Central and Eastern United States 

Seismic Source Characterization 

for Nuclear Facilities 

Volume 1: Chapters 1 to 4

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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(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 

U.S. GOVERNMENT. NEITHER THE U.S. GOVERNMENT NOR ANY AGENCY THEREOF, NOR ANY 

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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. 
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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
1-1 

1 

CHAPTER 1 

INTRODUCTION 

1.1 Background and History 

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. As such, the CEUS SSC model replaces regional seismic source 

models for this region that are currently accepted by the Nuclear Regulatory Commission (NRC) 

for assessing seismic design bases and their associated uncertainties satisfying the requirements 

of the seismic regulation, 10 CFR Part 100.23. The models being replaced are the Electric Power 

Research Institute–Seismicity Owners Group (EPRI-SOG) SSC model (EPRI, 1988) and the 

Lawrence Livermore National Laboratory (LLNL) SSC model (Bernreuter et al., 1989) 

sponsored by the NRC. 

Unlike the pioneering EPRI and LLNL projects, which were conducted independently, the CEUS 

SSC Project had multiple stakeholders who joined to sponsor it. They include the EPRI 

Advanced Nuclear Technology Program, the U.S. Department of Energy (DOE) Office of 

Nuclear Energy and Office of the Chief of Nuclear Safety, and the NRC Office of Nuclear 

Regulatory Research. Importantly, in the time since these early regional seismic source models 

were developed, the methodology for developing PSHA models has benefited from extensive 

application and regulatory review. As will be described in Section 1.1.2, following review of the 

EPRI and LLNL SSC models, which were developed using somewhat different process 

methodologies to evaluate and quantify uncertainties, the NRC, DOE, and EPRI jointly 

sponsored development of a standard methodology called the SSHAC methodology. This project 

used a SSHAC Level 3 assessment process in order to adequately ensure compliance with the 

requirement of the seismic regulations to properly quantify uncertainties in seismic design basis 

for nuclear facilities. 

The regional SSC model developed by this project can be used for site-specific PSHAs with 

appropriate site-specific refinements as required by current regulatory guidance. For example, 

NRC Regulatory Guide 1.208 requires the development of an up-to-date, site-specific earth 

science database to support every nuclear facility license application. In the course of developing 

the database, local refinements to the CEUS SSC model may be necessary to accommodate local 

information. 

The SSC model has incorporated earthquake source parameters in order to be compatible with 

current and anticipated ground-motion characterization (GMC) models. The current accepted 
Chapter 1 

Introduction 

1-2 

ground-motion models for use at nuclear facilities are those developed by EPRI (2004, 2006), 

The ongoing Next Generation Attenuation–East Project will provide ground motion models that 

are appropriate for use with the CEUS SSC model; these models are expected to be adopted as 

part of the seismic safety regulatory guidance, replacing the EPRI (2004, 2006) models. 

The remainder of this chapter provides a summary of the historical context for the CEUS SSC 

Project and a description of how the project meets the needs of the seismic hazard community. 

1.1.1 EPRI-SOG and LLNL Projects 

The CEUS SSC Project replaces the SSC components of the landmark seismic hazard projects 

conducted in the 1980s by EPRI-SOG (EPRI, 1988) and LLNL (Bernreuter et al., 1989). Both of 

these projects developed PSHA models for application in the broad region of the United States to 

the east of the Rocky Mountains. Recent licensing applications for nuclear facilities submitted to 

the NRC have followed regulatory guidance by using the EPRI-SOG SSC model as a starting 

point, with updates as appropriate on a site-specific basis for site-specific PSHAs. However, 

while the regional SSC model has been updated for specific sites, it has not been systematically 

updated to account for the significant new data in the CEUS. The CEUS SSC Project takes full 

advantage of the following historical and new sources: data used to develop the two previous 

CEUS models; new data and information developed over the past 20 years, including that 

developed for the U.S. Geological Survey (USGS) seismic hazard mapping program (Petersen et 

al., 2008); and other information and hazard analyses that were developed as part of licensing 

actions for proposed and existing nuclear power facilities. In addition to the new data, updated 

methods for evaluating the data and quantifying uncertainties have been implemented in the 

CEUS SSC Project. 

1.1.2 Development of the SSHAC Process 

Methodological guidance on how to perform a PSHA properly representing uncertainty was 

developed by the Senior Seismic Hazard Analysis Committee (SSHAC) in 1997 in a study 

jointly sponsored by the NRC, DOE, and EPRI (Budnitz et al., 1997). Both technical and 

procedural guidance was developed by SSHAC based on its evaluations of past PSHAs, which 

included the EPRI-SOG and LLNL models. Although both of those large projects relied on 

evaluations and assessments by multiple experts, there were significant technical and procedural 

differences between the two. There were also significant differences between the hazard results 

obtained at many of the same sites. The formation of SSHAC was motivated by the need to (1) 

understand these differences and (2) develop guidelines for evaluating and quantifying 

uncertainty in seismic hazard models—specifically, guidelines that would ensure that future 

PSHAs would satisfy the requirements for seismic safety regulation of nuclear facilities. The 

final guidelines resulting from the study were published in 1997 in NUREG/CR-6372 (Budnitz 

et al., 1997) and, following review by a committee of the National Academy of Sciences, were 

incorporated into the NRC’s seismic regulatory procedures guidance. 

The SSHAC guidelines provide a structured procedure for systematically compiling applicable 

data sets, evaluating those data relative to their application for SSC, assembling representatives 
Chapter 1 

Introduction 

1-3 

of alternative hypotheses and interpretations within the technical community for discussion of 

their hypotheses and associated uncertainties, and performing integration of a SSC model that 

represents the center, body, and range of technically defensible interpretations in light of the 

views of the larger technical community. The formalism imposed by the SSHAC process was not 

available at the time the EPRI-SOG and LLNL projects were conducted two decades ago, so it is 

timely that a new SSC model was developed that takes advantage of the technical and procedural 

knowledge gained since those studies were carried out. As will be discussed in Section 2.1, the 

CEUS SSC Project is only the latest in a number of PSHA model development projects 

conducted using the SSHAC guidelines since the time of their issuance. 

Under NRC sponsorship, the USGS completed an assessment of the lessons learned from the 

application of the SSHAC process in various projects since the SSHAC guidelines were issued. 

The results of that evaluation are given in Hanks et al. (2009). In light of the experience gained 

in actual SSHAC projects, the NRC (2011) has developed a NUREG document that provides 

detailed implementation guidance for conducting SSHAC Level 3 and 4 projects. That document 

will be issued later this year. 

1.1.3 Implementation of the SSHAC Methodology 

SSHAC concluded that how a seismic hazard project is carried out can be just as important as 

what is being assessed technically. This emphasizes that process methodology is important, and 

experience implementing the methodology is equally important. The project team assembled for 

the CEUS SSC Project is composed of distinguished experts from industry, government, and 

academia. These experts have extensive experience in developing PSHAs for sites both 

throughout the United States and worldwide. In addition, most of these experts have developed 

key data sets used for SSC in the CEUS and have participated in important studies that form the 

basis for conducting PSHAs. Most of the participants have considerable experience with 

implementing SSHAC processes as either expert evaluators or peer reviewers. The roles and 

responsibilities of participants in the CEUS SSC Project were explicitly defined, following 

SSHAC guidelines, for a successful Level 3 assessment project (see Section 2.2), and were 

diligently followed. Because many of the project participants have significant experience on 

recent and ongoing SSHAC projects, they knew these roles and appreciated their importance 

from the outset. All participants were reminded of their roles throughout the project. This 

experience makes the project team exceptionally qualified to develop the CEUS SSC model. 

1.1.4 Regional SSC Model for Nuclear Facilities 

The CEUS SSC Project is a user-community–based project for developing a regional SSC model 

in that it has the sponsorship of multiple user stakeholders. Site-specific seismic hazard 

assessments will be required as part of licensing proposed sites for next-generation nuclear 

power plants in the CEUS. Likewise, sites in the DOE nuclear facility complex require updated 

seismic hazard assessments. Conducting these assessments and updates independently is a timeconsuming, overlapping, and costly process; therefore, developing a regional seismic source 

model that can be applied to all sites in the CEUS is highly stabilizing and cost-beneficial. 

Furthermore, developing the CEUS SSC model using the SSHAC Level 3 process, which has 
Chapter 1 

Introduction 

1-4 

been developed and endorsed by nuclear utilities, the NRC, and the DOE, provides a stable basis 

for future site-specific PSHAs for any nuclear facility. Standardization at a regional level will 

provide a consistent basis for computing seismic hazard, which will assist regulators such as the 

NRC and the Defense Nuclear Facilities Safety Board (DNFSB) in their safety review and 

oversight of nuclear facilities. 

The CEUS SSC model was developed by a comprehensive implementation of a transparent, and 

traceable process, as described in this report. The model will be used by the following groups: 

• Utilities that have submitted or will submit an Early Site Permit (ESP) application or a 

Combined Construction and Operating License (COL) application for NRC review. 

• The NRC, DNFSB, and other regulatory and review groups that are responsible for ensuring 

the seismic safety of existing and new nuclear facilities. 

• The DOE, which is responsible for conducting seismic design studies and seismic safety 

evaluations of new and existing nuclear facilities. 

• The NRC and utilities that must respond to generic seismic safety issues for existing plants. 

1.1.5 Differences from USGS National Seismic Hazard Mapping Project 

In 2008, as part of the USGS National Seismic Hazard Mapping Project, national seismic hazard 

maps were released (Petersen et al., 2008) that are updates of previous seismic hazard maps 

developed by the USGS (e.g., Frankel et al., 1996, 2002). The national seismic hazard maps 

display the ground-motion hazard component of the seismic provisions of national building 

codes and support earthquake insurance rate structures and public policy decisions related to the 

national infrastructure. Earthquake strong ground motions for varying probability levels across 

the United States are displayed on these maps consistent with the seismic design basis 

requirements of national building codes. The maps are not intended to serve as seismic design 

bases for nuclear power plants, however. 

Although many of the same types of data underpin the development of both the USGS seismic 

hazard mapping project and the CEUS SSC model, the products have different uses and different 

demands. For example, the CEUS SSC model is used to obtain seismic hazard at lower annual 

frequencies of exceedance (AFEs) than those required for the USGS seismic hazard maps. This 

is because the CEUS SSC Project is focused on the needs of nuclear facilities, whose seismic 

design requirements are more stringent than those of conventional infrastructure facilities, and 

whose safety analyses depend on occurrence of rare ground motions because of the critical safety 

requirements of these facilities. Thus, while the national seismic hazard maps are focused on 

AFEs in the range of 10–2 to 4 × 10–4, the CEUS SSC model must support PSHAs focusing on 

AFEs in the range of 10–3 to 10–7 for design and safety evaluations for nuclear facilities. The 

properly complete representation of uncertainty at very low AFEs that must meet the 

requirements of the seismic regulations for nuclear facilities demands a focused effort to assess 

and represent low-probability hypotheses and parameter values, and also careful evaluation and 

characterization of large, rare earthquakes, such as those interpreted from the paleoseismic 

record, and maximum earthquake magnitudes for all seismic sources. 
Chapter 1 

Introduction 

1-5 

As part of the effort to ensure that these critical demands have been satisfied, the evaluation 

processes of the CEUS SSC Project involved the active participation of scientists who have 

contributed to the development of the national seismic hazard maps. Their participation was a 

major factor in ensuring that the CEUS SSC model properly represents the center, body, and 

range of current technical community knowledge. 

1.2 Purpose of the CEUS SSC Project 

The objective of this project is to develop a regional SSC model for the CEUS that can be used 

to obtain site-specific PSHAs for nuclear facilities and that includes the following: 

• A comprehensive project database as the basis for the evaluation and integration processes 

underpinning the development of the CEUS SSC model. 

• Assessment and incorporation of uncertainties in data and in the range of technical 

interpretations of earthquake processes that constitute current scientific community 

knowledge. 

• Detailed and traceable documentation of the evaluation and integration processes that support 

the SSC model. 

• A comprehensive participatory peer review of both the technical and process aspects of the 

project. 

The achievement of this objective provides reasonable assurance of stability and longevity for 

the SSC model. 

Experience has shown that stability and longevity are achieved through comprehensive 

characterization of current scientific knowledge and associated uncertainties. Assurance that this 

has been achieved is enhanced by the participatory involvement of the technical community, 

regulators, and oversight groups. The process guidance developed by SSHAC sets the goal of all

probabilistic hazard analyses, namely, to “represent the center, the body, and the range of the 

technical interpretations that the larger informed technical community would have if they were to 

conduct the study” (Budnitz et al., 1997). As documented in Section 2.1, there is assurance that 

the SSHAC goal has been met by the CEUS SSC Project’s implementation of the SSHAC 

Level 3 process. 

In using the CEUS SSC model for site-specific PSHAs in accordance with current regulations 

and regulatory guidance (e.g., NRC Regulatory Guide 1.208), site-specific studies will be 

required to identify any potential refinements needed for the regional seismic sources and any 

potential capable seismic sources within the site region and vicinity. The findings of these sitespecific studies could indicate possible local sources of seismicity (e.g., local faults with 

evidence of Quaternary activity, or nearby tectonic features with a significant probability of 

being seismogenic). 
Chapter 1 

Introduction 

1-6 

1.2.1 Implementation of SSHAC Level 3 Process 

SSHAC defines four “study levels” representing increasing process implementation complexity 

that can be used to evaluate and assess the knowledge and uncertainties in the important 

components of a PSHA. While the SSHAC labeled these “study levels,” they are described as 

levels of increasing complexity of process implementation. The SSHAC guidance emphasizes 

that independent of the process implementation complexity, the goal is to represent the center, 

body, and range of technically defensible interpretations in light of an evaluation of the available 

data, models, and methods in the larger technical community. 

According to the current SSHAC guidance (NRC, 2011), the two higher levels of process 

implementation complexity (Levels 3 and 4) should be used to develop regional PSHA models 

for sites requiring high levels of regulatory assurance—including nuclear facilities—to remain 

stable over an extended period of time, and for regions of complex seismotectonics where there 

are contentious alternative scientific interpretations. Lower SSHAC levels are recommended for 

non-nuclear facilities or for sites that have existing and viable Level 3 or 4 assessments. The 

higher assessment levels provide the degree of assurance required by the regulators for seismic 

safety decision-making. 

Both SSHAC Levels 3 and 4 implementation processes formalize interactions with the technical 

community through a series of workshops in which the peer reviewers fully participate and 

sponsors and other oversight groups may attend and offer observations. The key difference 

between Level 3 and Level 4 is that the former entails evaluations and integration of the SSC 

model by a Technical Integration (TI) team of evaluators, while the latter uses individual (or 

small teams) of evaluators. For both levels, the expert evaluators are charged with evaluating the 

current scientific community knowledge and performing as integrators in their characterization 

and assessment of current knowledge and uncertainty in the SSC model. These broad interactions 

lead to higher assurance that alternative interpretations of complex scientific/technical issues 

representing the range of knowledge of the scientific community have been completely evaluated 

and properly characterized and that the associated uncertainties are understood and properly 

assessed. 

Selection of a SSHAC level depends primarily on the amount and nature of uncertainty, 

controversy, and complexity involved, but also on regulatory concerns and public perceptions. 

The time and resources that the sponsor can commit to a proposed project may also be 

determinants of the level. As the SSHAC level increases, project costs and the number of 

participants involved increase; the broad acceptance of the final product, however, is also 

expected to increase. The lessons learned from conducting PSHAs at SSHAC Levels 3 and 4 

were compiled and evaluated in a joint USGS and NRC study that began in 2007 and was 

reported in USGS Open-File Report 2009-1093 (Hanks et al., 2009). These lessons learned were 

then used to develop more specific recommendations for the selection of SSHAC levels given in 

NRC (2011). 

From a review of Level 4 projects completed since the SSHAC guidance was written, the three 

or four years required to complete these projects and the high associated costs were cited as 

posing significant barriers for project sponsors (Hanks et al., 2009, p. 44). The additional time 
Chapter 1 

Introduction 

1-7 

and costs associated with Level 4 projects can be attributed to the need to train the experts in the 

evaluation process, conduct individual working meetings with each expert, and prepare 

individual documentation of the evaluations and assessments made by each expert. In contrast, 

the TI team on a Level 3 project is trained as a team in the evaluation process, works together in 

workshops and working meetings, and develops a single comprehensive report of its evaluation 

of the state of scientific knowledge and integration to characterize and represent the center, body, 

and range of technically defensible interpretations. Now that the SSHAC methodology has been 

in use for a number of years, a Level 3 process has been established as suitable for developing 

regionally applicable seismic hazard models intended for computing PSHAs at multiple sites 

over an extended time. 

The use of a Level 3 process is also consistent with the needs of the sponsors, who are 

responsible for safe design and operation of nuclear facilities. The CEUS SSC Project was 

conducted during a period when it could take full advantage of the experience gained from recent 

and ongoing SSHAC Level 3 projects, the lessons learned from a systematic review of past 

SSHAC projects (Hanks et al., 2009), and the NRC’s detailed implementation guidance for Level 

3 and 4 projects (NRC, 2011). 

The selection of the SSHAC Level 3 methodology for the CEUS SSC Project was made during 

the planning stages and is summarized in the Project Plan. The decision was made by the Project 

Manager in consultation with the Project Sponsors and the TI Lead. The detailed 

recommendations for the selection of SSHAC levels given in Chapter 6 of more recent guidance 

(NRC, 2011) were not available at that time, but the decision criteria given in the original 

SSHAC guidelines (Table 3-1 in Budnitz, 1997) were used. The SSHAC guidelines do not define 

an explicit “prescription” for the appropriate SSHAC study level for a given set of conditions, 

but they indicate that the decision should be based on a consideration of the “issue degree” and 

various “decision factors.” 

The issue degree includes consideration of whether the technical issue of interest (seismic source 

characterization in the CEUS, in this case) is uncertain, controversial, subject to diverse 

interpretations, complex, and significant to hazard. Clearly, all of these factors apply. The 

decision factors include regulatory concern, available resources, and public perception. Given the 

significant issue degree and in light of the decision factors, it was decided that the project should 

be conducted at a high SSHAC level (i.e., Level 3 or 4). A SSHAC Level 3 methodology was 

selected over a Level 4 because of the advantages in maintaining a reasonable cost and schedule 

for completion of the study. 

Comparison of the decision to use the SSHAC Level 3 methodology with the recommendations 

given in the current regulatory guidance (NRC, 2011, Ch. 6) supports the decision. For example, 

Chapter 6 in that document describes the decision criteria to be used in the selection of the 

SSHAC level as a function of the “viability” of the preexisting hazard study. The position taken 

in the guidance is that there is no significant difference in the degree of regulatory assurance 

provided by the SSHAC Level 3 or Level 4 methodology. As discussed in Section 6.3 and 

Table 6.1 of the NRC guidance (2011), SSHAC Level 3 or 4 methodologies are appropriate for 

nuclear facilities when the previous hazard study was either not conducted using the SSHAC 

methodology or was conducted using a Level 2 or lower SSHAC level, or where the existing 
Chapter 1 

Introduction 

1-8 

study is not viable. Viable is defined as (1) based on a consideration of data, models, and 

methods in the larger technical community; and (2) representative of the center, body, and range 

of technically defensible interpretations. 

Given these criteria, the existing regional seismic hazard studies in the CEUS would not be 

considered viable and, given the explicit application of the CEUS SSC Project for nuclear 

facilities, a SSHAC Level 3 or 4 would be consistent with the current regulatory guidance. 

Because of the equivalent levels of regulatory assurance for Level 3 and 4 studies, coupled with 

the cost and schedule advantages of Level 3, the selection of a Level 3 methodology for the 

CEUS SSC Project is reasonable and defensible. 

1.2.2 Goals: Stability and Longevity 

Stability and longevity are important goals of the SSHAC assessment methodology, and these 

goals are highly important to the CEUS SSC Project. Stability means that the integrated 

assessments that result from a SSHAC assessment process should generally not be subject to 

significant change without new hazard-critical scientific findings. This is because the knowledge 

of the affected scientific community has been systematically compiled and evaluated throughout 

the project, and uncertainties in the community knowledge have been appropriately characterized 

and represented in the CEUS SSC model. 

Longevity means that the model will last for a number of years before requiring a significant 

revision or update. New scientific findings will continue to be promulgated after the project is 

completed, along with new models and methods for interpreting data. Although evaluations of 

evolving scientific knowledge may potentially lead to the need to update elements of the model 

during site-specific use, it is likely that the regional model will remain viable, avoiding the need 

for an extensive revision for a number of years. Experience shows that community knowledge 

will not change in a systematic and significant way in a short time. The process of gathering 

scientific data, developing interpretations and hypotheses regarding those data, and vetting those 

hypotheses within the technical community takes time. With periodic updates, as necessary to 

reflect advances in the field as well as new data sources, the CEUS SSC model is expected to last 

several years before a significant revision is needed. 

1.2.3 Interface with Ground Motion Models 

After the EPRI-SOG project was completed, EPRI performed a major CEUS ground-motion 

project targeted on developing an understanding of ground motion variability. The project 

resulted in the EPRI ground-motion model for the CEUS (EPRI, 1993), which included an 

assessment of epistemic uncertainty in the median motions and an assessment of aleatory 

variability. The project involved nearly all of the then-active ground-motion modeling experts. 

Consequently, it stimulated follow-on research by a number of the participants who produced an 

equal number of ground motion models in the years following. The EPRI (1993) model, together 

with models developed by individual researchers, formed the body of knowledge for 

development of the EPRI (2004) GMC model for the CEUS, which updated the assessment of 

epistemic uncertainty in the median models and aleatory variability. 
Chapter 1 

Introduction 

1-9 

The EPRI (2004) ground-motion project was the first avowed application of a SSHAC Level 3 

process. The development of a composite understanding of ground motion attenuation is a 

contentious, complex issue, and uncertainty in ground motion contributes significantly to the 

uncertainty in PSHA. A SSHAC-defined Level 3 process was implemented, in which a TI team 

was responsible for conducting workshops involving the community of ground-motion-modeling 

scientists to compile and evaluate current knowledge. The TI team was additionally responsible 

for integrating the knowledge base and characterizing the range of knowledge and assessing the 

composite distribution of ground motion based on evaluations of available information, including 

interactions with ground motion experts. 

The TI team for the EPRI (2004) ground motion project brought together, in a series of three 

workshops, a panel of ground motion experts comprising proponents of the range of available 

models. The workshops were structured to gain a common understanding of the uncertainties in 

the modeling approaches and to develop the evaluation and assessment process for representing 

the uncertainty distribution of the technical community. The final product of the project was a 

ground-motion attenuation model defined by a set of equations and coefficients for estimating 

ground motion measures and their aleatory variability (standard deviation) as a function of 

earthquake magnitude and source-to-site distance. The model includes the epistemic uncertainty 

in the median estimate of ground motions and in the aleatory variability. The model is applicable 

to two general regions in the CEUS: the Midcontinent (CEUS excluding the Gulf Coast) and the 

Gulf Coast. The model is applicable to three classes of seismic sources: general conditions 

involving area sources; distant, large-magnitude sources; and nearby large-magnitude seismic 

sources. 

Shortly after completion of the EPRI (2004) project, another project (EPRI, 2006) was conducted 

at a SSHAC Level 2 to further examine the value of the standard deviation for the ground motion 

variability for the CEUS. The value of the standard deviation in the models developed in the 

EPRI (2004) ground-motion project was much larger than recent studies of large data sets of 

ground motions applicable to the Western United States (WUS) had shown. An evaluation of 

differences in the standard deviation in the CEUS and WUS, based on the variability of the 

source, path, and site terms, indicated that the WUS intra-event standard deviations are generally 

applicable to the CEUS, with some epistemic uncertainty about the effect of focal depth at short 

distances. The evaluation also indicated that the inter-event standard deviations may be larger in 

the CEUS than in the WUS, based on larger variability in the stress drops. Alternative models for 

the total standard deviation (combined intra-event and inter-event) were developed that can be 

applied to the CEUS. Overall, these new models show a significant reduction in the total 

standard deviation, particularly at short distances. Compared to the EPRI (2004) models, this 

lower value of the standard deviation tends to reduce the computed hazard. 

The EPRI (2004) GMC model and an updated assessment of aleatory variability (EPRI, 2006) 

together are the most current and applicable ground-motion model for the CEUS and are 

currently in use in ground motion analyses for COL applications. The ongoing Next Generation 

Attenuation–East project is aimed at replacing the GMC model developed by EPRI (2004, 2006). 

That effort has just begun and is not scheduled for completion until 2014. In anticipation of the 

types of ground motion models that will result from that project, the CEUS SSC Project provides 

outputs that are judged to be compatible with the needs of future ground-motion models. For 
Chapter 1 

Introduction 

1-10 

example, seismic sources are each characterized according to the characteristics of future 

earthquakes (see Section 5.4), such as the style of faulting, seismogenic crustal thickness, depth 

distributions, and orientation of ruptures. 

1.3 Study Region 

The project study region (Figure 1.3-1) is the region within which the CEUS SSC model has 

been developed. The SSC model is applicable to all sites within the project study region; 

however, for application at particular sites, such as those near the study region boundaries, 

additional seismic sources may need to be defined depending on the applicable regulations or 

guidance. The western boundary is located approximately along the foothills of the Rocky 

Mountains at longitude 105° W. On the north, the study region extends a minimum of 322 km 

(200 mi.) from the U.S.-Canadian border. On the south and east, the study region includes the 

offshore area a minimum of 322 km (200 mi.) from the coastline. Only seismic sources that lie 

within continental crust are included. The earthquake catalog developed for the CEUS SSC 

Project includes coverage of the entire area within the study region boundaries. 

Seismic sources that are not considered in this project are those in areas outside the study region 

boundaries; this applies to sources in the WUS, Mexico, Canada, and the Caribbean Plate 

boundary area. 

1.4 Products of Project 

The CEUS SSC Project resulted in a series of products that document the bases for the technical 

assessments made and that provide the inputs to probabilistic seismic hazard analyses at 

locations in the CEUS. These products are discussed below. 

1.4.1 Seismic Source Model for Study Region 

A seismic source model has been developed for the CEUS that contains descriptions of 

parameters that define the frequency of occurrence, spatial distribution, and rupture 

characteristics of potential future earthquakes. A conceptual SSC model was developed for use 

on the project, which is hazard-informed and takes advantage of knowledge gained from SSC 

projects conducted over the past several years. The framework includes a hierarchical approach 

to the identification and characterization of seismic sources that considers the importance of 

seismic source characteristics to the hazard results. The hierarchy calls for identifying seismic 

sources—and quantifying their characteristics—according to their importance to earthquake 

recurrence, maximum magnitudes, future earthquake rupture characteristics, and the activity of 

tectonic features. Following directly from this framework, sources of repeated large-magnitude 

earthquakes (RLMEs; magnitude [M] greater than 6.5) are identified where recurrence is defined 

primarily from the paleoseismic record. 

The choice of M 6.5 is simply because this is a magnitude earthquake that can usually be 

confidently identified within the paleoseismic record. Two alternative approaches to defining the 

spatial distribution of earthquakes outside of the RLME sources were (1) to define source 
Chapter 1 

Introduction 

1-11 

boundaries only on the basis of maximum magnitude differences, and (2) to define zones by their 

different seismotectonic characteristics. (Note that for simplicity in this section and later in the 

report, the term RLME is used to refer to the actual past earthquakes and the forecast of future 

occurrences; the term RLME source is used to refer to the seismic source used to model the 

spatial and temporal distribution of the RLMEs.) 

The spatial distribution of future earthquakes is defined by the geometry of the RLME sources, 

the maximum-earthquake source zones, and the seismotectonic zones. In all cases, uncertainties 

in these boundaries are captured by alternatives in the logic tree. In addition, the spatial 

distribution of the recurrence rate within the zones is defined using a spatial smoothing process 

that allows for spatial variation in a- and b-values. The temporal distribution of earthquakes that 

occur within RLME sources is defined by alternative temporal models that provide for the 

occurrence of temporally clustered behavior and, if the data suggest it, a temporal renewal 

process. The CEUS SSC model placed heavy emphasis on the compilation and analysis of 

paleoseismic data, reflecting the focus on these types of data by the larger technical community 

in recent years. 

The upper truncation of the earthquake recurrence relationships occurs at the maximum 

magnitude (Mmax), and these are estimated for all seismic sources. The assessment of Mmax for 

sources in stable continental regions (SCRs) such as the CEUS is subject to considerable 

uncertainty. The CEUS SSC Project employed two methods for assessing Mmax: a Bayesian 

methodology using an updated SCR database of earthquake magnitudes and related information, 

and a well-founded mathematical procedure that estimates Mmax based on seismic data (where 

sufficient) only for the source being considered. Many of the Mmax distributions are quite broad 

and reflect the uncertainties that currently attend the conceptual models and parameter 

uncertainties regarding constraints on Mmax. 

The identification and quantification of uncertainties associated with seismic source 

characteristics is an important component of a PSHA. As recognized by SSHAC (Budnitz et al., 

1997), a PSHA incorporates both aleatory variability and epistemic uncertainty. Aleatory 

variability is the natural randomness in a process that is known and understood. Examples of 

aleatory variabilities include an assessment of the size and location of the next earthquake, and 

the relative frequency of earthquakes having different rupture orientations. Epistemic uncertainty 

is the scientific uncertainty in a process that is due to limited data and knowledge. Examples 

include alternative recurrence models to describe future earthquakes, and the probability 

distribution describing the maximum magnitude of a particular seismic source. Epistemic 

uncertainties in the CEUS SSC model are captured in the master logic tree and the logic trees for 

each seismic source. 

Epistemic uncertainty is the result of limited data (often, very limited). In seismic hazard 

analyses, evaluating alternative models involves considering alternative simplified physical 

models, data from analogous regions, and empirical observations. These are subjective. In some 

cases, uncertainties are developed from formal statistical assessment of fitting models to data 

(e.g., recurrence rate and b-value parameters obtained from fitting the truncated exponential 

recurrence model to recorded seismicity). 
Chapter 1 

Introduction 

1-12 

The CEUS SSC model was developed in four stages. After the second workshop, a “sensitivity 

SSC model” was developed that was designed to incorporate all potentially important source 

characteristics. This model was used in hazard calculations and sensitivity analyses discussed at 

the third workshop as feedback. With that feedback, a “preliminary SSC model” was developed 

that focused more specifically on the quantification of uncertainties. After review of another 

round of hazard calculations and sensitivity analyses, a “Draft SSC model” was developed, 

which was described in the Draft Project Report. The TI Team and the PPRP reviewed the 

associated hazard calculations and sensitivity analyses for that model and made refinements that 

are now part of the “Final SSC model” described in this report. These refinements included 

additional work in the magnitude conversions for the CEUS SSC Project earthquake catalog and 

the inclusion of a range of smoothing parameters to express the epistemic uncertainty in the 

spatial variation of recurrence parameters. 

1.4.2 Hazard Input Document 

A hazard input document (HID; see Appendix H) was prepared to provide the documentation 

necessary for users to implement the CEUS SSC model in PSHA calculations for future 

applications. The HID contains all of the information required for a future user to exercise the 

model within a PSHA, but it does not include the technical basis or justification for the elements 

of the model. Included are the logic tree structure, all branches and weights, and tabulations of 

the outputs from all calculations conducted within the context of the source characterization 

effort. Such outputs include the Mmax distributions for all sources, recurrence calculations using 

paleoseismic data for the RLME sources, and spatially defined a- and b-values resulting from the 

smoothing algorithm. The purpose of the HID is to ensure that the expert assessments made by 

the TI Team are captured faithfully and accurately and delivered for use by the hazard analyst for 

a PSHA at a specific site. For the CEUS SSC Project, the final HID was used by the hazard 

analyst to carry out hazard calculations at seven demonstration sites (Figure 1.3-1), as 

summarized in Chapter 8. 

1.4.3 Documentation of Technical Bases for All Assessments 

The results of a PSHA serve a range of users with different needs, from earth scientists to 

engineers and regulators. The SSHAC process requires complete documentation of every step of 

the methodology used and the results obtained, thereby allowing all users to understand the 

technical justification for all parts of the assessment. This report documents the process and 

methodology followed for the project and the technical bases for the models, parameter values, 

and weights included in the source model. For example, Section 5.2 provides a detailed 

description of the methodology that was used to develop assessments of maximum magnitude 

(Mmax) for individual seismic sources, including the epistemic uncertainties that result from 

alternative conceptual models and from the range of parameter uncertainties. The Mmax 

methodology is then applied to each seismic source using the source-specific information related 

to the largest observed earthquakes within the zone, the numbers of earthquakes of various 

magnitudes, and the tectonic characteristics of the zone. The source-specific characteristics and 

resulting Mmax distributions are provided in the applicable sections of Chapters 6 and 7. 
Chapter 1 

Introduction 

1-13 

The documentation for the CEUS SSC Project describes the process used to compile and 

evaluate the data, models, and methods, and to integrate current knowledge and uncertainties in a 

logic tree format depicting alternatives that represent the center, body, and range of technically 

defensible interpretation. The goal of the project documentation is to provide an adequate basis 

for future users of the project to fully understand the process that was implemented, data that 

were used, evaluations that were performed, and the technical bases for the characterization and 

uncertainty assessments represented in the models. 

1.4.4 Other Key Products 

In addition to the key products identified above, which have direct application to future seismic 

hazard studies, the CEUS SSC Project also resulted in a number of other products that have 

value for future users. These products are described below. 

