located within an 

area having a defined radius of about 160 km. 

In a related talk, Dr. Scott Olson of the University of Illinois at Urbana-Champagne described a 

geotechnical approach to evaluate the strength of shaking associated with liquefaction 

phenomenon. His talk was titled ―Quantifying Uncertainties in Paleoliquefaction Studies.‖ Dr. 

Olson began by reviewing existing methods for paleoliquefaction back-analysis, including the 

cyclic stress method, the magnitude bound method, and several other approaches. The cyclic 

stress method is suitable for evaluating a lower bound for a best estimate of an earthquake 

magnitude. Dr. Olson noted the variety in worldwide estimates of different magnitude bounds, 

which are a function of source characteristics, transmission characteristics (attenuation and site 

effects), and regional soil liquefaction susceptibility. To develop a magnitude bound for the 

CEUS, he examined historical earthquakes having M > ~5 and the liquefaction features 

associated with these events. He compiled the best estimates of magnitudes made by 

seismologists and then looked for the farthest-distance liquefaction features that could be 

associated with a specific earthquake. From this data he developed a CEUS magnitude bound, in 

which M 5.5 is the minimum magnitude for liquefaction at close-in locations; increasingly 

larger-magnitude events can trigger liquefaction at greater distances. 

Sources of uncertainties in liquefaction susceptibility, field observations, seismicity, in situ 

testing techniques, and the magnitude bound approach were described. Then, Dr. Olson 

discussed aging, the process by which soils develop a structure that results in improved soil 

properties (e.g., shear strength); he noted that there may not be a need to make any correction for 

aging in many cases. He described characteristics of liquefaction severity (based on size of 

liquefaction features), and the factors of safety for different levels of liquefaction severity. A 

better tool than factor of safety, however, is a liquefaction potential index that incorporates 

stratigraphy, especially the depth and thickness of potentially liquefiable layers. Dr. Olson went 

on to discuss failure mechanisms and their relationship to liquefaction resistance. He listed a 

number of sources of uncertainty in field data, including depth of groundwater at the time of an 

earthquake, and variability of geologic settings. He then illustrated his approach by using data on 

the Vincennes earthquake. For this event he has calculated Mw 7.5 + 0.3. He noted that the 

Wabash Valley work was based on the availability of abundant geotechnical field data; by 

contrast, few sites in the New Madrid seismic zone have sufficient geotechnical data for 

conducting a good back-analysis of magnitude. 

Following a lunch break, the first talk of the afternoon session was given by Dr. Eric Calais of 

Purdue University, who talked about geodetic interpretations of New Madrid rates. Dr. Calais 

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began by describing the notion of a steady-state ―elastic rebound‖ model, in which geodesy and 

paleoseismology should agree. This model works particularly well for plate boundary faults, as 

present-day strain has predictive power. Current GPS measurements indicate an upper-bound 

movement of 0.02 mm/yr at New Madrid. Dr. Calais also showed velocities measured at about 

500 sites in North America with respect to a constant reference frame. Velocity analyses on 

deformation east of the Rocky Mountains have indicated that most measured velocities are not 

significant at a 95 percent confidence level. However, patterns in velocities, especially radial 

patterns, are apparent. Residual velocities of 0.6 mm/yr have been measured in the CEUS. 

Next, Dr. Calais showed residual velocities for areas worldwide, including Europe and Australia, 

where these velocities are about 0.4 mm/yr. Velocity results have been stable over the past 5 

years, so there can be high confidence in the measured rates. Available information indicates that 

velocities of 0.2 to 0.4 mm/yr are typical of stable continental areas as an upper bound. GPS 

detects with confidence only velocities of higher than 0.5 mm/yr and strain rates of 

approximately 10–9. The New Madrid region may contain the only ―active‖ intraplate system in 

the world where a local, continuous GPS network is available. Dr. Calais discussed the varying 

levels of precision and accuracy generally obtained from the 500 GPS stations in North America, 

and specific results for the New Madrid region. In the past few years, velocity uncertainties have 

decreased by at least a factor of two at all sites; residual velocities have decreased as well. In the 

same region, there are no significant strain rates at 95 percent confidence level. 

Dr. Calais then addressed recurrence of earthquakes indicated by paleoliquefaction. Assuming 

steady-state strain accumulation and release, there is a 500-year average repeat time over 12,000 

years. Dr. Calais concluded that the current strain accumulation rate in the New Madrid region 

cannot be sustained and is not in steady state. As a counterexample, he referred to the Wasatch 

fault in Utah, where GPS and paleoseismology are in good agreement. His hypothesis is that 

some slow faults are in steady state at the 10,000-year time scale but some are not. The New 

Madrid region is not in steady state because the loading (equal to stressing) rate varies with time, 

and/or fault strength varies with time. Dr. Calais remarked that it is time to think outside the 

―rebound model box,‖ noting that the more we measure, the closer to zero we get, but the more 

we look, the more potential active faults we seem to find. Local strain accumulation may not be a 

prerequisite for large earthquakes, as perhaps earthquakes can ―tap into‖ larger-scale reservoirs 

of strain. 

Dr. Seth Stein of Northwestern University gave the next talk, titled ―Rethinking Midcontinental 

Seismicity and Hazards‖. He explained the evolution of his thinking about seismicity patterns. 

Previously he believed that focused, quasi-periodic long-term seismicity occurred in weak zones, 

but lately he has been moving toward the concept of episodic, clustered, and migrating patterns 

of seismicity. The latter suggests that the past is an extremely poor predictor of the future and 

that seismicity migrates between zones of rocks of similar strength. Dr. Stein noted that GPS 

campaigns were started in the NMSZ in 1991. Initially, fairly high rates of movement were 

expected but by 1999 the GPS results indicated essentially no motion. In 1999 he postulated that 

we could be near the end of a seismic sequence; this idea has held up over time. Maximum 

motion steadily converges to zero, as rate precision improves with longer observations. Dr. Stein 

now believes that the past 2,000 years are not representative of long-term NMSZ behavior and 

that the recent large earthquake cluster in this zone may be ending. He noted that geology 

implies NMSZ earthquakes are episodic and clustered through the Holocene; similar episodic 

patterns are seen in other continental plate regions. He stated that the NMSZ is not hot, weak, or 

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special relative to surrounding regions of the CEUS. He also discussed differences between timeindependent hazard and time-dependent hazard; the latter approach generally predicts lower 

hazard levels in the CEUS. 

Dr. Stein then asked: how we can make better progress in understanding seismic hazard? He 

believes more and better data are needed, and that the dynamics of forces, faulting, and fault 

interactions in the plate interior need to be incorporated in a model and explored in detail. He 

noted that GPS is giving constraints on effects like postglacial rebound. In his conclusions he 

noted that geodetic deformation is probably required for large earthquakes, so its absence argues 

against large earthquakes any time soon. 

Continuing on the topic of using geodetic data, Dr. Bob Smalley of the University of Memphis 

gave a talk titled ―Geodetic Interpretations of New Madrid Rates.‖ Dr. Smalley noted that his 

work was based on the same data set that was described by the previous two speakers. He began 

by noting that maps of worldwide strain rates indicate that plate boundaries have the highest 

rates, which is in good agreement with plate tectonics. Multiple occurrences of large earthquakes 

in a few areas, like the NMSZ, are not explained by either plate tectonic or rebound paradigms. 

Dr. Smalley discussed theories of how plates might deform, and the extent to which deformation 

can be recognized using GPS. He noted that in concentrated zones of deformation within inactive 

regions, it is ―challenging‖ to see this deformation with GPS. From examination of plate tectonic 

dynamics, it is clear that strain rates in stable plate interiors are bound at very low rates. The 

challenge is to detect a small signal buried in a larger signal. Dr. Smalley believes that GPS is on 

the verge of not being significant for the NMSZ, thus it is difficult to see how this zone is 

different from the rest of North America. However, just because we see nothing there now, we 

cannot say this information is significant. Within the next 10 years, better data may be obtained 

for the New Madrid region. 

Dr. Smalley went on to discuss a number of explanations for stable continental region 

earthquakes, including reactivation of zones of weakness, crustal weakening by fluids, and stress 

changes due to deglaciation or sediment loading. For the design of a continuous GPS network for 

the NMSZ, local, crustal, and regional scales were considered in the placement of monuments. 

Questions about monument stability were acknowledged and are related to factors that include 

water level changes in the Mississippi River, and the rise and fall of groundwater levels due to 

pumping. A longer time period and a larger number of stations providing higher density and 

redundancy are needed to collect data. Dr. Smalley then gave GPS results for other stable 

continental regions in the United States, Europe, and India: rates are low, but in general there are 

few stations in these stable areas. He believes that short-term geodetic signals should be 

integrated with long-term geologic deformation rates. In his conclusion he noted that GPS will 

continue to improve, but both denser sampling at the scale of seismic structures and longer 

observation times are needed. 

Following a short break, Dr. Mark Zoback of Stanford University gave a talk titled‖ Intraplate 

Stress and Strain in the Central and Eastern United States and Their Relation to Intraplate 

Seismicity.‖ The work he has conducted indicates relatively uniform stress orientations across 

complex geologic boundaries. He noted that during the past several years (since the last World 

Stress Map effort) there has been little progress on mapping intraplate stress in the CEUS, but for 

the CEUS SSC project he has gathered the new stress information available and plotted it. He 

showed a series of Google Earth photographs with the stress data plotted, and discussed the new 

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data, including 38 earthquake focal mechanism data points. In the New Madrid area the new 

stress data indicates strong east-to-west trends, whereas the surrounding craton and eastern 

margin shows dominantly northeasterly stress directions. This area may have an anomalous crust 

and upper mantle structure in which the viscosity of the upper mantle may be lower than that of 

the surrounding mantle, thus leading to stress rotation. 