1.4.4.1 Data Evaluation and Data Summary Tables 

The CEUS SSC model development entailed the consideration of an extensive amount of data. 

Part of the responsibility of the TI team is to document the data that were used in the assessment. 

To supplement this documentation, the TI Team developed a series of tables that specifically 

identify all of the data that were considered by the team (Data Summary tables) and that indicate 

the team’s views of the quality of the data and the degree of reliance placed on any given data set 

(Data Evaluation tables). These tables provide a clear picture to future users of the data that were 

available at the time the project was conducted and how those data were used. The data tables are 

discussed in Section 4.1.2 and are given in Appendices C and D. 

1.4.4.2 Database of Geologic, Geophysical, and Seismological Data 

Because more than two decades have passed since the large regional seismic hazard studies 

(EPRI-SOG and LLNL) were conducted, the CEUS SSC Project entailed the compilation of a 

large amount of potentially applicable data. While no new data were gathered for the CEUS SSC 

Project (e.g., geologic mapping, paleoseismic investigations), a new regional database was 

developed for the project for use in SSC. The comprehensive database was formatted in a 

manner that allowed for dissemination of the data to all TI Team members during the course of 

the project. Where applicable, GIS data layers were developed that included new geophysical 

data compilations developed specifically for the project. A list of the available data sets included 

in the project database is provided in Appendix A. The project database, which includes an 

extensive bibliography of literature compiled for the project, was designed to be publically 

available following the completion of the project. In addition, a project website was developed 

for public use and can be found at www.ceus-ssc.com . 

1.4.4.3 Earthquake Catalog with Uniform Moment Magnitudes 

The CEUS SSC Project devoted a major effort to developing a comprehensive and uniform 

earthquake catalog for use on the project. Starting with the USGS national catalog and a number 

of regional catalogs, the various catalogs were updated to include all earthquakes through 2008. 

For modern PSHAs, moment magnitude is required for ground-motion prediction equations and 
Chapter 1 

Introduction 

1-14 

must be assessed for all earthquakes in the catalog. Accordingly, magnitude conversions between 

various instrumental magnitudes and moment magnitude were reassessed. Likewise, existing 

special studies of a number of historical earthquakes were reviewed in order to develop reliable 

moment magnitudes for these shocks. Uncertainties in the magnitude of all instrumental and 

historical earthquakes are included in the catalog. The CEUS SSC Project earthquake catalog is 

discussed in Chapter 3 and was used in defining and characterizing seismic sources as well as 

characterizing recurrence and Mmax parameters in the SSC model. 

1.4.4.4 Updated Paleoseismicity Data and Guidance 

Because of the significance of paleoliquefaction data in the CEUS, part of the scope of the 

project was to compile that data and develop written guidance for representing uncertainty in 

evaluations and interpretations of that data to estimate the locations, occurrence times, and 

magnitudes of causative earthquakes. The purpose of this study is to provide a basis for seismic 

source characterizers in the future to evaluate paleoseismic data relative to their quality and 

associated uncertainties. The results of the paleoseismicity study are given in Appendix E. 

1.4.4.5 Recommendations for Future Applications of SSC Model 

The CEUS SSC Project provides one of two models that are needed for PSHA calculations. Still, 

during the course of the project, hazard calculations were conducted for purposes of evaluating 

the significance of various SSC issues and providing that information as feedback to the TI 

Team. These calculations were carried out using the EPRI (2004, 2006) ground-motion models 

at seven demonstration sites for purposes of illustration. The area covered by this model is shown 

on Figure 1.3-1, along with the locations of the test sites used for hazard sensitivity calculations. 

In addition, as documented in this report, hazard was calculated for purposes of comparison with 

other hazard studies. 

This report contains an evaluation of the “precision” of the hazard estimates for use in evaluating 

whether changes to the seismic hazard are significant. This provides a basis for evaluating the 

significance of new findings and associated hazard changes in the future. And finally, the report 

includes a discussion of how the results of this project should be applied in the future. This 

discussion is given in Chapter 9.
Chapter 1 

Introduction 

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

2-1

2

CHAPTER 2 

SSHAC LEVEL 3 ASSESSMENT PROCESS 

AND IMPLEMENTATION 

This chapter describes the SSHAC Level 3 assessment process, how it was implemented to 

assess the CEUS SSC model, and how that implementation was accomplished in compliance 

with the SSHAC guidance. 

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 reasonably 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. 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). This reasonable representation of knowledge and 

uncertainties is referred to in the SSHAC guidance as ―the center, the body, and the range of the 

informed technical community.‖ The SSHAC assessment process, if properly implemented, 

provides high levels of confidence that the SSHAC goal has been met. Therefore, the way it is 

conducted is important and subject to ―process‖ as well as ―technical‖ peer view. A key 

responsibility of the Participatory Peer Review Panel (PPRP) is to ensure that the SSHAC 

assessment process has been properly implemented. 

SSHAC developed guidance for four ―study levels‖ of implementing an assessment that depend 

on the degree of uncertainty and contention involved and on the intended use of the seismic 

hazard model. SSHAC recommended that a Level 3 or Level 4 assessment process be used for 

complex assessments, the products of which have high public importance and attract public 

scrutiny, such as regional seismic hazard models intended to be used over a sustained time period 

as base-case models for site-specific PSHAs. Such models require the highest level of assurance 

that the community uncertainty distribution has been properly represented. For the CEUS SSC 

Project, the decision to use a SSHAC Level 3 assessment process was based on experience with 

implementing the SSHAC guidance, which has shown that a properly executed Level 3 

assessment process can provide a level of assurance of meeting the SSHAC goals comparable to 

that of Level 4, which is more costly and time-consuming to implement (selection discussed in 

the Project Plan and Section 1.2.1). 

Discussion of the SSHAC process in this chapter comes from four sources: 

1. The SSHAC document itself (Budnitz et al., 1997). 

2. A summary of workshops conducted to identify lessons learned from the implementation of 

SSHAC in actual projects (Hanks et al., 2009). 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

2-2

3. A summary of the ongoing efforts of the NRC to develop more specific SSHAC guidelines 

(Coppersmith et al., 2010). 

4. Draft NRC guidance for the implementation of SSHAC Level 3 and 4 projects (NRC, 2011). 

This chapter begins with a discussion of the fundamental SSHAC goals and activities that make 

up a SSHAC assessment process. This is followed by a discussion of the SSHAC Level 3 

assessment process implemented by the CEUS SSC Project, including the roles of key 

participants, project organization, key activities, and the PPRP. The final section summarizes 

how the CEUS SSC assessment process compares with the process prescribed in the SSHAC 

guidelines. 

2.1 Goals and Activities of a SSHAC Assessment Process 

Any PSHA requires that both knowledge and uncertainties be assessed and incorporated into the 

analysis. The SSHAC guidance expresses that fundamental goal in this way: 

Regardless of the scale of the PSHA study, the goal remains the same: to represent the 

center, the body, and the range of technical interpretations that the larger informed 

technical community would have if they were to conduct the study. (Budnitz et al., 1997, 

p. 21) 

An important part of the definition is the term ―informed,‖ which is defined by SSHAC:

Regardless of the level of the study, the goal in the various approaches is the same: to 

provide a representation of the informed scientific community‘s view of the important 

components and issues and, finally, the seismic hazard. (―Informed‖ in this sense 

assumes, hypothetically perhaps, that the community of experts were provided with the 

same data and level of interaction as that of the evaluators). (Budnitz et al., 1997, p. 26) 

Thus there are two aspects of what constitutes an ―informed‖ member of the technical 

community; the individual (1) is assumed to have knowledge of the project-specific and other 

relevant data, and (2) is assumed to have gone through the same interactive process that the 

evaluator experts have gone through in the project. Such an interactive process involves multiple 

workshops, structured interactions with proponents of alternative viewpoints to reveal the 

technical basis for various hypotheses, and feedback cycles to understand the implications of all 

technical assessments and associated uncertainties. The Technical Integration (TI) Team carries 

the responsibility of representing the center, body, and range of the views of the informed 

technical community. 

―The center, the body, and the range‖ is taken to mean an appropriate representation of 

knowledge and uncertainty in the important components to a hazard assessment and is referred to 

by the SSHAC as ―the community distribution.‖ A proper representation of the community 

distribution as defined in SSHAC appropriately meets the requirements of the NRC‘s seismic 

regulation, 10 CFR 100.23. 

After a review of multiple SSHAC projects and lessons learned, the NRC (2011) revisited the 

terminology associated with the SSHAC goals and proposed alternative wording: 

The key statement in the SSHAC guidelines, that encapsulates the ethos of the SSHAC 

approach, is as follows: ―Regardless of the scale of the PSHA, study the goal remains the 

same: to represent the center, the body, and the range that the larger informed technical 
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community would have if they were to conduct the study‖ (NUREG/CR-6372). For 

brevity, the ―center, body, and range of the informed technical community‖ is denoted 

CBR of the ITC. A key word in the concept is ―informed,‖ which is specifically defined 

in the SSHAC guidelines to mean an expert who has full access to the complete database 

developed for a project, and has fully participated in the interactive SSHAC process. In 

other words, the selected experts who participate in the PSHA study must endeavor to 

represent ―the larger informed technical community‖ by assuming the hypothetical case 

where the others in the larger technical community become ―informed‖ through 

participation in the same process. The SSHAC guidelines recognize that this is a 

hypothetical exercise, but the goal would be to ensure that a broad range of views are 

considered. In practice, however, the term ―informed‖ is often either ignored or 

misinterpreted as simply meaning expert in the field of interest. Thus, the process of 

capturing or representing the CBR of the ITC has been viewed by some as a process of 

somehow conducting a poll or surveying the larger community for their opinions. 

In the spirit of maintaining the fundamental SSHAC objective and clarifying the concept 

with terms that reflect actual practice, an alternative statement of the fundamental 

objective of the SSHAC process is presented in this report. This alternate description 

explains that the objective of the SSHAC guidance is actually achieved through a twostage process of evaluation followed by integration. Therefore, consistent with the 

original intent of the SSHAC guidance, we recast the goals of the SSHAC process in 

terms of the two main activities (i.e., evaluation and integration) by the following 

statement:

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). 

In light of these definitions, we propose that it is clearer to refer to the CBR of the 

―technically defensible interpretations‖ (TDI), instead of CBR of the ITC. However, it is 

important to emphasize that the careful evaluation of the larger technical community‘s 

viewpoints remains a vital part of the SSHAC process. We simply have removed the term 

―informed‖ because of its specialized definition in the original SSHAC guidelines. 

Similarly, we propose to replace the term ―community distribution‖ that is used 

frequently in the original SSHAC guidelines to describe the outcome from a SSHAC 

assessment process with the term ―integrated distribution.‖ This is to remove any 

perception that the final assessments and models were arrived at through a mere poll of 

the community.‖ (NRC, 2011) 

As discussed extensively in the SSHAC report (Budnitz et al., 1997) and affirmed in NRC

(2011), a SSHAC assessment process consists of two important sequential activities, which, for a 

Level 3 assessment, are conducted by the TI Team under the leadership of the TI Lead: 

evaluation and integration. Each activity is discussed below related to the particular CEUS SSC 

model-development activities that are entailed. 
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2.1.1 Evaluation 

The TI Team evaluates relevant data, models, and methods that pertain to SSC inputs to a hazard 

analysis. The activities associated with evaluation are as follows: 

Identify hazard-significant issues. Hazard calculations and sensitivity analyses are performed 

at the beginning of the project to help steer the data compilation toward hazard-significant 

issues. After a preliminary model is developed, hazard calculations are done again to 

evaluate hazard sensitivity for feedback. 

Identify and compile project-specific data in a database. The project database is a 

fundamental tool with which the TI Team makes its evaluations. Workshop #1 helps in the 

data identification process as resource experts are assembled, and contacts with the larger 

technical community are made outside the workshop throughout the evaluation process. 

Collect new data. If resources allow, new data may be gathered that address particular SSC 

issues. 

Conduct and document the data evaluation process. A comprehensive review of pertinent 

data is conducted to identify their relevance to SSC (Data Summary tables) and to evaluate 

the data relative to their use in the SSC model (Data Evaluation tables). The data evaluation 

process continues throughout the integration process. 

Evaluate alternative data, models, and methods that exist within the technical community. 

The purpose of this evaluation is to gain a clear understanding of the data, models, and 

methods that have been proposed in the community, including their technical bases, 

strengths, weaknesses, and uncertainties. Facilitated discussions among proponent and 

resource experts can help with this in Workshop #2 and other communications outside the 

workshop. It is important to focus the discussions on the specific issues of importance to 

SSC. 

2.1.2 Integration 

Integration is model-building by the TI Team to arrive at a defensible expression of knowledge 

and uncertainty in inputs to SSC. This includes the full expression of the model elements (logic 

tree branches), their relative weights, and the range of credible uncertainties. The activities 

associated with integration are as follows: 

Understand expert assessment issues: The TI Team must understand the tools and issues 

associated with quantifying epistemic uncertainty and aleatory variability. It must also 

understand—and counter—common expert assessment issues (anchoring, availability, and 

other cognitive biases). 

Develop SSC models: The TI Team must identify technically defensible conceptual models 

and parameter values and include them in the SSC logic tree. Weights are assigned that 

reflect the degree of support for the models and parameter values in the available data and 

current technical understanding. The TI Team can develop new and innovative models to 

explain the available data, and it can develop new methods for analyzing the data and 

building the models, as long as the methods are consistent with the goal of expressing 

knowledge and uncertainties about the key issues. This activity is done at least twice: once 
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for a preliminary SSC model and again for the final SSC model. For the CEUS SSC Project, 

model-building occurred four times: for the SSC Sensitivity model, SSC Preliminary model, 

Draft SSC model, and Final SSC model. 

Perform hazard sensitivity calculations and collect feedback: These are run based on the 

preliminary SSC model developed by the TI Team in order to identify the most significant 

model elements and the importance of the uncertainties to the hazard results. These are 

provided as feedback and were discussed at Workshop #3. Hazard calculations and 

sensitivity analyses are also conducted, based on the final SSC model, to provide additional 

understanding of the model components and associated uncertainties. 

Document the bases for the assessments: The TI Team is responsible for documenting 

activities so that the reader can understand the basis for the model elements and the 

expressions of uncertainty made (weights on tree branches, parameter distributions, etc.). 

New data gathered for the project, along with new models and methods developed by the TI 

Team, impose the burden of high levels of documentation in order for reviewers of the report 

to understand their technical basis and application. 

As noted previously, the evaluation and integration process is sequential during the SSHAC 

assessment process. During the evaluation phase, the applicable data are compiled and evaluated 

and the views of the technical community—expressed by proponent and resource experts—are 

duly considered. During the integration phase, models are developed by the TI Team as part of

the evaluation process. Integration does not entail a poll or vote of the views of the larger 

technical community. It is model-building by the TI Team that is informed by its careful 

evaluation of all applicable data, its knowledge of the views of the community on certain issues, 

its discussions in workshops, and its direct communication with members of the community. The 

TI Team constructs an integrated model, usually expressed as a logic tree, which reflects 

knowledge and uncertainties in models and parameter values. 

2.2 Roles of CEUS SSC Project Participants 

The roles that various participants play in a SSHAC assessment process are important and are 

defined specifically in the SSHAC guidelines (Budnitz et al., 1997). The CEUS SSC Project was 

conducted in accordance with SSHAC guidelines for Level 3 projects, which explicitly define 

the roles of project participants who contribute to a PSHA project. Beginning with the review of 

the Project Plan at the Kick-Off Meeting on May 8, 2008, all project participants were informed 

of their expected roles before their participation, and they were reminded of their roles at the 

beginning of each workshop, at working meetings, and at other opportunities throughout the 

project. Table 2.2-1 identifies the meetings that were conducted during the course of the project, 

including the participants and meeting dates. SSHAC descriptions of the Project Sponsor; Project 

Manager; Technical Integrator; resource, proponent, and evaluator experts; and participatory 

peer reviewers are described below. NRC (2011, Section 3.6) provides additional discussion of 

these roles and responsibilities in a review of projects conducted using the SSHAC guidelines. 

Organization for the CEUS SSC Project, including its structure and lines of communication 

within that structure, is explained in Section 2.3. 

The Project Sponsor is the entity that provides financial support for a project and ―owns‖ the 

results of the study in the sense of property ownership. The CEUS SSC Project has three 
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sponsors: the NRC, DOE, and EPRI. The Project Manager is defined as the individual 

responsible for maintaining project scope, budgets, and schedules and coordinating 

communications among the project participants and the Project Sponsor(s). The Technical 

Integrator is defined as a single entity—e.g., an individual or team—that is responsible for 

conducting the evaluation and integration processes. As discussed in Section 2.1, a Level 3 

assessment includes evaluation and integration by a TI Team under the technical leadership of 

the TI Lead. 

Three types of experts having distinctive roles are identified in a SSHAC assessment process: 

resource experts, proponent experts, and evaluator experts. A resource expert is a technical 

expert with specialized knowledge of a particular data set, model, or method of importance to the 

hazard analysis. The expertise may be in the form of site-specific experience, or knowledge of 

particular methodologies or procedures. A number of resource experts participated in Workshop 

#1 and summarized their data sets. In addition, a number of resource experts were contacted 

outside the workshop environment to provide their data and expertise (Table 2.2-2). A proponent

expert is an expert who advocates a particular hypothesis or technical position. At Workshop #2, 

several proponent experts presented their tectonic hypotheses to the TI Team and debated the 

merits of their models. The workshop also provided the opportunity for the TI Team to question 

the proponent experts regarding the technical support and uncertainties associated with their 

models. An evaluator expert is an expert who can evaluate the relative credibility of multiple 

alternative hypotheses to explain a given set of observations. Each evaluator expert uses 

professional judgment to quantify uncertainties, based on review and evaluation of all potential 

hypotheses and available data. An evaluator may challenge a proponent‘s position and question 

the technical basis for conclusions as a means of gaining insight into the uncertainties. 

The members of the CEUS SSC TI Team were charged with fulfilling the roles of evaluator 

experts. At the outset of their participation on the project, the Team members were instructed in 

working meetings, and later reminded at workshops, that their role as evaluator experts would 

entail an objective evaluation and integration process, as described in Section 2.1 of this report. 

The need for removal of a member who would not assume the proper evaluator expert role was 

described, as was the process that would be followed by the TI Lead to carry out the removal, 

should it be necessary. The TI Lead is responsible for ensuring that all TI Team members know 

their roles as evaluators and that they maintain those roles throughout the course of the project. 

Peer review is considered a key aspect of the Level 3 assessment process. This is to ensure that 

the process followed is adequate, uncertainties are properly considered and incorporated into the 

analysis, and the results provide a reasonable representation of the diversity of views of the 

technical community. Technical peer review is the review of the earth sciences aspects of a 

study, including a review to ensure that all applicable technical hypotheses have been 

considered. A review of how the study is structured and executed is referred to as a process peer 

review. Two different methods for peer review are described in SSHAC. Participatory peer 

review is defined as an ongoing or continuous process that provides the peer reviewers with full 

and frequent access throughout the entire project, in contrast to a late-stage peer review that 

occurs when a project has almost been completed. The principal benefit of a participatory peer 

review is that if problems are discovered, the opportunity exists for a mid-course correction 

without the need for work to be substantially redone at the end. SSHAC strongly recommends 

the use of a participatory peer review for both technical and process reviews for projects in 
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which a Level 3 approach is used. Accordingly, a participatory peer review process was used on 

the CEUS SSC Project. 

2.3 CEUS SSC Project Organization 

The project organization is shown on Figure 2.3-1, and the functions are summarized below. 

Project Sponsors: The CEUS SSC Project was jointly sponsored by the DOE, NRC, and 

utilities and vendors under the auspices of the EPRI Advanced Nuclear Technology (ANT) 

program, Action Plan Committee (APC). The joint sponsorship of the study by both public and 

private sector representatives is unique for regional seismic hazard assessments in the United 

States. It signifies the recognition by the multiple parties that they have common needs—a fully 

defensible seismic source model that can be used for nuclear facility sites throughout the 

CEUS—and common goals of seismic hazard inputs that are stable and long-lived. Sponsor 

representatives were present at all workshops and key project meetings. 

Project Management: Project management responsibilities were divided between those related 

to contract management; technical communication with sponsors, the TI Lead, and the PPRP; 

and those related to scope, budget, and schedule. EPRI assumed responsibility for contract 

management and provided the fundamental interface for contracts. These responsibilities 

included contracting with sponsors and CEUS SSC Project participants, providing support for 

workshops, and establishing requirements for the project report and website. The Project 

Manager was responsible for developing the project plan; communicating with the sponsors, TI 

Lead, and the PPRP; and developing project tools for maintaining project scope, budgets, and 

schedules. The lines of communication for the project are shown on Figure 2.3-2. Jeffrey F. 

Hamel, EPRI ANT Program, communicated directly with the CEUS SSC Project Manager, 

Lawrence A. Salomone. Mr. Salomone, who established the industry-government partnership for 

the CEUS SSC study, was the principal interface with the TI Lead, the PPRP, and the project 

sponsor representatives (Figure 2.3-2). He assisted EPRI management in establishing and 

maintaining project budgets and schedules and preparing status reports, and he had primary 

responsibility for the delivery of all technical products. He was the principal spokesperson to the 

outside community, which included the DOE, NRC, USGS, and industry. 

Participatory Peer Review Panel (PPRP): Members of the PPRP were responsible for 

reviewing both the technical and process aspects of the CEUS SSC Project. They were observers 

at the majority of the technical meetings held during the course of the project (see Table 2.2-1). 

They attended all project workshops and provided feedback and written comments after each 

workshop. They attended 8 of the 11 TI Team working meetings to observe the process and 

progress of the project. They also attended three PPRP briefings to review in depth the technical 

assessments being made by the TI Team at key points during the study. A fourth PPRP briefing, 

the closure briefing, was held to bring closure to the entire project review process. Throughout 

the project, the PPRP provided verbal and written comments that assisted the TI Team in 

carrying out its assessments. PPRP responsibilities included reviewing and providing written 

comments on the Project Plan and reviewing both the Draft Project Report and the Final Project 

Report developed by the TI Team. 

Technical Integration (TI) Team: The TI Team, led by Kevin J. Coppersmith, had primary 

responsibility for developing and documenting the technical basis for all project assessments and 
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products, as described in Section 2.4. The 12-member TI Team was responsible for 

implementing the SSHAC Level 3 methodology throughout the project, including all key 

assessment steps of evaluation and integration. Such steps include working with the Project 

Manager to develop the Project Plan, developing the project database, conducting three 

workshops, facilitating the requisite expert interactions, conducting 11 working meetings, 

communicating with the PPRP, and documenting all process and technical aspects of the study in 

a project report. Members of the TI Team and the Project Manager wrote the project report. 

Database Manager: The Database Manager was responsible for retrieving and compiling 

applicable data for use in developing the SSC model. These data sets were provided in the 

formats appropriate for use in the TI Team‘s deliberations. The Database Manager provided 

support for resolving copyright issues, working meetings, workshops, and PPRP briefings, as 

needed. 

Technical Support: The TI Team was assisted in a number of areas by several individuals. The 

technical support team provided support to the hazard calculations, interpretations of the 

paleoliquefaction database, compilation of the geophysical databases, assistance with graphics 

and GIS, and development of workshop summaries and the project report. 

Resource Experts, Proponent Experts, Specialty Contractors, and Other Project 

Participants: A large number of representatives of the larger technical community participated 

in the project as resource experts, proponent experts, and specialty contractors. Steps were taken 

by the TI Team, as supported by the PPRP, to ensure that the participation of resource experts 

and proponent experts in Workshops #1 and #2 was appropriate and complete in order to be 

representative of the range of current scientific community interpretations, for which awareness 

and knowledge were required. The PPRP reviewed the list of resource experts and proponents 

selected for Workshop 1 and Workshop 2, respectively. Specialty contractors were engaged on 

the project to provide certain technical products, including geophysical maps, stress 

interpretations, and guidance for the assessment of paleoliquefaction. Personnel from the USGS 

played an extended role in this project to ensure that all supportable interpretations of the 

scientific community were fully identified, evaluated, and represented in the SSC model. Several 

USGS personnel provided detailed review and feedback on specific issues (e.g., the earthquake 

catalog, Mmax, and methods), which were considered in the assessment of the SSC model by the 

TI Team. 

Technical knowledge and experience on specific topics of discussion were provided at the 

workshops by resource experts and proponent experts. The workshops provided an important 

opportunity for the TI Team evaluators to gain knowledge regarding specific databases in 

Workshop #1 and to question and challenge the findings of the proponent experts in 

Workshop #2. Table 2.2-2 provides a list of the resource experts who gave presentations at 

Workshop #1 and the proponent experts who participated in Workshop #2. Throughout the 

project, a number of technical experts provided their insights, data, and viewpoints at the request 

of members of the TI Team. These individuals are listed in Table 2.2-2. Their participation was 

invaluable in keeping the TI Team abreast of current data, models, and methods and for 

providing a basis for assessing the technical bases and uncertainties associated with recent and 

ongoing studies in the technical community. 
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2.4 Key Tasks and Activities 

As outlined at the beginning of the project in the Project Plan, the CEUS SSC Project was 

structured around a set of tasks and activities that would fulfill the requirements of a SSHAC 

Level 3 project (Coppersmith et al., 2010). The key tasks and activities that define the CEUS 

SSC Project are described in this section. The components of a typical SSHAC Level 3 or 4 

project and their interactions are illustrated on Figure 2.4-1. 

2.4.1 Database Development 

A fundamental resource developed as part of the CEUS SSC Project is the project database. The 

database mainly provides information for the use of the TI Team in its evaluation and integration 

processes. Most of the database consists of publications from the professional literature, maps, 

and similar documents. To respond to project needs, many of the maps in the database were 

entered into a GIS format. All documents were entered in a format that allowed them to be 

displayed, geo-registered, and superposed for the consideration of the TI Team in working 

meetings. A summary of the project database is given in Appendix A, and a description of the 

data is provided in the metadata files, which provide a means of searching by data type. 

Although the major data compilation effort occurred early in the project, the project database 

continued to be developed throughout the course of the project. Identification of the data sets that 

populate the database began at project initiation, based on the SSC experience of the TI Team 

members. More data sets were identified in Workshop #1 (Significant Issues and Data). 

Resource experts who participated in the workshop presented their own specific data and, after 

the workshop, they provided lists of recommended references for consideration by the project. 

Throughout the course of the project, members of the TI Team communicated with a large 

number of researchers in the technical community and continued to identify data that were in the 

process of being developed and could be included in the project database. To supplement the 

existing data, certain new data were compiled for use by the project, including gravity maps, 

magnetic anomaly maps, an update to the U.S. stress map, and a compilation of paleoliquefaction 

data. In addition, a new earthquake catalog was developed using existing catalogs and new 

magnitude conversions and other updates (see Chapter 3). No new data were collected (e.g., field 

geologic investigations, geophysical surveys) as part of the CEUS SSC Project. 

The database is considered a deliverable of the project, and it has been placed in a format that 

will allow it to be used by researchers in the future via a dedicated website www.ceus-ssc.com . 

An allied activity to the development of the database development was the development of a 

conceptual SSC framework, which is documented in Chapter 4. The framework was developed 

in light of the knowledge and understanding of earthquake processes in the technical community, 

the experiences of the TI Team in characterizing seismic sources in the CEUS and other stable 

continental regions (SCRs), and suggestions and feedback from members of the PPRP. Among 

other things, the conceptual SSC framework provides a documented approach to identifying 

relevant data, evaluating those data for their specific use in the SSC model, and defining seismic 

sources according to a prioritized set of criteria that are hazard-informed. The conceptual SSC 

framework, which was developed early in the project and reviewed by the PPRP and during 

Workshops #1 and #2, provided a basis for all the evaluation and integration activities conducted 

by the TI Team. 
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2.4.2 Identification of Significant Issues 

SSC for purposes of a PSHA is a specialized activity, and the technical issues within SSC that 

are important to seismic hazard are a subset of the larger range of issues that define seismologic, 

geologic, and tectonic interpretations. To provide a focus on the data, models, and methods of 

greatest importance to the hazard, sensitivity calculations were conducted. The experience by the 

TI Team gained from past seismic hazard analyses was also considered in the identification of 

hazard-significant issues. Workshop #1 was partially devoted to the identification and discussion 

of the technical SSC issues of greatest significance to a PSHA conducted for purposes of the 

design and review of nuclear facilities. The goal in that discussion was to focus on the data that 

would be most useful in defining the SSC model at the annual frequencies of interest (e.g., 10–3

to 10–7/yr) for nuclear facilities. For example, data were identified that would be important to 

constraining maximum magnitudes, paleoseismic recurrence estimates, and the recurrence rate of 

larger-magnitude earthquakes. Likewise, information was identified that could be used to 

quantify the uncertainties in these assessments, such as the characteristics of global SCR 

earthquakes, age estimates of paleoseismic earthquakes, and uncertainties in earthquake catalog 

completeness as a function of location, time, and magnitude. 

Also, as discussed in Chapter 4, throughout the project an effort was made to keep the project 

―hazard-informed‖ in the sense that highest priority would be given to the issues having the most 

significance to the hazard results. The goal was not to eliminate issues but to ensure that those 

issues of highest significance were adequately addressed. This is especially important in a 

regional study of this kind that includes extensive earth sciences data sets developed for a variety 

of purposes by numerous researchers. 

2.4.3 Workshop #1—Key Issues and Available Data 

The goals of Workshop #1 were as follows: 

Introduce the participants in the project to the goals, expectations, and schedule for the 

project. 

Identify the key issues that would need to be addressed in the course of the SSC. 

Review the available data, including data quality. 

Identify the path forward for the project. 

The workshop began with a description of the importance of the CEUS SSC Project to groups 

involved with the nuclear industry, including utilities, regulators, and oversight groups. By 

assembling a single team of experts to develop a new and stable CEUS SSC, the science for 

seismic hazard assessment would be advanced, plus there would be cost and schedule-related 

benefits for existing and planned nuclear facilities. An explanation of SSHAC assessment 

process goals, study levels, and responsibilities was provided. This included a discussion of the 

roles of the TI Team members as evaluator experts. The Team was reminded, as they were in all 

subsequent workshops and working meetings, that they were expected to be objective evaluators 

of the available data, models, and methods. They were also reminded that the SSHAC 

assessment process would entail both evaluation and integration, as defined in the SSHAC 

guidelines. 
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Three questions are involved in defining SSC: Where will future earthquakes occur? How large 

will they be? and How frequently will they happen? The scientific assessments needed for SSC 

were described, including quantification of uncertainties, and examples from projects conducted 

in the United States and other countries. 

The first session of the workshop focused on a review of the technical issues of importance to the 

CEUS SSC Project in the context of preparing a PSHA. The sensitivity of seismic hazard results 

to input parameter choices and associated uncertainties was discussed for several localities, 

including the New Madrid and Charleston regions. Defining and properly considering 

sensitivities is an important goal of the project. It was noted that for seismic sources having 

potentially large earthquake magnitudes (e.g., New Madrid and Charleston regions), assessments 

of parameters such as characteristic magnitude distributions and source zone locations are 

particularly important because these sources could potentially affect local and distant sites. 

The next session of the workshop focused on data that are available and that may be useful in 

addressing the key issues discussed in the previous session. The structure of the database being 

developed for the project was described. Additional analysis was planned for some data sets to 

make them more useful for the project. After hearing a review of the data documentation process 

and a brief description of the data sets that had been compiled, workshop participants considered 

possible gaps in the available data sets. 

The bulk of the workshop focused on data and information that could potentially be used for SSC 

in the CEUS. Data presentations were made by resource experts who had been involved in the 

development of pertinent databases. Before the workshop, the TI Team reviewed the data being 

compiled in the database and identified resource experts to participate in the workshop (Table 

2.2-2). The list of resource experts was reviewed by the PPRP to ensure that a broad spectrum of 

experts from the scientific community were identified. Although it is not possible to allow the 

participation of all resource experts in the technical community, the TI Team identified a 

representative group of participants from the spectrum of disciplines that are important to 

seismic source characterization. Those resource experts who were not already participants in the 

workshop were contacted by TI Team members to discuss their data and gain access to it. 

Members of the community who provided their data and interpretations are listed in Table 2.2-2. 

At the workshop, the resource experts had been asked to focus on data accessibility, formats, and 

applicability. While first-order interpretations of data were provided, discussions of alternative 

interpretations and models of the data were kept to a minimum for this workshop. First, 

presentations were given on gravity data, magnetic data, and a global seismic refraction catalog. 

Next, the complexities of the origins of earthquakes within stable continental regions were 

described, as were tectonic features of the Precambrian basement in the Midcontinent, in situ 

stress and earthquake focal mechanisms, strain fields in the Eastern United States, and 

paleoliquefaction at localities within the CEUS. The final session of the workshop was focused 

on the seismicity catalog to be compiled, including the primary sources of earthquake data and 

the plans to identify dependent events and to assess catalog completeness. Presentations were 

also made on the approaches used to develop the USGS catalog and selected regional catalogs, 

including work to identify historical earthquakes. 

Workshop #1 was documented on a CD. The CD, which contained the agenda, presentations, a 

workshop summary, a list of participants, the PPRP letter report, and a photo album of 
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participants, was distributed to all participants; the contents are posted on the EPRI website. The 

TI Lead and Project Manager hosted a half-day briefing for international observers and young 

professionals prior to the workshop to improve their understanding of the context of the 

workshop and its role in the SSHAC assessment process. 

2.4.4 Workshop #2—Alternative Interpretations 

The goals of Workshop 2 were as follows: 

Review the project SSHAC Level 3 methodology, ground rules, expert roles, and peer review 

processes. 

Provide an opportunity for the project (TI) team to understand proponent views on important 

technical issues. 

Discuss the range of alternative views and uncertainties within the larger technical 

community. 

Discuss the path forward for the project. 

The goals of the workshop were accomplished by a series of presentations and discussions 

designed to provide the TI Team with information it would need to develop a preliminary SSC 

model. In the development of this model, the knowledge and uncertainties in available data, 

models, and methods must be taken into consideration. A series of workshop presentations were 

made by proponent experts who had been asked to provide their views on key technical issues 

posed in written questions from the TI Team that were provided to each proponent before the 

workshop. The proponents were also asked to include discussions of the uncertainties associated 

with their views. The workshop provided an important opportunity for the TI Team to gain a 

better understanding of the community‘s views, to directly question the experts regarding the 

technical bases for their interpretations, and to debate alternative viewpoints regarding key SSC 

issues. In several cases, the proponent experts were encouraged to debate the pros and cons of 

their hypotheses among themselves in a facilitated format, thus allowing the TI Team to 

understand the key technical bases and uncertainties associated with the alternative models. 

Before the workshop, the TI Team reviewed those data, models, and methods being proposed by 

the technical community having relevance to SSC in the CEUS. The team then identified 

members of the community who would provide a summary of their viewpoints during the course 

of the workshop. The list of proponent experts was reviewed by the PPRP to ensure that a broad 

spectrum of views in the scientific community were represented. Representatives from the USGS 

were also asked to provide their views on whether there were additional models or methods that 

should be represented. Those proponent experts are identified in Table 2.2-2. Although it is not 

possible to allow the participation of all proponent experts in the technical community, the TI 

Team identified a representative group of participants from across the spectrum of applicable 

data, models, and methods of importance to the CEUS seismic source characterization. Those 

proponent experts who were not already participants in the workshop were contacted by 

members of the TI Team to gain access to their published and unpublished interpretations, and an 

understanding of their viewpoints and the uncertainties in their interpretations. Members of the 

community who participated in providing their interpretations are identified in Table 2.2-2.

After the introductory session of the workshop, presentations were made on the following topics: 
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Seismicity and seismic parameters, including maximum magnitudes, in selected areas of the 

CEUS (e.g., the Charlevoix and lower St. Lawrence Seaway regions). 

Tectonic features throughout the CEUS, including neotectonic features in the Appalachian 

Piedmont, Ouachita sub-detachment structures, rifts in the Midcontinent, faults and folds in 

the Illinois Basin, and Quaternary deformation features in the New Madrid region. 

Paleoliquefaction evidence throughout the CEUS, including in the Mississippi Valley and the 

Wabash Valley, and methods for quantifying uncertainties in paleoliquefaction studies. 

Alternative interpretations of the state of stress, strain, and earthquake hazards in the regions 

surrounding the epicenters of the large-magnitude New Madrid and Charleston earthquakes. 

Seismic sources in the Gulf of Mexico. 

Source model features of the 2008 USGS national hazard maps for the CEUS, focused on 

source characterization in the New Madrid and Charleston. 

During the course of these presentations, facilitated discussions occurred, focused on 

implications to SSC for hazard analysis, including the conceptual models that would represent 

the range of interpretations and the degree of support of the models based on available data. 

Proponents provided all references related to their work after the workshop. 

Workshop #2 was documented on a CD. The CD, which contained the agenda, presentations, a 

workshop summary, a list of participants, the PPRP letter report, and a photo album of 

participants, was distributed to all participants; the contents are posted on the EPRI website. The 

TI Lead and Project Manager hosted a half-day briefing for international observers and young 

professionals prior to the workshop to improve their understanding of the context of the 

workshop and its role in the SSHAC assessment process. 

2.4.5 Working Meetings 

Although the workshops provided an opportunity for the TI Team to consider and discuss a 

variety of topics, much of the actual SSHAC assessment processes of evaluation and integration 

occurred at the working meetings that took place between and after the workshops. Eleven 

working meetings were held with the entire TI Team (Table 2.2-1), most meetings typically 

lasting two to three days, and many other subgroup meetings, webinars, and conference calls 

were held to discuss and resolve the numerous technical issues associated with the project 

assessments. Each working meeting was focused on one or more agenda items that required 

attention by the TI Team, including the following: 

Identification of potential participants at workshops, including resource experts at Workshop 

#1 to discuss their data sets, and proponent experts at Workshop #2 to discuss their 

alternative models and methods. 

Development of a conceptual SSC framework and the associated master logic tree. 

Approaches to developing the Data Summary and Data Evaluation tables. 

Issues associated with the new earthquake catalog. 
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Alternative approaches to Mmax assessment and updates to the Bayesian approach and their 

implications. 

Approaches to spatial smoothing. 

Defining and characterizing repeated large-magnitude earthquake (RLME) sources. 

Use of the paleoseismic data to define the size and recurrence of RLME sources. 

Renewal vs. Poisson recurrence models. 

Alternatives to seismotectonic zones. 

Structure of logic trees, alternatives to include as logic tree branches, and weights on 

branches. 

Hazard feedback and recurrence sensitivity analyses. 

Much of the planning for the workshops in terms of developing the agendas and identifying 

participants was conducted in the working meetings. This allowed the entire TI Team to consider 

the larger technical community and ensure that a representative cross section of experts was

asked to participate in the workshops. Although the workshops provided a forum for interaction 

among the large number of resource and proponent experts who participated, additional contacts 

were made with members of the larger technical community outside the workshops (see Table 

2.2-2); the working meetings provided the opportunity for all TI Team members to discuss the 

results of those additional communications. At the same time, the TI Team members devoted 

considerable effort to completing their Data Evaluation and Data Summary tables that document 

the data, models, and methods that were considered. These are provided in Appendices C and D. 

The working meetings were typically held in a conference room environment, with the project 

database available at all times for projection and discussion. Working Meetings #10 and 11 were 

held using a conference-call/webinar format. One to three representatives from the PPRP 

attended 8 of the 11 working meetings in order to observe the deliberation and technical 

assessment processes (Table 2.2-1). Each working meeting ended with a set of actions for 

various members of the TI Team to pursue and to bring back to the entire team at the next 

meeting. 

2.4.6 SSC Sensitivity Model Development 

As discussed in Section 2.1, a SSHAC assessment process begins with evaluation of available 

data, models, and methods, followed by the integration process of model-building to incorporate 

knowledge and uncertainty. The integration process on the CEUS SSC Project occurred in four 

stages beginning with development of the ―SSC Sensitivity model‖ and associated hazard 

calculations, development of the ―SSC Preliminary model‖ and associated hazard calculations, 

development of the ―Draft SSC model‖ and associated hazard calculations, and development of 

the ―Final SSC model‖and associated hazard calculations. As a tool to assist the TI Team in the 

development of its SSC model, a ―conceptual SSC framework‖ was developed (Chapter4) that 

provided a basis for documenting the data consideration and evaluation process, defining the key 

criteria for identifying seismic sources, and structuring the SSC model around a master logic 

tree. As the integration process ran through the four stages of SSC model development, the 

conceptual SSC framework provided a common structure for the TI Team. 
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A key part of a SSHAC Level 3 assessment process is the opportunity to receive and consider 

feedback about the implications of preliminary assessments. To do so, the SSC Sensitivity model 

was developed, which included a wide range of conceptual models and parameter values. Based 

on the conceptual SSC framework, a master logic tree was developed that describes the basic 

approaches and conceptual models for characterizing the spatial and temporal distribution of 

future seismicity. For example, the master logic tree for the SSC Sensitivity model included 

alternative approaches to the spatial characterization of seismicity, ranging from the smoothing 

of all past earthquakes to the identification of seismotectonic source zones. Paleoseismic data 

were included in the definition and characterization of RLME sources, and the background zones 

were defined based on observed seismicity. A key aspect of the SSC Sensitivity model was 

including models and parameter values that describe a wide range of uncertainty so that the 

feedback calculations could be carried out to show the relative importance of these assessments. 

The focus of the SSC Sensitivity model was not on the weights on the logic tree, but the range of 

branches on the logic tree in order to show their effect on the calculated hazard results and their 

potential contributions to uncertainty. These hazard calculations and sensitivity analyses were the 

subject of Workshop #3 Feedback. 

2.4.7 Workshop #3—Feedback 

The goals of Workshop 3 were as follows: 

Review the progress of the project in terms of meeting key milestones, such as development 

of the database and earthquake catalog. 

Review the SSHAC assessment process being followed. 

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. Basic principles of 

the SSHAC assessment process and their implementation in the CEUS SSC Project were 

described. A discussion was presented on the TI Team‘s role in the evaluation process of 

evaluating the data, models, and methods of the larger technical community, and in the 

integration process of building models that represent current knowledge and uncertainties. 

Discussion was presented regarding the need to document the data, models, and methods that 

have been considered during the evaluation phase of the project. A case history was described 

that traced the CEUS SSC Project documentation of an alternative model that postulates that the 

New Madrid seismic zone will not be seismically active in the future. Proponents for these 

models participated in Workshop #2, they were contacted and responded to requests for their 

current relevant data and interpretations, Data Summary and Data Evaluation tables documented 

that the TI Team has considered the data and proponent views, a representation of the model 
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could be found in the SSC logic tree, and discussion of the proposed model would be 

documented in the project report in the description of seismic sources associated with the New 

Madrid seismic zone. It was concluded that there is clear documented evidence that the data and 

interpretations provided by the proponent experts were evaluated and documented appropriately 

by the TI Team. 

Development of the CEUS SSC earthquake catalog was described next, including compilation 

and merging existing catalogs, magnitude conversions to define all earthquakes by moment 

magnitude, declustering, and assessment of catalog completeness. A preliminary earthquake 

catalog was completed for use in preparing the hazard sensitivity analyses to be discussed in the 

workshop. Representatives from the USGS were present at the workshop and were specifically 

asked to provide their views on the various aspects of the earthquake catalog. Maximum 

magnitude distributions under development for the CEUS SSC Project source zones were 

described. Representatives from the USGS also provided their views on the the maximum 

magnitude methodologies being used. 

Hazard results for seven demonstration site locations were presented. The seismic sources 

contributing to the hazard, the various parameter estimation approaches used, and model 

sensitivity were discussed for each of the demonstration sites. Both RLME and regional source 

zones were described and the sensitivity results were compared. Based on these calculations and 

sensitivity analyses, a set of conclusions was drawn regarding the most important SSC issues that 

either contribute most to mean hazard or are important contributors to the uncertainty in the 

hazard. In addition to hazard sensitivity, calculated results were discussed pertaining to the SSC 

issues that contribute most to Mmax and earthquake recurrence. The outcome of these feedback 

studies was that the TI Team could set priorities for focusing on the SSC issues and uncertainties 

of most significance in developing the SSC Preliminary model. 

Quantifying the precision of seismic hazard results in the CEUS was discussed in the next 

presentation. The purpose of the analysis described was to derive quantitative estimates of how 

seismic hazard results might change if studies were repeated by different researchers using the 

same basic information. This type of quantification gives an indication of how well the hazard is 

understood and how precise our calculated hazard values are. This can also provide information 

in the future on whether changes in hazard due to new findings should be considered significant. 

(A discussion of the hazard precision results and conclusions is given in Section 9.4.) The final 

workshop presentations focused on the path forward for the project, including how the project 

results will be used. 

Workshop #3 was documented on a CD. The CD, which contained the agenda, presentations, a 

workshop summary, a list of participants, the PPRP letter report, and a photo album of 

participants, was distributed to each participant; the contents are posted on the EPRI website. 

The TI Lead and Project Manager hosted a half-day briefing for international observers and 

young professionals before the workshop to improve their understanding of the context of the 

workshop and its role in the SSHAC assessment process. 

2.4.8 SSC Preliminary Model Development 

After Workshop #3 and armed with the feedback information, the TI Team proceeded to develop 

the SSC Preliminary model. Unlike the SSC Sensitivity model, which contained a number of 
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elements strictly for purposes of sensitivity analysis, the SSC Preliminary model included a logic 

tree that was intended to represent knowledge and uncertainties, or the center, body, and range of 

technically defensible interpretations (NRC, 2011). The ranges of branches on the SSC logic tree 

and their relative weights assigned to the branches were developed by the TI Team through 

extensive discussions of the available data, models, and methods. The integration process 

requires that the Team members objectively evaluate the available information and define the 

center, body, and range of technically defensible interpretations. To do so, the Team was 

encouraged to consider all methods for uncertainty treatment (e.g., logic trees, continuous 

probability distributions) and, if desired, build new models to capture current knowledge and 

uncertainty. For example, strong belief that the available paleoseismic data related to the 

existence and location of RLMEs are compelling led to spatial models that include these sources 

and that define the uncertainties in their geometry. 

Alternative models regarding the spatial variations in Mmax and future earthquake 

characteristics led to alternative models of seismic sources (e.g., Mmax zones versus 

seismotectonic zones). Consideration of spatial variation of recurrence parameters led to the 

refinement of approaches to expressing spatial stationarity and the aleatory variability of future 

recurrence parameters through smoothing. The degree of support in the available data that the 

model elements hold were expressed as weights on alternative branches of the logic tree. 

Uncertainties in parameter values were expressed as probability distributions. The sequence of 

nodes within the logic tree expresses the dependencies of assessments from general conceptual 

models on the left to parameter distributions that define the models on the right. 

2.4.9 Finalization and Review of SSC Draft and Final Model 

After the SSC Preliminary model was developed, a second round of hazard calculations and 

sensitivity analyses was conducted to provide feedback to the TI Team. These analyses focused 

on the remaining issues of most importance to the model. The elements of the SSC Preliminary 

model were presented to the PPRP in a briefing as a means of keeping the PPRP informed of the 

TI Team‘s deliberations. During the briefing, the PPRP provided its comments on the key 

elements of the SSC model and identified key issues that required resolution as the modeldevelopment process continued. Another version of the earthquake catalog was developed, after 

incorporating comments provided by the USGS and other outside experts, and working meetings 

were held to finalize the SSC Draft model. Discussions focused on the most important technical 

issues, the weights on alternative elements of the logic tree, and the final quantification of 

uncertainties. For example, the issue of alternative approaches to maximum magnitude 

assessments was debated and a series of meetings and conference calls were conducted in order 

to consider the implications and relative defensibility of alternative conceptual models governing 

the Mmax estimates. Consideration and discussion also centered on the most appropriate 

approaches to smoothing of recurrence parameters. The approach used (discussed in Section 

5.3.2) allows for a number of assessments to be made (e.g., strength of the prior distribution on 

the a-, and b-values) and a number of sensitivity analyses were conducted in order to understand 

the implications of different aspects of the model, and to compare it to other smoothing 

approaches. 

The SSC Draft model was completed and, as defined in the SSHAC guidelines, it is based on a 

systematic evaluation of the data, models, and methods proposed by the larger technical 
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community and an integration process that provides the TI Team‘s representation of the center, 

body, and range of technically defensible interpretations. The model was documented in a 

Hazard Input Document (HID) and Draft Project Report, which were issued to the PPRP and 

other groups for review (see Section 2.4.10).

In anticipation of detailed reviews, the TI Team continued its refinement of the SSC Draft model 

after submittal of the Draft Report and while it was being reviewed. A key issue concerned the 

assessments of earthquake recurrence, which showed for many sources that the ―predicted‖ 

recurrence rate averaged over the source based on the smoothing approach adopted was 

overpredicting the rates of ―observed‖ larger-magnitude earthquakes in the catalog. A number of 

exploratory analyses were conducted to shed light on the reason for this mismatch. Issues related 

to the earthquake catalog were considered, including the merging of multiple catalog sources, 

spatial variations in completeness, conversions of various magnitudes and intensity to moment 

magnitude, and declustering. At the same time, issues related to recurrence estimation were 

evaluated, including the use of various magnitudes in constraining the exponential recurrence 

distributions, the influence of the strength of the prior distribution on b-values, and the degree of 

spatial stationarity between the locations of large-magnitude earthquakes and future largemagnitude events. 

As discussed in Section 2.5.2, the PPRP issued a comprehensive set of comments on the Draft 

SSC model and identified key issues that would require resolution in the development of the 

Final SSC model. Working Meeting #9 on February 7 and 8, 2011, was later conducted with 

observation by the full PPRP to review these last key issues associated with the earthquake 

catalog and the recurrence assessments. Working Meetings #10 and 11 were conducted using a 

webinar format to review the results of ongoing and exploratory work. A few remaining issues, 

many identified in the comments from the PPRP on the Draft Report, were also dealt with at this 

time, such as the bases for the weights given in the master logic tree and methods for assessing 

seismogenic crustal thickness. 

The SSC Final model includes refinements that deal with the outstanding issues identified. For 

example, the refined model shows reasonable agreement between the recurrence rates for various 

seismic sources and the observed frequency of earthquakes. Likewise, the review of the catalog 

led to refinements of the spatial and temporal distribution of catalog completeness estimates. 

Also, conversions were refined to provide consistent estimates of intensity-to-mb-to-M and 

intensity-to-M. Accordingly, the refined conversions could be used for moment magnitude 

estimates for the entire catalog and, in turn, the observed frequency of observed earthquakes was 

recalculated for all seismic sources. Hazard calculations were conducted using the refined SSC 

Final model and associated sensitivity analyses were carried out. These hazard results and 

sensitivity analyses are included in this report. 

The refinements to the SSC model, associated hazard results, and revisions made to the project 

report were reviewed and discussed with the PPRP in a briefing held on June 21 and 22, 2011. 

The briefing provided an opportunity for the PPRP members to gain a full and complete 

understanding of the process and technical aspects of the project and to provide oral comments 

on the SSC Final model. 
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2.4.10 Documentation 

The SSC Final model was documented in an HID (as was done earlier for the Draft SSC model 

and the Draft Project Report) to provide a basis for hazard calculations, and the Final Project 

Report was developed. The steps involved in this documentation are summarized below. 

2.4.10.1 Development of the Hazard Input Document 

Upon completion of the SSC Final model, the essential elements of the model were documented 

in the HID for the project (Appendix H). The HID is the key deliverable of the project that can 

be used for hazard calculations in the future. Specifically, this document is meant for the hazard 

analyst—providing clarity about the model to be implemented and obviating the need to distill 

the model from the full report. The HID helps ensure that implementation of the model, which 

can be challenging due to its size and complexity, is as intended.The technical assessments that 

constitute the SSC Final model are not justified or discussed in the HID. Rather, the HID 

includes the logic tree structure for all assessments, the associated branches and weights, and the 

output recurrence and Mmax distributions that are required for the PSHA. The technical 

justifications for the assessments in the HID are given in this project report. 

2.4.10.2 Development of Earlier Draft Report 

The Draft Project Report documented all the assessments made by the TI Team in 2010 and 

summarizes the methodology that was used to make the assessments. The Draft Report was 

developed by all members of the TI Team and the Project Manager. It summarized all the key 

process steps, discussed their consistency with a SSHAC Level 3 assessment process, provided a 

description of all key project deliverables, and provided a technical discussion and explanation 

for all elements of the SSC Final model. The appendices to the report provided project-specific 

documentation of key products such as the final HID, Data Evaluation and Data Summary tables, 

the project database including the earthquake catalog, and summaries of the workshops and 

project written communications. The goal of both the Draft and Final Project reports is to 

provide a self-contained complete description of all aspects of the project such that future readers 

of the report will understand the methodology, the technical elements of the SSC model, and the 

technical bases for all assessments. 

2.4.10.3 Draft Report Review 

Review of the Draft Report was conducted by the PPRP, sponsors, USGS, and other groups, and 

written review comments were provided to the TI Team for its consideration. The TI Team was 

instructed to give highest priority to the PPRP comments, but to consider all the reviewer 

comments in making revisions to the project report. All reviewer comments were considered by 

the TI Team, and the responses to reviewer comments were summarized in comment response 

tables. The goal of the report review process was to provide the PPRP and other stakeholders an 

opportunity to comment on the completeness, clarity, and consistency of the documentation of 

the SSC model. Consistent with its role within a SSHAC process, the PPRP provided its 

comments pertaining to both the documentation of the process followed in the project as well as 

the technical assessments included in the SSC model. 
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Review of the Draft Report by the sponsors was facilitated by briefings held with members of the 

TI Team and the NRC (on August 10, 2010); with the utilities (on November 4, 2010); and with 

the utilities, NRC, and DOE (held February 9–10, 2011). A Final Report was developed that 

reflects revisions made in light of reviewer comments as well as a description of all refinements 

made to the model by the TI Team after issuance of the Draft Report (described above in Section 

2.4.9). The Final Report was issued to the PPRP and Sponsor reviewers in two installments, on 

June 16 and August 5, 2011, for their review and concurrence. To assist the review, a briefing 

was held with the PPRP to review all aspects of the SSC model and the report documentation 

(June 21–22, 2011).

2.4.10.4 Final Report Development 

The fundamental bases for revisions to the Draft Report were the written comments provided by 

the PPRP and other reviewers. In addition, the TI Team recognized the need to refine certain 

elements of the SSC Draft model and improve the documentation of the process aspects and 

technical assessments made for the project. A systematic process was followed for responding to 

each of the reviewer comments to ensure that all comments were addressed. The Final Report 

was issued to the PPRP for its final review and concurrence, and a final PPRP closure briefing 

was held September 7–8, 2011.

2.5 Participatory Peer Review Panel 

2.5.1 Roles and Responsibilities 

SSHAC guidance specifies that if a PSHA project is to be successful, the crucial need for a 

strong peer review process cannot be overemphasized. The members of the PPRP met the 

SSHAC criteria that peer reviewers ―must be  ̳peers‘ in the true sense: recognized experts on the 

subject matter under review‖ (Budnitz et al., 1997, p. 48). The purpose of peer review is to 

provide assurance of the following: 

A proper SSHAC Level 3 process has been followed. 

The diversity of views prevailing within the technical community has been considered. 

Knowledge and uncertainties have been properly quantified and incorporated into the 

analysis. 

Documentation is clear and complete. 

The CEUS SSC Project used a participatory peer review process, which involved continuous 

review throughout all phases of the project. As recommended by the SSHAC guidelines, the 

PPRP was responsible for reviewing both the technical and process aspects of the project. The 

peer reviewers interacted frequently with the TI Team, provided formal written comments at 

regular intervals, and reviewed and approved the project report. 

2.5.2 Reviews and Feedback 

The purpose of a participatory peer review process, as opposed to a ―late-stage‖ process, is to 

provide advice and recommendations during the course of the study and not just near the end. 

Such feedback is valuable to the TI Team and improves the focus and quality of the evaluation 
Chapter 2 

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and integration processes. For example, early in the project, the PPRP reviewed the Project Plan 

and provided its views on the planned work activities. Also, members of the PPRP identified 

data sets that could be considered by the TI Team. PPRP review comments were instrumental in 

the TI Team‘s developing a data documentation process—including Data Evaluation and Data 

Summary tables—that would benefit future users of the study. As another example, the PPRP 

provided its views on how feedback calculations should be considered by the TI Team and 

cautioned that the calculations should not limit the team‘s approach to representing the full range 

of legitimate views within the technical community. These reviews and recommendations were 

invaluable in assisting the TI Team in enhancing the assessment process being followed. The 

technical reviews also greatly assisted the team in focusing on key technical issues and ensuring 

a complete evaluation of all applicable data, models, and methods. 

To assist in the PPRP‘s monitoring and review of the project, PPRP briefings were held with the 

TI Team on May 13, 2009; March 24, 2010; and June 21–22, 2011; as well as the final closure 

briefing September 7–8, 2011 (Table 2.2-1). These briefings served as opportunities for the 

PPRP to ask questions and gain clarification about the SSC Sensitivity model, SSC Preliminary 

model, SSC Draft model, and SSC Final model. They also provided the TI Team with feedback 

on the models and alerted the Team to the need to provide technical bases and documentation on 

the key technical assessments. In addition to the briefings, representatives from the PPRP were 

present as observers at 8 of the 11 working meetings of the TI Team. This provided the PPRP 

with additional perspective on the technical assessments being made by the TI Team. 

In terms of written review of the project report, the PPRP provided an extensive set of comments 

on the Draft Report that addressed both technical issues and process issues. The TI Team 

members responded to all the comments and summarized their responses in Comment Reponse 

tables, which are included in Appendix I. After revision of the Draft Report in light of comments 

from the PPRP, as well as comments from the sponsors and other groups (i.e., Defense Nuclear 

Facilities Safety Board, USGS), a draft Final Report was issued. The PPRP then provided a 

detailed review of that document (see comments in Appendix I). The PPRP comments on the 

draft Final Report were defined as either ―mandatory,‖ meaning that the review comments must 

be addressed by the TI Team in its final documentation of the project report, or ―nonmandatory,‖ meaning that the comments are intended solely to help improve the Final Report. 

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

Process Issues 

The SSHAC guidelines highly recommend that a participatory peer review process be followed 

and that the peer review process for a Level 3 project be directed at both the technical and 

process aspects of the study (Budnitz et al., 1997, p. 50). The ―technical‖ aspects include the TI 

Team‘s evaluation process for considering the applicable data, models, and methods that exist 

within the larger technical community, and the integration process that represents the center, 

body, and range of technically defensible interpretations. The technical aspects require a high 

level of technical expertise on the part of the PPRP, while the process aspects require a 

knowledge and experience in the application of SSHAC assessment processes. ―Process‖ aspects 

include carrying out all methodological steps, such as developing a project database, conducting 

workshops, developing feedback, encouraging technical interaction and debate, and 

documentation. The PPRP for the CEUS SSC Project included the requisite expertise and 
Chapter 2 

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experience to fulfill both aspects of its charge. Individual members of the panel are 

acknowledged experts in the technical fields related to SSC, and most members have had 

considerable project experience related to SSHAC studies or studies using similar methodologies 

(see Appendix G). 

The final product of the SSHAC peer review process is a final closure letter from the PPRP 

providing its views on whether the TI Team has successfully implemented a SSHAC Level 3 

process and whether, as a result, the technical assessments included in the SSC model are 

technically defensible and adequately documented. The PPRP was presented with the Final 

Report of the project as well as written comment response forms that documented the manner in 

which all written comments provided by the PPRP, sponsors, USGS, and other reviewers were 

addressed. To support its final review, a closure briefing was held with the PPRP on September 7 

and 8, 2011. The final activity conducted by the PPRP was the development of its closure letter, 

which is included in this report. 

2.6 Consistency of CEUS SSC Assessment Process with 

SSHAC Guidelines 

The SSHAC Level 3 assessment process is a structured technical assessment process accepted in 

the NRC‘s seismic regulatory guidance for ensuring that uncertainties in data and scientific 

knowledge have been properly represented in seismic design ground motions. The TI Team is 

responsible for meeting and documenting these goals, and peer reviewers are responsible for 

evaluating whether these goals have been met. As an accepted expert assessment process that 

includes participatory peer review of both the process and technical aspects, the SSHAC Level 3 

assessment process, if conducted properly, provides confidence that the data, models, and 

methods of the larger technical community have been considered and that the center, body, and 

range of technically defensible interpretations have been represented. 

This section compares the process followed in the CEUS SSC Project with that prescribed in the 

SSHAC guidelines in order to draw conclusions about whether the SSHAC assessment process 

has been adequately followed. Chapter4, Methodology for Characterizing Seismic Sources, of 

the SSHAC report (Budnitz et al., 1997) is the applicable section for evaluating the CEUS SSC 

assessment process. The SSHAC report devotes most of the methodology discussion to attributes 

of a Level 4 assessment process, with only minor attention given to the attributes of a Level 3 

assessment process. Nevertheless, experience on projects conducted over the past 15 years has 

shown that the differences in the implementation of Levels 3 and 4 are small (mainly related to 

the assessment by individual evaluator experts rather than an evaluator team). Therefore, the 

methodology steps specified in the SSHAC guidelines for a Level 4 assessment for SSC (Budnitz 

et al., 1997, p. 70) can serve as the basis for comparison with the CEUS SSC assessment process. 

The following discussion will first present the methodology steps exactly as given in the SSHAC 

guidelines, and then provide a summary of how each step was addressed in the CEUS SSC 

Project. Aspects of the steps that pertain to Level 4 projects are adjusted, as appropriate, to 

pertain to a Level 3 project. 

The basic steps in the recommended methodology for SSC are given below in terms of 

the specific application to SSC. 
Chapter 2 

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1. Conduct careful expert selection. The process of expert selection should be based on 

a clear set of criteria aimed at capturing a full range of diversity of expert interpretations. 

The members of the CEUS SSC TI Team were selected based on their experience and technical 

expertise. As a group, the Team‘s expertise spanned the wide range needed to conduct SSC, 

including the disciplines of geology, geophysics, tectonics, seismology, and hazard analysis. The 

team members are acknowledged experts in their respective fields and are thoroughly acquainted 

with the active researchers in those fields, as well as in the areas of important ongoing research. 

In addition to having disciplinary expertise, the TI Team had considerable experience in 

conducting an SSC for a PSHA. As a result, the team members understood the important issues 

for such an analysis as well as the current tools for uncertainty treatment. 

In addition to the TI Team, a large number of representatives of the larger technical community 

participated in the project as resource experts, proponent experts, and specialty contractors. Steps 

were taken by the TI Team, as supported by the PPRP, to ensure that the participation of 

Resource Experts and Proponent Experts in Workshops #1 and #2 was appropriate and complete 

in order to be representative of the range of current scientific community interpretations. 

Specialty contractors were engaged on the project to provide certain technical products, such as 

geophysical maps, stress interpretations, and guidance for the assessment of paleoliquefaction. 

Personnel from the USGS played an extended role in this project to ensure that all supportable 

interpretations of the scientific community were fully identified, evaluated, and represented in 

the SSC model. Several USGS personnel provided detailed review and feedback on specific 

issues (e.g., the earthquake catalog, Mmax, and methods), which were considered in the 

assessment of the SSC model by the TI Team. 

2. TFI role. The technical facilitator/integrator should play a strong role, running 

workshops and expert interactions, monitoring the behavior and participation of the 

experts, conducting calculations and sensitivity analyses, documenting the final results, 

and taking intellectual responsibility for the results of the project. 

The SSHAC Level 3 equivalent of the TFI is the TI Lead, who has technical responsibility for 

the assessment, leads the TI Team, and works with the specialty contractors charged with certain 

activities (e.g., hazard calculations, database management, report production). For the CEUS 

SSC Project, the TI Lead was responsible for organizing all workshops, working meetings, and 

PPRP briefings. The TI Lead also was responsible for establishing the SSHAC ground rules for 

all these interactions and for ensuring that all project participants understood and abided by their 

particular SSHAC-prescribed roles. Throughout the assessment process it was emphasized to all 

TI Team members that they would be required to assume intellectual ownership of all aspects of 

the SSC model. The TI Lead was responsible for organizing the report preparation process and 

for ensuring completeness and consistency in the contributions from the various team members. 

3. Provide a uniform data base to all experts. SSC-related data sets, as defined by the 

experts themselves, should be provided to all of the experts in formats most useful to the 

experts. 

From the outset of the CEUS SSC Project, database development was a strong focus. An 

earthquake catalog was developed from a variety of sources, and considerable effort was 

associated with providing an estimate of moment magnitude for all earthquakes in the catalog. 

An accessible database was developed for use by the TI Team that was derived from both 

existing information and newly compiled data sets, including GIS-based components such as 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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magnetic anomaly, gravity, and stress data. Workshop #1—Significant Issues and Available Data

was devoted to the identification of available data that would be specifically applicable to 

addressing the key SSC issues. A number of resource experts with knowledge of applicable data 

sets made presentations on their data sets and provided a basis for the project data development 

process. The resource experts provided information related to the quality of the data, their 

formats, and the history of data development in key regions throughout the CEUS. In addition to 

the geophysical data sets, the project also sponsored the compilation and evaluation of 

paleoseismic data because of the importance of that data to the identification and characterization 

of seismic sources in the region. 

As part of the Conceptual SSC Framework for the project (see Chapter 4), a process was 

instituted for documenting the data that were considered by the TI Team in its evaluations. First, 

in a ―generic‖ table that is generally applicable to the entire study region, the applicable types of 

data were identified that have potential use in SSC. Then all data that were considered for 

particular subregions or source zones were identified in Data Summary tables, which include a 

description of each data source‘s relevance to SSC. Then, for those data that are used in the 

source characterization process, Data Evaluation tables for each seismic source were developed 

that provide an evaluation of the quality of the data and degree of reliance given to each data 

source in the source characterization process. The goal of these tables is to provide clear 

documentation of the data sets that were available to the TI Team at the time of its evaluations; 

the tables also provide an evaluation of the data relative to their specific use on the CEUS SSC 

Project. 

The Data Summary and Evaluation tables are viewed by both the TI Team and the PPRP as 

critical to the success of the project. This is the first project to rigorously and systematically 

document this information, and it is viewed by the PPRP as essential information to support the 

descriptions and discussion found in Chapters 6 and 7. Early in the project, the PPRP encouraged 

the TI Team to create a system that would more effectively document the data identification and 

data evaluation processes, and the TI Team developed the format for the Data Summary and 

Data Evaluation tables. It is expected that the structure of these tables will provide a valuable 

methodology step for future SSHAC Level 3 projects. 

4. Conduct multiple expert interactions. Interaction among SSC experts is strongly 

recommended, through such vehicles as workshops, small working meetings, etc. 