Next, Dr. Zoback reviewed focal mechanism data for recent earthquakes, including the 2002 Mw 

Caborn earthquake in the Wabash area, which had slip on a west-northwest plane consistent with 

east-to-west stress. He noted that with uncertainties incorporated, significantly different results 

could be obtained, and additional well-constrained data are needed. The characteristics of New 

Madrid seismicity were then reviewed. Dr. Zoback. discussed the hypothesis that the retreat of 

the glacial ice sheets triggered Holocene earthquakes. The use of a localized weak-mantle model 

indicates there will be concentrated deformation locally for tens of thousands of years, as that is 

the amount of time needed for the mantle to recover. Dr. Zoback concluded by asserting that the 

New Madrid region is unique and that he believes earthquake recurrence rates are not likely to 

change in the near future. 

Dr. Coppersmith opened the workshop to questions from all participants. After further discussion 

about New Madrid seismicity, the association of earthquakes with glacial unloading, stress 

accumulation in the crust vs. the mantle, and other topics, Dr. Coppersmith commented that these 

topics could be discussed again on Day 3 of the workshop. He thanked all the presenters and 

noted that the meeting would reconvene the following morning. 

DAY 3–FRIDAY, FEBRUARY 20, 2009 

Dr. Coppersmith welcomed the workshop participants to the third and final day of the workshop. 

The first talk of the day was by Dr. Martitia (Tish) Tuttle of USGS and was titled ―Clustered 

Model for New Madrid Earthquakes.‖ Dr. Tuttle began with a review of the timing, location, 

magnitude, and recurrence times estimated for New Madrid region paleoearthquakes. She 

described evidence for paleoliquefaction, noting that sand blows usually provide the best 

opportunities to provide minimum and maximum age estimates for paleoearthquakes because 

they may contain in situ materials (e.g., charcoal, sticks) that can be dated. Dating methods 

include radiocarbon and OSL (optically stimulated luminescence) dating, artifact analysis, and 

dendrochronology; age date uncertainties can range from + 1 to 1,000 years. The New Madrid 

earthquake chronology based on paleoliquefaction has age estimate clusters at 1450 a.d., 900 

a.d., and 2350 b.c. Independent paleoseismic studies have provided data that support these event 

ages. Dr. Tuttle believes the clusters formed during very large New Madrid–type events. In 

addition to the 1811–1812 New Madrid earthquakes, possible analog events include the 2001 M 

7.6–7.7 Bhuj, India, earthquake. Available information suggests the New Madrid region 

earthquakes have an approximately 500-year repeat time. Clustered earthquakes (i.e., separated 

by days or months) are indicated by stratigraphic information associated with sand blows. 

Dr. Tuttle reviewed all the paleoseismology information available for the Reelfoot Rift. Faults in 

the rift region were active at different times during the past 5,000 to 15,000 years; the most 

recent earthquake activity in the migration pattern is focused on the New Madrid region. She 

went on to discuss negative evidence for paleoearthquakes. Certain conditions need to be present 

(e.g., loose and sandy sediments, water-saturated conditions, and good exposures of older 

deposits) to conclude that liquefaction could have occurred; however, even if these conditions 

F-29
are met and no liquefaction features are found, the occurrence of earthquakes cannot be ruled 

out. Next, Dr. Tuttle discussed studies in the Charlevoix seismic zone. Three generations of 

liquefaction features within the past 10,000 years were identified along rivers in this region. 

These features were likely produced by earthquakes of M > 6.2. In the Quebec City–Trois 

Rivieres region, which is located in a historically seismically quiet part of the St. Lawrence 

Valley, similar river exposures were examined but no paleoliquefaction features were found; 

however, the occurrence of paleoearthquakes cannot be ruled out. 

The following talk by Dr. Shelley Kenner was titled ―New Madrid Model for Repeated Events: 

Geodetic Signature along the Southeast Margin and Elsewhere.‖ Dr. Kenner began by reviewing 

intraplate seismicity, noting that the majority of knowledge of earthquake physics has been 

developed from plate boundary regions. She then noted key differences between intraplate and 

plate boundary regions with respect to the (1) kinematics and temporal characteristics of 

seismicity; (2) reason for stress localization; and (3) source of stress that drives seismicity. She 

reviewed reasons for stress accumulation along faults and described the crustal stress cycle that 

consists of localized loading, coseismic rupture, postseismic relaxation, and associated localized 

loading that induces clusters of earthquakes. She also reviewed aspects of the NMSZ, 

emphasizing the location above a failed rift that has been reactivated repeatedly, and the increase 

in seismicity during the Holocene. 

Dr. Kenner discussed aspects of weak zone model behavior and the question of whether such a 

zone could be present in regions of concentrated intraplate seismicity. Triggers for seismicity 

may include glaciation and sedimentation in the Mississippian embayment. Dr. Kenner then 

spoke about weak zone relaxation and described aspects of associated seismicity over time, 

including earthquake recurrence intervals. Analyses have indicated that the total duration of 

transient relaxation processes is very long and may last more than 20 times longer than the 

characteristic relaxation time of weak zone material even though surface deformation rates are 

low. To examine the temporal evolution of where shear zones take place, three-dimensional (3-

D) weak zone models were developed and their behavior assessed. Total plastic strain plots show 

that with increasing time, shear zones move toward weak zone boundaries. In summary, stress 

loading from an underlying weak zone is a physically plausible mechanism for earthquake 

generation. Sequences of earthquakes due to weak zone relaxation may be triggered by 

temporally variable localized stress transients 

Dr. Coppersmith asked Dr. Stein and Dr. Zoback for their thoughts about Dr. Kenner’s model. 

Dr. Stein commented that if the New Madrid region is special or representative of a large number 

of faults everywhere, then does that indicate a weak zone is present under each of the many 

places where large intraplate earthquakes have occurred? Many crustal faults are known and he 

dislikes the concept of having to associate a weak zone with each of these faults. Dr. Zoback 

indicated that he agreed with Dr. Stein in terms of the global implications of Dr. Kenner’s model. 

He noted that conceptually, Dr. Kenner’s model is similar to other models proposed to explain 

the Holocene record of earthquakes in the New Madrid region, and it would satisfy the other 

criteria that are unique to New Madrid, such as the absence of a geodetic signature and the small 

amount of cumulative deformation. He suggested exercising caution in applying models too 

broadly. 

Dr. Alessandro Forte of the University of Quebec at Montreal gave the next talk, titled ―Physical 

Processes Occurring in the Mantle under the EUS and Their Implications for Surface Stress and 

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Deformation.‖ He noted that plate tectonics is a 3-D process, in which deep-seated forces that 

drive horizontal motions also drive substantial vertical displacements that contribute to crustal 

stress. Vertical motions, however, are below the current level of resolution of GPS. Dr. Forte 

reviewed several previously proposed dynamic models of the origin of stress and seismicity in 

the NMSZ. He then showed his work on tomographic imaging of the shallow mantle structure 

below North America. In the past five years he has been working on modeling present-day 

mantle flow dynamics in fully global calculations of mantle flow. His tomography-based mantle 

convection model successfully predicts plate velocities and observations of surface gravity and 

topography on the North American Plate. 

With viscosity structure and driving forces available, the differences in direction of 

subcontinental mantle flow at various depths can be evaluated. Dr. Forte showed a cross section 

of mantle flow below the CEUS that indicates downward movement (flow foundering) beneath 

the New Madrid and Mississippi region at depths below approximately 400 km. He showed a 

map of mantle-flow-induced horizontal tractions on the crust in the region of NMSZ. He noted 

that the Mississippi Valley region is being pulled down dynamically because of drag from the 

descending Kula-Farallon slab below. Descent of the slab into the lower mantle induces a region 

of maximum horizontal flow convergence and maximum compressive surface stresses directly 

below the CEUS oriented in a northeasterly direction. Stress directions are modeled as the same 

along the eastern margin of the continent, but their amplitude is lower. These stresses are 

generated on mantle-convection time scales, which are on the order of millions of years and can 

therefore support long-lived seismicity. Dr. Forte showed a video of time-dependent mantle 

dynamics and surface flexure (topography) over the past 30 million years. He noted that mantleflow-induced surface depression and associated bending stress may be an important and longlived contributor to the clustered and migrating seismic activity in the Mississippi Basin, 

extending from the Great Lakes to the Gulf of Mexico. 

Following a short break, Dr. Martin Chapman of Virginia Polytechnic Institute spoke about 

seismicity in the southeastern United States in a talk about the Eastern Tennessee and Charleston 

fault models. The Eastern Tennessee seismic zone (ETSZ) is the most seismically active area in 

the Southern Appalachians. Seismicity in the zone is associated with a major potential field 

anomaly known as the New York–Alabama lineament. Dr. Chapman reviewed key findings of 

previous studies of Eastern Tennessee seismicity. He showed maps that indicated correlation of 

NOAA magnetic data and Bouguer gravity data with earthquake epicenters in the southern 

Appalachian region. From focal mechanism data, earthquake epicenters are northeast trending 

and many appear to be aligned along a north-dipping plane. Studies indicate that earthquakes are 

occurring in response to a highly uniform regional stress, with strike-slip motion predominant. 

The New York–Alabama lineament marks an abrupt boundary between zones of different 

seismicity; however, the geologic nature of this feature remains a mystery. 

Dr. Chapman then talked about seismicity in the Charleston area, noting liquefaction features 

and the identified earthquake epicenters. Greggs Landing on the Ashley River is the focus of 

current seismicity and is also the location of strong shaking in the 1886 Charleston event. A 

seismic reflection profile in this area provides clear evidence of Cenozoic reactivation of 

Mesozoic extensional faulting. In the Summerville area, seismic profiles show possible faulting 

of Cenozoic sediments to shallow depths in close proximity to a strong magnetic gradient. Dr. 