The heart of the SSHAC assessment process is technical expert interaction. These interactions 

allow the TI Team members to carry out their evalution and integration processes, including 

identifying and evaluating data; witnessing the debate of alternative hypotheses by members of 

the technical commmunity; challenging the views of proponent experts in order to understand the 

uncertainties; developing models that portray the knowledge and uncertainties in SSC model 

components; considering feedback related to preliminary assessments; and arriving at an 

integrated model that represents current knowledge and uncertainties. Considerable learning and 

reexamination of held views occurs and is encouraged during the course of these interactions. 

The CEUS SSC Project took full advantage of this notion in conducting three topical workshops, 

11 working meetings, four PPRP briefings, and three meetings to brief the international 

observers and young professionals attending the workshops. In addition, numerous subgroup 

meetings, conference calls, and webinars were held among the TI Team members during the 

course of the development of the SSC Sensitivity model, the SSC Preliminary model, the SSC 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Draft model, and the Final SSC model. Each interaction was structured and facilitated to focus 

on the goals of the SSHAC assessment process, and participants were reminded of their roles and 

responsibilities within that context. 

In addition to the interactions among the TI Team members, all members interacted extensively 

with members of the technical community through personal visits, e-mails, telephone calls, and 

attendance at professional society meetings. Such communication allowed team members to be 

apprised of current research and to gain an understanding of the uncertainties associated with 

available data, models, and methods. Team members were also participants in pertinent 

professional meetings, such as the NRC-sponsored workshop on methods for assessing 

maximum magnitudes held at the USGS in Golden, Colorado (Wheeler, 2009), the USGS 

workshop on the CEUS Earthquake Hazards Program held in Memphis, Tennessee, October 

28–29, 2009, and the Seismological Society of America meeting in Memphis, Tennessee, April 

13–15, 2011. The goal in these interactions was to gain an understanding of the current 

knowledge and uncertainties regarding the technical issues of significance to seismic sources in 

the CEUS.

5. Elicit SSC judgments from experts. Individual expert elicitations should be 

conducted through person-to-person interviews. Elicitations of expert teams are also 

acceptable. 

The notion of individual expert elicitations is specific to a Level 4 assessment process and thus 

not directly applicable. However, the assessment and evaluation process that occurs within such 

expert interviews was carried out by the TI Team. Nine of the 11 working meetings (see Section 

2.4.5) were multi-day meetings of the TI Team to review data and develop the SSC assessments. 

Each working meeting was structured around particular aspects of the ongoing evaluation and 

integration process. 

One or more members of the PPRP participated as observers in 6 of the 9 multi-day working 

meetings and in 8 of the 11 total working meetings. Between working meetings, subgroups 

developed their interpretations of specific aspects of the model (e.g., geometries of particular 

zones, paleoseismic recurrence parameters) and their findings were brought to the entire TI Team 

for evaluation at the working meetings. It was emphasized throughout the assessment that all 

members of the TI Team would be expected to claim intellectual ownership of the integrated 

SSC model. 

6. Conduct sensitivity analyses and submit feedback to experts. Following the 

elicitations, extensive sensitivity analyses should be conducted by the TFI and provided 

to the experts. They then should interact again as a group to review their interpretations. 

A hallmark of a SSHAC Level 3 or 4 assessment process is the consideration of feedback by the 

expert evaluators and the use of that information to gain additional insights into the importance 

of various aspects of the models. Feedback is provided in terms of both implications to 

calculated seismic hazard results and implications to various components of the SSC model itself 

(e.g., earthquake recurrence rates). Three complete feedback cycles were conducted in the CEUS 

SSC Project. In the first, an SSC Sensitivity model was developed that provided a complete 

expression of the knowledge and uncertainties regarding seismic source characteristics in the 

study area. The elements of the model and their uncertainties were quantified using a logic tree 

approach, thus allowing for hazard calculation and sensitivity studies that isolated the relative 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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significance of various assessments in the model. The SSC Sensitivity model included some 

elements that were designed to illustrate the significance of various technical issues and their 

uncertainties. The feedback results from the SSC Sensitivity model were presented at Workshop 

#3—Feedback, where conclusions were drawn regarding the most important contributors to the 

mean hazard at seven demonstration sites throughout the study region. This information provided 

a basis for focusing the subsequent effort on the significant issues. For example, the magnitude 

and recurrence rate of RLME sources were shown to be quite important, particularly those like 

the Meers and Cheraw faults whose recurrence rates based on paleoseismic evidence is higher 

than rates based solely on observed historical seismicity. 

After the first round of feedback, the SSC Preliminary model was developed. This model defined 

the source characteristics and their uncertainties, as expressed in the logic tree branches and 

associated weights. All the data evaluations and information gained from expert interactions 

were brought to bear in the development of this model. A second round of feedback was 

collected to help focus the effort further. This feedback was discussed in a briefing with the 

PPRP, and the key technical issues were identified. The discussion centered on the range of 

views on these issues that had been considered during the evaluation process and the way 

knowledge and uncertainties had been represented in the SSC Preliminary model. The feedback 

discussions led to a number of focused activities, including additional work in developing a 

uniform earthquake catalog, consistent and statistically appropriate treatment of the paleoseismic 

data, refinement of the approach to spatial smoothing of seismicity to allow for variable a- and 

b-values, new approaches to reanalyzing the available worldwide database of earthquakes within 

stable continental regions for purposes of estimating maximum earthquakes, and approaches to 

incorporating paleoearthquakes into the assessment of the largest observed events for purposes of 

Mmax assessment. The calculated feedback coming from exercising the SSC Preliminary model 

was indispensable, and the comments and insights provided by members of the PPRP were 

valuable as well. The feedback was used to develop the Draft SSC model, which was included in 

the Draft Project Report along with hazard calculations and sensitivity analyses designed to 

provide insight into the relative importance of various aspects of the model. The Draft SSC 

model was reviewed in the Draft Project Report by the PPRP, and a briefing was held to review 

all of its components. In light of this feedback, the Final SSC model was developed; the model is 

described in detail in this Final Project Report. 

7. Finalize SSC interpretations and combine at hazard level. Integration/aggregation 

of SSC interpretations usually occurs at the hazard level. The TFI should create the 

proper conditions, through the application of 1 through 6 above, to combine the expert 

judgments using equal weights. Allowance should be made for cases where unequal 

weights are appropriate. 

As discussed in Section 2.1, the SSHAC assessment process calls for two important activities: 

evaluation and integration. This methodology step is integration and, although the specific issues 

related to combining multiple-expert assessments are not applicable to a Level 3 process, the 

need for an integration step is applicable and vital. Integration is model-building and the proper 

representation of current knowledge and uncertainties. Throughout the project, the TI Team 

members fulfilled their roles as evaluators of available data, models, and methods by 

representing their knowledge and uncertainties in the SSC assessments. They further fulfilled 

their integrator roles by defining branches and weights on the logic tree that they believed would 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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best represent the views of the larger technical community if it had a similar knowledge of the 

project databases and if it had gone through the same interactive process. 

Speaking to a Level 4 assessment process, the SSHAC guidelines allow for the TFI to consider 

combining expert assessments using unequal weights. This allowance (which has never been 

applied in an actual SSHAC project) is provided in case the experts do not fulfill their roles as 

evaluators and integrators. In that case, the TFI is given the authority to adjust the weights on the 

component expert models in order to provide—in aggregate—an integrated model that properly 

represents the center, body, and range of technically defensible interpretations. It is likewise 

possible to imagine a similar situation within a Level 3 TI Team, whereby a team member does 

not play the role of an evaluator and integrator. In such a situation, the TI Lead would be 

responsible for reminding the person of his or her proper role and, if necessary, removing the 

person from the team. Because all team members are responsible for all aspects of the model, 

however, it is unlikely that any individual team member would have a significant effect on the 

integration process. In fact, no such problems presented themselves on the CEUS SSC Project. 

8. Peer review. An active or ―participatory‖ peer review should be conducted throughout 

the study with the particular focus of the process that was followed in conducting the 

SSC assessment. 

A participatory peer review process is essential for a SSHAC Level 3 project, and the SSHAC 

guidelines call for review of both the technical and process aspects of the project. The technical 

part of the review entails identifying any data, models, or methods that exist within the technical 

community that the TI Team may not be aware of, reviewing the evaluation process in 

workshops and working meetings to offer advice regarding hypotheses and views of members of 

the community, and reviewing the technical bases provided by the TI Team regarding their 

integration process to represent the center, body, and range of technically defensible 

interpretations in light of the data, models, and methods available in the larger technical 

community. The advantage of a participatory peer review process over a late-stage review 

process is that the review comments and advice of the PPRP can be used to make mid-course 

corrections. There were several such comments that led to improvements in the CEUS SSC 

Project, as follows: 

Numerous data sets were identified by PPRP members for inclusion in the project database. 

New data compilations developed for the project (e.g., aeromagnetic anomaly, gravity, stress, 

and paleoliquefaction) were suggested and assisted by the PPRP. 

The structure of the database and associated metadata benefited from PPRP advice. 

The concept of more explicit data documentation led to the development of the Data 

Summary and Data Evaluation tables. 

Written comments after each workshop provided suggestions for process and technical 

aspects of the project. 

Detailed feedback and questioning at three PPRP briefings offered perspectives on the 

sensitivity and preliminary SSC models and on their success at representing current 

knowledge and uncertainties. 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Ongoing comments and suggestions led to improvement in addressing several key SSC 

issues, including approaches to Mmax assessment, magnitude conversions for the earthquake 

catalog, recurrence smoothing approaches, consistency of recurrence rates with observed 

frequencies, and application of criteria for identification of seismic sources. 

The PPRP provided a review of the Draft Report and commented on its clarity and completeness 

in documenting the technical and process aspects of the project. 

In addition to the PPRP, other groups provided review comments on the Draft Report. These 

included the sponsors, USGS, and others. The USGS provided a review of two important aspects 

of the project: advice regarding any data, models, or methods that should be considered by the TI 

Team, and review of the project earthquake catalog. Likewise, the sponsors of the CEUS SSC 

Project provided their review comments in the spirit of ensuring a clear and complete 

documentation of the project and its technical assessments. 

As summarized above, each of the methodology steps in the SSHAC guidelines for SSC was 

followed in the CEUS SSC Project. In some cases, additional steps were added to ensure that the 

intent of the SSHAC assessment process was fulfilled. 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Table 2.2-1 

Technical Meetings Conducted as Part of the CEUS SSC Project

Meeting Title Date Participants Observers

Kick-Off Meeting May 8, 2008 TI Lead, Project Manager (PM), 

PPRP

International (Int’l) 

Observers Briefing

July 21, 2008 TI Lead, PM, Int’l Observers

Workshop #1 July 22–23, 2008 TI Team, PM PPRP, Sponsors,

USGS, International

Observers

Working Meeting #1 Sept. 12–13, 2008 TI Team, PM

Working Meeting #2 Nov. 3–4, 2008 TI Team, PM PPRP

Working Meeting #3 Jan. 5–6, 2009 TI Team, PM PPRP

Int’l Observers Briefing Feb. 17, 2009 TI Lead, PM, Int’l Observers

Workshop #2 Feb. 18–20, 2009 TI Team, PM PPRP, Sponsors, 

USGS, Int’l Observers

Working Meeting #4 March 3–4, 2009 TI Team, PM

Working Meeting #5 April 21–22, 2009 TI Team, PM

PPRP Briefing May 13, 2009 TI Team, PM, PPRP

Int’l Observers Briefing Aug. 24, 2009 TI Lead, PM, Int’l Observers

Workshop #3 Aug. 25–26, 2009 TI Team, PM PPRP, Sponsors, 

USGS, Int’l Observers

Working Meeting #6 Oct. 20–21, 2009 TI Team, PM PPRP

Working Meeting #7 Jan. 12–13, 2010 TI Team, PM PPRP

PPRP Briefing March 24, 2010 TI Team, PM, PPRP

Working Meeting #8 April 13–14, 2010 TI Team, PM PPRP

NRC Briefing Aug. 10, 2010 TI Lead and Team Reps, PM, 

NRC

Utilities Briefing Nov. 4, 2010 TI Lead and Team Reps, PM, 

Utilities/EPRI

Working Meeting #9 Feb. 7–8, 2011 TI Team, PM PPRP

Sponsors Briefing Feb. 9–10, 2011 TI Team, PM, Sponsors

Working Meeting #10 

(webinar)

April 1, 2011 TI Team, PM PPRP

Working Meeting #11 

(webinar)

May 12, 2011 TI Team, PM PPRP

PPRP Briefing June 21–22, 2011 TI Team, PM, PPRP

Sponsors Briefing 

(webinar)

July 21, 2011 TI Team, PM, Sponsors

PPRP Closure Briefing Sept. 7–8, 2011 TI Team, PM, PPRP, Sponsors
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Table 2.2-2 

Contributors to the CEUS SSC Project 

Resource Experts at Workshop #1

Ebel, John Boston College

Hatcher, Robert University of Tennessee, Knoxville

Keller, Randy University of Oklahoma

Mooney, Walter USGS

Mueller, Charles USGS

Munsey, Jeffrey Tennessee Valley Authority

Newman, Andrew Georgia Tech

Obermeier, Steve USGS, retired

Ravat, Dhananjay University of Kentucky

Tuttle, Martitia (Tish) M. Tuttle & Associates

Van Schmus, Randy University of Kansas

Zoback, Mark Stanford University

Proponent Experts at Workshop #2

Adams, John Natural Resources Canada

Angell, Michael Fugro William Lettis & Associates

Calais, Eric Purdue University

Chapman, Martin Virginia Tech

Cox, Randy University of Memphis

Drahovzal, James University of Kentucky 

Ebel, John Boston College

Forte, Alessandro University of Quebec

Givler, Robert Fugro William Lettis & Associates

Green, Russell Virginia Tech

Kafka, Alan Boston College

Kenner, Shelley Consultant

Mazzotti, Stephane Geological Survey of Canada

McBride, John Brigham Young University

Mueller, Charles USGS

Olson, Scott University of Illinois

Pazzaglia, Frank Lehigh University

Petersen, Mark USGS

Smalley, Bob University of Memphis
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

2-31

Stein, Seth Northwestern University

Talwani, Pradeep University of South Carolina

Thomas, William University of Kentucky

Tuttle, Martitia (Tish) M. Tuttle & Associates

Van Arsdale, Roy University of Memphis

Zoback, Mark Stanford University

Technical Experts Who Contributed During Course of CEUS SSC Project

Adams, John Geological Survey of Canada

Atkinson, Gail University of Western Ontario

Bakun, Bill USGS

Baldwin, John Fugro William Lettis & Associates

Baranoski, Mark Ohio Division of Geology

Berry, Henry Maine Geological Survey

Boyd, Oliver USGS

Brown, Larry Cornell University

Calais, Eric Purdue University

Chapman, Martin Virginia Tech

Clowes, Ron University of British Columbia

Counts, Ron University of Kentucky

Cox, Randy University of Memphis

Crain, Kevin AREVA, University of Oklahoma

Crone, Anthony USGS

Dhananjay, Ravat University of Kentucky

Dineva, Savka University of Western Ontario

Dyer-Williams, Kathleen Consultant

Ebel, John Boston College

Esch, John Michigan Department of Environmental Quality

Frankel, Arthur USGS

Givler, Robert Fugro William Lettis & Associates

Green, Russell Virginia Tech

Halchuck, Stephen Geological Survey of Canada

Hansen, Mike Ohio Department of Natural Resources

Harrison, Rich USGS

Hatcher, Robert University of Tennessee, Knoxville

Hough, Susan USGS
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

2-32

Hurd, Owen Stanford University

Johnston, Arch CERI

Keller, Randy University of Oklahoma

Luza, Ken Oklahoma Geological Survey

Magnani, Beatrice University of Memphis

Mahan, Shannon USGS

Mahdi, Hanan University of Arkansas at Little Rock

Maybee, Steve Office of Massachusetts State Geologist

McCollough, Jane West Virginia Geological Survey

Mitchell, Frances Queen’s University

Mueller, Charles USGS

Munsey, Jeffrey Tennessee Valley Authority

Niemi, Tina University of Missouri–Kansas City

Olson, Scott University of Illinois at Urbana-Champaign

Pratt, Tom USGS

Reger, Jim Maryland Geological Survey

Ruff, Larry University of Michigan, Ann Arbor

Ruffman, Alan Geomarine Associates, Ltd.

Rupp, John Indiana Geological Survey

Sharnburger, Charles Millersville University, Pennsylvania

Al-Shukri, Haydar University of Arkansas at Little Rock

Tinsley, John USGS

Van Arsdale, Roy University of Memphis

Vaughn, James Consultant

Wang, Zhenming Kentucky Geological Survey

Wheeler, Russell USGS

Williams, Robert USGS

Withers, Mitch University of Memphis

Woolery, Ed University of Kentucky
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Figure 2.3-1 

CEUS SSC Project organization 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Figure 2.3-2 

Lines of communication among the participants of the CEUS SSC Project 
Chapter 2 

SSHAC Level 3 Assessment Process and Implementation 

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Figure 2.4-1 

Essential activities associated with a SSHAC Level 3 or 4 project (Coppersmith et al., 2010) 

3-1 

3 

CHAPTER 3 

EARTHQUAKE CATALOG 

This chapter describes the development of the earthquake catalog for the CEUS SSC Project. 

The catalog development consists of four major steps: catalog compilation, assessment of a 

uniform size measure to apply to each earthquake, identification of dependent earthquakes 

(catalog declustering), and an assessment of the completeness of the catalog as a function of 

location, time, and earthquake size. Each of these steps is described in detail in the chapter. The 

result is an earthquake catalog covering the entire study region defined in Chapter 1 for the time 

period of 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 for CEUS earthquakes. 

3.1 Goals for the Earthquake Catalog Development 

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 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 the buildup and release of 

crustal stresses are difficult to identify. Because the earthquake catalog will be used to 

characterize 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 are described in the following sections. 

3.1.1 Completeness 

The goal of compiling an earthquake catalog is to record the occurrence of all known 

earthquakes in the magnitude range considered important to the characterization of future 

earthquake hazards. It is recognized that there have been extensive past efforts put forward 

toward this goal. In the United States, the work performed in the EPRI-SOG project (EPRI, 

1988), subsequently revised by Seeber and Armbruster (1991), ultimately led to the catalog used 

by the U.S. Geological Survey (USGS) for seismic hazard mapping (Mueller et al., 1997; 

Petersen et al., 2008). Similarly, work by the Geological Survey of Canada (GSC) to develop an 

earthquake catalog for seismic hazard analysis (Adams and Halchuk, 2003) provides an equally 

important source catalog for earthquakes in the northern portion of the study region. The CEUS 

SSC Project relied on the work underlying the USGS and GSC catalogs to form the backbone of 

the updated project earthquake catalog. 

The USGS and GSC catalogs each represent a synthesis of catalog information from many 

sources into simple one-line catalog entries of date, time, location, and selected estimate(s) of 
Chapter 3 

Earthquake Catalog 

3-2 

earthquake size. In that process, some information important to the use of the earthquake catalog 

for this project may not have been retained. Therefore, an extensive review of original catalog 

sources was performed as part of the catalog compilation, among them Stover and Coffman 

(1993); Smith (1962, 1966); the Southeastern United States Network (SUSN) catalog; and the 

USGS/National Earthquake Information Center (NEIC) Preliminary Determination of Epicenters 

(PDE) catalog. In addition, numerous special studies of individual earthquakes, earthquake 

sequences, and specific geographic areas were reviewed and the information compiled as part of 

the catalog development. The use of these studies is described in subsequent sections of this 

chapter. A number of these studies included information on important parameters (e.g., moment 

magnitudes) that is not included in the more regional catalogs. 

It is also recognized that the process of catalog compilation from many sources may lead to 

inclusion of duplicate entries for some earthquakes and inclusion of nontectonic events that have 

been excluded from other catalogs. To address this issue, catalogs of identified nontectonic 

events and false entries were also examined and a list of identified nontectonic events was 

compiled. This list forms one product of the CEUS SSC Project (see Appendix B). The catalog 

was also reviewed line by line to identify potential duplicate entries not readily identified by 

automatic means. 

3.1.2 Uniformity of Catalog Processing 

An important goal of catalog compilation was to use an earthquake size measure that is 

consistent with the ground motion models that will be used to compute seismic hazards. Most 

recent ground motion models applicable to the CEUS use the moment magnitude scale, M, as the 

earthquake size measure, and it is expected that the next generation of ground motion models 

being developed in the near future will continue to use the moment magnitude scale. 

Unfortunately, however, this is not the magnitude scale that has been used for routine earthquake 

monitoring and catalog compilation. The current practice for many hazard analyses in the CEUS 

is to estimate earthquake occurrence rates in terms of the catalog magnitude (commonly, bodywave magnitude, or mb) and then use conversion relationships from this magnitude scale to M as 

part of the ground motion estimation. This introduces an additional source of uncertainty, 

particularly since many of the catalog magnitude entries are themselves converted from other 

size measures, such as shaking intensity for pre-instrumental earthquakes. 

The EPRI-SOG project (EPRI, 1988, Vol. 1) developed techniques to produce a catalog with a 

uniform size measure that is appropriate for unbiased estimation of earthquake occurrence rates 

for use in seismic hazard assessment. These techniques were used in the EPRI-SOG study to 

develop a uniform catalog of mb magnitudes. A goal of the catalog development efforts in this 

project is to use the same techniques to produce a uniform catalog of moment magnitude values 

that have properly accounted for the uncertainty in size estimation as part of development of 

earthquake occurrence rates. This will eliminate the need for magnitude conversion as part of the 

hazard calculation and avoid propagation of unnecessary uncertainty through the hazard analysis. 

To achieve this goal, updated conversions were developed from a variety of earthquake size 

measures to moment magnitude. 

An equally important task was to obtain the original size measures for catalog entries in order to 

use a direct conversion to moment magnitude rather than introduce additional uncertainty by 

converting previously converted size estimates. One example is that a number of the magnitudes 
Chapter 3 

Earthquake Catalog 

3-3 

listed in the GSC catalog are designated local magnitude, ML. Yet many of these earthquakes 

occurred in the pre-instrumental period. Examination of the magnitude entries suggests that they 

were in fact converted from maximum intensity, I0, using the Gutenberg and Richter (1956) 

relationship. Therefore, the original source for the catalog of intensity data was obtained (Smith, 

1962, 1966) and the I0 values for these earthquakes were entered into the catalog in order to 

make a direct conversion from I0 to M. 

3.1.3 Catalog Review 

Development of earthquake catalogs is a complex and a tedious process in which there are many 

sources of uncertainty and opportunities for either missing important sources of information or 

adding unwanted or fictitious information. Therefore, an important part of the catalog 

development process was reviewed by seismologists with extensive knowledge and experience 

in catalog compilation. The first draft of the catalog was reviewed by Dr. Charles Mueller and 

Margaret Hopper from the USGS, Dr. John Ebel from Boston College, Dr. Martin Chapman 

from Virginia Tech, Dr. Pradeep Talwani from the University of South Carolina, Dr. Donald 

Stevenson from Savannah River Nuclear Solutions, and James Marrone from Bechtel. The 

following summarizes the main review comments and the actions taken to implement the 

reviewers’ recommendations in the development of the final project catalog. 

Use Original Sources 

Several reviewers made the comment that original source catalogs should be used as much as 

possible instead of relying on the compilation catalogs. To address this issue, the entries in the 

project catalog were traced back to their original sources to the extent possible. For example, the 

USGS catalog (Mueller et al., 1997; Petersen et al., 2008) considers all earthquake magnitudes as 

mb. However, the USGS catalog also lists the source of the magnitude estimate for many 

earthquakes. These sources were used to identify the proper magnitude type (e.g., mbLg versus 

MN). The primary source for the USGS catalog is the NCEER-91 catalog (Seeber and 

Armbruster, 1991, 1993), which updates the EPRI-SOG (EPRI, 1988) catalog. In the case of 

instrumentally recorded earthquakes, the preferred magnitude listed in the NCEER-91 catalog is 

typically the largest among the various magnitude types available in the EPRI-SOG (EPRI, 

1988) catalog (e.g., the largest value among magnitude types mb, mbLg, MN, MCß MD, or ML). 

Each of these magnitude types, if present for a particular earthquake, was entered into the project 

catalog. In addition, to the extent possible, the magnitude entries included the original source of 

the magnitude estimate (e.g., Weston Observatory; Lamont-Doherty Earth Observatory; the 1983 

Nuttli catalog; Dewey and Gordon, 1984). 

The NCEER-91 catalog also contained a field in which a flag indicated whether the preferred 

magnitude was based on instrumental magnitudes (type 1), felt area (type 2), or maximum 

intensity (type 3). These flags were used to identify those reported magnitudes that were in fact 

based on shaking intensity measures so that the original size measure, intensity, rather than an 

estimated magnitude from intensity was used to provide an estimate of moment magnitude. In a 

similar manner, the Southeastern United States Seismic Network (SEUSSN) catalog (Virginia 

Tech) provided codes that indicated the source and type of body-wave magnitude reported for 

each earthquake. These were entered into the project catalog to indicate the type of magnitude 

and to indentify earthquakes whose magnitudes were derived from macroseismic data. 
Chapter 3 

Earthquake Catalog 

3-4 

A number of original sources of data suggested by the reviewers were reviewed and added to the 

project catalog. For example, the Dewey and Gordon (1984) catalog was digitized and included 

in the project catalog. Felt areas listed in the published paper version of Stover and Coffman 

(1993) were also digitized and added to the project catalog. The additional catalogs that were 

reviewed are described in Section 3.2.3. 

Examine Individual Magnitude Types 

Several reviewers suggested that potential differences in body-wave magnitude types may exist 

due to differences in the approaches used by various agencies to calculate magnitude. To address 

this issue, body-wave magnitudes reported by various agencies for the same set of earthquakes 

were examined for systematic differences. The results of this examination led to inclusion of 

regional and time-dependent effects in the correlation between various magnitude scales and M,

as described in Section 3.3. Examination of ML magnitudes reported in the catalog obtained from 

the GSC indicated that many of the reported values were actually based on maximum intensity 

converted to ML using the relationship given in Gutenberg and Richter (1956). Moment 

magnitudes for these catalog entries were estimated using correlations with maximum intensity 

instead of with instrumental ML. 

Provide Recommendations for Specific Catalog Entries

Individual reviewers provided specific recommendations for a number of catalog entries. For 

example, Dr. Ebel provided suggestions for the catalog entries in the time period 1500–1700 and 

the larger earthquakes post-1700 in the northeastern portion of the study region. Dr. Talwani and 

Dr. Stevenson reviewed the catalog entries in the vicinity of the 1886 Charleston, South 

Carolina, earthquake. The suggestions made by the reviewers included indications of possible 

false, duplicate, or erroneous catalog entries, and changes to earthquake locations and times. 

These suggestions were implemented in the project catalog with indications of the source of the 

catalog update. Dr. Mueller recommended specific catalog sources and in particular catalog 

entries from the International Seismological Centre (ISC) for the study region. Review of the 

project catalog, however, indicated that a number of catalog entries with ISC magnitude values 

of about 3 were derived from local catalogs that contained either much smaller magnitude entries 

for the earthquake or no entry at all. Therefore, the ISC catalog was not used as a source in 

developing the final catalog. 

Create a Catalog of Nontectonic Events 

A number of reviewers suggested that a separate catalog be created listing nontectonic events 

identified as part of the catalog compilation. Appendix B contains a listing of the nontectonic 

events (e.g., explosions, mine collapses, false entries) identified during the course of the catalog 

development and includes the reference for the event classification. 

3.2 Catalog Compilation 

The process used for catalog compilation was to provide each entry in a source catalog with a 

unique ID number specific to that catalog. The catalogs were merged by sorting all records in 

chronological order based on the calculated Julian date of each earthquake. After merging, each 

earthquake was assigned a project ID number that is common to multiple entries from different 

catalogs (duplicates). As an example, the 1897/5/31 Giles County earthquake is reported by eight 

catalogs: USGS (record number 1065); NCEER (record number 1079); Ohio Geological Survey 
Chapter 3 

Earthquake Catalog 

3-5 

(record number 61); SEUSSN (record number 1743); Hopper (record number 97); USHIS 

(record number 101); EPRI (record number 840); and Reinbold and Johnston (1987; record 

number 39). Each of these catalog entries receives the same project ID number (TMP02921) 

indicating that each of the eight records is a duplicate entry for the Giles County earthquake. In 

the following sections the major sources of catalog data are described. 

3.2.1 Continental-Scale Catalogs 

The catalogs developed by the USGS and the GSC were the primary sources for earthquake 

entries. The primary earthquake listing that forms the basis for the USGS catalog was obtained 

from Dr. Charles Mueller, and the primary earthquake listing that forms the basis for the GSC 

catalog was obtained from Dr. Steven Halchuk. Figure 3.2-1 shows the areal coverage of these 

two catalogs. The region outlined by the blue box in the figure indicates the portion of each 

catalog that was used to develop the project catalog. The USGS catalog was updated through the 

end of 2008 using the NEIC PDE catalog website, and the GSC catalog was updated through the 

end of 2008 using data from the National Earthquake Database (NEDB) of Canada. 

The USGS catalog is itself a compilation based on a number of other sources including the 

catalogs of Stover and Coffman (1993); Stover et al. (1984); EPRI (1988) as updated by Seeber 

and Armbruster (1991) and Armbruster (2002); NEIC PDE; U.S. Advanced National Seismic 

System (ANSS), and the Centennial Catalog (Engdahl and Villasenor, 2002). The purpose of 

including all these additional sources in the compilation of the CEUS SSC catalog was to obtain 

as much information as possible on size measures for the earthquakes. A principal example is 

obtaining shaking intensity values for pre-instrumental earthquakes that are not given in the 

primary sources. In some cases, the printed copies of catalogs were used to make hand entries of 

size measures into the database. For example, the felt area data listed in Stover and Coffman 

(1993) was entered into the database. As described above in Section 3.1.3, the magnitude type 

for the entries in the USGS catalog was identified using the source designation provided in the 

USGS catalog. The source for most of the entries in the USGS catalog was the NCEER-91 

catalog (Seeber and Armbruster, 1991), and the NCEER-91 catalog entries were included in the 

combined earthquake compilation, along with the primary source for the NCEER-91 catalog, the 

EPRI-SOG catalog (EPRI, 1988). The NCEER-91 catalog contains entries for multiple 

magnitude types based on the entries in the EPRI-SOG catalog. These entries were used to 

identify the magnitude type reported in the USGS catalog. For example, if the source of a USGS 

record is an NCEER record obtained from the EPRI-SOG catalog, and the source used in EPRISOG is Dewey and Gordon (1984), all the records (EPRI, NCEER, and USGS) were modified to 

reflect that the magnitude type is mbLg and the magnitude source is Dewey and Gordon (1984). 

The GSC catalog entries consist primarily of two magnitude types, ML and MN. The source of 

the pre-1900 ML values is most likely intensity. Figure 3.2-2 shows a histogram of ML

magnitudes from the GSC catalog for the time period 1660–1899 for the region east of longitude 

–105° and south of latitude 53°. The dashed vertical lines indicate magnitudes computed using 

the Gutenberg and Richter (1956) relationship ML = 2⁄3I0 + 1. The magnitudes clearly line up on 

values computed from specific modified Mercalli intensity scale (MMI) I0 values spaced at 

1⁄2 intensity units. Figure 3.2-3 shows the data for the period 1900–1930. With the exception of a 

few entries, the magnitudes again line up with specific I0 values. Figure 3.2-4 shows the data for 

the period 1930–1979, and Figure 3.2-5 shows the data for the period 1980–2007. These plots 

indicate that after 1980, most ML values are probably instrumental, but during the period 1930–
Chapter 3 

Earthquake Catalog 

3-6 

1980, the GSC catalog likely contains a mixture of intensity-based and instrumental ML

magnitudes. 

To sort out intensity-based ML magnitudes in the GSC catalog, the catalogs of Smith (1962, 

1966) were used to identify those earthquakes where instrumental ML values were reported. In 

addition, the SUSN and EPRI/NCEER catalogs were used to separate instrumental from I0 based 

magnitudes. Where no primary source catalog provided an indication that an instrumental 

magnitude was recorded, the reported ML values that are consistent with ML = 2⁄3I0 + 1 for the I0

value in the catalog in the time period after 1928 (the earliest reported ML in the Smith catalogs) 

were considered to be computed from I0. If not, the values were considered to be instrumental 

ML magnitudes. Figure 3.2-6 shows the histogram of what are interpreted to be instrumental ML

magnitudes in the GSC catalog for the time period 1928–1979. For the most part, the values 

appear to indicate an exponential distribution, although some I0 based magnitudes may remain in 

the catalog. 

An additional source of shaking intensity data for recent earthquakes is the USGS “Did You Feel 

It?” (DYFI) program (http://earthquake.usgs.gov/earthquakes/dyfi/; Wald et al., 1999). Two 

types of data are available from the DYFI website: (1) the archives, which list date, time, 

location, magnitude, and intensity of each earthquake; and (2) the reports, which contain the 

number of responses, average MMI for a specific zip code (not rounded), and distance for each 

zip code. The epicentral intensity reported in the DYFI data for an earthquake is the maximum 

intensity observed, independent of the distance and/or the number of observations. For some 

earthquakes, felt reports are prepared using geocoding, a technique that assigns latitude and 

longitude to street addresses, but this kind of report is available only for a limited number of 

earthquakes because observers often do not disclose their address. While reports based on zip 

code were used in this project, it should be noted that they do not describe how the distance from 

the epicenter to each observation is determined. If the distance is calculated from the center of 

the zip code, it may introduce a bias if the zip code covers a very large area. 

The DYFI archives were downloaded and compared to the corresponding earthquake records in 

the CEUS SSC catalog. It was found that all the earthquakes occurred within the study region 

listed in the DYFI archives were already in the catalog. In more than half of the cases, the I0 level 

in the catalog corresponds to the intensity from the DYFI archives. In one-third of the cases, the 

intensity from the DYFI archive was higher (typically by one level) than the I0 value in the 

catalog. In a few cases (2001/6/3 Lake Erie, OH; 2004/7/20 South Carolina; 2005/2/23 

Maryland), the difference between the DYFI intensity and the I0 in the catalog (from NEIC) was 

as high as three levels. To find an explanation for this difference, the felt reports of these three 

earthquakes were downloaded and analyzed. In all cases, the intensity assigned by DYFI is 

reported by few observers (in some cases just one) at great distance from the epicenter (100 km, 

or 62 mi., or more). The I0 obtained from NEIC for the same earthquakes approximates the 

largest intensity observed at short distance. 

Approximately 20 earthquakes with I0 ≥ 4 MMI in the DYFI archives did not have a 

corresponding intensity value in the CEUS SSC catalog. Because the same intensity is assigned 

to the entire zip code, maps of the earthquake effects from DYFI are very different from 

isoseismal maps, and the appropriate intensity level for the earthquake may not be immediately 

visible. Therefore, the felt reports for the earthquakes that do not have an intensity measure in the 

CEUS SSC catalog were carefully analyzed. Intensities obtained from just a few responses at 
Chapter 3 

Earthquake Catalog 

3-7 

very great distances were disregarded. In almost all cases, it was found that the estimated 

maximum intensity needed to be adjusted to reflect the responses at close distance to the 

epicenter and to take into account the number of responses. This is consistent with the approach 

followed by Stover and Coffman (1993), who select I0 as the maximum intensity observed, and it 

can be argued from their isoseismal maps that it is typically very close to the epicenter. 

If there are no observations within 20–30 km (12–18.5 mi.) of the epicenter, I0 is calculated 

adding one level to the average observed MMI at the closest distance. This accounts for a decay 

of about one degree in 30 km, consistent with the Atkinson and Wald (2007) MMI attenuation 

relation assuming a M 4 ± 0.5, which is an appropriate value for the earthquakes analyzed. In 

four cases, the responses were too sparse and/or too distant and a value of I0 was not assigned. 

3.2.2 Regional Catalogs 

The following regional catalogs were included in the compilation: 

• Center for Earthquake Research and Information (CERI) catalog 

• Saint Louis University (Nuttli, microearthquake, and moment magnitude catalogs) 

• Lamont-Doherty Cooperative Seismographic Network catalog (LDO) 

• Weston Observatory catalog (WES) 

• Ohio Seismic Network catalog 

• Department of Conservation and Natural Resources of Pennsylvania catalog 

• Reinbold and Johnston (1987) 

• Oklahoma Geological Survey catalog (OKO) 

• South Carolina Seismic Network (SCSN) catalog 

• Southeastern United States (SUSN) catalog (Virginia Tech) 

These catalogs were used to obtain additional information on the size measures for earthquakes 

and to identify the magnitude types reported for each earthquake. For example, the Nuttli catalog 

from Saint Louis University indicates when the reported mb values are instrumental and when 

they are based on shaking intensity data. The SUSN catalog contains both earthquakes recorded 

by SEUSSN and data taken from Stover et al. (1984). Included in the SUSN catalog is 

information on the type and source of individual magnitude values that was incorporated into the 

project catalog. Based on the recommendation of Dr. John Ebel (e-mail comm., January 13, 

2011), magnitudes reported in the Weston Observatory catalog were classified as MN for years 

prior to 1995 and as mLg(f) based on the use of the Ebel (1994) formula for 1995 and later years. 

3.2.3 Catalogs from Special Studies 

A number of published studies contain information on specific earthquakes in limited 

geographical areas, often providing seismic moment or moment magnitude values and revised 

locations and/or depths, or indicating events of nontectonic origin. Information from the 

following studies was included in the catalog development: Adams and Simmons (1991); 

Atkinson et al. (2008); Basham et al. (1979); Bent (1992, 1995, 1996a, 1996b, 2009); Bent and 
Chapter 3 

Earthquake Catalog 

3-8 

Hasegawa (1992); Bent and Perry (2002); Bent et al. (2002, 2003); Boatwright (1994); Brown 

and Ebel (1985); Dineva et al. (2004); Du et al. (2003); Ebel (1996, 2000, 2006a); Ebel et al. 

(1986); Faust et al. (1997); Fujita and Sleep (1991); Kim et al. (2006); Lamontagne and Ranalli 

(1997); Lamontagne et al. (2004); Larson (2002); Leblanc (1981); Ma and Atkinson (2006); Ma 

and Eaton (2007); Ma et al. (2008); Macherides (2002); Nabelek and Suarez (1989); Nicholson 

et al. (1988); Pomeroy et al. (1976); Reagor et al. (1980); Ruff et al. (1994); Scharnberger 

(1990); Seeber and Armbruster (1993); Seeber et al. (1998); Shedlock (1987); Shumway (2008); 

Stevenson and McColluh (2001); Street and Turcotte (1977); Street et al. (1975, 2002); and 

Sykes et al. (2008). 

For the most part, the authors of these studies indicate the specific magnitude type reported, and 

this information was included in the project catalog. For example, Jones et al. (1977) and Street 

and Turcotte (1977) provide mbLg values. Bollinger (1979) uses Nuttli’s (1973) formula to 

determine mbLg for 17 earthquakes in the southeastern United States, using World-Wide 

Standardized Seismograph Network (WWSSN) records. His study indicates that Nuttli’s (1973) 

formula is applicable to earthquakes in this region, provided that epicentral distance is less than 

2,000 km (1,243 mi.). However, Dr. Ebel (e-mail comm., January 13, 2011) pointed out that 

Nuttli’s formula should only be applied to Lg waves with periods ranging between 0.7 and 1.3 

sec. In Table 2 of Bollinger (1979) the period of the Lg wave used in some stations is smaller 

than the specified range; therefore, these magnitudes are considered in the CEUS catalog as MN

rather than mbLg. The catalog by Basham et al. (1979) is a mix of different magnitudes (mI0, 

mFA, ML, mb, mbLg, MN), all assumed to be equal. Since in most cases it was impossible to 

determine what kind of magnitude was indicated, the CEUS catalog does not specify any kind of 

magnitude for the events that originate in the Basham et al. (1979) catalog. Instead, the 

magnitudes were cross-checked against other sources to identify the magnitude type. 

In addition to the above, catalogs from three studies addressing historical earthquakes were 

included in the composite catalog. The first was the catalog of earthquakes in New Brunswick 

identified from historical records by Burke (2009). The second was the catalog developed by 

Metzger et al. (2000) covering the region around New Madrid. The third was the catalog 

developed by Munsey (2006) from newspaper archives for the region of Kentucky and 

Tennessee and adjoining areas. These studies provide either felt area or maximum intensity 

measures of earthquake size. 

3.2.4 Focal Depth Data 

The compiled catalog contains a variety of depth estimates from different agencies and authors. 

Depths are routinely determined by the software used to locate the earthquakes (e.g., HYPO71, 

HYPOELLIPSE, etc.) and may have an associated flag that ranks the quality of the solution, 

and/or a flag that identifies depths fixed or assigned by a geophysicist. Depths of this kind are 

found in most regional (e.g., CERI, Saint Louis University, SUSN, LDO) and national (e.g., 

NEIC, NEDB, GSC) catalogs and in studies such as Brown and Ebel (1985); Dineva et al. 

(2003); Shedlock (1987); and Shumway et al. (2009). In addition, a number of studies (i.e., 

Atkinson, 2008; Bent, 1992, 1995, 1996a, 1996b; Bent and Hasegawa, 1992; Bent and Perry, 

2002; Bent et al., 2002; Du et al., 2003; Ebel, 1986; Ma and Atkinson, 2006; Ma and Eaton, 

2007; Ma et al., 2008; Nabelek and Suarez, 1989) calculate earthquake depths from regional 

depth phases or moment tensor analysis. 
Chapter 3 

Earthquake Catalog 

3-9 

Depths were added to the catalog from studies published in the literature. Studies by Chapman 

and Bollinger (1984); Chapman et al. (1997); Dunn et al. (2010); Johnston et al. (1985); Pulli 

and Guenette (1981); Rhea (1987); Shoemaker et al. (2009); Talwani (1982); Teague et al. 

(1986); and Vlahovic et al. (1998) calculate earthquake depth while relocating earthquakes and 

microearthquakes. However, only the depths obtained by Chapman and Bollinger (1984); 

Chapman et al. (1997); Johnston et al. (1985); Shoemaker et al. (2009); and Stepp (2008) have 

been added to the project catalog because the other studies either do not provide tables with data, 

or focus on microearthquakes that are not included in the project catalog because of their very 

small magnitude. 

The depth flags in the project catalog were standardized as follows: depths assigned to historical 

events are flagged by the letter H; fixed depths by F; depths obtained from regional depth phases 

or moment tensor analysis by D; and unreliable or questionable depths by a question mark (?). 

The latter include all the depths calculated by inversion software with quality of solution D, 

which according to Johnston et al. (1985) are unreliable. 

Histograms of the earthquakes depth distribution for the events that are not flagged as fixed, 

historical, or unreliable show clear peaks at 5, 10, 18, and 33 km (3, 6, 11, and 20.5 mi.). These 

depths correspond to the typical fixed depth values adopted by Ohio, Oklahoma, and 

Pennsylvania catalogs (5 km), NEIC and other U.S. regional catalogs (10 km [6 mi.] for shallow 

and 33 km [20.5 mi.] for deep events), and Canadian catalogs (18 km, or 11 mi.]). This indicates 

that a number of fixed depths have not been flagged in the original catalogs and consequently in 

the project catalog. Only a small number of these depths are calculated depths that have been 

rounded to the nearest integer. For example, Shedlock (1987) calculated a depth of 10.11 km 

(6.28 mi.) for the 1978/09/07 earthquake at coordinates 33.063°N, -80.209°E. This earthquake is 

contained in the NCEER catalog but the depth was rounded to a value of 10 km (6 mi.). 

3.2.5 Nontectonic Events 

Nontectonic and erroneous earthquake entries were identified using lists compiled by ANSS, 

ISC, NEDB, and the NEIC Mining Catalog 

(http://earthquake.usgs.gov/earthquakes/eqarchives/mineblast/), and using information given in 

the SEUSSN bulletins and in a number of the studies listed in Section 3.2.3 (e.g., Seeber and 

Armbruster, 1993, 2002; Fujita and Sleep, 1991; Scharnberger, 1991a, 1991b; Street et al, 2002; 

Ma et al., 2008; Sykes et al., 2008; Burke, 2009; Ebel, 1996, 2010). In addition, Dr. Charles 

Mueller at the USGS shared a personal working file containing a list of nontectonic earthquakes; 

this has been checked against the information already in the catalog. Comments from Dr. John 

Ebel, Dr. Pradeep Talwani, and Dr. Donald Stevenson were used to identify many false events, 

particularly in the historical portion of the catalog. Earthquakes of nontectonic origin include 

mining-related activity (quarry blasts, collapses); reservoir-induced events; explosions; 

cryoseism; and other disturbances (sonic booms, storms, etc.). If the nontectonic origin of an 

earthquake is suspected but not confirmed, the classification is considered “probable.” A separate 

catalog of events of nontectonic (or probable nontectonic) origin is contained in Appendix B. 

3.2.6 Identification of Unique Earthquake Entries 

The compiled master catalog listing containing all entries from multiple sources is retained in the 

CEUS SSC Project database. This listing is described in Appendix B. The final stage of catalog 
Chapter 3 

Earthquake Catalog 

3-10 

compilation was the identification of duplicate entries for individual earthquakes within the 

master listing. 

Duplicates were first identified by an algorithm that flags all events that occurred within a 

narrow time window. The time window is specified as difference in Julian date and it is larger 

for older events and smaller for newer events. The time windows were determined by running 

tests on different portions of the catalog. 

An initial check of the catalog of duplicates identified indicated that many more duplicates still 

needed to be removed. The main issue appeared to be the difference between local and universal 

time. In order to identify these events, each line of the catalog was manually checked to confirm 

or modify the results of the algorithm. Information contained in some of the studies listed in 

Section 3.2.3 (e.g., Sykes et al., 2008; Fujita and Sleep, 1991; Bent, 2009) and reviewers’ 

comments were used to identify and flag earthquake records with errors in date or time. In all 

cases, the date and time listed in the original record was retained but the record was considered a 

duplicate of the correct catalog entry, and a short explanation was added in the “Comment” field 

of the master catalog listing. 

The master listing was then searched for earthquakes identified by only a single source. These 

earthquake sources were then rechecked to verify the master listing entries. For example, a 

number of entries have as a single source the SUSN catalog. A list of these events was submitted 

to Dr. Martin Chapman at Virginia Tech who provided references for all of them. Another source 

of information that was useful in verifying the correctness of several records was the USGS’s 

online Earthquake History by State (http://earthquake.usgs.gov/earthquakes/states/). 

Upon completion of these reviews, the master catalog listing was then re-examined line by line 

to verify the assignment of individual entries to unique earthquake identification numbers. 

Earthquake entries from different catalogs with similar origin times, locations, and sizes were 

typically assigned the same identification number unless visual examination indicated multiple 

earthquakes from one of the source catalogs. Comments were added to the “Comment” field of 

the master catalog listing to indicate interpretations of duplicate entries. 

The next step in catalog processing was to select a preferred entry for each unique earthquake 

number while retaining the relevant information on various size measures for use in assigning a 

uniform magnitude and identification of a nontectonic entry. The following order of preference 

was used for selection of the preferred time and location for each catalog entry. If the earthquake 

was included in one of the special studies listed in Section 3.2.3, then that entry was used as the 

preferred entry. Otherwise, if the earthquake was contained in one of the two national catalogs 

used for seismic hazard mapping, the USGS catalog for earthquakes south of the U.S.-Canada 

border and the GSC/NEDB catalogs north of the border, then that catalog’s entry was selected as 

the preferred entry. This choice was based on the assumption that these two catalogs have 

already undergone considerable review within each agency. If the earthquake was not contained 

in one of these two catalogs, then the local regional catalog entry was selected as the preferred 

entry (e.g., SUSN, CERI, Weston, Saint Louis University, Lamont-Doherty, the Oklahoma 

Geological Survey). 

Finally, if the earthquake was listed only in other compilations, such as ANSS or Stover and 

Coffman (1993), then that entry was used as the preferred entry. Entries for earthquakes within 

the study region that only appear in the ISC catalog were not retained in the final catalog. This 
Chapter 3 

Earthquake Catalog 

3-11 

decision was based on the observation that if the ISC reported magnitudes for these entries were 

of sufficient size (typically magnitude 3 or larger), then the earthquakes should have been 

contained in one or more regional catalogs. Questions about ISC catalog entries were raised by 

Dr. Charles Mueller of the USGS during the review of the draft catalog. 

The multiple entries of earthquake size were used for assessing the uniform magnitude for each 

earthquake. Different values reported for the same magnitude scale by different source catalogs 

were not resolved, as this would require obtaining the original records and reassessing the 

magnitudes, a task well beyond the scope of the present study. Instead, these different 

magnitudes were retained and factored into the uncertainty in the assigned uniform magnitude 

measure for each earthquake. 

The final project catalog contains 3,298 individual earthquakes of uniform moment magnitude 

E[M] 2.9 and larger (the development of the uniform moment magnitude estimate E[M] is 

described in Section 3.3). Most of these earthquakes (2,642) are also contained in the USGS 

seismic hazard mapping catalog (Petersen et al., 2008). Table 3.2-1 summarizes the number of 

additional earthquakes as a function of time period, and Table 3.2-2 summarizes the sources of 

the added earthquakes. Figure 3.2-7 shows a map of the final CEUS SSC Project. The locations 

of the earthquakes added to the USGS catalog are denoted by the colored symbols with the 

catalog source indicated by the color code in the legend. The largest group added to the USGS 

catalog (319) are smaller-magnitude earthquakes that occurred in the time period 1960–2006 and 

are contained in multiple other catalog sources. The second largest group of added earthquakes 

(190) occurred in the period 1800–1899. Many of these earthquakes were identified in the 

studies of historical documents conducted by Burke (2009), Metzger et al. (2000), and Munsey 

(2006). 

3.3 Development of a Uniform Moment Magnitude Earthquake Catalog 

As stated in Section 3.1.2, an important goal is to provide an earthquake catalog that can be used 

to develop unbiased estimates of the recurrence of earthquakes as a function of magnitude using 

a magnitude scale that is consistent with modern ground motion prediction equations for the 

CEUS: the moment magnitude scale defined by Hanks and Kanamori (1979). Because the size 

measures available for most of the earthquakes in the project catalog are different from this scale, 

a process for converting from a variety of magnitude and shaking intensity measures to moment 

magnitude is needed. In addition, it has been shown by Veneziano and Van Dyck (1985) and 

Tinti and Mulargia (1985) that uncertainty in the magnitudes reported in an earthquake catalog 

can lead to bias in the estimation of earthquake recurrence rates unless appropriate adjustments 

are applied. The EPRI-SOG project (EPRI, 1988) developed an approach for assigning a uniform 

magnitude measure to earthquakes in an earthquake catalog and producing unbiased recurrence 

parameters from that catalog. The EPRI-SOG approach was updated for application in the CEUS 

SSC Project. 

3.3.1 Approach for Uniform Magnitude and Unbiased Recurrence Estimation 

The magnitudes for all earthquakes reported in an earthquake catalog contain some amount of 

uncertainty. This uncertainty arises from the estimation process as magnitude is typically 

assigned as a statistical average of measurements obtained by a number of seismograph stations. 

In addition, the process of conversion from one magnitude scale to another introduces additional 
Chapter 3 

Earthquake Catalog 

3-12 

uncertainty. If the reported magnitudes are used to estimate earthquake recurrence parameters 

using standard techniques, such as the Weichert (1980) maximum likelihood approach using 

earthquake counts in magnitude bins, then the uncertainty in the magnitudes leads to a bias in the 

estimated recurrence rate. This bias arises because of the underlying exponential distribution of 

earthquake magnitudes in a large source region. Considering the number of earthquakes in 

magnitude bin mi, the exponential distribution in magnitude means that there are more 

earthquakes in the next smaller magnitude bin, mi-1 and fewer earthquakes in the next larger 

magnitude bin, mi+1. The unequal numbers of earthquakes in adjacent magnitude bins means that 

more earthquakes are shifted from magnitude bin mi-1 to mi due to statistical magnitude 

uncertainty than are shifted from magnitude bin mi to bin mi-1. A similar and consistent bias in 

the shifted earthquake counts occurs between magnitude bins mi and mi+1. 

The effect of uncertainty on recurrence parameter estimation is readily illustrated through 

simulation. The process used is to simulate a catalog of 10,000 earthquakes from a truncated 

exponential distribution in the magnitude range of M 3 to M 7 with a recurrence rate of 100 

earthquakes per year of M 3 and larger and a b-value of 1.0. A catalog of observed magnitudes, 

Mˆ , is simulated by adding a normally distributed random error to each earthquake magnitude 

with a standard deviation of 0.2 magnitude units. The resulting catalogs of M and Mˆ are then 

used to compute recurrence parameters for magnitudes of M 4 and larger using the Weichert 

(1980) method with a magnitude bin width of 0.5 units. The purpose of using magnitudes of 4 

and larger is to eliminate the truncation effects at the lower end of the magnitude range that 

result from starting the magnitude simulation at magnitude 3. The process was repeated for 500 

simulations. The following table lists the average earthquake counts in each magnitude bin and 

the resulting average values of N(M≥4) and b-value. The table also contains results for the 

adjusted magnitude M* that is described below. 

Average Results from 500 Simulated Catalogs of True M, M ˆ , and M* 

Parameter True M Mˆ M* 

Number 4.0 ≤ M < 4.5 685 762 685 

Number 4.5 ≤ M <5.0 216 241 217 

Number 5.0 ≤ M < 5.5 68 76 69 

Number 5.5 ≤ M < 6.0 21 24 21 

Number 6.0 ≤ M < 6.5 7 7 7 

Number 6.5 ≤ M < 7.0 2 2 2 

N(M≥4) 10.00 11.13 10.01 

b-value 1.004 1.003 1.005 

As indicated by these results, the counts of Mˆ in each magnitude bin are larger than those for the 

true magnitudes, and the resulting estimate of N(M≥4) is biased, although the b-value estimate is 

unbiased. 

Tinti and Mulargia (1985) explored this bias, finding that the estimated b-value is unaffected by 

the magnitude uncertainty (as long as the same uncertainty applies to all magnitudes). They 

introduced a correction to the recurrence rate estimated from Mˆ given by 
Chapter 3 

Earthquake Catalog 

3-13 

}exp{) ˆ ()( 2 N M = N M −γ True (3.3.1-1) 

with 

2

] ˆ [

22

2 σβ MM

γ = (3.3.1-2) 

Parameter β is equal to the b-value in natural log units (β = bln{10}) and ] ˆ σ[ MM is the 

standard deviation of the normally distributed error in the observed magnitudes. Using the fitted 

b-value of 1.0 and ] ˆ σ[ MM = 0.2 yields γ

2

 equal to 0.106. Applying Equation 3.3.1-1 to the 

value of N(M≥4) estimated from Mˆ in the table above yields a value of 10.01, very close to the 

correct value of 10.00 obtained from the true M catalog. 

The EPRI-SOG project (EPRI, 1988, Vol. 1) developed an alternative approach for obtaining 

unbiased recurrence parameter estimates.1

 An adjusted magnitude, M*, was introduced defined 

by the expression: 

2/] ˆ [ ˆ * MM −= βσ2 MM (3.3.1-3) 

Recurrence parameters estimated using the adjusted magnitudes were shown to be unbiased. The 

simulations described above were repeated to include the calculation of M* for each earthquake 

in each simulated catalog using Equation 3.3.1-3. The right-hand column of the above table 

shows the resulting average counts by magnitude bin and the resulting recurrence parameters. 

The values are very close to those obtained using the true M values. These results are to be 

expected as the adjustment defined by Equations 3.3.1-1 and 3.3.1-2 is equivalent to the 

adjustment defined by Equation 3.3.1-3 as the value of ( ) 2/] ˆ [* ˆ 2 βγ MM =−×= σβ 22 MM . 

Figure 3.3-1 shows this equivalence graphically. 

The EPRI-SOG project (EPRI, 1988, Vol. 1) extended the adjustment defined by Equation 

3.3.1-3 to the case where the magnitudes M are estimated from a vector of other size measures 

X, such as other magnitude scales or shaking intensity measures. In this case, the adjusted 

magnitude M* is given by 

2/][][E* 2 XMM += βσ XM (3.3.1-4) 

The change in sign of the adjustment occurs because, as also shown by EPRI (1988), the 

expected value of the true magnitude, E[M], given uncertainty ] ˆ σ[ MM and an underlying 

exponential distribution in magnitude is given by 

] ˆ [ ˆ ][E MM −= βσ2 MM (3.3.1-5) 

 

1

 The EPRI-SOG project used mb as the uniform magnitude scale. However, the relationships developed there for 

obtaining unbiased recurrence estimates and uniform magnitudes are not dependent on the chosen magnitude 

scale. 
Chapter 3 

Earthquake Catalog 

3-14 

Applying Equation 3.3.1-5 to Equation 3.3.1-3 yields 

2/] ˆ [][E* MM += βσ2 MM (3.3.1-6) 

Thus, the adjustments from E[M] to M* are the same regardless of whether E[M] is estimated 

from other size measures X or from the observed magnitudes Mˆ . 

The process of using Equation 3.3.1-4 to correct for bias when M is estimated from X was also 

tested using simulation. The simulation steps consisted of the following: 

1. Simulate a catalog of true values of M from a truncated exponential distribution in the 

magnitude range of 3 to 8 with a b-value of one. 

2. Add a normally distributed random error to M to produce observed magnitudes Mˆ . 

3. Simulate associated values of mb using the relationship mb = M + 0.3. Include a normally 

distributed random error with standard deviation 0.3 to simulate randomness in the 

relationship between M and mb from earthquake to earthquake. (Note that inclusion of 

measurement error in mb in effect just adds to the random difference between M and mb and 

it is unimportant to separate this component from the total random difference between the 

two magnitude scales). 

4. Regress Mˆ against mb and obtain the values of E[M|mb] and σ[Mˆ b ]m for each simulated 

mb. This is performed by first trimming the catalog to mb ≥ 4 to remove the truncation effect 

at the low end resulting from the initial limit of M to ≥ 3. 

5. Use Equation 3.3.1-4 to obtain a catalog of M*. Trim off the events below M* 4 to remove 

the edge effect and estimate the seismicity parameters N(M≥4) and b-value from the counts 

of M*. 

6. Estimate the recurrence parameters for the simulated catalogs using the true M values, the 

E[M] values, and the M* values. 

The following table presents the results averaged over 500 simulations. 

Average Results from 500 Simulated Catalogs of True M, Mˆ , mb, and M* 

Parameter True M E[M] M* M*adjusted

N(M≥4) 10.00 8.02 10.68 10.06 

b-value 1.000 1.001 1.001 1.001 

Use of the catalog of E[M] values results in an underestimate of the true recurrence rate. Use of 

the catalog of adjusted magnitudes M* produces a close but slight overestimate of the true rate. 

Examination of Equation 3.3.1-4 indicates that the source of the difference is that the adjusted 

magnitudes should be based on the value of ]m[ σ M b , the variability in true M given mb, while 

the results of the regression between the observed values of the two magnitude scales produces 

σ[Mˆ b ]m . The latter value is inflated over ]m[ σ M b due to the random error in the observed 
Chapter 3 

Earthquake Catalog 

3-15 

values of Mˆ used in the regression. This suggests that a modified value of M* be computed 

using the relationship 

( ) 2/] ˆ [] ˆ [][E* M adjusted XM += σβ 2 −σ2 MMXM (3.3.1-7) 

using the assumption that 

] ˆ [] ˆ [][ σ2 = σ2 −σ2 MMXMXM

 (3.3.1-8) 

where ] ˆ [ σ2 MM is the variance in the observed values Mˆ used in the regression of X versus 

Mˆ . 

The right-hand column of the above table shows that the use of Equation 3.3.1-7 to compute M* 

results in predicted recurrence parameters very close to those obtained using the simulated true 

M values. 

As part of the simulation testing, the average value of (true M – M b ]m[E ) was found to be less 

than 0.01, indicating that the regression of mb against Mˆ produces E[M]. 

The advantage of the M* approach is that it allows inclusion of the variability in the values of 

] ˆ σ[ MM and σ M X ][ from earthquake to earthquake. EPRI (1988) provided the following 

relationships for the case where E[M] is estimated from a vector Xˆ of R observed size 

measures: 

[ ] [ ] [ ] [ ] M ( ) [ ] XM

M

XM XM ˆ |1 ˆ |E ˆ |

ˆ | ˆ |E 2

2

2

βσ

σ

σ

−+

⎭

⎬

⎫

⎩

⎨

⎧

= ∑ ⋅ RX

i X i

i

(3.3.1-9) 

and 

[ ] [ ]

1

2

2

ˆ |

1 ˆ |

−

⎪

⎭

⎪

⎬

⎫

⎪

⎩

⎪

⎨

⎧

= ∑

i M Xi

XM

σ

σ (3.3.1-10) 

where Xi

ˆ is a single member of Xˆ . The individual values of ][

i

σ M X should include the 

adjustment given by Equation 3.3.1-8. Use of Equation 3.3.1-9 represents a variance weighted 

estimate of E[M]. The final term of Equation 3.3.1-9 is needed to adjust for bias introduced by 

the underlying exponential distribution in magnitude. Simulation testing using multiple size 

measures showed that Equation 3.3.1-9 produced the correct value of E[M] and the use of 

Equation 3.3.1-7 to compute M* with the variance given by Equation 3.3.1-10 resulted in 

unbiased recurrence parameters. 
Chapter 3 

Earthquake Catalog 

3-16 

The procedure developed by Tinti and Mulargia (1985) can also be applied to the case of E[M] 

estimated from Xˆ . The parameter γ

2

 is computed using the variance defined by Equation 

3.3.1-10. However, in this case the adjustment to the computed recurrence rate is given by 

}exp{])[E()(

2 N M = N M +γ True (3.3.1-11) 

The change in sign is due to the true rate being underestimated from the E[M] magnitudes and is 

a direct result of relationship between Mˆ and E[M] defined by Equation 3.3.1-5. 

The above results were obtained using earthquake catalogs that had the same level of 

completeness at all magnitude levels; that is, the catalogs contain all earthquakes that occurred 

during the time period used for the simulation. The process was repeated using simulation of 

partially complete catalogs in which the completeness of reporting for smaller magnitudes is less 

than for the larger magnitude, the typical case encountered in practice. These tests showed that 

the use of the M* correction did not lead to unbiased estimates of the earthquake recurrence 

parameters; in general, the values of N(M≥4) and b-value were biased low. The source of this 

bias can be envisioned by comparing the EPRI (1988) and Tinti and Mulargia (1985) bias 

adjustments. If one considers the magnitude interval mi (e.g., magnitudes 4.5 ≤ M < 5), the true 

rate of earthquakes in that interval, λi, is equal to n

C

i/TCi, where n

C

i is the count of true M in the 

catalog completeness period for that magnitude interval TC

i. 

In the case where the catalog contains the observed magnitudes Mˆ , the results of Tinti and 

Mulargia (1985) show that the counts of Mˆ are too large by the factor exp{γ

2

} and the true rate 

can be obtained by multiplying the observed counts by the factor exp{-γ

2

}. The M* approach of 

EPRI (1988) is to shift the observed magnitudes down by the factor MM ˆ [/ 2 2 = βσβγ ] such 

that the counts in the interval mi are effectively reduced by the same factor exp{-γ

2

}. If the 

catalog instead consists of the expected magnitudes E[M], then the adjustment is in the opposite 

direction. The counts of E[M] are too low by the factor exp{+γ

2

} and one can either adjust the 

rate using Equation 3.3.1-11 or shift the magnitudes using Equation 3.3.1-7 to effectively 

increase the counts by the same factor. Where the problem lies is that when the completeness for 

earthquakes in the next lowest magnitude interval is less than for magnitudes in the interval in 

question (TC

i-1 < TCi), then insufficient earthquakes are shifted from magnitude interval mi-1 to mi

using the M and the true rate remains underestimated. 

The solution to this problem is to use the approach of Tinti and Mulargia (1985) to adjust the 

earthquake counts in each magnitude interval rather than use the EPRI (1996) adjusted 

magnitudes M*. However, to maintain the EPRI (1988) ability to account for differences in 

magnitude uncertainty for individual earthquakes, the adjustment is applied individually, 

earthquake by earthquake, rather than globally to the total earthquake counts in a magnitude 

interval. The earthquake catalog is processed to obtain values of E[M] and σ[M] for each 

earthquake as described above. Each earthquake is then assigned an equivalent count N* defined 

as 
Chapter 3 

Earthquake Catalog 

3-17 

{ }

{ }2/][exp*

or

2/] ˆ [exp*

22

22

XM

MM

σβ

σβ

=

=

N

N

 (3.3.1-12) 

The rate of earthquakes in the magnitude interval mi is then obtained by summing the values of 

N* for earthquakes with values of E[M] in the magnitude interval and dividing by period of 

completeness for the magnitude interval. Earthquake recurrence parameters are thus computed 

using standard approaches, such as maximum likelihood, and the effective counts N* rather than 

the observed counts. 

The performance of the use of the N* approach compared to the M* approach was tested on 

simulated catalogs. The simulation steps were as follows: 

1. Simulate a catalog of true values of M from a truncated exponential distribution in the 

magnitude range 3 ≤ M ≤ 8 with a recurrence rate of 25 M ≥ 3 earthquakes per year and a 

300-year complete catalog. 

2. Add random error to each value of M to produce a catalog of observed magnitudes. 

3. Simulate an estimate of size measure X for each M with random variability in the 

relationship between X and M. 

4. Regress against X to obtain the values of E[M|X] and σ[M|X]. 

5. Use Equation 3.3.1-7 to obtain a catalog of M*. 

6. Use Equation 3.3.1-12 to obtain N* for each earthquake. 

7. Assign to each earthquake a probability of being observed based on its size and specified 

relative values of equivalent periods of completeness as a function of magnitude. 

8. Reduce the simulated catalog to the observed one in the periods of completeness for each 

magnitude. 

9. Trim off the events below M* 4 to remove the edge effect and estimate the seismicity 

parameters N(M≥4) and b-value from the counts of M*. 

10. Trim off the events below E[M] = 4 to remove the edge effect and estimate the seismicity 

parameters N(M≥4) and b-value from the counts of N*. 

11. Repeat the process for 500 simulations and compute the average difference between the 

values of N(M≥4) and b-value obtained by steps 9 and 10 from the values computed from the 

full catalog of simulated true values of M. 