Chapman also showed COCORP lines that indicate a faulted Mesozoic section underlying the 

Summerville and Charleston region. The imaged faulting in these areas is within the zone of 

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modern earthquake activity. Dr. Chapman concluded his talk by saying that progress in 

understanding the seismicity of this area requires a long-term commitment to secure precision 

hypocenter locations and focal mechanism determinations. 

Following a lunch break, Dr. Pradeep Talwani of the University of South Carolina gave a talk 

titled ―The Source and Magnitude of the Charleston Earthquakes.‖ He began by describing the 

revised tectonic framework for the region that he and his colleagues have developed. He showed 

a map of seismicity from 1974 to 2004 and the varied focal mechanisms associated with these 

events. Earthquakes were relocated to develop the revised tectonic framework that shows a series 

of faults, which he showed projected onto a series of cross sections. Dr. Talwani described 

structural features in the region, including the uplifted zone of river anomalies (ZRA) and the 

East Coast fault system (ECFS). Results of the new seismotectonic framework indicate that 

seismicity is occurring primarily at the compressional left step within the southernmost segment 

of the ECFS. Dr. Talwani discussed paleoliquefaction studies that indicate seven separate 

earthquake events. Using his new work, he can link these events to faults. He described offset in 

the thick walls of Fort Dorchester during the 1886 earthquake event. A trench was excavated on 

the projection of the fault that offset the fort walls. Although the fault was not seen in the trench, 

a sand blow was revealed. Age dating indicated the sand blow formed in a pre-1886 event. 

Geotechnical data, including piezometer tests and cores, were collected in the area. Using these 

data, the magnitude of the earthquake was back-calculated to be ~M 6.2. 

Next Dr. Talwani reviewed results of GPS studies in the Charleston region. Delaunay triangle 

modeling indicates that the strain rate in the vicinity of Charleston is high. Dr. Talwani showed 

magnitude estimates for the 1886 Charleston earthquake from intensity data; the latest value is M

6.9. He also provided a list of magnitudes of prehistoric regional earthquakes associated with 

liquefaction from in situ SPT (Standard Penetration Test) data. In his conclusions, Dr. Talwani 

noted that the 1886 Charleston earthquake and seismicity that is currently being recorded are 

related to the Woodstock fault and associated faults at a compressional left step in the Middleton 

Place–Summerville seismic zone. He believes that only this southernmost segment of the ECFS 

is seismically active and poses a seismic hazard. 

The next talk, titled ―Seismotectonic Setting and Seismic Sources of the Northern Gulf of 

Mexico,‖ was given by Mr. Michael Angell of William Lettis & Associates. Mr. Angell began 

by stating that although the Gulf of Mexico region has generally low seismicity, three 

earthquakes having Mb > 4.5 (Mw 5.8 was the largest) occurred in the northern Gulf in 2006. 

Causative mechanisms for these earthquakes were a topic of his talk, and he proceeded to 

describe the historical seismicity, bathymetry, and stress indicators in the Gulf region. He noted 

that numerous growth faults (faults driven by gravitational forces) are located above salt diapirs 

(mobile salt beds). Then he reviewed the information available on the 2006 earthquakes. Two of 

these events occurred within an area containing growth faults. 

Next Mr. Angell reviewed the tectonic setting of this region. Interpretations of the tectonic 

history indicate that a block of oceanic crust was emplaced in the late Jurassic. Oceanic crust can 

be delineated on seismic lines and with gravity and magnetic data. Mr. Angell described different 

models that show the distribution of the oceanic crust in the Gulf of Mexico. Some of the largest 

recorded earthquakes occurred within this crust. Large, northwest-southeast-trending fracture 

zones are located to the east of the earthquakes. Turning to a discussion of seismic source models 

for the Gulf, Mr. Angell reviewed existing alternative models for seismic hazard. Apparent 

F-32
alignments of seismicity suggest a possible underlying source and association with deep 

structure. 

Mr. Angell went on to describe growth fault settings and the associated seismicity. He discussed 

aspects of the February and April 2006 earthquakes, which have been modeled as gravity-driven 

on a shallow-dipping plane. He noted that the most appropriate model for the Gulf may be twolayered, having shallow seismic sources in growth fault areas and deeper seismotectonic sources 

in the basement. He discussed the possibility of a link between upper and lower faulting, 

mentioning that a trigger could originate from an event in either the upper or lower zone. He 

concluded by stating that earthquakes associated with growth faults have limited depth extent (to 

about 5 km), are ―slow‖ (i.e., they do not radiate high-frequency energy), and have low 

magnitudes (M < 5); therefore they may not be significant in seismic hazard assessments. 

The next talk was given in two parts by Dr. Mark Peterson and Dr. Chuck Mueller, both of the 

U.S. Geological Survey. Dr. Petersen spoke first in a talk titled ―2008 USGS Seismic Source 

Model for the Central and Eastern U.S.‖ The national hazard maps released in April 2008 were 

based on the 2002 and 2006 USGS models. Dr. Petersen briefly described some of the changes 

made for the 2008 CEUS model, including development of maximum magnitude distributions 

for seismicity. He reviewed New Madrid and Charleston area site-characterization details. 

Branches of a logic tree were used to evaluate fault rupture models (clustered and unclustered), 

location uncertainty, recurrence intervals, and Mmax alternatives. To obtain alternative Mmax, the 

recorded M 7.1 to 7.7 magnitudes of earthquakes in stable continental regions worldwide were 

considered. 

During the second part of the talk, Dr. Mueller focused on how seismicity was used in the USGS 

seismic hazard model. His talk was titled ―Hazard from Seismicity: the USGS Approach.‖ He 

listed organizing principles for the hazard model: specific fault sources considered, historical 

seismicity gridded and smoothed, and large background zones defined based on geologic criteria. 

He described the various zones delineated on the hazard map and what earthquake catalogs were 

used, and he addressed regional completeness levels and b values. He reviewed how historical 

seismicity was gridded based on analyses from four different models, and he showed example 

results of smoothed seismicity for the different models used. He noted that gridded seismicity 

models are essentially a localized, variable b-value model. Dr. Mueller concluded his talk by 

describing seismic hazard studies previously conducted for the CEUS and associated hazard 

assessed for selected nuclear power plant sites. 

With the workshop’s technical talks completed, Dr. Coppersmith commented on the path 

forward for the project. He showed the task schedule and described the work to be completed in 

the next few months. The tasks include constructing the preliminary SSC model, compiling the 

seismicity catalog, and completing preliminary hazard calculations and sensitivity analyses that 

will be presented at Workshop 3. Dr. Coppersmith then thanked the presenters and 

complimented them on the high professional level of their interactions. 

Mr. Salomone closed the meeting with several remarks. First he described the role of the 

Participatory Peer Review Panel (PPRP) and their review relationship with the TI team. He 

acknowledged the members of the PPRP, beginning with the co-chairs, Drs. Carl Stepp and 

Walter Arabasz. Then he acknowledged the participation at the workshop of the international 

observers as well as the younger professionals, who will ultimately take over the process of 

hazard assessment. He thanked EPRI for its support of the workshop. Finally, he observed that 

F-33
the original vision of what the workshop organizers had hoped would occur had, indeed, 

happened. 

REFERENCES 

Bernreuter, D.L., J.B. Savy, R.W. Mensing, and J C. Chen. 1989. “Seismic Hazard 

Characterization of 69 Nuclear Plant Sites East of the Rocky Mountains,” Report NUREG/CR5250, Vols. 1–8, prepared by Lawrence Livermore National Laboratory for the U.S. Nuclear 

Regulatory Commission. 

Budnitz, R.J.; G. Apostolakis, D.M. Boore, L.S. Cluff, K.J. Coppersmith, C.A. Cornell, and P.A. 

Morris. 1997. Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on the 

Uncertainty and Use of Experts, NUREG/CR-6372. Two volumes. U.S. Nuclear Regulatory 

Commission, Washington, D.C. 

Electric Power Research Institute and Seismicity Owners Group (EPRI-SOG), 1988. Seismic 

Hazard Methodology for the Central and Eastern United States, Technical Report NP-4726-A, 

Vols. 1–10.

Johnston, A.C., Coppersmith, K.J., Kanter, L.R. & Cornell, C.A. 1994: The Earthquakes of 

Stable Continental Regions. Volume 1, Assessment of Large Earthquake Potential. 

Electric Power Research Institute (EPRI) TR-102261-VI, v. 1. 

F-34
Table 1: 

Key Questions and Topics That Workshop 2 Presenters Were Asked to Address 

Topic Presenter Questions/Topics to Address at WS2

Geodetic observations in St. Lawrence and 

implications to Mmax; big picture tectonic framework; 

limits of glacial rebound

Mazzotti, Stephane What criteria should be used to define seismic sources?

Do glacial rebound processes influence seismicity (rates-focal 

mechanisms) and should this be considered in defining seismic 

source zones? 

What are rates and uncertainties on geodetic observations? What is 

geographic area of coverage for geodetic observations? 

What is your confidence that observed geodetic rates reflect longterm tectonic deformation rates or short term seismicity pattern and 

rates? 

What weight would you give geodetic vs seismicity in establishing 

rate of EQ occurrence?

Size of 1663 Charlevoix earthquake; treating St. 

Lawrence seismicity zones as aftershocks

Ebel, John What is your confidence that current patterns of seismicity represent 

aftershocks from large historic or prehistoric events? What maximum 

magnitude range and source zone geometry would you assign to 

sources in the St Lawrence-Charlevoix area? 

Use of seismicity to define seismic sources, 

application in the eastern North America region.

Kafka, Alan What approaches should be used to capture uncertainty in 

stationarity of seismicity with regard to defining seismic sources? 

Use of geological structures and assessing Mmax for 

Canadian nationa hazard maps

Adams ,John What methodology is being used to define Mmax distributions for 

source zones? 