Simulations were performed for three cases: mb was computed from M using the expression 

mb = M + 0.3; I0 was computed from M using the expression I0 = 3(M-1)/2; and a mixture of the 

two. Three levels of catalog completeness were used as listed in the table below. The partial 

completeness cases consist of TC

i for magnitude 4 being about two-thirds of the catalog length 

(“Two-thirds” case) and TC

i for magnitude 4 being half of the catalog length (“Half” case). 
Chapter 3 

Earthquake Catalog 

3-18 

Completeness Cases Used in Simulations 

Completeness 

Case 

Equivalent Period of Completeness (years) for Magnitude Interval: 

3–3.5 3.5–4 4–4.5 4.5–5 5–5.5 5.5–6 6–6.5 6.5–7 7–7.5 7.5–8

Full 300 300 300 300 300 300 300 300 300 300 

Two-thirds 200 210 220 230 240 250 260 280 300 300 

Half 100 125 150 175 200 225 250 275 300 300 

The results of the simulations are listed in the following table. Shown for each case are the 

average percent errors between the values of N(M≥4) and b-value obtained using the M* and N* 

approaches and the values obtained using the simulated true values of M. The X cases labeled 

“Mixture” consist of the use of I0 for the first 200 years and mb for the last 100 years, consistent 

with the general mix of size measures in the CEUS SSC Project catalog. For the case of full 

completeness, either method works as well as the other. However, as the relative completeness in 

the lower magnitudes becomes smaller, the bias in the M* estimates increases while the results 

obtained using the N* approach remain close to those obtained using the true simulated values of 

M. These results indicate that the N* approach performs better than the M* approach for 

earthquake catalogs with variable levels of completeness as a function of magnitude. As this is 

the case for the CEUS SSC Project catalog, the N* approach was used to obtain unbiased 

estimates of earthquake recurrence parameters. Consistent with this approach, the uniform 

magnitude measure adopted for the CEUS SSC Project catalog is E[M], the expected value of 

moment magnitude for each earthquake given the uncertainty in estimating its size. 

Results of Simulation Testing of M* and N* Approaches for Partially Complete Catalogs 

X Case

Completeness 

Case 

Percent Error In Parameters Obtained by: 

Estimation Using M* Estimation Using N* 

N(M≥4) b-value N(M≥4) b-value 

I0 Full 2.29% 0.56% 1.79% –0.14% 

I0 Two-thirds –25.00% –2.37% 1.11% 0.96% 

I0 Half –48.42% –11.28% 1.19% 0.36% 

mb Full 0.10% 0.04% 0.14% 0.21% 

mb Two-thirds –26.02% –3.87% –0.52% 0.09% 

mb Half –48.09% –12.01% –1.34% 0.00% 

Mixture Full 1.49% 0.48% 1.25% 0.17% 

Mixture Two-thirds –25.32% –3.29% 1.05% 0.20% 

Mixture Half –49.59% –12.52% –0.83% –0.69% 
Chapter 3 

Earthquake Catalog 

3-19 

3.3.2 Estimation of E[M] for the CEUS SSC Project Catalog 

This section summarizes the relationships used to develop the uniform moment magnitude 

estimate E[M] for earthquakes in the CEUS SSC Project catalog. Two general types of data are 

available for the estimation of E[M], either direct observation of moment magnitudes, Mˆ , or 

observations of other size measures X that require development of scaling relationships from X

to E[M]. The majority of earthquakes in the project catalog that occurred after about 1930 have 

reported values of instrumental magnitude in one or more of the magnitude scales mb, mbLg, MN, 

MS, ML, MC, or MD. The data in the project catalog were used to develop scaling relationships 

between these magnitude scales and moment magnitude. The final relationships are listed in 

Table 3.3-1. 

Before presenting these relationships, the issue of the effect of rounding off in reported 

magnitudes will be addressed. 

3.3.2.1 Effect of Magnitude Rounding on Statistical Tests

As part of the development of scaling relationships from various magnitude scales to moment 

magnitudes, statistical tests were performed to identify potential differences in scaling between 

different catalog sources. Most of the magnitudes are reported in various catalogs to the first 

decimal place. The issue of the effect of rounding in reported magnitudes has been examined by 

Felzer (2008) with regard to the effect on seismicity rates, with emphasis on the effect of 

rounding to the nearest 0.5 magnitude units. For the CEUS SSC Project, the issue is the potential 

impact of rounding of data to the first decimal place on results of t-tests for nonzero values of the 

difference between magnitudes reported by source A and by source B (e.g., the difference 

between MN reported by the GSC and that reported by Weston for a set of common earthquakes). 

The impact of rounding to the nearest 0.1 magnitude unit was examined by simulating 

hypothetical data sets for Source A and Source B with specified average differences in 

magnitude and specified random variability in the magnitude differences. A t-test is performed 

comparing the mean difference between the magnitudes from Source A and Source B to see if a 

nonzero difference is statistically significant at the 5 percent level (p-value = 0.05) This 

corresponds to the absolute value of the mean difference divided by the standard deviation of 

mean differences being greater than 2.13. The simulated magnitudes from the two sources are 

then rounded to the nearest 0.1 magnitude units and the t-test is repeated. Differences in the test 

results for the unrounded and rounded simulated samples would indicate that rounding 

potentially affects the ability to properly detect differences in reported magnitudes. The selected 

5 percent significance level means that even if the true average difference in magnitude reported 

by the two agencies is zero, one would expect to see a statistically significant difference in 5 

percent of random samples. 

The following table reports the results of simulation tests performed for magnitude sample sizes 

of 50 and 100. For each case, a mean difference in magnitude was specified along with the 

standard deviation for the random variability in magnitudes reported by the two agencies. Then 

10,000 simulations of each data set were performed. The percentage of simulated samples that 

indicated a statistically significant difference is given in the table below. For the cases with 

specified mean difference of zero, approximately 5 percent of the simulated samples show a 

statistically significant difference, consistent with expectation. Comparison of the results in the 

last two columns indicates that nearly the same percentages are obtained for the unrounded and 
Chapter 3 

Earthquake Catalog 

3-20 

rounded samples. The results indicate that the rounding to 0.1 magnitude units does not cause a 

significant disruption in t-test results for identifying mean differences in magnitudes between 

two magnitude sources, and its effect can be ignored. 

Simulation of t-Test Results for Differences in Magnitudes 

Sample 

Size 

Specified Mean 

Difference 

Specified Standard 

Deviation of 

Difference of 

Individual 

Magnitudes 

Percentage with 

p-value ≤ 0.05 for 

unrounded sample 

Percentage with 

p-value ≤ 0.05 for 

rounded sample 

100 0 0.1 5.1 5.1 

100 0 0.2 5.2 5.0 

100 0 0.3 5.1 5.1 

100 0.1 0.1 100 100 

100 0.1 0.2 99.9 99.9 

100 0.1 0.3 91.4 91.1 

100 0.2 0.3 100 100 

100 0.2 0.4 99.8 99.8 

50 0 0.1 4.9 5.2 

50 0 0.2 5.3 5.2 

50 0 0.3 5.0 5.0 

50 0.1 0.1 100 100 

50 0.1 0.2 93.4 92.9 

50 0.1 0.3 63.8 63.6 

50 0.2 0.3 99.6 99.6 

50 0.2 0.4 93.6 93.4 

3.3.2.2 Moment Magnitude Data 

Moment magnitude data for earthquakes in the project catalog provide both a direct assessment 

of E[M] and the necessary data for the development relationships between moment magnitude 

and other size measures. Two types of moment magnitude data were used. The first are 

published moment magnitudes for specific earthquakes that are assumed to be based on a reliable 

assessment of seismic moment from inversions of either long-period waveforms or surface-wave 

spectra. Table B-2 in Appendix B lists the 272 earthquakes with reported values of M that were 

used for both observed values of M for specific earthquakes and for developing the magnitude 

conversions. 

As discussed in Section 3.3.1, the reported values of moment magnitude represent Mˆ , 

magnitude measured with uncertainty. These magnitude values are adjusted to E[M] using 

Equation 3.3.1-5. The values of ] ˆ σ[ MM are taken from the source of the reported magnitude 

estimate, if available. If an uncertainty was not reported, then the following average values for 
Chapter 3 

Earthquake Catalog 

3-21 

moment magnitude estimation as a function of time were used. The average of the values of 

uncertainty in moment magnitude estimates presented by Johnston (1996a, Table B2) gives 0.28 

for the period prior to 1960, 0.15 for earthquakes in the time period 1960–1974, and 0.13 for the 

period 1975–1990. The average uncertainty in M for the seven CEUS earthquakes in the Harvard 

Centroid Moment Tensor catalog in the period 1978–1984 is 0.12 and for the eight earthquakes 

in the period 1985–present is 0.10. Using this information, the following nominal uncertainty 

values were assigned to instrumental moment magnitudes when data for a specific earthquake 

was not available. 

Assigned Values of ] ˆ σ[ MM

Time Period Nominal ] ˆ σ[ MM

1920–1959 0.30 

1960–1975 0.15 

1975–1984 0.125 

1985–2008 0.10 

The second type of moment magnitude estimates are those obtained by approximate means in the 

studies of Atkinson (2004a, 2004b), Boatwright (1994), and Moulis (2002). These approximate 

moment magnitudes were corrected for minor biases as described below before using them to 

augment the M data set. 

Atkinson (2004) Study 

Atkinson (2004a, 2004b) developed estimates of moment magnitudes for eastern Canada 

earthquakes based on analysis of Fourier spectra. Figure 3.3-2 compares her estimates of M with 

moment magnitudes listed in Table B-2 in Appendix B for earthquakes in common. The moment 

magnitude values obtained by Atkinson (2004a, 2004b) are close to reported moment 

magnitudes for values of M above magnitude 4, but they overestimate M by about 0.2 units for 

smaller values. The one exception is the estimate for the 1989 Ungava, Quebec, foreshock. 

Atkinson (pers. comm., 2011) indicates that her estimate for this event is unreliable given the 

great distances between the earthquake and the stations she used. Ignoring this one event, a 

locally weighted least-squares fit to the data shown on Figure 3.3-2 was used to adjust the values 

of moment magnitudes reported in Atkinson (2004b) to values of M used in this study. 

Boatwright (1994) Study 

Boatwright (1994) inverted vertical recordings from the Eastern Canada Telemetered Network 

(ECTN) to obtain estimates of earthquake source spectra, including seismic moment. 

Figure 3.3-3 compares Boatwright’s (1994) estimates of moment magnitude with moment 

magnitudes listed in Table B-2 in Appendix B for earthquakes in common. The moment 

magnitude values obtained by Boatwright (1994) are close to reported moment magnitudes for 

values of M below 3.5 and tend to slightly underestimate the value of M at larger values. A 

locally weighted least-squares (Loess) fit to the data shown on Figure 3.3-3 was used to adjust 

the moment magnitudes reported in Boatwright (1994) to values of M used in this study. 
Chapter 3 

Earthquake Catalog 

3-22 

Moulis (2002) Study 

Moulis (2002) developed estimates of moment magnitudes for northeastern United States 

earthquakes using a coda wave technique. Figure 3.3-4 compares her estimates of moment 

magnitude with moment magnitudes listed in Table B-2 in Appendix B for earthquakes in 

common. The moment magnitude values obtained by Moulis (2002) are close to reported 

moment magnitudes, albeit with more scatter than shown by the Atkinson (2004a, 2004b) and 

Boatwright (1994) estimates. A least-squares fit to the data shown on Figure 3.3-4 was used to 

adjust the moment magnitudes reported in Moulis (2002) to values of M used in this study. 

Combined Estimates 

The relationships shown on Figures 3.3-2, 3.3-3, and 3.3-4 were used to compute E[M] for each 

earthquake with an approximate moment magnitude estimate from the three studies described 

above. Where multiple estimates are available from two or three of the studies, they were 

combined using the variance weighing approach defined by Equations 3.3.1-9 and 3.3.1-10. 

Table B-3 in Appendix B lists the resulting approximate moment magnitudes. 

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

Two types of body-wave magnitudes are contained in the catalog data, magnitudes computed 

from the amplitude of compression waves, and mbLg magnitudes computed from amplitude of Lg 

waves. The latter are sometimes denoted as MN or Nuttli magnitudes, referring to Nuttli (1973), 

who originally proposed the relationship for defining the mbLg scale. The distinction between 

mbLg and MN is maintained in the project catalog as not all agencies compute Lg magnitudes in 

exactly the same way. Herrmann and Kijko (1983) discuss this issue and suggest the magnitude 

scale mLg(f) to indicate what frequencies were used to compute the magnitude. This scale is 

currently being used by the Weston Observatory (see below). Catalog data were examined to 

assess the potential for regional/time/network differences in the conversion from various bodywave magnitude scales to M.

Comparison of Body-Wave Magnitudes Reported by Various Agencies 

The largest differences found in comparing magnitudes reported by different agencies were in 

comparison of MN magnitudes for earthquakes in the northeastern United States and southeastern 

Canada reported by the GSC and Weston Observatory. Figure 3.3-5 shows the difference in 

reported magnitudes for the same earthquake as a function of time. John Ebel (pers. comm., 

2011) indicates that the history of magnitude calculations reported in the Weston Observatory 

catalog consists of four periods: 

• 1938–1962: MN computed from the original Weston Observatory Benioff system (Ebel, 

1987) 

• 1962–1975: MN computed from the Weston Observatory WWSSN system (Ebel, 1987) 

• 1975–1994: MN computed from the Weston Observatory Develocorder system or early 

digital system (NEUSSN bulletins and the Weston Observatory earthquake catalog) 

• 1994–present: mLg(f) computed from the evolving seismometer and digital systems at Weston 

Observatory 
Chapter 3 

Earthquake Catalog 

3-23 

The MN magnitudes reported in the GSC and National Earthquake Database (NEDB) for Canada 

are computed using Nuttli’s formula but with a broader frequency range than originally defined 

by Nuttli (1973) without making a specific frequency correction (J. Adams, pers. comm., 2011). 

The data on Figure 3.3-5 show clearly that there are time periods where the two magnitude scales 

cannot be considered equivalent: 1938–1975, and after about 1997. The time periods of 

differences in magnitude reporting generally coincide with changes in magnitude calculation 

methods used by Weston Observatory, as indicated by the color coding on Figure 3.3-5. 

The SUSN catalog also contained a number of earthquakes in the northeastern United States. The 

catalog indicated that the magnitude data were obtained from the Earth Physics Branch (EPB) of 

Canada. Tests of these magnitudes against MN magnitudes reported in the GSC/NEDB catalog 

indicate that the mean difference is small (~0.03 units) and is only statistically significant when 

using a combination of mb and mbLg magnitudes reported by EPB. Therefore, the SUSN 

magnitudes reported with a sited source of EPB were considered equivalent to GSC MN

magnitudes. 

The other major seismic network in the northeastern United States is the Lamont-Doherty 

network. Earthquake magnitudes in the catalog obtained from the Lamont-Doherty catalog have 

the source designation LDO or PAL (Palisades), or are based on work by Sykes et al. (2008). 

Testing of the difference between magnitudes reported by Lamont and magnitudes reported by 

Weston Observatory indicate a small (–0.08 magnitude unit) difference that is statistically 

significant. 

For the remaining portions of the study region, the magnitudes come from a variety of sources. 

The SUSN catalog lists the following sources for magnitudes in the CEUS: 

B—Bollinger (1975), Southeastern U.S. Catalog 1754–1974 

E—Earth Physics Branch (EPB), Canadian catalog 

G—USGS State Seismicity Maps (Stover et al., 1984) 

I—EPRI-SOG Catalog (EPRI, 1988) 

M—Sibol et al. (1987) 

N—Nielsen (1982)—Stanford Data Base 

O—Nuttli (1974) 

R—Barstow et al. (1981) (Rondout Associates), NUREG/CR-1577 

S—Street and Turcotte (1977) 

T—Reinbold and Johnston (1987) 

U—Earthquake History of the U.S./U.S. Earthquakes (Stover and Coffman, 1993) 

V—SEUSSN Bulletins (Virginia Tech Publication) 

W—Nuttli et al. (1979) 
Chapter 3 

Earthquake Catalog 

3-24 

The separation of magnitude source and type was achieved using the following earthquake 

catalog sources. 

• Although all earthquakes in the USGS seismic hazard mapping catalog are considered to be 

mb magnitude, the catalog does provide references for the assigned magnitude. These were 

used to indicate the magnitude type according to the magnitude source. The major source 

was NCEER and the NCEER magnitude (last column of the NCEER-91 catalog) was used as 

the assigned magnitude. 

• For those events where the magnitude source was “NCEER,” the NCEER-91 catalog was 

used to determine which of the several magnitude types was used to define the “NCEER 

Magnitude.” In the case of instrumental magnitudes, this was typically the magnitude type 

with the largest reported magnitude, which in a number of cases is ML or MC. The USGS 

magnitude type was corrected to correspond to the specified type used in NCEER, and the 

NCEER source was indicated in the catalog where possible, based on comparisons of the 

magnitude with those reported by other sources. The SUSN catalog was particularly useful in 

inferring the source of many of the NCEER/EPRI magnitudes. 

• The Nuttli (1983) catalog from Saint Louis University was also reviewed to change those 

magnitudes with source NUT that were determined from macroseismic data from mb to mI0

or mFA, as appropriate. 

• The Dewey and Gordon (1984) catalog was reviewed to include those earthquakes for which 

Dewey and Gordon (1984) calculated the mbLg magnitude and for these the magnitude source 

was indicated as D&G. 

Comparisons of magnitudes among these different sources indicated differences in some cases of 

0.1 to 0.2 units (e.g., comparing D&G mbLg with mb from other sources) or differences of less 

than 0.1 (e.g., comparing D&G mbLg with mbLg from other sources), although these comparisons 

were often for small samples. 

Analysis of Regional/Network Differences in Body-Wave Magnitude to Moment Magnitude 

Scaling 

The comparisons among body-wave magnitudes reported from various sources indicated that 

there may be regional/catalog source differences in scaling from body-wave magnitudes to 

moment magnitude. The next step was to test the scaling from body-wave magnitudes to moment 

magnitude. The largest differences appeared to be in the northeastern portion of the study region 

(northeastern United States and southeastern Canada). Therefore, separate investigations were 

performed for this portion of the study region and for the remaining portion of the study region. 

Scaling from mb to M in the Midcontinent Portion of the Study Region

The first phase was testing for magnitude differences among sources in the main portion of the 

study region, excluding the northeastern United States and southeastern Canada. Figure 3.3-6 

shows the spatial distribution of earthquakes with reported body-wave and M magnitudes (112 

earthquakes) color-coded by magnitude source. The primary sources for the M magnitude for 

these earthquakes were Street et al. (1975) and Dr. Robert Herrmann at Saint Louis University 

(http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/). 
Chapter 3 

Earthquake Catalog 

3-25 

Figure 3.3-7 shows the mb-M data set for these earthquakes, together with three published 

relationships that have been used in the past for conversion from mb to M for hazard 

calculations. After eliminating the data for mb < 3 to remove truncation effects, a linear 

relationship was fit to the data, resulting in a slope of 0.96 ± 0.03. The linear fit included all 

specified values for body-wave magnitude for each earthquake, with equal weights assigned to 

each value. Testing of the linear fit versus an offset model, M = mb + C, indicated that the linear 

model did not have greater predictive power as measured by the Akaike (1974) information 

criterion (AIC). The AIC is often used to select between models, in this case between a linear 

model with two parameters and an offset model with a single parameter. In selecting among 

models, the one with the lower AIC value is typically preferred. The test results indicate that the 

slope parameter difference from 1.0 is not statistically significant, and the offset model provides 

a satisfactory fit to the data. The resulting constant is –0.28 ± 0.02, and the offset line is shown 

on Figure 3.3-7. It is recognized that at larger magnitudes, there is a tendency for saturation of 

the mb scale with increasing moment magnitude (e.g., Boore and Atkinson, 1987). However, the 

focus in catalog development is in estimating M from instrumentally derived mb magnitudes in 

the magnitude range of 3 to 6. All the larger earthquakes in the CEUS SSC catalog have been 

subjected to special studies, and more robust estimates of M have been developed from these 

efforts. 

Testing of inclusion of the mb source as a predictor showed no statistical significance for any 

source differences. Testing of magnitude type indicated no statistical difference between mb and 

mbLg and a weak difference for Mn, which is based on only 9 earthquakes. Thus it is concluded 

that in the midcontinent portion of the study region, the various reported magnitudes mb, mbLg, 

and the few MN values can be considered equivalent for purposes of estimating E[M]. 

Figure 3.3-8 shows a plot of the residual for the offset model (Figure 3.3-7) against earthquake 

year. There is an apparent shift in the residuals after about 1995 such that the average mb-M

difference becomes about 0.1 magnitude units. There are 26 earthquakes in the post-1995 data 

set scattered throughout the region, and the difference shown on Figure 3.3-8 appears to be 

statistically significant, although it does not correspond to a known change in network 

configuration. Because the difference is small and has not been independently reported, it was 

not factored into the magnitude scaling used for the CEUS SSC Project catalog. 

Scaling from mb to M in the Northeastern Portion of the Study Region

The data for the northeastern United States and southeastern Canada come from two principal 

sources, the GSC and the Weston Observatory. Figure 3.3-9 shows the spatial distribution of 

earthquakes with both body-wave and M magnitudes (580 earthquakes), color coded by 

magnitude source. 

Figure 3.3-10 shows the mb-M data. There are two types of M magnitudes for these earthquakes. 

The points shown as solid circles were determined mostly from waveform modeling by various 

researchers. The open circles indicate the data where approximate methods were used to estimate 

the seismic moment. These represent the work of Atkinson (2004a, 2004b), Boatwright (1994), 

and Moulis (2002). Also shown on the figure are the three scaling relationships shown on 

Figure 3.3-7 plus the Sonley and Atkinson (2005) relationship between MN and M. 

To examine the correlation between the magnitude scales, the data were again limited to the 

magnitude range of primary interest (mb ≥ 3.5). The very limited data for mb > 6 were also 
Chapter 3 

Earthquake Catalog 

3-26 

removed to eliminate the effects of mb saturation. Testing again showed that a linear fit has a 

slope near 1 (0.97 ± 0.02) and an offset model produces a lower AIC value. However, for this 

data set, there are marginally significant differences among the sources, with the largest 

difference between the GSC and other sources. A statistically significant difference among the 

body-wave magnitude types in this data set was found, principally between mb and other 

magnitude types. 

Figure 3.3-11 shows a plot of the residuals from the fit shown on Figure 3.3-10 versus time. The 

red points indicate the mb magnitude types. Time-dependent changes in residuals may be at least 

partly an effect of magnitude type. Testing of the effect of magnitude type for data prior to 1980 

indicates that type becomes much less significant. Exploring further, Figures 3.3-12 and 3.3-13 

show the residuals from Figure 3.3-10 versus year for only the GSC and Weston (WES) data, 

respectively. These two data sets show shifts in scaling that occur at different times: at about 

1995 for the GSC data and about 1980 for the WES data. Both offsets appear statistically 

significant. The difference in MN to M scaling in the GSC data has been noted previously by 

Bent (2010). The difference in MN to M scaling in the WES data corresponds to about the time 

of a change in magnitude processing and also to the period where the MN magnitudes are most 

similar between the GSC and WES data (Figure 3.3-5). These results indicate that time 

dependent scaling of mb to M should be included in converting the GSC and WES body-wave 

magnitudes. 

Figure 3.3-14 shows the residuals from the fit shown on Figure 3.3-10 versus year for the other 

catalog sources. A similar time trend to that shown by the WES data can be seen. The sources for 

most of the data shown on the figure are EPRI and SRA (Stover et al., 1984). Both of these are 

compilations of other catalog sources and the data are following the trends seen in the primary 

regional catalogs. As the EPRI and SRA source catalogs are compilations, the assignment of 

magnitudes to a specific network was made by assuming that if that network source (e.g., GSC 

or WES) reports the same magnitude value as in the compilation, then that region catalog is the 

likely source of the EPRI or SRA magnitude. In this manner, most of the magnitudes listed in 

these two catalogs could be assigned to either the GSC or WES source. 

The other important magnitude source in the region is the Lamont-Doherty Earth Observatory 

(LDO) catalog. There are only three earthquakes in the catalog with both body-wave magnitudes 

attributed to LDO and moment magnitudes so the scaling cannot be tested for this catalog source. 

Comparison of body-wave magnitudes from LDO to those from other sources is also 

inconclusive. Figure 3.3-15 shows a plot of the difference between body-wave magnitudes 

attributed to LDO and those from other sources. The results do not suggest any difference as the 

time period when most of the earthquakes were recorded corresponds to the period when the 

GSC and WES magnitudes are essentially equivalent (Figure 3.3-5). 

Figure 3.3-16 shows the spatial distribution of earthquakes with reported GSC body-wave 

magnitudes and moment magnitudes. Figure 3.3-17 shows the M-mb(MN) difference as a 

function of time for the data with both reported magnitudes. There is a suggestion that the mb-M

scaling is different in the midcontinent region (southwest of the dashed line on Figure 3.3-16), 

but this may be due to the GSC reporting magnitudes determined by other sources. 

Another source of body-wave magnitudes is the Oklahoma Geological Survey Leonard 

Geophysical Observatory (OKO) catalog, which reports both mbLg and m(3Hz) magnitudes. 

Figure 3.3-18 shows the difference between mbLg and m(3Hz) in that catalog as a function of 
Chapter 3 

Earthquake Catalog 

3-27 

mbLg. For magnitudes in the range of interest to this study (mbLg > 3) there is no statistically 

significant difference between the two magnitudes and m(3Hz) was considered equivalent to 

mbLg for purposes of estimating E[M]. 

Model for Scaling from mb to E[M]

Based on the analyses presented above, the a model for scaling body magnitudes to E[M] was 

developed as follows. A data set of mb-M pairs was created for study region using the following 

criteria: 

• Magnitudes from composite catalogs (e.g., SRA, EPRI, LLL) were assigned a source from 

one of the primary source catalogs (e.g., WES, GSC) when the reported magnitude was the 

same. 

• Magnitudes with source GSC in the midcontinent area were discarded unless they represent 

the only reported magnitude for an earthquake. 

• Magnitude types mb, mbLg, MN, mLg(f), and m(3Hz) are considered equivalent. However, 

catalog source designations are retained. 

Figure 3.3-19 shows the resulting data set. It was found that if the data below magnitude about 

mb 3.5 were removed, then an offset model, M = mb + C, has a better (lower) AIC value; that is, 

the difference from a slope of unity is not statistically significant. A change in slope can be seen 

in the data for lower magnitudes. This change may be due to the effects of data truncation or 

actual changes in the scaling relationships between the two magnitude scales. However, the 

lower magnitudes are not of primary interest in developing earthquake recurrence relationships 

for assessing seismic hazard. At the upper end of the magnitude range there is the issue of 

saturation of the mb scale, which has been shown from numerical modeling (e.g., Boore and 

Atkinson, 1987). Truncation of the data set to remove magnitudes above mb 6 resulted in little 

change to the value of C or the statistical significance of a departure from a slope of unity. 

The data from the GSC were then analyzed to identify the best year for the transition in scaling, 

which was found to be 1997. A similar analysis was performed to identify the best year for a 

transition in scaling in the WES data, which was found to be 1982. Differences in scaling 

between the earthquakes in the midcontinent region and the GSC catalog and earthquakes in the 

midcontinent and the WES catalog (post-1982) were both found to be statistically significant 

with a difference of about 0.1 magnitude units. The difference in scaling between GSC and WES 

data after 1982 and before 1997 was found to be only 0.02 units and is not statistically different 

from zero. It is difficult to determine if the difference between scaling in the northeastern United 

States applies only to the WES catalog or to both WES and LDO, but the limited data that can be 

attributed to LDO show no clear difference from the WES catalog (Figure 3.3-15), and the LDO 

magnitudes were assumed to be equivalent to the WES. The resulting form of the scaling 

relationship is 

E[M] = mb – 0.316 – 0.118ZNE – 0.192Z1997GSC + 0.280Z1982NE

σM|mb = 0.24 
Chapter 3 

Earthquake Catalog 

3-28 

where ZNE is 1 for earthquakes located in the northeast (northeast of the dashed line on 

Figure 3.3-16 including GSC data) and 0 otherwise; 

Z1997GSC is 1 for earthquakes occurring after 1997 recorded by the GSC and 0 otherwise; 

and 

Z1982NE is 1 for earthquakes occurring in the Northeast prior to 1982 recorded by other 

than the GSC and 0 otherwise. 

The value of σM|mb = 0.24 reflects the value of 0.29 obtained from regression reduced by the 

average value of ] ˆ σ[ MM =0.16 for the earthquakes used in the regression (Equation 3.3.1-8). 

A test of the model that accounts for a difference between the long-period spectral estimates of 

M and the corrected approximate values of M found a statistically insignificant difference of 

0.02 magnitude units. 

Examination of the residuals indicated that there is more scatter (larger variance) for the data 

prior to 1980 than for the data after 1980. The ratio of the variances, 1.6, is statistically 

significant using an F-test. However, use of variance weighted regression produces only about 

0.01 unit magnitude differences in the scaling relationships and even less in the N* corrections. 

Therefore, the variance weighted results were not used. 

3.3.2.4 Estimation of E[M] from ML Magnitudes 

Local magnitudes, ML, are reported by a number of agencies. These magnitudes were calibrated 

by the various agencies to correspond to the original local magnitude definition given by Richter 

(1935). Figure 3.3-20 shows the spatial distribution of earthquakes with reported instrumental 

ML magnitude of 3 and larger in the project catalog. There are a number of earthquakes in the 

region offshore of Canada. These are ML(Sn) magnitudes (J. Adams, pers. comm., 2011) that may 

need different conversion relationships than the onshore ML data. However, they occur primarily 

outside of the CEUS SSC model study region and are not analyzed further. Figure 3.3-21 shows 

the spatial distribution of earthquakes that have both ML and M magnitudes in the project 

catalog. The spatial distribution of the ML-M pairs is limited and is insufficient to examine 

regional or catalog differences in ML to M scaling in the CEUS directly. 

Figure 3.3-22 shows the ML-M data set. The data for the two offshore Canada earthquakes fall 

within the distribution of the other data. The data for the two earthquakes in the western part of 

the study region also lie within the distribution of the other data. Shown on the figure are the 

relationships developed by Johnston (1996a) and Miao and Langston (2007). The trend of the 

data on Figure 3.3-22 displays the typical flattening of slope at the lower magnitudes. To 

minimize the influence of this flattening on the estimation of M in the range of interest, the data 

below ML 3.5 were not used in fitting the model. The presence of a few outlying data points 

suggests the use of robust regression and the resulting fitted linear model is shown. 

The data shown on Figure 3.3-22 suggest that for the larger ML values, the slope of the ML-M

relationship may approach 1. Herrmann and Nuttli (1982) report that ML and mbLg values are 

nearly equal in the western United States. Kim (1998) found that ML and mbLg were nearly equal 

for earthquakes in eastern North America. This suggests that the better defined mb to M scaling 

might be used for the ML data. 
Chapter 3 

Earthquake Catalog 

3-29 

Figure 3.3-23 compares MN and ML magnitudes reported by the GSC. For MN ≥ 3, the data are 

well fit by the relationship ML = MN + 0.21, with a standard error of 0.30. Robust regression was 

used because the observed scatter suggests possible outliers in the data. However, ordinary least 

squares produced only a 0.02 magnitude unit difference in the offset factor and a small increase 

in the standard error to 0.34. Also shown on Figure 3.3-23 is the relationship developed by Kim 

(1998). The difference between the results shown for the GSC data and the Kim (1998) 

relationship may be due to the fact that Kim (1998) used PDE mbLg magnitudes and computed 

ML, while the data shown on Figure 3.3-23 are based on the reported GSC magnitudes from the 

project catalog. The data shown on Figure 3.3-23 indicate that the GSC ML magnitudes can be 

converted to E[M] by subtracting 0.21 magnitude units and then using the MN to M conversion, 

with an increase in standard error to account for the additional step. This would bring the 

standard error to a value of 0.42, similar to that for the fitted relationship shown on 

Figure 3.3-22. 

The ML data from the remaining portion of the study region require variable treatment. 

Figure 3.3-24 shows the data for earthquakes in the northeastern portion of the study region with 

reported ML magnitudes and either MC or MD magnitudes from catalog sources other than the 

GSC. There are two MD values reported by CERI in this region, the largest being for the 

1983/10/07 earthquake. Analysis of the data above MC or MD values of 2.5 indicates that on the 

average ML is equivalent to MC or MD, although with considerable scatter. As will be shown in 

Section 3.3.2.6, there is a large sample with which to estimate the MC to M scaling. Figure 

3.3-25 shows the data for earthquakes in the northeastern portion of the study region with M

magnitudes a ML magnitude from sources other than the GSC. Shown on the figure is the 

relationship developed in Section 3.3.2.6 for converting MC to M. Testing of the difference 

between the observed values of M and those predicted assuming ML equivalent to MC showed no 

statistically significant difference. For ML ≥ 2.5, the mean offset (using robust estimation) is 0.11 

± 0.06 and for ML ≥ 3 the mean offset is –0.06 ± 0.08. Therefore, in the northeastern portion of 

the study region, ML magnitudes were be converted using the MC conversion relationship, with 

an increased standard error of 0.46 to account for the larger scatter in the data compared to that 

for the MC-M data. 

As shown on Figure 3.3-20, only a few earthquakes outside of the northeastern portion of the 

study region have reported ML and M magnitudes. Therefore, scaling relationships for ML

magnitudes in this portion of the study region were based on correlation of ML with other 

magnitude scales. The two principal examples are as follows: 

• The ML magnitudes reported by SCSN are equivalent to the MC magnitudes reported by 

SCSN. 