What is the Canadian perspective on the limitations of the Johnston 

et al. (EPRI) approach and prior distributions? 

What are reasonable worldwide analogs for stable continental regions 

appropriate for CEUS and Canada? 

F-35
Topic Presenter Questions/Topics to Address at WS2

Seismicity and potential faults in NYC, Pennsylvania, 

Ohio, New England

Seeber, Leonardo 

(Nano)

What are reasonable criteria for defining seismic source zones in NE 

US? 

Previous models have used hotspot tracks, onshore extensions of 

older transforms, evidence for reactivated structures along the Fall 

Zone and Mesozoic rift basins—are these still valid concepts? 

What is your preferred causative mechanism for seismicity in the 

region? 

What is your preferred seismic source model (geometry, Mmax) for 

the NY region?

Ouachita, sub-detachment structures Thomas, Bill What is the influence of any of older structures (e.g., Iapetan 

transforms) are present seismicity. 

What is the evidence for reactivation of these structures in the 

Mesozoic? 

What is your confidence that the Ouachita basement structure 

represents a seismogenic source?

Rift structures in the mid-continent (Rough Creek 

Graben, Rome Trough, East Continent rifts)

Drahovzal, James Is there evidence to suggest that the Rough Creek and Rome Trough 

may be continuous features? 

Is there any evidence of Mesozoic reactivation of either structure? 

What is the relationship of the East Continent gravity high to the 

Rome Trough and to regions of elevated seismicity in Eastern 

Tennessee? 

F-36
Topic Presenter Questions/Topics to Address at WS2

Integration of seismic reflection, geopotential field, 

and subsurface information in southern Illinois Basin

McBride, John Previous publications suggest that moderate earthquakes (like the 

1968 event may have occurred on thrust faults in the basement? 

What if any structural relationship is there between these structures 

and the Commerce Geophysical lineament? 

Is there sufficient evidence to model other structures such as the 

DuQuoin monocline as potential fault sources? 

What are your thoughts on the distributed paleoliquefaction ‘energy 

centers’—is there other geologic information to suggest local sources 

of moderate events or are these features more likely due to more 

distant larger magnitude events? 

Should the faults in the Flurospar Area complex region be modeled 

as independent active faults in the current tectonic environment and if 

so, what are your thoughts on the timing, maximum magnitude, and 

recurrence of events on these structures?

Margins of Reelfoot and update on Kentucky River 

fault zone

Van Arsdale, Roy What are the constraints on the continuity and length of possible fault 

sources along the margins of the Reelfoot rift? Are there 

paleoseismic data that can be used to estimate Mmax? 

Is there evidence of paleoliquefaction associated with events on the 

margin fault sources? 

Please comment on the southern continuation on potential continuity 

of the NM and Saline River source zones.

Commerce lineament and northwest boundary of New 

Madrid

Baldwin, John What data is available to constrain or estimate Mmax for fault-specific 

sources along the northwestern margin of the Reelfoort rift? 

What is the extent, origin, and seismogenic potential of the 

Commerce Geophysical lineament?

Saline River and Reelfoot Rift Cox, Randy What are the uncertainties in the timing and relationships of 

paleoliquefaction events in the Saline River area relative to the 

central part of the NMSZ? 

Please comment on the southern continuation or potential continuity 

of the NM and Saline River source zones. 

Have you identified a tectonic feature as a potential seismic source 

responsible for observed liquefaction in the Saline River area?

F-37
Topic Presenter Questions/Topics to Address at WS2

Geotechnical evaluation of the Vincennes event in 

southern Illinois

Green, Russell How can this analysis be used to constrain the dimensions of the 

Vincennes earthquake seismic source? 

Can you use similar approaches to evaluate smaller energy centers 

that have been identified elsewhere in southern IL and IN—i.e., what 

methods can be used to assess the issue of local small events versus 

larger more distant earthquakes? What is your uncertainty in using 

liquefaction to assess Mmax? 

Magnitude bound relation for the Wabash Valley 

seismic zone; Geotechnical analysis of paleoseismic 

shaking using liquefaction effects

Olson, Scott What are limitations of the magnitude bound approach? 

What is your uncertainty in using liquefaction to assess Mmax? What 

Mmax would you assign to NM, Charleston, Wabash, based on 

paleoliquefaction observations? 

Please comment on the minimum magnitude required to generate 

liquefaction? 

Geodetic interpretations of New Madrid rates Calais, Eric What is your confidence that observed geodetic rates reflect longterm tectonic deformation rates or short term seismicity pattern and 

rates? 

What weight would you give geodetic vs seismicity in establishing 

rate of EQ occurrence? 

Do current data allow one to discern tectonic rates from 

measurement uncertainties?

Rates and recurrence in New Madrid Stein, Seth What is the relationship between geodetic deformation and 

earthquake occurrence? 

Have you compared the geodetic signature of other zones of 

seismicity in stable continental regions? 

Is the absence of evidence for geodetic deformation a definitive 

indicator of future earthquake potential?

Geodetic interpretations of New Madrid rates Smalley, Bob What is the relationship between geodetic deformation and 

earthquake occurrence? 

How do you relate relatively short-term geodetic deformation rates to 

longer-term geologic deformation rates? 

Have you compared the geodetic signature of other zones of 

seismicity in stable continental regions?

F-38
Topic Presenter Questions/Topics to Address at WS2

Update of stress map, strain localization, New Madrid 

rates

Zoback, Mark Do available stress and strain data provide sufficient resolution to aid 

in defining local source zones? 

What is the cause of stress of intraplate stress? 

What are mechanisms to localize stress? 

Are observed rates of historic and prehistoric seismicity consistent 

with observed stress and strain rates?

Clustered model for New Madrid events Tuttle, Tish What are the resolution issues for identifying individual events and 

estimating the size of such events? 

What is your confidence that the regional absence of liquefaction in 

susceptible deposits reflects an absence of large magnitude (>6) 

earthquakes?

New Madrid model for repeated events; geodetic 

signature along the southeast margin and elsewhere

Kenner, Shelley What are likely triggering events? 

Is the absence of a significant geodetic signal across the NMSZ 

consistent with this model? 

What are implications of the model for future large magnitude 

earthquakes (location, timing)?

Physical processes occurring in the mantle under the 

Eastern US and their implications for surface stress 

and deformation

Forte, Alessandro Do mantle processes influence current seismicity? 

Can these patterns be used as criteria for defining seismic source 

zones? 

Do mantle processes occur at rates that should influence short term 

(10-1) or long-term (10-3) seismicity? 

What is your confidence that available heat flow data can be used to 

detect mantle anomalies?

F-39
Topic Presenter Questions/Topics to Address at WS2

Update on eastern TN and Charleston; fault model for 

these sources

Chapman, Martin Please comment on your interpretation of the causative mechanism 

for the events in ETSZ? 

Do current seismicity analyses support previous models of 

alignments of seismicity as potential fault sources? 

What is the influence of the NYAL lineaments on patterns of 

seismicity? 

Are there unique conditions (fluid pressures, basement rocks, etc.) 

that distinguish ESTZ from other seismically active regions of the 

Appalachians, (i.e., Giles Co.)? 

Is there any current new information that can be used to assess 

Mmax? 

Please comment on your interpretation of the causative mechanism 

for the Charleston earthquake?

The source and magnitude of the Charleston 

earthquakes

Talwani, Pradeep Please comment on your interpretation of the causative mechanism 

for the Charleston earthquake? 

Is there evidence to suggest that the tectonic features (i.e., 

Woodstock fault, and related thrust faults in the step over regions) 

that appear to be likely candidates for the source of the repeated 

large magnitude Charleston events extend along the full length of the 

postulated ECFS-S? 

Approaches Used to Identify and Evaluate 

Neotectonic Features in Appalachian 

Piedmont/Coastal Plain Setting

Pazzaglia, Frank What influence if any do the broad regional flexures have on current 

patterns of seismicity? 

Should these features be explicitly considered in defining seismic 

sources? 

Please comment on your interpretation of the causative mechanism 

for earthquakes in the northeastern US? 

Gulf coast faulting and seismicity Angell, Mike Please comment on your interpretation of the causative 

mechanism(s) for earthquakes in the Gulf?

F-40
Topic Presenter Questions/Topics to Address at WS2

Seismic source model for the US National Hazard 

maps

Peterson, Mark Current modeling tools (smoothed seismicity) reduce the need for 

using discrete seismic source zones to capture areas of elevated 

seismicity. 

Please comment on what characteristics (i.e., Mmax) would warrant 

defining a separate source zone? 

F-41
WORKSHOP 3: FEEDBACK 

August 25-26, 2009 

Electric Power Research Institute 

3420 Hillview Ave. 

Palo Alto, California 94304 

The Workshop on Feedback was the third in a series of workshops jointly sponsored by the 

Electric Power Research Institute (EPRI) Advanced Nuclear Technology (ANT) Program, U.S. 

Nuclear Regulatory Commission (NRC), and U.S. Department of Energy (DOE) in support of 

the Central and Eastern United States (CEUS) Seismic Source Characterization (SSC) for 

Nuclear Facilities Project. The objective of the CEUS SSC is to develop a comprehensive and 

up-to-date SSC for a probabilistic seismic hazard analysis (PSHA) that is appropriate for use at 

any site in the CEUS. The technical integration (TI) team and TI staff are charged with 

developing a seismic source model that captures the knowledge and uncertainties within the 

larger informed technical community. 

The goals of this workshop were as follows: 

Review the progress of the project in terms of meeting key milestones, such as the database 

development and earthquake catalog. 

Review the processes being followed to attain the SSHAC goal of capturing the informed 

technical community. 

Discuss the seismicity catalog developed for the CEUS SSC project. 

Discuss the seismic source characteristics of the SSC sensitivity model. 

Present feedback to the TI team and staff in the form of SSC sensitivity analyses and hazard 

sensitivity analyses. 

Identify the key issues of most significance to the SSC models. 

Discuss the analyses being conducted related to hazard significance. 

Discuss the path forward for the CEUS SSC project. 

These goals were accomplished by a series of presentations and discussions. 

DAY 1–TUESDAY, AUGUST 25 

Workshop participants were welcomed by Mr. Frank Rahn (EPRI), who reviewed workshop 

logistics. Mr. Lawrence Salomone, project manager for the CEUS SSC project, then welcomed 

workshop participants and thanked them for attending. He reviewed the project goals: 

Replace the previous EPRI Seismicity Owners Group (EPRI-SOG) and Lawrence Livermore 

National Laboratory (LLNL) seismic hazard studies that were conducted in the 1980s (EPRISOG, 1988; Bernreuter et al., 1989). 

Capture the knowledge and uncertainties of the informed scientific community using the 

SSHAC process (documented in NUREG/CR-6372; Budnitz et al., 1997). 

F-42
Present a new CEUS SSC model to the NRC, DOE, and others for review. 

Next Mr. Salomone showed a map of the study area and the demonstration sites used for 

sensitivity analyses for the project. He reviewed the topics of the previous two workshops, noting 

the contributions of numerous resource experts, and went over the goals of Workshop 3. He also 

described communications with the Participatory Peer Review Panel (PPRP) and project and 

tracking milestones. The project appears to be on track to meet the target completion date in 

December 2010. 

Dr. Kevin Coppersmith (Coppersmith Consulting, Inc.), the lead of the TI team, then welcomed 

the workshop participants. He began by reviewing aspects of the SSHAC project, including basic 

principles for a PSHA, key attributes of the process, and expert roles. He reviewed the purpose 

and goals of Workshop 3. The TI team has developed a sensitivity SSC model that is complete in 

that it captures the range of views in the technical community, but the TI team has not devoted a 

lot of effort to weighting the alternative branches of the model until they see the results of the 

sensitivity analyses. Sensitivity analyses to be presented in the workshop will allow 

understanding of the importance of key assessments of most significance to the SSC models. Dr. 

Coppersmith clarified that a draft data summary package—consisting of the Data Summary and 

Data Evaluation Tables—completed prior to the workshop and distributed to PPRP members is a 

―work in progress‖ (i.e., it is incomplete and subject to revision). Nonetheless, he noted that the 

data evaluation process was conducted with a focus on identifying and evaluating the data, 

models, and methods that have credibility. By understanding the potentially important elements 

of the SSC model, subsequent work for the CEUS SSC can be prioritized. 

Dr. Coppersmith went on to give a talk titled ―SSHAC Goal of Capturing the Informed Technical 

Community.‖ He explained that the talk is based on his experience both from being a SSHAC 

member and from subsequently implementing SSHAC processes during the years since the 1997 

SSHAC study was completed. After giving a brief historical context to probabilistic risk studies 

and the use of expert assessments, he noted that there has been increasing recognition of the 

importance of uncertainties. Probabilistic hazard is important to risk analysis, and uncertainties 

are important to hazard, thus quantifying uncertainties is an important aspect of the analysis. Dr. 

Coppersmith stated that more stable estimates of hazard are obtained by incorporating the range 

of views within the expert community. Based on this knowledge, there has been increased 

attention to concerns about expert issues, including representativeness, independence, consensus, 

and aggregation. Of particular importance have been strategies to deal with potential outlier 

judgments that may have a disproportionately large influence on results. 

Dr. Coppersmith described the SSHAC concept of integration as capturing the view of the 

informed technical community (ITC). (Being ―informed‖ in this case refers to being familiar 

with site-specific databases as well as participating in the SSHAC interactive process.) He stated 

that integration is not just an aggregation process for parameter values across a panel of experts, 

as very few parameters can be directly assessed in PSHA. Instead it is necessary to evaluate data, 

develop models, and quantify uncertainties. Obtaining a composite, or community, distribution is 

the most important objective of consensus in the SSHAC process. 

Dr. Coppersmith described the steps taken in the CEUS SSC project to ensure that the views of 

the ITC have been captured. All participants understood their roles and agreed to abide by them 

within the framework of the SSHAC process. The TI team and staff, as well as members of the 

PPRP, have first-hand knowledge of data sets, reflecting their extensive experience in SSC for 

F-43
the CEUS. They have developed and are using explicit data evaluation processes to demonstrate 

a thorough awareness of all applicable data. Dr. Coppersmith noted that the interactive workshop 

processes used have proven to be a highly effective mechanism for identifying all available data 

and models that presently exist or are under development. In addition, he noted that the TI team 

and staff have expertise with the integration process. He said steps are in place that will ensure 

that the views of the ITC are reflected in the final results of the CEUS SSC project. 

Dr. Coppersmith then gave a case history for the CEUS SSC project and traced the 

documentation in place to date. The case history was about the work of Drs. Eric Calais and Seth 

Stein, both of whom made presentations at Workshop 2, who suggested a lack of deformation in 

the New Madrid seismic zone and the potential that the zone will not be seismically active in the 

future. Dr. Coppersmith showed the questions they were asked to address in their talks, as well 

as a photograph of them as workshop participants, slides from their presentations, text included 

in the Workshop 2 summary and in a letter from the PPRP, text in a data summary table, and the 

logic tree used to model the hazard associated with the New Madrid fault source. He noted that 

the full documentation of the evaluations made by the TI team and the justification for all 

elements of the final SSC model will be part of the project final report. Dr. Coppersmith 

concluded his talk by stating that the SSHAC study will provide approaches that are instrumental 

in achieving the goal of capturing the views of the ITC. These approaches have been followed in 

the CEUS SSC project and they provide reasonable assurance that the ITC has been captured. 

Workshop participants then discussed such concepts as ―range of the technical opinions that the 

informed technical community would have,‖ outlier judgments, and reasonable assurance. 

Regarding range of opinions, sensitivity studies are useful for showing when an analysis input 

has little or no hazard significance. There has been a gradual move away from a when-in-doubtput-it-into-the-analysis approach and toward more careful consideration of whether or not an 

input is credible (e.g., tails on distributions that extend to infinity), as these approaches affect 

computational efforts and analysis results differently. 

Workshop participants also discussed the possible subjectivity inherent in efforts to limit outlier 

views by promoting evaluator roles instead of proponent roles for expert inputs. A representation 

of the distribution of community judgments, as represented by the ITC, is the goal of the SSHAC 

process and underlies the importance of the evaluator role. Finally, the group addressed the 

concept of reasonable assurance as an accepted standard for safety decision making, based on 

meeting standards of practice. A member of PPRP and others at the workshop believe that the 

SSHAC process, if properly implemented, goes beyond the standard of preponderance of 

evidence in assuring that the views of the ITC have been considered and represented. 

Following a short break, Dr. Robert Youngs (AMEC Geomatrix, Inc.) gave a talk on 

development of the CEUS SSC earthquake catalog. A preliminary earthquake catalog was 

completed for use in preparing the sensitivity analyses. Dr. Youngs reviewed the catalog 

development beginning with compilation of earthquakes from available existing catalogs, 

through the process of declustering, noting that the approaches used for several of these steps 

were initially used for the EPRI-SOG study. The primary earthquake catalogs used for the 

compilation were from the U.S. Geological Survey (USGS) and the Geological Survey of 

Canada (GSC), but several other national, regional, and historical catalogs were also used. 

Information on relocated events was obtained from studies described in published literature. 

Nontectonic events (particularly blasts) were identified. Moment magnitudes were assessed for 

F-44
all events, and Dr. Youngs showed plots of the alternative relationships used to convert different 

magnitude scales into moment magnitude. He described the process used to combine estimates 

from multiple magnitude measurements, when available, into a uniform magnitude scale. After 

conversions were completed, additional corrections were made to account for the bias in 

recurrence parameters due to magnitude uncertainty. 

Next, Dr. Youngs explained how declustering was performed and how of the 26,426 total events 

in the catalog, 14,674 dependent events were identified. The final step in the catalog 

development process was to assess catalog completeness for events of various magnitudes. He 

showed the plots of catalog completeness regions within the study region for 15 different regions 

identified based on instrumentation and population history. He has sent the catalog to PPRP, 

USGS, GSC, and TVA colleagues to review selected preferential catalog entries, identify any 

additional data sources, evaluate conversions to moment magnitude, and garner any other 

suggestions. Response is needed by the end of 2009. At the conclusion of Dr. Youngs’s talk, the 

workshop participants discussed the declustering approach and the identification of earthquakes 

related to blasts and located in offshore regions. 

Dr. Youngs then gave a talk titled ―The ―EPRI‖ Bayesian Mmax Approach for Stable Continental 

Regions (SCR)—Updated Priors.‖ In the EPRI (1994) study, SCRs were divided into domains 

based on crustal type, geologic age, stress regime, and stress angle with structures. For the CEUS 

SSC project source zones, observed Mmax distributions were developed based on the SCR 

domains identified for the 1994 study. In the project update, revised magnitude estimates were 

added for the New Madrid (M7.8) and Charleston (M6.9) events, and additional worldwide 

earthquakes were added from recent catalogs. The number of M > 4.5 events in the SCR 

increased from 940 to 1,550 earthquakes. Dr. Youngs described an interesting case of a large 

1917 earthquake in China and the differences in the size and location of this event as reported in 

various catalogs. Next he discussed bias adjustment, which is used to move from the relatively 

small number of observed maximum earthquakes toward what could be expected if more data 

were available. He described domain ―pooling,‖ in which estimates of bias adjustment can be 

obtained by pooling similar domains to increase sample sizes (essentially, trading space for 

time). He concluded the talk by describing work that needs to be completed, including the 

criteria used to distinguish and combine domains and to examine bias correction techniques. 