• The ML magnitudes reported by ANSS in the vicinity of New Madrid are equivalent (with 

minor exception) to the MD magnitudes reported by CERI for MD ≥ 3. 

3.3.2.5 Estimation of E[M] from MS Magnitudes 

Surface wave magnitudes, MS, are computed from the amplitude of low frequency (< 0.1 Hz) 

surface waves. Figure 3.3-26 shows the spatial distribution of earthquakes with MS magnitude of 

3 and larger in the project catalog. Figure 3.3-27 shows the MS-M data set. Also shown on 

Figure 3.3-27 is the quadratic relationship developed by Johnston (1996a). This relationship was 

developed using larger magnitudes and does not extrapolate well into the magnitude range of the 
Chapter 3 

Earthquake Catalog 

3-30 

CEUS SSC data set. A quadratic polynomial was fit to the data. Figure 3.3-27 shows the fitted 

model, the 90% confidence interval of the mean, and the 90% prediction interval. At MS > 5, the 

fitted model is very similar to the Johnston (1996a) global model. The resulting conversion 

relationship is 

E[M] = 2.654 + 0.334MS + 0.040MS

2

σM|Ms = 0.20 

The value of σM|Ms = 0.20 reflects the value of 0.24 obtained from regression reduced by the 

average value of ] ˆ σ[ MM =0.13 for the earthquakes used in the regression (Equation 3.3.1-8). 

3.3.2.6 Estimation of E[M] from MC and MD Magnitudes 

The coda magnitude scale, MC, and the duration magnitude scale, MD, are based on correlations 

of the length of the seismic signal and earthquake size measured in other magnitude scales, 

typically mb or ML. They are typically applied to smaller magnitude earthquakes. The spatial 

distribution of earthquakes with Mc magnitudes ≥ 2.5 in the project catalog is shown on Figure 

3.3-28. These include many earthquakes with magnitude type labeled “UNK” in the LDO 

catalog that appear to be MC magnitudes based on values reported by other agencies. The major 

sources of data are the WES, LDO, and Southeastern United States (SEUS) networks. The 

spatial distribution of earthquakes with Mc magnitudes ≥ 2.5 and M magnitudes are shown on 

Figure 3.3-29. The data are only sufficient for estimating the scaling of MC to M in the 

northeastern portion of the study region, predominantly magnitudes reported by WES and LDO. 

Figure 3.3-30 shows the spatial distribution of earthquakes with MD magnitude of 3 and larger in 

the project catalog. The major sources of data are the CERI, SEUS, OKO, and SNM (Sanford et 

al., 2002) networks. The spatial distribution of earthquakes with both MD and M magnitudes is 

shown on Figure 3.3-31. These data indicate that direct comparisons between MD and M

magnitudes are limited primarily to data from CERI in the midcontinent portion of the study 

region and to data from WES and LDO in the northeastern portion of the study region. 

Scaling to E[M] for the Northeastern Portion of the Study Region 

Figure 3.3-32 shows the MC-M data set. Testing for differences in scaling between the WES and 

LDO sources found no statistically significant differences. This was true both assuming that the 

LDO “UNK” magnitudes are MC from that source and using only the magnitudes actually 

labeled MC. The green symbols indicate the few MD magnitudes that differ from the reported MC

magnitudes for the same event. These data points fall well within the mass of the data, consistent 

with assuming that MC and MD magnitudes can be considered equivalent in the northeastern 

portion of the study region. Testing indicated that a linear fit to the data with slope less than 1 

provided a better fit than an offset model. Tests for outliers gave conflicting results that suggest 

that one may be present. However, a robust regression fit to the data produced nearly the same 

regression coefficients. Therefore, the ordinary least-squares result was used. The resulting 

model is 

E[M] = 0.633 + 0.806MC 

σM|MC = 0.27 
Chapter 3 

Earthquake Catalog 

3-31 

The value of σM|MC = 0.27 reflects the value of 0.31 obtained from regression reduced by the 

average value of ] ˆ σ[ MM =0.15 for the earthquakes used in the regression (Equation 3.3.1-8). 

Scaling in Midcontinent East of Longitude 100°W 

As indicated on Figures 3.3-29 and 3.3-31, the spatial distribution of MC-M magnitude pairs and 

MD-M magnitude pairs is limited. The possibility of combining the two magnitude measures was 

examined by comparing MC and MD magnitudes across the study region. Figure 3.3-33 shows 

the spatial distributions of the data sets investigated. 

Figures 3.3-34, 3.3-35, 3.3-36, 3.3-37, and 3.3-38 compare the MC and MD magnitudes for each 

data set shown on Figure 3.3-33. Figure 3.3-34 compares MC and MD magnitudes for 

earthquakes with magnitude values coming from either the WES or LDO catalog. The data 

indicates that these two scales can be considered equivalent in the northeastern portion of the 

study region. 

Figure 3.3-35 shows that the MC or MD magnitudes reported in the OKO catalog are essentially 

equivalent to values of MC or MD reported in other catalogs. Figures 3.3-36 and 3.3-37 show 

similar comparisons for the CERI and SCSN catalogs, respectively. Figure 3.3-38 shows the 

comparison for other catalog sources. In all cases, MC and MD can be considered essentially 

equivalent for magnitudes above about 2.5. Note that there is only one earthquake west of 

longitude 100°W that can be used to compare magnitudes. 

Figure 3.3-39 shows the data set for MD and M magnitudes for the midcontinent portion of the 

study region. Also shown on the figure are the limited data for MC-M and ML-M pairs for the 

same region. These data are generally consistent with the MD-M data. In addition, the 

relationship developed by Miao and Langston (2007) between ML and M is plotted. The Miao 

and Langston relationship is also consistent with the data. A linear regression was performed of 

data larger than magnitude 2.9, resulting in the relationship shown by the red curves on 

Figure 3.3-39. Inclusion of differences between MC, MD, and ML did not produce a statistically 

significant improvement in the fit. The resulting relationship is 

E[M] = 0.869 + 0.762 (MC, MD, or ML)

σM|MC = 0.25 

The value of σM|MD = 0.25 reflects the value of 0.28 obtained from regression reduced by the 

average value of ] ˆ σ[ MM =0.11 for the earthquakes used in the regression (Equation 3.3.1-8). 

Scaling in the Region Between Longitudes 105°W and 100°W 

The portion of the study region between longitudes 105°W and 100°W has very few earthquakes 

with reported moment magnitudes. Figures 3.3-40, 3.3-41, and 3.3-42 compare the various 

magnitude scales for earthquakes in this region contained in the CEUS SSC Project catalog. 

These comparisons indicate that mb correlates fairly well with the other magnitude scales, except 

for ML prior to 1970 (the events on Figure 3.3-41 prior to 1970 occurred after 1960). Therefore, 

the mb-M scaling relationship was applied to scale those events in the region of longitude 105°W 

to 100°W when only MC, MD, or ML magnitudes were available. 
Chapter 3 

Earthquake Catalog 

3-32 

3.3.2.7 Estimation of E[M] from the Logarithm of Felt Area 

Figure 3.3-43 shows the spatial distribution of earthquakes in the project catalog with reported 

values of ln(FA), where FA is felt area measured in km2. The red symbols denote those 

earthquakes that also have a reported value of M. The point located offshore Newfoundland is 

the 1929 Grand Banks earthquake. 

Figure 3.3-44 shows the ln(FA)-M data from the project catalog. The form of the relationship 

used to fit the data was that proposed by Frankel (1994) based on theoretical grounds. This form 

was used by Johnston (1996b) to fit data from a worldwide database of SCR earthquakes. The 

Johnston (1996b) relationship, shown on Figure 48, is generally consistent with the data from the 

project catalog. 

The data were trimmed below ln(FA) = 8.5 to limit the effects of sample truncation at low 

magnitude values. The resulting relationship is shown by the red curves on Figure 3.3-44. 

Trimming the data at larger values of ln(FA) produced greater differences between the fitted 

model and the Johnston (1996b) relationship. 

The data set used to develop the model included the ln(FA) value for the 1929 Grand Banks 

earthquake. The fact that this earthquake occurred offshore increases the uncertainty in 

estimation of the felt area. Removal of the earthquake from the data set produced a small 

reduction in the predicted magnitudes for large felt area of about 0.2 magnitude units, less than 

one standard deviation in the prediction for a single earthquake. The data from this earthquake 

were used by Johnston (1996b) and are used to develop the model for used for the CEUS SSC 

Project. The fitted model is 

22.0

00087.0)ln(218.041.1][E

)ln( =

+×+=

FAM

FA FA

σ

M 

The value of σM|ln(FA) = 0.22 reflects the value of 0.29 obtained from regression reduced by the 

average value of ] ˆ σ[ MM =0.185 for the earthquakes used in the regression (Equation 3.3.1-8). 

Note that the standard error is comparable to the estimation of M from mb. 

A t-test of the difference between the project data and the Johnston (1996b) predictions for 

ln(FA) ≥ 10 (the region where Johnston’s data lie) showed a statistically significant difference 

from zero, indicating that the above relationship provides a better fit to the CEUS project data 

than the Johnston (1996b) relationship. 

3.3.2.8 Estimation of E[M] from the Maximum Intensity, I0

The size measure available for most pre-instrumental earthquakes is maximum shaking intensity, 

I0, predominately reported in the MMI scale. Figure 3.3-45 shows the spatial distribution of 

earthquakes in the project catalog with reported values of maximum intensity, I0, which is 

assumed to be epicentral intensity. The red symbols denote those earthquakes that also have a 

reported value of M. The blue symbols denote offshore earthquakes where the assessment of I0 is 

problematic. The offshore earthquakes were not used in the development of the I0 to E[M] 

scaling. 
Chapter 3 

Earthquake Catalog 

3-33 

Figure 3.3-46 shows the I0-M data from the project catalog. The red curves show a locally 

weighted least-squares (Loess) fit to the CEUS data, treating the I0 values as numeric quantities. 

The blue dashed curve shows the relationship derived by Johnston (1996b) from a worldwide 

data set of SCR earthquakes consisting primarily of values for I0 of V and larger. The Johnston 

(1996b) relationship overpredicts the value of M derived from the CEUS data set for intensities 

values between IV and VII.

The Loess fit to the CEUS data shows a pronounced change in slope at about I0 equal to V. 

Similar changes in scaling have been observed previously in developing relationships between I0

and mb. Figure 3.3-47 shows the I0 and mb data pairs from the NCEER-91 catalog (Seeber and 

Armbruster, 1991), together with the relationships between I0 and mb developed by the EPRISOG project (EPRI, 1988) and Sibol et al. (1987). EPRI-SOG (EPRI, 1988) proposed that a 

linear fit was adequate for the intensity range of interest, although the observed data for I0 III fall 

generally above the fitted relationship. Sibol et al. (1987) proposed a variety of fits, including the 

nonparametric fits to the data for individual intensity classes shown on Figure 3.3-47. The Sibol 

et al. (1987) nonparametric fits were used by Seeber and Armbruster (1991) to develop the 

intensity-based magnitude estimates in the NCEER-91 catalog. 

The departure from a linear I0–magnitude relationship is much less pronounced for the mb

magnitude data shown on Figure 3.3-47 than for the M data shown on Figure 3.3-46, particularly 

at mb values of 3 and larger that have been used to develop earthquake occurrence relationships 

by EPRI-SOG (EPRI, 1988) and by the USGS (e.g., Petersen et al., 2008). Therefore, the 

nonlinearity likely has had minimal effect on the estimation of seismicity parameters. However, 

the stronger departure from linear scaling observed for the I0-M pairs, coupled with the 

incorporation of uncertainty in magnitude estimates through the use of M* or N* adjustments, 

produced significant departures from exponential behavior in initial estimates of earthquake 

recurrence rates as a function of magnitude as well as possible overestimation of magnitudes 

from small intensities. The change in scaling slope may be due to inherent nonlinearity in the 

I0-M relationship, or it may be affected by truncation in the observed data at the lower magnitude 

and intensity levels. Truncation of the data is likely on the magnitude axis because of the limited 

number of small values of M reported in the literature and in various catalogs. Truncation of the 

data is likely on the intensity axis because of the lack of intensity reporting for recent 

earthquakes in earthquake catalogs and the limited felt areas of small earthquakes. 

In order to investigate the possible effects of magnitude truncation on the scaling, the I0-M data 

were analyzed in reverse order (i.e., I0 is estimated a function of M). Figure 3.3-48 shows the 

data from Figure 3.3-46 plotted with M as the independent variable. The value of I0 as a function 

of M can be considered as a categorical response, one that falls into discrete categories. For the 

intensity data, the categories are ordered. One method of modeling ordered categorical responses 

is the proportional odds model (e.g., Fox, 2002), which provides the probability of a response 

being in the individual classes as a function of the predictor variables. This is a generalization of 

the logistic model for dichotomous (0-1) response variables. The result of fitting the model is a 

relationship between M and the probability of observing a specific category of I0. Figure 3.3-49 

shows examples of these relationships from fits to the data shown on Figure 3.3-48. The 

magnitude at which the maximum probability is obtained for each intensity class is shown by the 

red circles on Figure 3.3-48. These results indicate an approximately linear relationship between 

the value of M that maximizes the probability of observing a particular intensity class and the 

nominal intensity class value for M 3 and greater and I0 IV and greater. 
Chapter 3 

Earthquake Catalog 

3-34 

The proportional odds model imposes the requirement that the logistic models for each intensity 

class differ only by their intercepts; that is, they have the same coefficient applied to magnitude. 

A less restrictive model is the multinomial logit model, in which the order of the categories is not 

important. Applying this model produces the values of M that maximize the probability of 

observing a particular intensity class shown by the blue diamonds on Figure 3.3-48. These results 

are more scattered at the edges of the data as the model parameters are less restricted by the 

functional form. However, the multinomial results also suggest an approximately linear trend 

over the same range as the proportional odds model. Based on these results it is concluded that a 

linear relationship between I0 and M is appropriate for the CEUS SSC catalog data, at least for I0

above IV. 

Initial analysis of the I0-M data produced scaling relationships that appeared inconsistent with 

published relationships between I0 and mb and the relationships between mb and M developed 

here, suggesting a possible bias in the data sample. Figure 3.3-50 shows the data from the project 

catalog for earthquakes with reported values of I0 and mb (mb, mbLg, MN, mLg(f)). The solid circles 

indicate those earthquakes that also have a value of M. The blue and red curves show locally 

weighed least-squares (Loess) fits to the entire data set and only those earthquakes with reported 

values of M, respectively. As can be seen, there is an offset in the fit for the subset of 

earthquakes with reported values of M compared to the fit of the larger data set. Also shown on 

Figure 3.3-50 are the relationships between I0 and mb developed by EPRI (1988) and Sibol et al. 

(1987). 

As discussed above, linear relationship between I0 and magnitude is appropriate in the magnitude 

range of interest for this study. Figure 3.3-51 shows a linear least-squares fit to the data for 

values of I0 ≥ V. Again, the subset with M shows an offset in the scaling relationship compared 

to that obtained for the full I0-mb data set. Figures 3.3-52 and 3.3-53 show the effect of repeating 

the analysis using values of mb adjusted for differences in mb to M scaling found in Section 

3.3.2.3. These results show the same effect as the analysis of the reported mb values without 

adjustment. 

To address the apparent bias in the sample of earthquakes with just I0 and M data, the regression 

data set was augmented with the much larger data set of earthquakes, with I0 and mb using M

estimated from mb for those earthquakes without values of M. However, the effect of the 

underlying exponential distribution in earthquake sizes needs to be accounted for in mixing the 

data from earthquakes with values of M with data where M is estimated from mb. The reported 

values of moment magnitude are designated Mˆ to indicate that they are measured with 

uncertainty. As described in Section 3.3.1, regression of M versus mb produces the estimate 

E[M]. Equation 3.3.1-5 shows that adjusting the values of E[M|mb] to be consistent with Mˆ

requires addition of the factor β ][2 σ M mb . Using the value of ][2 σ M mb of 0.24 found in 

Section 3.3.2.3 and a b-value of 0.95 (the value typically obtained from analysis of the catalog), 

the estimated values of E[M|mb] were adjusted upward by 0.12 magnitude units before 

combining with the Mˆ data set. 

Figure 3.3-54 shows the resulting composite data set used to estimate the I0 to M conversion. 

Plotted on the figure is a locally weighted least-squares (Loess) fit to the data. Also plotted are 

the relationships of EPRI (1988) and Sibol et al. (1987) shifted by an average mb to M factor of 
Chapter 3 

Earthquake Catalog 

3-35 

–0.32. The fit to the I0-M data is now consistent with past models for the relationship between I0

and mb and the relationship between mb and M found in this study. 

The Loess model fit indicates a break in slope between I0 IV and V, consistent with the 

indication that a linear relationship between I0 and M is appropriate for larger intensity values. 

Therefore, the data set was trimmed to remove I0 ≤ IV. Figure 3.3-55 shows a linear fit to the 

data for I0 > IV. Although there is large scatter, tests of the residuals using the method of Grubbs 

(1950) did not indicate the presence of outliers in the data set. In addition, a robust regression 

produces a relatively small reduction in standard error from 0.56 to 0.49. The linear model has a 

slope of 2/3. 

Cavallini and Rebez (1996) propose that a linear model is not appropriate for relating I0 to 

magnitude over the entire range because I0 is bounded; in particular, as magnitude increases, I0 is 

limited to a maximum of XII. They propose instead the use of an inverse sigmoid curve, which is 

represented by the inverse of the error function (Erf) and the function form: 

⎥⎦

⎤ ⎢⎣⎡ += − − 1 6 2 0 1

21

I ErfCCM (3.3.2-1) 

The model represented by Equation 3.3.2-1 was also fit to the data, with the result of a very 

slight improvement in the fit. However, one issue with the form specified by Cavallini and Rebez 

(1996) is that it does not allow for I0 to reach its maximum of XII. There are insufficient data in 

the project catalog with which to define an appropriate shape at the upper end. In order to allow 

for I0 equal to XII, Equation 3.3.2-1 was modified to the following form: 

⎥⎦

⎤ ⎢⎣⎡ − += −

5.6

)6( 2 0 1

21

I ErfCCM (3.3.2-2) 

The fit of Equation 3.3.2-2 to the project data is shown on Figure 3.3-55. The fit is essentially 

identical to the linear model over most of the range of the data, and is slightly better at the upper 

end. The inverse sigmoid model has a slightly lower AIC value. 

The resulting linear model is 

E[M] = 0.017 + 0.666I0 

σM|I0 = 0.50 

and the inverse sigmoid model is 

E[M] = 4.008 + 3.411x ⎥⎦

⎤ ⎢⎣

− ⎡ −

5.6

)6( 2 0 1 I Erf

σM|I0 = 0.50 

The value of σM|I0 = 0.50 reflects the value of 0.56 obtained from regression reduced by the 

average value of ] ˆ σ[ MM =0.25 for the earthquakes used in the regression (Equation 3.3.1-8), 

which includes the estimates of M from mb. 

F-tests for unequal variances at I0 values above and below I0 VI and above and below I0 VII 

found no statistically significant differences. 
Chapter 3 

Earthquake Catalog 

3-36 

Another issue with the form proposed by Cavallini and Rebez (1996) occurs at the lower end of 

the intensity scale. An assigned intensity value of I0 = I means the event was too small to be felt, 

but this does not require an extremely small negative magnitude. For this project the differences 

between the linear and inverse sigmoid fit are insignificant over most of the I0 range of interest. 

Therefore, the linear fit was used for I0 ≤ VI and the inverse sigmoid fit was used for I0 > VI. 

3.3.2.9 Uniform Moment Magnitude Catalog of E[M] and N* Values 

As described in Section 3.3.1, the uniform magnitude measure used in the CEUS SSC 

earthquake catalog is E[M], the expected value of moment magnitude given its uncertainty in 

estimation. The hierarchy of estimates used to develop this size measure is as follows: 

1. If an estimate of moment magnitude from assessment of the long-period amplitude of the 

source spectrum is available (e.g., a Harvard Centroid Moment Tensor solution), then it is 

used as the only size measure. The estimate is designated Mˆ to indicate that it is measured 

with uncertainty. This is consistent with the approach used to develop the EPRI-SOG catalog 

and is based on the assumption that a direct estimate of moment magnitude is greatly 

preferred over one estimated from other size measures. 

2. Special studies of larger pre-instrumental earthquakes have derived estimates of M from the 

area of isoseismals (e.g., Johnston et al., 1994; Johnston, 1996b) or from the intensity field 

and its fall-off with distance (e.g., Bakun and Hopper, 2004b; Bakun et al., 2003). If these are 

available for an earthquake, then they are preferred overestimates developed from the 

regressions against intensity measures developed in this study. Moment magnitude estimates 

based on use of isoseismal areas given in Johnston et al. (1994) and Johnston (1996b) were 

used, as the Johnston et al. (1994) relationships between felt area and M are consistent with 

the project catalog data, and the use of multiple isoseismal areas is considered preferable to 

the use of just felt area. However, moment magnitudes given in Johnston et al. (1994) based 

on conversion from I0 were not used because the conversion relationships developed for the 

CEUS SSC Project are considered more appropriate for moderate-sized earthquakes in the 

CEUS than the relationships developed by Johnston et al. (1994) and Johnston (1996b) from 

worldwide I0 data. 

3. Approximate moment magnitudes from the studies of Atkinson (2004a, 2004b), Boatwright 

(1994), and Moulis (2002) provide estimates of M. These are treated as estimates of M from 

size measure X with its associated uncertainty and are combined with estimates from other 

size measures. 

4. For the majority of earthquakes, the values of E[M] are based on other size measures, X. 

These include other magnitude scales and the macroseismic values of ln(FA) or I0. The 

estimates from the available size measures X are combined using the variance weighted 

approach of Equations 3.3.1-9 and 3.3.1-10. 

The values of E[M] and σ[M] obtained for each earthquake are given in the project catalog listed 

in Appendix B, Table B-1. Using the values of σ[M] and a b-value of 0.95 determined from 

initial analysis of the catalog, values of the equivalent counts N* are computed using Equation 

3.3.1-12. These values are also listed in the project catalog (Table B-1). 
Chapter 3 

Earthquake Catalog 

3-37 

3.4 Identification of Independent Earthquakes 

The PSHA formulation typically used to model the occurrence of distributed seismicity is based 

on the Poisson model for the occurrence of independent earthquakes. Therefore, dependent 

earthquakes (foreshocks and aftershocks) must be identified and not included in the earthquake 

statistics used to develop estimates of earthquake recurrence rates. This process is referred to as 

catalog declustering. There are several techniques in use for the identification of dependent 

earthquakes. One of the first methods to be developed was that proposed by Gardner and 

Knopoff (1974), in which all smaller earthquakes within a fixed time and distance window 

around a larger earthquake are classified as dependent earthquakes. Gardner and Knopoff (1974) 

developed estimates of the size of the time and distance windows as a function of earthquake 

magnitude from analyses of Southern California earthquakes. Their approach and time and 

distance windows are widely used and form the basis for the identification of dependent 

earthquakes in the earthquake catalog used by the USGS for seismic hazard mapping in the 

CEUS (Petersen et al., 2008). Other applications of this approach have developed alternative 

criteria for the magnitude-dependent time and distance windows of foreshock and aftershock 

sequences, such as those developed by Grünthal (1985) for central Europe earthquakes. 

Another approach was developed by Reasenberg (1985) based on fitting an Omori aftershock 

decay model to earthquakes in the space-time vicinity of a larger earthquake to define the length 

of an aftershock sequence. Again, all earthquakes that occur within a fitted aftershock sequence 

are identified as dependent earthquakes. 

EPRI-SOG (EPRI, 1988, Vol. 1) developed a somewhat different approach for identification of 

dependent earthquakes involving the use of statistical testing to indentify clusters of earthquakes. 

The basic concept is illustrated on Figure 3.4-1. The earthquake catalog is analyzed starting with 

the largest earthquake and proceeding to the smallest. In the vicinity of an earthquake selected 

from this ordered sequence, two space-time windows are constructed according to user specified 

criteria. The first is a local window, Wl, in the immediate vicinity of the selected earthquake with 

space-time volume Vl. The second is a much larger extended window, We, with volume Ve. The 

local and extended windows contain observed earthquake counts of nl and ne, respectively. 

Assuming that the occurrence of earthquakes in the space-time vicinity of the earthquake being 

tested is a stationary Poisson process with unknown intensity parameter μ, then the random 

counts of earthquakes in each window, Nl, and Ne, would have expected values proportional to 

the volume of each window, μVl and μVe, respectively. The null hypothesis that there is no 

elevated seismicity in the space-time vicinity of the earthquake being tested is given by 

e

e

l

l

V

NE

V

NE

H ][][ : 0 = (3.4-1) 

The alternative hypothesis that the earthquake intensity μ is higher in the local window (i.e., 

there is local clustering in space and time) is given by 

e

e

l

l

V

NE

V

NE

H ][][ : 1 > (3.4-2) 
Chapter 3 

Earthquake Catalog 

3-38 

Citing Lehmann (1959), EPRI (1988, Vol. 1) indicates that under the null hypothesis H0 and 

assuming that the expected value of Ne equals the observed value ne, the hypothesis can be tested 

assuming that the number of earthquakes in the local window Nl had a binomial distribution with 

ne trials and probability of success p = Vl/Ve. The distribution for Nl is given by 

1 1 ( ) )-(1 nn

p

n

p

n

n

nNnNP e

l

e

eell

−

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

=== (3.4-3) 

The hypothesis H0 is rejected when nl exceeds the rejection limit nl

R

 given by 

= { } for which min .( eell ) ≤=> α R

l nn nNnNP (3.4-4) 

where α is a suitable low significance level. A value of 0.02 is recommended for α in EPRI 

(1988, Vol. 3). 

Parts (b) and (c) of Figure 3.4.1 illustrate two additional tests performed if the null hypothesis is 

not rejected. Part (b) applies to the case where a local cluster extends outside the initial local 

window Wl such that the counts affect the estimated background rate in the extended window. A 

buffer around the local window is defined, Wb, and the volume and earthquake counts within the 

buffer are removed. The test of H0 is then performed comparing the number of earthquakes 

within the local volume to the rate estimated from the extended window without the buffer 

region. Part (c) applies to the case where the cluster is too small (in time and/or space) to be 

observed within the initial local space-time window. A contraction factor is applied to the local 

window parameters to construct a smaller local window and the test is repeated. 

If the null hypothesis is rejected, then the procedure moves to identifying the extent of the local 

cluster. This is accomplished by testing adjacent space and time windows around the local 

window for clustering by comparing the counts in these adjacent portions with the counts in the 

extended window We, ignoring those earthquakes already identified as a cluster. The process is 

continued until no additional space-time segments are identified that reject the null hypothesis. 

The final step is illustrated on Figure 3.4-2. The EPRI (1988) procedure does not classify all 

earthquakes within the identified space-time window of the cluster as secondary (dependent) 

earthquakes. Instead, it uses a process of thinning the earthquake counts in the cluster region to 

the point where the intensity matches the background rate in the extended window We. This is 

accomplished by simulating a Poisson process within the cluster region using the background 

intensity μ. These simulated earthquakes are illustrated by the pluses in the top plot on 

Figure 3.4-2. The nearest neighbor among the recorded earthquakes to each simulated earthquake 

is indentified as a primary earthquake (i.e., main shock). All the rest are then identified as 

secondary (dependent) earthquakes. The result is a space-time pattern of earthquakes that is 

consistent with the background rate, as shown in the bottom plot of Figure 3.4-2. 

After the first pass through the earthquake catalog, the process is repeated for a second iteration 

with the secondary earthquakes identified in the first pass removed. It is suggested in EPRI 

(1988, Vol. 3) that two iterations are typically all that are needed. 

The advantages of the EPRI (1988) approach are that it is insensitive to incompleteness, as a 

homogeneous Poisson process is only assumed in the general vicinity of the earthquake sequence 

being tested (the extended window We) and it does not assume a priori a shape for the clusters. 
Chapter 3 

Earthquake Catalog 

3-39 

Testing during its development on synthetic catalogs generated by a Poisson process showed that 

it retained nearly all earthquakes as independent occurrences (Van Dyck, 1986). 

Figure 3.4-3 shows the results of application of the EPRI (1988) declustering approach to the 

CEUS SSC catalog. The EPRI-SOG (EPRI, 1988) computer program EQCLUSTER was used 

for the calculations. The data points represent the length in days of individual clusters and the 

maximum distance between earthquakes assigned to a cluster and the identified mainshock. The 

red dashed lines indicate the average values as a function of E[M]. The blue dashed lines 

indicate the starting values for cluster size used in the declustering algorithm. These were taken 

from EPRI (1988), adjusting for the conversion from mb to E[M]. Shown for comparison are the 

time and distance windows developed by Gardner and Knopoff (1974) for Southern California 

earthquakes and by Grünthal (1985) for central Europe earthquakes. The Gardner and Knopoff 

(1974) time windows shown are their published aftershock time windows multiplied by 1.5 to 

add a foreshock window based on the difference between the Grünthal (1985) aftershock and 

foreshock time windows. It should be noted that the time and distance windows developed by 

Gardner and Knopoff (1974) and Grünthal (1985) represent optimized envelopes to their 

observations. The average spatial dimension of the clusters identified in the project catalog is 

less than the published distance window envelopes, and the average time length of a cluster is 

comparable to the published envelope values. The EPRI (1988) procedure does identify some 

clusters that have a much longer duration than the published time windows. 

In order to provide a comparison of the effect of alternative declustering approaches, the Gardner 

and Knopoff (1974) method was applied to the CEUS SSC catalog using the computer program 

CAT3E developed by Dr. Charles Mueller at the USGS for use in earthquake catalog processing 

for seismic hazard estimation. Table 3.4-1 compares the results of the two methods in terms of 

the number of independent earthquakes in various magnitude intervals. The two methods 

produce very similar results, with the overall difference in the number of independent 

earthquakes being about 1.5 percent. The largest difference is the numbers in the E[M] 2.9 to 

3.6 magnitude bin, but this difference is only 4.4 percent. Thus, it is concluded that the use of the 

alternative Gardner and Knopoff (1974) declustering approach would not have a significant 

effect on earthquake recurrence rates computed from the declustered catalog. 

The dependent earthquakes identified with the EPRI (1988) procedure are indicated in the 

earthquake catalog listed in Appendix B, Table B-1. 

3.5 Catalog Completeness 

The assessment of earthquake catalog completeness is necessary in order to prevent 

underestimation of earthquake recurrence rates. One approach is to evaluate the detection 

capability of seismic networks as a function of time on the basis of density of stations and type of 

instrumentation. An example is McLaughlin et al.’s (1997) analysis of the capability of the U.S. 

National Seismic Network (USNSN). However, the more common approach is the use of the 

general technique first proposed by Stepp (1972). This approach evaluates the catalog 

completeness for specific magnitude ranges by starting at the present and moving back in time 

and counting the total number of earthquakes in the catalog in each magnitude interval. At each 

point in time when an earthquake in the specified magnitude interval occurred, the rate of 

earthquakes in the magnitude interval is computed by dividing the sum of the number of 

earthquakes from that point in time to the end of the catalog by the length in time from that point 
Chapter 3 

Earthquake Catalog 

3-40 

to the end of the catalog. Assuming that the rate of earthquakes is constant in time, plotting these 

values versus date for the complete portion of the catalog will show an approximately horizontal 

line. As one moves further back in time, eventually the plotted line will start to trend downward, 

indicating that not all earthquakes are being reported (again assuming stationarity in time of the 

true rate). The point at which this downward trend begins indicates the beginning of the complete 

period of catalog reporting for the specific magnitude interval. These plots are sometimes 

referred to as “Stepp” plots, after their originator. 

A common practice is to use this technique to identify the period of complete catalog reporting 

for each magnitude interval and then use only the data from that portion of the catalog to assess 

earthquake recurrence parameters. The length of catalog completeness is typically a function of 

magnitude, with larger magnitudes having longer completeness periods. The data identified in 

this way would be used to assess recurrence parameters using a procedure such as Weichert’s 

(1980) maximum likelihood formulation for binned magnitude data. 

Using only the complete portion of the catalog may be quite satisfactory where the change in 

slope on a Stepp plot can be clearly defined and often may correspond to known seismic network 

changes. However, in regions with a long history of earthquake reporting through felt effects, 

there may be a long gradual decline in the level of completeness. Ignoring the data from the 

partially complete period may mean discarding information that is important to the assessment of 

seismic hazards. 