Following a lunch break, Dr. Youngs briefly described the talks planned for the afternoon; these 

consisted of feedback on various parameters and their effects on hazard, calculated for the seven 

demonstration sites examined in the study. Dr. Youngs gave the first talk, titled ―Logic Tree 

Structure for Seismic Source Sensitivity Model.‖ He began by describing the master logic tree 

developed for the CEUS SSC sensitivity model. Two types of seismic sources are recognized: 

(1) distributed seismicity within regional source zones, characterized using historical and 

instrumental seismicity, and (2) repeated large-magnitude earthquake (RLME) sources 

characterized using the paleoearthquake record. For each of these sources, zoneless and 

seismotectonic structure approaches are used for characterizations and assessment of Mmax. 

Distributed seismicity sources have two alternative geometries based on different extended and 

non-extended crust delineations. 

Next, Dr. Youngs discussed the two alternative methods used to address spatially varying 

seismicity rates. These are the kernel model approach, based on a constant b-value and a cell-bycell model approach that uses a variable b-value. The uncertainties and advantages and 

F-45
disadvantages of using each of these approaches were discussed. Dr. Youngs then described the 

use of a zoneless treatment of RLMEs based on use of an earthquake catalog that includes 

paleoearthquakes, noting that an important issue is completeness with respect to spatial and 

temporal earthquake coverage. What to do in areas that have not been examined in detail is 

problematic; hence this model is not yet ready to be used. Dr. Youngs also described the logic 

tree structure used for the structure-specific approach to assessing RLMEs. 

Dr. Youngs moved on to a talk titled ―One Approach for Spatially Varying Seismicity,‖ in which 

he discussed the kernel model smoothing approach in detail. This approach assumes a constant 

b-value within a zone and a variable ―a.‖ Uncertainty in overall seismicity parameters is largely 

decoupled from estimation of spatial density. Dr. Youngs discussed testing for spatial nonuniformity to assess if seismicity is occurring in clusters. He showed kernel density estimation in 

one dimension, depicting a ―classical‖ uniform density graph and Gaussian kernels approach. 

When combined, these approaches give information important for assessing the size of the 

kernel, which is an important parameter. 

Next, Dr. Youngs described alternative kernel forms and how they affect data density. Kernel 

size can be adjusted as a function of data density using an adaptive kernel. Dr. Youngs showed 

examples of fixed kernel estimates and adaptive kernel estimates and how they affect display of 

data using a normalized density. He described the issue of varying completeness and how to 

account for this using a single catalog; possibilities include using minimum completeness for the 

lowest magnitude used (minimum data) and assigning a weight to each earthquake interval based 

on specific measures of relative completeness. He reviewed the approaches of high smoothing 

using uniform spatial density and low smoothing using adaptive kernel density estimation. He 

concluded by describing estimation of uncertainty distributions for earthquake rate and b-value. 

The next talk, given by Dr. Gabriel Toro (Risk Engineering, Inc.), was titled ―Characterization of 

Variable Seismicity: Penalty Approach with Variable a and b.‖ Dr. Toro stated that the variable 

seismicity approach is essentially a modification of the 1988 EPRI study approach developed by 

Veneziano and Van Dyke (1988). He began with an overview of the 1988 EPRI study approach 

and described the key elements and equations. Next he discussed the new features included in the 

updated approach, including smaller (0.25 degree) cell size and a new solution algorithm that 

estimates uncertainty in certain parameters and objectively estimates penalty terms to use in the 

calculation (i.e., downweighting is applied if there is a large difference in value between a cell 

and the adjoining cells). 

He then described the solution algorithm and the results that can be obtained. The approach has 

been used for two cases: (1) a low smoothing case using objectively determined smoothness 

penalty terms and a low prior of b = 1, and (2) a high smoothing case with fixed smoothness 

penalty terms and no prior on b. Dr. Toro displayed the results of the CEUS SSC earthquake 

catalog using these approaches; with low smoothing there are more local peaks depicted than 

with high smoothing. He compared these results with results of the approaches used by Dr. 

Youngs and noted that they are similar. 

Dr. Toro moved on to a discussion of uncertainty characterization for the variable seismicity 

approach, which represents a significant improvement over the EPRI 1988 model. He described 

the objective and approach, which includes randomization, and showed sample results obtained 

for low smoothing and high smoothing examples. His conclusions included the observation that 

the variable b approach is particularly well suited for large source zones, and that the approach 

F-46
allows both objective (data-driven) and subjective specification of the smoothing parameter (i.e., 

penalty terms). Finally, Dr. Toro described additional work that could be conducted in the future 

to make improvements in the application of the updated approach. 

Dr. Youngs presented maps of the historical seismicity of the CEUS that depicted the alternative 

spatial density models, plotted as frequency of occurrence (i.e., events per year per 0.25 degree). 

These maps provided feedback for the project team on the results produced by different 

smoothing approaches. Dr. Youngs showed three sets of maps displaying M > 5, M > 6, and M

> 7 events for each of the alternative models. He described and compared the results of different 

models for selected regions. The number and magnitude of earthquakes within a particular region 

can have a strong effect on the nature of the boundary between adjoining zones. Workshop 

participants discussed some of the results of the various models, as well as the basis for defining 

the boundary between extended and non-extended crust. 

After a break, Dr. Youngs announced that talks for the remainder of the afternoon would provide 

a whirlwind tour of seismic hazard in the CEUS. He began by showing a map of locations of the 

regional sources, RMLE sources, and the seven demonstration sites that are being analyzed for 

the CEUS SSC project. He described the master logic tree used to assess all the seismic sources 

and discussed various parameter estimation approaches. He showed results of Mmax assessments 

for the regional sources. Next he described in detail the analyses for the Cheraw fault and 

Wabash area RLME sources. He showed the logic trees used for these sources and discussed 

results of analyses of event frequency and magnitude distributions for each source. He then went 

on to describe the New Madrid RLME. The analysis is based on two groups of sources (a central 

zone of faults and a set of faults on the boundary of the rift) and three models of characterization 

(one with all structures in active mode; one with all structures turned off and a default to 

background seismicity; and one with only the Reelfoot thrust active). Dr. Youngs concluded his 

talk by showing the results of analyses of event frequency and magnitude distributions for the 

various structures associated with the New Madrid RLME. 

Dr. Robin McGuire (Risk Engineering, Inc.) gave the next talk, titled ―Seismic Hazard 

Sensitivity in the CEUS,‖ noting that he would be giving his opinions of what is or is not 

important for hazard analyses. He began by discussing general sources of imprecision, including 

random and systematic errors, variability and unpredictability, expert disagreement, and 

approximations. Next he reviewed the hazard from the New Madrid RLME source at two 

demonstration sites (Central Illinois and Jackson, Mississippi). For each site he first showed 

PGA hazard fractiles and the mean for hard rock. He then showed the sensitivity to the ground 

motion model used, the cluster frequency, the characteristic magnitude, and rupture length 

scenarios. For the dependence on cluster frequency he noted that we are less then halfway into 

the recurrence interval following the 1811-1812 earthquakes; thus the renewal recurrence model 

gives higher hazard than the Poisson model. After showing the sensitivity results, Dr. McGuire 

showed the mean and fractile hazard results at 1 and 10 Hz spectral acceleration. 

Next, Dr. McGuire showed PGA hazard curves from three New Madrid seismic zone models 

(2008 USGS, 2003 Geomatrix, and 2009 CEUS SSC) that had been computed by different 

analysts at Risk Engineering, and he noted that all give near-identical results. The hazard curve 

for additional faults (e.g., Commerce and Fluorspar) and the hazard curves for 1 and 10 Hz are 

also all virtually identical. Dr. McGuire also showed hazard results at the Topeka, Kansas, 

demonstration site. Again, at 1 and 10 Hz, the newly calculated hazard results are virtually the 

F-47
same as those obtained in the 2008 USGS and 2003 Geomatrix studies. Dr. McGuire emphasized 

that this comparison was not done using total hazard, but with the hazard contributions from the 

New Madrid seismic sources only. Workshop participants discussed the agreement between the 

different models, which is based in part on the long source-to-site distances. Also, it was noted 

that results from pre-2000 models would have varied, in part because these were based only on 

observed seismicity (i.e., no paleoearthquakes). 

The next speaker was Ms. Allison Shumway (William Lettis & Associates, Inc.), who described 

hazard results from the Cheraw fault and Wabash Valley seismic sources at the Topeka 

demonstration site. The recurrence rate parameter for the Cheraw fault has the greatest effect on 

hazard at the Topeka site. For the Wabash Valley source, two alternative source geometry 

interpretations were used: narrow and wide (circular shape, consistent with the 2008 USGS 

source zone); the geometry has a moderate effect on hazard. The source recurrence rates used in 

the analysis give a factor-of-10 range, however, so this parameter is the most sensitive. The 

paleoseismic record appears to indicate a higher recurrence rate than the historical seismicity. To 

clarify the basis for the source logic trees, Ms. Kathryn Hanson (AMEC Geomatrix, Inc.) briefly 

described the paleoseismic record of the Cheraw fault, which includes three events in the past 

20,000 years. For the Wabash source, she described the basis for rates from the paleoearthquakes 

near Vincennes, Indiana. 

Dr. Youngs spoke next about the Oklahoma Aulacogen (OKA)/Meers fault RLME; the Meers 

fault is located within the OKA, so the two sources are always linked. He showed the logic tree 

and reviewed the branches for an in- or out-of-earthquake cluster, source geometry, earthquake 

model, rupture size relation, magnitude approach, and recurrence approach. A separate logic tree 

has been developed for OKA with broad and narrow source geometry and with the Meers fault in 

or out of a cluster. Additionally, given the alternative that the Meers fault is ―turned off,‖ there is 

a probability that seismic activity will move to another location within the OKA but have the 

same source characteristics as the Meers fault. This alternative was added because numerous 

structures have been identified within the OKA that parallel the Meers fault. 

The Alabama-Louisiana-Mississippi source (ALM; this source includes the Saline River region) 

located on the southern edge of the Reelfoot rift system was described next by Dr. Youngs. Four 

alternative source geometries were evaluated and Dr. Youngs described the data used to develop 

each alternative. Logic tree branches included consideration of event correlation or no 

correlation for paleoliquefaction interpretations, plus alternative numbers of paleoearthquakes 

related to these interpretations. This region does not have elevated seismicity, but 

paleoliquefaction evidence is present and possibly represents multiple earthquakes. 

Ms. Shumway showed sensitivity results for the OKA/Meers fault RLME source. Alternative 

geometries may be sensitive, but this interpretation needs to be checked. The background Mmax

earthquake within the aulacogen only (i.e., without the influence of the Meers fault) is also 

potentially important. Next she discussed the ALM source. Four alternative geometries are 

considered and hazard was calculated for the highest weighted source (the Cox/Quaternary 

alternative) at the Jackson, Mississippi, and Houston, Texas, sites. Randomly oriented structures 

that are or are not allowed to extend beyond the boundary of the source zone were tested 

(―leaky‖ or ―strict‖ source cases) and shown to have low sensitivity. Recurrence rate has a high 

sensitivity, and Ms. Shumway noted that with more small events, higher hazard is indicated at 

F-48
higher probabilities. Workshop participants discussed the paleoliquefaction data and hazard 

sensitivity results for the ALM source. 

Dr. Coppersmith adjourned the meeting for the day. 

DAY 2–WEDNESDAY, AUGUST 26 

Mr. Salomone welcomed the group to the second day of the workshop. He announced that in 

October there would be a workshop on earthquake hazards sponsored by the USGS; this 

workshop is one of several synergistic projects currently under way that overlap the work being 

conducted as part of the CEUS SSC project. He introduced Mr. Oliver Boyd (of the USGS), who 

is an organizer of the upcoming earthquake hazards workshop. Mr. Boyd said that the workshop 

will be held October 27-28, 2009, in Memphis, Tennessee. It will provide an opportunity for 

researchers to present and discuss their recent investigations, discuss upcoming New Madrid 

bicentennial activities, and identify topics for future research priorities. 

Dr. Coppersmith gave a summary of the model sensitivity information presented on Day 1 of the 

workshop. He noted the apparently large impact locally on predicted rate density of alternative 

interpretations of the position of the extended/non-extended crust boundary and seismotectonic 

zone boundaries. Some of the smoothing results show a distinct rate change (step function) at the 

boundary, which could be important for sites very near the boundary. This also highlights the 

potential importance of evaluating the need for source boundaries or boundaries for purposes of 

Mmax assessment (i.e., the extended/non-extended boundary). For the repeated large-magnitude 

earthquake (RLME) sources, he noted that comparisons made the previous day showing 

similarity in hazard for post-2000 PSHAs near New Madrid indicate that these studies are 

comparable in their treatment of the New Madrid seismic zone. 

Given that the RLME sources are within a cluster, there is strong sensitivity to the recurrence 

rate. Sensitivity analyses have not yet been conducted to demonstrate the differences between 

within-cluster and out-of-cluster hazard at nearby sites, but it is expected that there will be strong 

sensitivity to in- or out-of-earthquake-cluster recurrence rates, as well as to characteristic 

magnitude distributions at all RLME sources. A renewal model was developed and exercised for 

some of the RLME sources; the short elapsed time at New Madrid relative to the mean RLME 

repeat time results in somewhat lower hazard estimates than the Poisson model. The results 

illustrate the importance of the parameters of the renewal model, including the coefficient of 

variation (COV) of the mean repeat time. Sensitivity studies for the Central Illinois site (which is 

not immediately adjacent to the New Madrid source) indicate little sensitivity to alternative 

models for the rupture of the northernmost segment and to rupture length models. With 

increasing distances to an RLME source, the background or regional seismotectonic zones are 

increasingly important and contribute more than the RLME sources.

Dr. Coppersmith also reviewed the particular sensitivities associated with the RLME sources at 

the test sites. He listed additional feedback information that will be needed, including the hazard 

significance of all logic tree branches at all logic tree nodes at all seven demonstration sites. He 

noted that he would be adding to this list as the day progressed and would review it with the TI 

team at the end of the day. 

Dr. Youngs continued the presentations on sensitivity models by discussing the Charleston, 

South Carolina, RLME source. He described the weights on various logic tree branches, 

F-49
including alternative interpretations for in- or out-of-earthquake-cluster recurrence rates; four 

source geometry configurations; various paleoliquefaction scenarios, including length of 

paleoliquefaction record (2,000 versus 5,000 years); the range of maximum magnitude (Mmax) 

values (M 6.7 to 7.5); and the possible overlap in the earthquake magnitudes included within this 

RLME and those that are accounted for within the surrounding regional source zone. 

Next, Ms. Shumway described the geometry, rate, and Mmax sensitivity studies for the Charleston 

RLME and the resulting hazard at the Savannah, Georgia, and Chattanooga, Tennessee, 

demonstration sites. The hazard results reflect the wide range of input parameters. There is high 

sensitivity to earthquake recurrence models. The renewal (time-dependent) model results in 

lower recurrence rates for the next 50 years because the elapsed time since the large 1886 

earthquake is relatively short compared to the mean repeat time for RLME events. Workshop 

participants discussed the relative merits of using renewal versus Poisson recurrence models. 

Weights on these model branches may need to reflect the maturity of the structures involved; 

additional feedback on sensitivity is needed. 

Dr. Youngs recounted early discussions about placing an RLME source around the Charlevoix 

region. The project team decided this was unnecessary as the recurrence rate from the observed 

seismicity is comparable to or even exceeds the rates identified using paleoliquefaction data. 

Neither the cell-by-cell nor kernel-smoothing methods provide a close fit, in part because of 

uncertainty in the record of paleoliquefaction events. Checking the relative fit of the two 

smoothing methods using an RLME-equivalent source in the St. Lawrence and Charlevoix 

region may provide useful information. 

Dr. Coppersmith asked PPRP members for their opinions about the use of the renewal versus 

Poisson smoothing approaches. Dr. Stepp remarked that if the in-cluster alternative is selected 

for the Charleston RLME, then a tectonic interpretation is being made and therefore the renewal 

model needs to be highly weighted. Dr. Coppersmith observed that the renewal model is 

sensitive to knowledge of COV and time since the last event; when the uncertainties in both of 

these factors are added, the problem is moved toward a Poissonian approach. Workshop 

participants discussed the use of the renewal approach for known seismic sources (e.g., structures 

in the New Madrid region). There was agreement that more work on COVs is needed, as there is 

extreme uncertainty in this parameter for many areas and thus the use of the renewal model may 

not be reasonable. Workshop participants also discussed how to structure a logic tree given that 

an in-cluster state is assumed. Dr. Coppersmith noted that the influence of the in-cluster versus 

out-of-cluster models on hazard still needs to be examined. 

Following a break, Dr. Coppersmith announced that the next talks would address regional 

seismic source zones. Dr. Toro gave the first talk, titled ―Sensitivity Results for CEUS Source 

Zones.‖ He began by comparing the CEUS SSC project hazard results (for the source zones only; 

no RLME sources) with hazard results using the zones defined by the USGS. In general, the 

hazard levels calculated for the CEUS project are lower than those for the USGS study, but this 

is likely due to not including the RLME events in the comparison. At the Savannah site the 

difference in hazard levels is about 50 percent; for the Chattanooga and Manchester, New 

Hampshire, sites the difference is closer to 20 percent. For the Central Illinois, Houston, Jackson, 

and Topeka sites, the hazard curves are closer together. 

Dr. Toro then discussed hazard sensitivity results for seismic source zones for each of the seven 

demonstration sites. He noted that he would concentrate on the results from the CEUS SSC 

F-50
study, which incorporates SSC uncertainty but does not address ground motion uncertainty. For 

each demonstration site, he showed hazard results at PGA and 1 Hz and discussed the 

contributions to hazard for the dominant seismic sources. He also showed the mean and fractile 

hazard curves and described sensitivity to branches of the master logic tree, focusing on Mmax

and recurrence for the dominant sources. 

Dr. Toro stated that for all sites there is moderate sensitivity to choice of smoothing approach 

(i.e., kernel or variable a and b) and to selection of Mmax values. He believes that in areas having 

higher levels of seismicity (e.g., many low-magnitude events), the two smoothing approaches are 

in better agreement; however, this observation needs to be tested further. Dr. Coppersmith noted 

that areas having higher levels of seismicity tend to have lower uncertainty in the recurrence 

parameters and, hence lower sensitivity to most alternative input parameters. These observations 

apply to the Savannah, Manchester, Central Illinois, Topeka, and Chattanooga sites. The hazard 

results for the two sites in regions of lower seismicity, Houston and Jackson, have more 

pronounced differences in sensitivity between PGA and 1 Hz hazard curves. For both sites there 

is a moderately high sensitivity to the Mmax of the Gulf of Mexico source zone and to choice of 

smoothing parameter. Dr. Toro noted that these differences can be at least partially attributed to 

the low seismicity (fewer data points) in these regions. Another potential contributor to these 

differences is the use of the Gulf of Mexico attenuation equations for local zones and the 

Midcontinent attenuation equations for distant zones. 

Workshop participants discussed whether or not to keep all of the branches of the logic tree used 

for the initial hazard calculations, given the apparent low sensitivity of many branches. 

Advantages include the relative ease of making future changes to update the models; 

disadvantages include longer computational time. Several individuals noted that results will vary 

by site. The general preference of the group was to keep all of the branches as the study moves 

forward, since this will serve to demonstrate that all alternative hypotheses have been 

considered. Although the CEUS SSC project is applicable to the entire CEUS, its future 

applications will be for individual sites and it will be possible to simplify (e.g., by pruning the 

logic tree) for individual sites by showing that there is no sensitivity to more distant sources in 

the model. 

Following a lunch break, Dr. Coppersmith showed a slide with a list of additional feedback items 

needed, based on the discussions at the workshop, as follows: 

the hazard significance of all logic tree branches, at all logic tree nodes, at all seven 

demonstration sites; 

additional evaluation of predicted versus observed seismicity for the entire CEUS and all 

seismotectonic zones; 

differences in earthquake recurrence related to smoothing approach and alternative zone 

boundaries; and 

the issue of a migrating RLME (e.g., the Meers fault versus another structure within the OKA 

source region). 

Dr. Coppersmith indicated that these items would be addressed by the TI team during an 

upcoming telephone conference call. Workshop participants discussed these and related topics, 

including the zoneless model concept (smoothing of seismicity used in place of defined zone 

F-51
boundaries); separating large-magnitude events within the RLME sources from events in the 

surrounding host zones; offshore earthquakes in the Gulf region; and appropriate truncation of 

Mmax distributions. 

Dr. McGuire gave the next talk, titled ―Quantifying the Precision of Seismic Hazard Results in 

the CEUS.‖ The purpose of the analysis described in the talk was to derive quantitative estimates 

of how seismic hazard results might change if studies were repeated by different researchers 

using the same basic information. Dr. McGuire began by listing many general sources of 

imprecision, which include random error and statistical variation, overconfidence in estimating 

uncertainties, unpredictability, expert disagreement, and the use of approximations. Then he 

listed the hazard studies that provided data used to quantify levels of precision of seismic hazard 

results. Data on SSC was obtained from the 1989 EPRI-SOG study, the PEGASOS project that 

evaluated seismic hazard for nuclear power plant sites in Switzerland, and recent 

characterizations of the Charleston and New Madrid seismic sources. 

Dr. McGuire explained the formula he used for combining sources of imprecision. He showed 

hazard results obtained from the PEGASOS project, including COV of mean hazard from SSC 

expert teams. Turning to the 1989 EPRI-SOG project, he showed COV of hazard at various 

levels for each of the seven demonstration sites used for the CEUS SSC project. He then 

provided a summary of uncertainties for the Charleston source by showing logic tree alternatives 

and weights. He also described the mean and variance of hazard when weights on models are 

variable (depending on who is making the interpretation) and how COV can be calculated for 

various weighted alternatives. Similar analyses were shown for the New Madrid source. 

Turning to the ground motion and site response components of seismic hazard analysis, Dr. 

McGuire showed the relevant hazard results from the PEGASOS and 2004 EPRI Ground Motion 

studies. Next he used the data from the 2004 EPRI study to assess the COV of hazard versus 

hazard results at each of the seven demonstration sites. He noted that there is a tendency to get 

much lower COV from seismic source and ground motion models, relative to site response. He 

then listed several conclusions: 

There is less uncertainty in site response than other components of hazard. 

The source parameter contribution is smaller for area sources than RLME sources. 

For ground motion equations, area sources have a higher COV than RLME sources. 

Dr. McGuire showed a plot of these results, which indicate that a minimum estimate of 

uncertainty in mean hazard varies between a COV of mean hazard of 0.2 to a COV of mean 

hazard of 0.4 for an annual frequency of exceedance of 1 10–4to 1 10–6, respectively. Dr. 

McGuire stated that an overall level of precision in mean hazard estimates would be a COV of 

0.25 in annual frequency, which corresponds to a precision in ground motion of +/–8%. He said 

that to apply this knowledge going forward, this method of quantification would give confidence 

in levels of mean hazard and how much they could change with additional analyses, which 

reflects on how well the hazard is understood. 

Dr. Coppersmith followed this presentation with the final talk of the workshop. In this talk, titled 

―Path Forward,‖ he identified short-term activities to occur within the following few weeks, 

including meetings between the TI team and staff and preparation and distribution of 

documentation for Workshop 3. He then showed key dates and activities for the remainder of the 

F-52
calendar year, including delivery of new data sets of reprocessed gravity and magnetic field data 

and an updated world stress map. The preliminary SSC model will be completed by the end of 

February 2010, and discussed in a briefing with the PPRP in mid-March. The final SSC model is 

to be completed at the end of April 2010 and the draft report by the end of July 2010. The final 

project report will be delivered at the end of December 2010. The group discussed the schedules 

for the review of CEUS SSC project components by the NRC and USGS staff. Mr. Salomone 

will work with the NRC and the USGS to ensure the process goes smoothly. 

Concluding remarks were made by Mr. Salomone, who noted that Workshop 3 was the last 

formal workshop for the project. For this reason he wanted to provide an engineering perspective 

and review the larger project context by looking at industry and government use of what will be 

developed for this project. He reviewed the following general guiding principles on which the 

project is based: 

Managing the seismic issue is critical to control cost and delays for critical mission nuclear 

facilities. 

Having a stable, consistent, and defensible seismic design spectrum throughout the design 

phase of critical mission nuclear facilities is essential. 

Accomplishing more for less with reduced risk through standardization and partnering is 

important to advance science and the state of practice. 

Mr. Salomone showed a flow chart titled ―Disciplined, Systematic Approach to Seismic Safety.‖ 

Key steps in the disciplined, systematic approach to seismic safety included: 

1. Define scope of work as per regulatory and owner guidance documents. 

2. Analyze seismic hazards by performing PSHAs using the CEUS SSC model and 

available attenuation models from studies such as the EPRI 2004/2006 CEUS 

Ground Motion and the Next Generation of Ground Motion Attenuation Models 

—East (in development). . 

3. Develop controls through installation of strong motion seismic monitoring 

instrumentation and settlement monitoring instrumentation. 

4. Perform work by designing, building, and operating facilities. 

5. Obtain feedback from regulatory oversight and technical exchanges using 

qualified consultants and expert panel members; modify surface spectrum as 

required. 

Mr. Salomone stated that the CEUS SSC project is part of an initial step to analyze hazards and 

will ultimately be used for facility design. He cautioned that factors used for increased 

conservatism should be applied to the design spectrum used by structural engineers and not the 

geologically, seismologically derived spectrum used by geotechnical engineers when performing 

soil response analyses. 

Mr. Salomone finished by thanking Mr. Rahn for the hospitality of EPRI, and the workshop 

participants for their contributions to the CEUS SSC project. 

F-53

BIBLIOGRAPHIC DATA SHEET

(See instructions on the reverse)

NRC FORM 335

(12-2010)

NRCMD 3.7

U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

 (Assigned by NRC, Add Vol., Supp., Rev.,

 and Addendum Numbers, if any.)

NUREG-2115

Vol. 5

3. DATE REPORT PUBLISHED

MONTH

January

YEAR

2012

4. FIN OR GRANT NUMBER

K6877

2. TITLE AND SUBTITLE

Central and Eastern United States Seismic Source Characterization for Nuclear Facilities

Volume 5: Appendices C to F

5. AUTHOR(S)

G. Stirewalt (NRC), L. Salomone (Savannah River Nuclear Solutions, LLC), S. McDuffie (DOE),

K. Coppersmith (Coppersmith Consulting, Inc), Fugro William Lettis & Associates, Inc.: C. Fuller,

R. Hartleb, W. Lettis, S. Lindvall, R. McGuire, G. Toro, D. Slayter, R. Cumbest, A. Shumway, F.

Syms, AMEC Geomatrix, Inc: L. Glaser, K. Hanson, R. Youngs, S. Bozkurt, V. Montaldo Falero,

R. Perman, R. McGuire (Risk Engineering), M. Tuttle (M. Tuttle & Associates)

6. TYPE OF REPORT

Technical

7. PERIOD COVERED (Inclusive Dates)

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (If NRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address; if contractor,

U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, Washington DC 20555

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC, type "Same as above"; if contractor, provide NRC Division, Office or Region, U.S. Nuclear Regulatory Commission, 

U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, Washington DC 20555

provide name and mailing address.)

and mailing address.)

10. SUPPLEMENTARY NOTES

11. ABSTRACT (200 words or less)

This report describes a new seismic source characterization (SSC) model for the Central and Eastern United States (CEUS). It

will replace the Seismic Hazard Methodology for the Central and Eastern United States, EPRI Report NP-4726 (July 1986) and

the Seismic Hazard Characterization of 69 Nuclear Plant Sites East of the Rocky Mountains, Lawrence Livermore National

Laboratory Model, (Bernreuter et al., 1989). The objective of the CEUS SSC Project is to develop a new seismic source model

for the CEUS using a Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 assessment process. The goal of the

SSHAC process is to represent the center, body, and range of technically defensible interpretations of the available data,

models, and methods. Input to a probabilistic seismic hazard analysis (PSHA) consists of both seismic source characterization

and ground motion characterization. These two components are used to calculate probabilistic hazard results (or seismic hazard

curves) at a particular site. This report provides a new seismic source model.

12. KEY WORDS/DESCRIPTORS (List words or phrases that will assist researchers in locating the report.)

Probabilistic seismic hazard analysis (PSHA)

Seismic source characterization (SSC)

Seismic source characterization model

Central and Eastern United States (CEUS)

14. SECURITY CLASSIFICATION

13. AVAILABILITY STATEMENT

unlimited

(This Page)

unclassified

(This Report)

unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (12-2010)

U.S. Department of Energy, 1000 Independence Avenue SW, Washington DC 20585

Electric Power Research Institute, 3420 Hillview Avenue, Palo Alto, CA 94304

U.S. Department of Energy, 1000 Independence Avenue SW, Washington DC 20585

Electric Power Research Institute, 3420 Hillview Avenue, Palo Alto, CA 94304