The EPRI-SOG Project (EPRI, 1988, Vol. 1) developed an approach for incorporating the 

catalog data in the partially complete period into the assessment of earthquake recurrence 

parameters. Assuming that earthquakes in magnitude interval i occur as a constant Poisson 

process in time with rate λi, then the expected number of earthquakes to have occurred during the 

period of complete reporting Ti

C

 for magnitude interval i is equal to λiTi

C

. The maximum 

likelihood estimator for λi is given by 

C

i

C

i

i

T

N

λ = (3.5-1) 

where Ni

C

 is the number of earthquakes in magnitude interval i observed during the period of 

complete recording Ti

C

. EPRI (1988) extended this concept into the period of incomplete 

recording. A parameter called the probability of detection, PD, was defined that represented the 

probability that an earthquake in any point in time would be recorded and would appear in the 

seismic record. Again under the assumption of a stationary Poisson process, the expected number 

of earthquakes that would be observed in any time interval Tj is given by the expression 

 ) ][E ji ,,( XTmPTN D λ jiij ××= (3.5-2) 

where E[Nij] is the expected number of earthquakes and PD(mi,Tj,X) is the average probability of 

detection of earthquakes in magnitude interval mi during time period Tj and over spatial 

locations X. Assessment of the rate parameter λirequires knowledge of PD. If one assumes that 

the larger magnitudes are complete at present, and imposes the constraints that PD should 

decrease more or less monotonically with increasing time into the past and should increase 

monotonically with magnitude at each point in time, then—again invoking stationarity—the 

parameters λi and PD can be estimated jointly from the earthquake catalog data. Considering only 
Chapter 3 

Earthquake Catalog 

3-41 

a single magnitude interval and ignoring the spatial aspect for the moment, the likelihood 

function for the observed number of earthquakes over the total duration of the catalog is given by 

( ) = ∏

j

ij

j

D

iji

ij

j

D

iji

N

TP N TP

L

!

λ exp(λ )

 (3.5-3) 

where Pij

D is a shortened notation for PD(mi,Tj). The maximum likelihood solution for λi becomes 

∑

∑ =

j

j

D

ij

j

ij

i

TP

N

λ (3.5-4) 

If the values of Pij

D are known (or have been estimated previously), then the term in the 

denominator of Equation 3.5-4 can be replaced by what is called the effective period of 

completeness, Tij

E

, given by the expression 

= ∑

j

j

D

ij

E

ij TPT (3.5-5) 

The maximum likelihood estimator of λi becomes equal to the total number of earthquakes in the 

catalog in magnitude interval i divided by the effective period of completeness for that 

magnitude interval. 

EPRI (1988) developed an approach to jointly estimate the recurrence parameters that define λi

and its spatial variability along with PD(mi,Tj,X). The approach is termed penalized likelihood 

and is described in detail in Section 5.3.2, along with refinements developed for the CEUS SSC 

Project. The original formulation assessed earthquake recurrence parameters and PD(mi,Tj,X) 

using a one-degree-longitude-by-one-degree-latitude discretization of the CEUS. While the 

enhancements of the methodology presented in Section 5.3.2 extend the methodology to smaller 

cell sizes, the original discretization is sufficient for the estimation of the probability of 

detection, as it is not expected to vary rapidly spatially across the CEUS. The original 

formulation as implemented in the EPRI-SOG program EQPARAM (EPRI, 1988, Vol. 3) was 

used to perform the assessment of PD(mi,Tj,X). The program was modified to use the concept of 

N* by changing the counting of earthquakes to the summing of the N* values. 

Through analysis of the history of population growth and earthquake recording, EPRI (1988) 

defined 13 completeness regions covering most of the CEUS. These regions represent portions of 

the CEUS where catalog completeness as a function of time and magnitude is assessed to be 

sufficiently similar such that it can be treated as the same. These completeness regions are shown 

on Figure 3.5-1 along with the independent earthquakes in the EPRI-SOG earthquake catalog. 

With the exceptions noted below, the information on the history of population growth and 

seismic network instrumentation has not changed significantly from what was available in the 

mid 1980’s. Therefore, the EPRI (1988) completeness regions were used for the CEUS SSC 

Project with some modifications. The revised completeness regions together with the CEUS SSC 

Project catalog are shown on Figure 3.5-2. The modifications address additional sources of 

historical earthquakes used in the CEUS SSC Project that modify the history of catalog reporting 
Chapter 3 

Earthquake Catalog 

3-42 

used in the EPRI-SOG study, and the extension of the completeness regions to cover the entire 

SSC model. 

Two interior boundary modifications were made. First, the analysis of historical records, 

principally by Metzger et al. (2000), has extended the catalog coverage in the area around New 

Madrid. Consequently, the western boundary of Completeness Region 4 was extended to the 

southwest to incorporate the longer period of reporting in that area into the relatively long period 

of catalog reporting centered on New Madrid. The second significant change was to 

Completeness Regions 3 and 12. As shown on Figure 3.5-1, Completeness Region 3 covers both 

the Midwestern states west of New Madrid and the southern states all the way to eastern 

Tennessee and northern Georgia. The review of historical documents by various investigations, 

principally Munsey (2006), has greatly extended the completeness in the eastern portion of 

Completeness Region 3. Based on discussions with Jeffrey Munsey (pers. comm., 2011), 

Completeness Region 12 was expanded to cover this area, as the history of newspaper publishing 

in eastern Tennessee and northern Georgia is more similar to that of the western Carolinas than 

to the Midwestern states west of New Madrid. Other modifications include combining and 

extending Completeness Region 11 to cover the area north of the U.S.-Canada border, extending 

Completeness Region 11 into the northeastern Great Plains, and extending Completeness Region 

1 to cover Texas. An additional Completeness Region 14 was added to cover the Gulf of Mexico, 

as offshore earthquakes in that area are important to the assessment of seismic hazards along the 

Gulf Coast. 

EPRI (1988) defined time periods over which catalog completeness was assessed to be relatively 

constant. These time periods were 1625–1779, 1780–1859, 1860–1909, 1910–1949, 1950–1974, 

and post-1974. Figure 3.5-3 shows space-time plots of the independent earthquakes in the CEUS 

SSC catalog. The red lines denote the boundaries of the time periods defined by EPRI (1988). 

For the most part, these time periods coincide with changes in the density of recorded 

earthquakes and were retained for use in estimating completeness for the CEUS SSC catalog. An 

additional time period of 1995–2008 was added to accommodate the potential for recent 

improvements in earthquake recording. 

More detailed examinations of catalog completeness as a function of time can be made on 

Figure 3.5-4. Shown are “Stepp” plots for each completeness region. These plots show a long 

history of earthquake recording in many areas of the CEUS with the typical trend of a gradual 

decay in completeness with increasing time into the past. These results indicate the importance 

of using a methodology that allows for the incorporation of most of this history into the 

assessment of earthquake recurrence rates and their spatial variation across the CEUS. 

The catalog completeness analysis and subsequent assessment of earthquake recurrence 

parameters uses earthquakes binned in magnitude intervals. These magnitude intervals were 

centered on E[M] values obtained from conversion of whole-degree values of I0 to mimic the 

grouping of the converted magnitudes. These magnitude intervals are 2.9 to 3.6, 3.6 to 4.3, 4.3 to 

5.0, 5.0 to 5.7, 5.7 to 6.4, 6.4 to 7.1, and 7.1 and higher. 

Following EPRI (1988), the probabilities of detection were calculated using no spatial smoothing 

on the rate parameter, and medium smoothing on b, and no prior on b. As discussed in 

Section 5.3.2, several analysis cases were performed that assign different weights to the lower 

magnitude intervals to address potential departures from exponential behavior. These are Case A, 

full weight on all magnitude intervals; Case B with a reduced weight of 0.1 on the lowest 
Chapter 3 

Earthquake Catalog 

3-43 

magnitude interval; and Case E with elimination of the first magnitude interval and 0.3 weight on 

the second interval. 

McLaughlin et al. (1997) analyzed the capability of the USNSN and associated regional 

networks to detect at least four P waves for each earthquake. The analysis shows that for most of 

the eastern United States, there is 80 percent probability of detecting earthquakes with mbLg = 

3.25. The detection capability decreases toward the Atlantic Ocean to the east and toward the 

Gulf of Mexico to the south. The probability of detection is less than 80 percent in parts of 

southern Indiana, Illinois, and western Kentucky due to the scarcity of stations in the upper 

Midwest. If the Canadian stations are added to the USNSN, the probabilities increase in the 

northern United States and southern Canada. During 2004–2006, the USNSN was upgraded and 

expanded to become the current ANSS backbone national network of nearly 100 stations, and 

many ANSS regional network stations have been added in the CEUS during the past decade. 

However, the USNSN analysis still serves as a useful baseline for assessing the level of catalog 

completeness at the end of the twentieth century. 

Based on the results presented in McLaughlin et al. (1997), the earthquake catalog for the study 

region was assumed complete (probability of detection of 1.0) for all magnitude intervals in the 

time period 1995–2008 in most of the completeness regions. Locally, the probability of detection 

of the first two magnitude intervals was calculated, and the results are lower than 1.0. 

The estimated probabilities of detection for the magnitude and time intervals are given in Tables 

3.5-1, 3.5-2, and 3.5-3 for Cases A, B, and E, respectively. 

The final step in the catalog analysis was the computation of regional b-values for the CEUS. 

These values were used as prior values to aid in the penalized-likelihood estimation of 

earthquake recurrence parameters as described in Section 5.3.2. The regional b-values were 

computed using the Weichert (1980) formulation, with N given by the sum of the N* values and 

T defined as TE

 for each magnitude and completeness region. The calculations were made 

assuming a homogeneous seismicity rate in each completeness region that was allowed to vary 

from completeness region to completeness region, but a constant b-value over the entire CEUS. 

The following table lists the computed regional b-values. 

Regional b-Values Assessed for the CEUS SSC Project Catalog 

Magnitude Weighting Case Regional b-value 

A 1.02 

B 0.99 

E 1.00 
Chapter 3 

Earthquake Catalog 

3-44

Table 3.2-1 

Summary of Earthquakes Added–USGS Earthquake Catalog by Time Period 

Time Period

Number of Earthquakes in E[M] Magnitude Range

2.9–3.6 3.6–4.3 4.3–5.0 5.0–5.7 5.7–6.4 ≥6.4 Total

1558 through 1799 9 6 1 1 0 0 17

1800 through 1899 106 58 23 3 0 0 190

1900 through 1959 40 10 13 5 0 1 69

1960 through 2006 285 27 5 2 0 0 319

2007 and 2008 49 8 3 1 0 0 61
Chapter 3 

Earthquake Catalog 

3-45

Table 3.2-2 

Summary of Earthquakes Added–USGS Earthquake Catalog by Source 

Source

Number of Earthquakes in E[M] Magnitude Range

2.9–3.6 3.6–4.3 4.3–5.0 5.0–5.7 5.7–6.4 ≥6.4 Total

Metzger et al. (2000) 20 21 9 2 0 0 52

Munsey (2006) 44 17 11 0 0 0 72

GSC/NEDB and Burke (2009) 44 6 1 2 0 0 53

SUSN only 54 2 2 1 0 0 59

Single source, such as 

Lamont-Doherty; Ohio 

Survey; Oklahoma Survey;

Reinbold and Johnston 

(1987); Seeber and 

Armbruster (1987); Saint

Louis University; Weston 

Observatory; Adams and 

Simmons (1991); Bent 

(2003); CERI; Ma and 

Atkinson (2006); SCSN;

Stover and Coffman (1993);

Sykes et al. (2008)

70 16 5 1 0 0 92

Contained in multiple other 

sources

208 39 14 5 0 1 267
Chapter 3 

Earthquake Catalog 

3-46

Table 3.3-1 

Conversion Relationships Used–Develop Uniform Moment Magnitudes E[M] 

Size Measure Conversion Relationship

 XM ][

Body-wave 

magnitude 

(mb, mbLg, mLg(f), 

MN)

E[M] = mb – 0.316 – 0.118ZNE – 0.192Z1997GSC + 

0.280Z1982NE

ZNE = 1 for earthquakes located in the Northeast (northeast 

of the dashed line on Figure 3.3-16, including GSC 

data), and 0 otherwise

Z1997GSC = 1 for earthquakes occurring after 1997 recorded 

by GSC, and 0 otherwise

Z1982NE = 1 for earthquakes occurring in the Northeast

before 1982 recorded by other than GSC, and 0 

otherwise

0.24

ML reported by 

GSC Compute mb = ML – 0.21 and use mb conversion 0.42

MS E[M] = 2.654 + 0.334MS + 0.040MS

2

0.20

MC, MD, ML in 

northeastern 

United States 

(other than 

GSC)

E[M] = 0.633 + 0.806(MC MD or ML) 0.27

MC, MD, ML in 

midcontinent 

United States 

east of 

longitude 

100°W

E[M] = 0.869 + 0.762 (MC, MD, or ML) 0.25

MC, MD, ML in 

midcontinent 

United States 

west of 

longitude 

100°W

Use mb conversion 0.24

Ln(FA)

(in km2)

M .1][E 41 .0 218 FA  00087.0)ln( FA

0.22

I0

for I0 <= VI

E[M] = 0.017 + 0.666I0

for I0 > VI

E[M] = 4.008 + 3.411x







  

5.6

)6(

2

0

1 I

Erf

0.50
Chapter 3 

Earthquake Catalog 

3-47

Table 3.4-1 

Comparison of CEUS SSC Catalog Declustering Results Obtained Using the 

EPRI (1988) Approach with the Gardner Knopoff (1974) Approach 

E[M] Magnitude 

Range

Number of Earthquakes in E[M] Magnitude Range

Entire Catalog

Independent 

Earthquakes 

Using EPRI 

(1988) Approach

Independent 

Earthquakes 

Using Gardner 

Knopoff (1974) 

Approach

2.9–3.6 2333 1787 1865

3.6–4.3 696 554 530

4.3–5.0 204 168 155

5.0–5.7 44 36 33

5.7–6.4 13 13 13

6.4–7.1 4 4 3

7.1–7.8 3 2 0

7.8–8.3 1 1 1
Chapter 3 

Earthquake Catalog 

3-48

Table 3.5-1 

Probability of Detection and Equivalent Periods of Completeness for the CEUS for 

Magnitude Weighting Case A 

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 1

2.9–3.6 0 0 0 0.141 0.265 0.595 0.673 33.6 1910

3.6–4.3 0 0 0 0.212 0.531 0.595 1 47.7 1910

4.3–5.0 0 0 0 0.212 0.713 0.751 1 55.3 1910

5.0–5.7 0 0 0 0.961 0.961 1 1 96.5 1860

5.7–6.4 0 0 1 1 1 1 1 149.0 1860

6.4–8.3 0 0 1 1 1 1 1 149.0 1860

Region 2

2.9–3.6 0 0 0.111 0.239 0.391 1 1 58.9 1860

3.6–4.3 0 0 0.181 0.672 1 1 1 94.9 1860

4.3–5.0 0 0 0.261 0.672 1 1 1 98.9 1860

5.0–5.7 0 0 0.261 1 1 1 1 112.1 1860

5.7–6.4 0 0 0.261 1 1 1 1 112.1 1860

6.4–8.3 0 0 0.261 1 1 1 1 112.1 1860

Region 3

2.9–3.6 0 0 0.08 0.199 0.243 0.859 1 49.2 1860

3.6–4.3 0 0.056 0.381 0.529 0.743 0.859 1 94.4 1780

4.3–5.0 0 0.056 0.977 0.977 0.977 0.977 1 150.4 1780

5.0–5.7 0 0.428 1 1 1 1 1 183.2 1780

5.7–6.4 0 0.428 1 1 1 1 1 183.2 1780

6.4–8.3 0 0.428 1 1 1 1 1 183.2 1780

Region 4

2.9–3.6 0 0 0.242 0.431 0.449 1 1 74.6 1860

3.6–4.3 0 0.239 0.756 0.756 0.756 1 1 140.1 1780

4.3–5.0 0 0.288 1 1 1 1 1 172.0 1780

5.0–5.7 0 0.56 1 1 1 1 1 193.8 1780

5.7–6.4 0 0.621 1 1 1 1 1 198.7 1780

6.4–8.3 0 0.621 1 1 1 1 1 198.7 1780

Region 5

2.9–3.6 0 0.072 0.444 0.636 0.839 1 1 108.4 1780

3.6–4.3 0 0.5 0.567 0.788 0.839 1 1 154.8 1780

4.3–5.0 0.345 0.5 1 1 1 1 1 242.5 1625

5.0–5.7 0.345 0.5 1 1 1 1 1 242.5 1625

5.7–6.4 1 1 1 1 1 1 1 384.0 1625

6.4–8.3 1 1 1 1 1 1 1 384.0 1625
Chapter 3 

Earthquake Catalog 

3-49

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 6

2.9–3.6 0 0.164 0.735 0.735 1 1 1 138.3 1780

3.6–4.3 0 0.981 0.981 0.981 1 1 1 225.8 1780

4.3–5.0 0.434 1 1 1 1 1 1 296.3 1625

5.0–5.7 0.434 1 1 1 1 1 1 296.3 1625

5.7–6.4 0.434 1 1 1 1 1 1 296.3 1625

6.4–8.3 0.434 1 1 1 1 1 1 296.3 1625

Region 7

2.9–3.6 0 0 0.185 0.185 0.446 0.635 0.635 49.4 1860

3.6–4.3 0 0 1 1 1 1 1 149.0 1860

4.3–5.0 0 0 1 1 1 1 1 149.0 1860

5.0–5.7 0 0 1 1 1 1 1 149.0 1780

5.7–6.4 0 0.746 1 1 1 1 1 208.7 1780

6.4–8.3 0 0.948 1 1 1 1 1 224.8 1780

Region 8

2.9–3.6 0 0 0 0 0.38 1 1 43.5 1950

3.6–4.3 0 0 0 0 0.499 1 1 46.5 1950

4.3–5.0 0 0 0 0 1 1 1 59.0 1950

5.0–5.7 0 0 0 0 1 1 1 59.0 1910

5.7–6.4 0 0 0 0 1 1 1 59.0 1910

6.4–8.3 0 0 0 1 1 1 1 99.0 1910

Region 9

2.9–3.6 0 0 0 0.257 0.543 0.652 0.652 46.0 1910

3.6–4.3 0 0 0.146 0.332 0.932 0.932 1 76.5 1860

4.3–5.0 0 0 0.244 1 1 1 1 111.2 1860

5.0–5.7 0 0 0.244 1 1 1 1 111.2 1860

5.7–6.4 0 0 0.244 1 1 1 1 111.2 1860

6.4–8.3 0 0 0.424 1 1 1 1 120.2 1860

Region 10

2.9–3.6 0 0 0.107 0.451 0.774 1 1 76.7 1860

3.6–4.3 0 0.045 0.295 1 1 1 1 117.3 1780

4.3–5.0 0 0.49 0.49 1 1 1 1 162.7 1625

5.0–5.7 0 1 1 1 1 1 1 229.0 1625

5.7–6.4 0 1 1 1 1 1 1 229.0 1625

6.4–8.3 0 1 1 1 1 1 1 229.0 1625
Chapter 3 

Earthquake Catalog 

3-50

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 11

2.9–3.6 0 0 0 0 0.192 0.371 0.371 17.4 1950

3.6–4.3 0 0 0 0 0.59 0.59 1 40.5 1950

4.3–5.0 0 0 0 0 1 1 1 59.0 1910

5.0–5.7 0 0 0 0 1 1 1 59.0 1910

5.7–6.4 0 0 0 0 1 1 1 59.0 1910

6.4–8.3 0 0 0 0.673 1 1 1 85.9 1910

Region 12

2.9–3.6 0 0.033 0.224 0.243 0.419 1 1 68.0 1780

3.6–4.3 0 0.109 0.373 0.373 0.926 1 1 99.4 1780

4.3–5.0 0 0.597 1 1 1 1 1 196.8 1625

5.0–5.7 0 1 1 1 1 1 1 229.0 1625

5.7–6.4 0 1 1 1 1 1 1 229.0 1625

6.4–8.3 0 1 1 1 1 1 1 229.0 1625

Region 13

2.9–3.6 0 0 0.419 0.834 0.834 0.834 1 105.8 1860

3.6–4.3 0 0 0.995 1 1 1 1 148.7 1860

4.3–5.0 0 0 0.995 1 1 1 1 148.7 1860

5.0–5.7 0 0 0.995 1 1 1 1 148.7 1860

5.7–6.4 0 0 0.995 1 1 1 1 148.7 1860

6.4–8.3 0 0 0.995 1 1 1 1 148.7 1860

Region 14

2.9–3.6 0 0 0 0 0 0 0.505 7.1 1995

3.6–4.3 0 0 0 0 0 0.364 0.505 14.3 1975

4.3–5.0 0 0 0 0 0.901 0.901 1 54.5 1950

5.0–5.7 0 0 0 0 0.901 0.901 1 54.5 1950

5.7–6.4 0 0 0 0 0.901 0.901 1 54.5 1950

6.4–8.3 0 0 0 0 1 1 1 59.0 1950
Chapter 3 

Earthquake Catalog 

3-51

Table 3.5-2 

Probability of Detection and Equivalent Periods of Completeness for the CEUS for 

Magnitude Weighting Case B 

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

Period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 1

2.9–3.6 0 0 0 0.156 0.292 0.587 0.746 35.7 1910

3.6–4.3 0 0 0 0.218 0.553 0.587 1 48.3 1910

4.3–5.0 0 0 0 0.218 0.697 0.735 1 54.8 1910

5.0–5.7 0 0 0 0.885 0.885 1 1 91.5 1860

5.7–6.4 0 0 1 1 1 1 1 149.0 1860

6.4–8.3 0 0 1 1 1 1 1 149.0 1860

Region 2

2.9–3.6 0 0 0.109 0.235 0.386 1 1 58.5 1860

3.6–4.3 0 0 0.175 0.651 1 1 1 93.8 1860

4.3–5.0 0 0 0.252 0.651 1 1 1 97.6 1860

5.0–5.7 0 0 0.252 1 1 1 1 111.6 1860

5.7–6.4 0 0 0.252 1 1 1 1 111.6 1860

6.4–8.3 0 0 0.265 1 1 1 1 112.2 1860

Region 3

2.9–3.6 0 0 0.072 0.178 0.217 0.697 1 44.1 1860

3.6–4.3 0 0.053 0.358 0.496 0.697 0.697 1 87.3 1780

4.3–5.0 0 0.053 0.964 0.964 0.964 0.964 1 148.4 1780

5.0–5.7 0 0.45 1 1 1 1 1 185.0 1780

5.7–6.4 0 0.45 1 1 1 1 1 185.0 1780

6.4–8.3 0 0.45 1 1 1 1 1 185.0 1780

Region 4

2.9–3.6 0 0 0.201 0.356 0.372 0.735 1 62.3 1860

3.6–4.3 0 0.21 0.663 0.663 0.663 0.735 1 121.7 1780

4.3–5.0 0 0.267 1 1 1 1 1 170.4 1780

5.0–5.7 0 0.547 1 1 1 1 1 192.8 1780

5.7–6.4 0 0.644 1 1 1 1 1 200.5 1780

6.4–8.3 0 0.644 1 1 1 1 1 200.5 1780

Region 5

2.9–3.6 0 0.078 0.482 0.69 0.958 0.958 1 115.1 1780

3.6–4.3 0 0.525 0.598 0.831 0.958 0.958 1 162.2 1780

4.3–5.0 0.352 0.525 1 1 1 1 1 245.6 1625

5.0–5.7 0.352 0.525 1 1 1 1 1 245.6 1625

5.7–6.4 1 1 1 1 1 1 1 384.0 1625

6.4–8.3 1 1 1 1 1 1 1 384.0 1625
Chapter 3 

Earthquake Catalog 

3-52

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

Period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 6

2.9–3.6 0 0.175 0.782 0.782 1 1 1 143.4 1780

3.6–4.3 0 1 1 1 1 1 1 229.0 1780

4.3–5.0 0.438 1 1 1 1 1 1 296.9 1625

5.0–5.7 0.438 1 1 1 1 1 1 296.9 1625

5.7–6.4 0.438 1 1 1 1 1 1 296.9 1625

6.4–8.3 0.438 1 1 1 1 1 1 296.9 1625

Region 7

2.9–3.6 0 0 0.187 0.187 0.466 0.646 0.646 50.4 1860

3.6–4.3 0 0 1 1 1 1 1 149.0 1860

4.3–5.0 0 0 1 1 1 1 1 149.0 1860

5.0–5.7 0 0 1 1 1 1 1 149.0 1780

5.7–6.4 0 0.72 1 1 1 1 1 206.6 1780

6.4–8.3 0 0.943 1 1 1 1 1 224.4 1780

Region 8

2.9–3.6 0 0 0 0 0.537 1 1 47.4 1950

3.6–4.3 0 0 0 0 0.61 1 1 49.2 1950

4.3–5.0 0 0 0 0 1 1 1 59.0 1950

5.0–5.7 0 0 0 0 1 1 1 59.0 1910

5.7–6.4 0 0 0 0 1 1 1 59.0 1910

6.4–8.3 0 0 0 1 1 1 1 99.0 1910

Region 9

2.9–3.6 0 0 0 0.329 0.696 0.834 0.834 58.9 1910

3.6–4.3 0 0 0.165 0.376 1 1 1 82.3 1860

4.3–5.0 0 0 0.24 1 1 1 1 111.0 1860

5.0–5.7 0 0 0.24 1 1 1 1 111.0 1860

5.7–6.4 0 0 0.24 1 1 1 1 111.0 1860

6.4–8.3 0 0 0.24 1 1 1 1 111.0 1860

Region 10

2.9–3.6 0 0 0.131 0.554 0.949 1 1 86.4 1860

3.6–4.3 0 0.049 0.324 1 1 1 1 119.1 1780

4.3–5.0 0 0.479 0.479 1 1 1 1 161.3 1625

5.0–5.7 0 1 1 1 1 1 1 229.0 1625

5.7–6.4 0 1 1 1 1 1 1 229.0 1625

6.4–8.3 0 1 1 1 1 1 1 229.0 1625
Chapter 3 

Earthquake Catalog 

3-53

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

Period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 11

2.9–3.6 0 0 0 0 0.229 0.442 0.442 20.8 1950

3.6–4.3 0 0 0 0 0.673 0.673 1 44.3 1950

4.3–5.0 0 0 0 0 1 1 1 59.0 1910

5.0–5.7 0 0 0 0 1 1 1 59.0 1910

5.7–6.4 0 0 0 0 1 1 1 59.0 1910

6.4–8.3 0 0 0 0.671 1 1 1 85.8 1910

Region 12

2.9–3.6 0 0.04 0.27 0.293 0.506 1 1 75.1 1780

3.6–4.3 0 0.121 0.415 0.415 1 1 1 106.0 1780

4.3–5.0 0 0.619 1 1 1 1 1 198.5 1625

5.0–5.7 0 1 1 1 1 1 1 229.0 1625

5.7–6.4 0 1 1 1 1 1 1 229.0 1625

6.4–8.3 0 1 1 1 1 1 1 229.0 1625

Region 13

2.9–3.6 0 0 0.277 0.469 0.552 0.552 1 71.4 1860

3.6–4.3 0 0 0.707 0.707 1 1 1 122.6 1860

4.3–5.0 0 0 0.707 0.707 1 1 1 122.6 1860

5.0–5.7 0 0 0.707 0.707 1 1 1 122.6 1860

5.7–6.4 0 0 0.707 0.86 1 1 1 128.7 1860

6.4–8.3 0 0 0.841 0.961 1 1 1 139.5 1860

Region 14

2.9–3.6 0 0 0 0 0 0 0.209 2.9 1995

3.6–4.3 0 0 0 0 0 0.209 0.209 7.1 1975

4.3–5.0 0 0 0 0 0.633 0.633 1 42.5 1950

5.0–5.7 0 0 0 0 0.633 0.633 1 42.5 1950

5.7–6.4 0 0 0 0 0.633 0.633 1 42.5 1950

6.4–8.3 0 0 0 0 1 1 1 59.0 1950
Chapter 3 

Earthquake Catalog 

3-54

Table 3.5-3 

Probability of Detection and Equivalent Periods of Completeness for the CEUS for 

Magnitude Weighting Case E 

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

Period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 1

3.6–4.3 0 0 0 0.168 0.595 0.595 1 47.5 1910

4.3–5.0 0 0 0 0.168 0.743 0.784 1 55.0 1910

5.0–5.7 0 0 0 0.921 0.921 1 1 93.9 1860

5.7–6.4 0 0 1 1 1 1 1 149.0 1860

6.4–8.3 0 0 1 1 1 1 1 149.0 1860

Region 2

3.6–4.3 0 0 0.177 0.584 1 1 1 91.2 1860

4.3–5.0 0 0 0.255 0.584 1 1 1 95.1 1860

5.0–5.7 0 0 0.255 1 1 1 1 111.7 1860

5.7–6.4 0 0 0.255 1 1 1 1 111.7 1860

6.4–8.3 0 0 0.255 1 1 1 1 111.7 1860

Region 3

3.6–4.3 0 0.038 0.325 0.451 0.634 0.634 1 79.9 1780

4.3–5.0 0 0.038 0.939 0.939 0.939 0.939 1 143.8 1780

5.0–5.7 0 0.475 1 1 1 1 1 187.0 1780

5.7–6.4 0 0.475 1 1 1 1 1 187.0 1780

6.4–8.3 0 0.475 1 1 1 1 1 187.0 1780

Region 4

3.6–4.3 0 0.15 0.473 0.473 0.473 0.473 1 89.9 1780

4.3–5.0 0 0.229 1 1 1 1 1 167.3 1780

5.0–5.7 0 0.568 1 1 1 1 1 194.4 1780

5.7–6.4 0 0.845 1 1 1 1 1 216.6 1780

6.4–8.3 0 0.845 1 1 1 1 1 216.6 1780

Region 5

3.6–4.3 0 0.434 0.562 0.781 0.793 0.793 1 143.7 1780

4.3–5.0 0.324 0.434 1 1 1 1 1 233.9 1625

5.0–5.7 0.324 0.434 1 1 1 1 1 233.9 1625

5.7–6.4 1 1 1 1 1 1 1 384.0 1625

6.4–8.3 1 1 1 1 1 1 1 384.0 1625

Region 6

3.6–4.3 0 1 1 1 1 1 1 229.0 1780

4.3–5.0 0.432 1 1 1 1 1 1 296.0 1625

5.0–5.7 0.432 1 1 1 1 1 1 296.0 1625

5.7–6.4 0.432 1 1 1 1 1 1 296.0 1625

6.4–8.3 0.432 1 1 1 1 1 1 296.0 1625
Chapter 3 

Earthquake Catalog 

3-55

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

Period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 7

3.6–4.3 0 0 1 1 1 1 1 149.0 1860

4.3–5.0 0 0 1 1 1 1 1 149.0 1860

5.0–5.7 0 0 1 1 1 1 1 149.0 1780

5.7–6.4 0 0.681 1 1 1 1 1 203.5 1780

6.4–8.3 0 0.931 1 1 1 1 1 223.5 1780

Region 8

3.6–4.3 0 0 0 0 0.53 0.628 0.628 34.6 1950

4.3–5.0 0 0 0 0 1 1 1 59.0 1950

5.0–5.7 0 0 0 0 1 1 1 59.0 1910

5.7–6.4 0 0 0 0 1 1 1 59.0 1910

6.4–8.3 0 0 0 1 1 1 1 99.0 1910

Region 9

3.6–4.3 0 0 0.161 0.365 1 1 1 81.7 1860

4.3–5.0 0 0 0.218 1 1 1 1 109.9 1860

5.0–5.7 0 0 0.218 1 1 1 1 109.9 1860

5.7–6.4 0 0 0.218 1 1 1 1 109.9 1860

6.4–8.3 0 0 0.218 1 1 1 1 109.9 1860

Region 10

3.6–4.3 0 0.055 0.362 1 1 1 1 121.5 1780

4.3–5.0 0 0.499 0.499 1 1 1 1 163.9 1625

5.0–5.7 0 0.991 1 1 1 1 1 228.3 1625

5.7–6.4 0 0.991 1 1 1 1 1 228.3 1625

6.4–8.3 0 0.991 1 1 1 1 1 228.3 1625

Region 11

3.6–4.3 0 0 0 0 0.75 0.75 1 47.7 1950

4.3–5.0 0 0 0 0 1 1 1 59.0 1910

5.0–5.7 0 0 0 0 1 1 1 59.0 1910

5.7–6.4 0 0 0 0 1 1 1 59.0 1910

6.4–8.3 0 0 0 0.661 1 1 1 85.4 1910

Region 12

3.6–4.3 0 0.123 0.422 0.422 1 1 1 106.8 1780

4.3–5.0 0 0.627 1 1 1 1 1 199.2 1625

5.0–5.7 0 1 1 1 1 1 1 229.0 1625

5.7–6.4 0 1 1 1 1 1 1 229.0 1625

6.4–8.3 0 1 1 1 1 1 1 229.0 1625
Chapter 3 

Earthquake Catalog 

3-56

Magnitude 

Interval

Probability of Detection for Time Period Equivalent 

Period of 

Completeness, 

TE

(years)

Beginning 

of Usable 

Period

1625–

1780

1780–

1860

1860–

1910

1910–

1950

1950–

1975

1975–

1995

1995–

2009

Region 13

3.6–4.3 0 0 0.393 0.393 0.779 0.779 1 84.4 1860

4.3–5.0 0 0 0.393 0.393 0.779 0.779 1 84.4 1860

5.0–5.7 0 0 0.393 0.393 0.779 0.779 1 84.4 1860

5.7–6.4 0 0 0.535 0.798 1 1 1 117.7 1860

6.4–8.3 0 0 0.779 0.954 1 1 1 136.1 1860

Region 14

3.6–4.3 0 0 0 0 0 0.155 0.155 5.3 1975

4.3–5.0 0 0 0 0 0.535 0.535 1 38.1 1950

5.0–5.7 0 0 0 0 0.535 0.535 1 38.1 1950

5.7–6.4 0 0 0 0 0.535 0.535 1 38.1 1950

6.4–8.3 0 0 0 0 1 1 1 59.0 1950
Chapter 3 

Earthquake Catalog 

3-57

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. 
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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° 
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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° 
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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° 
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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° 
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Figure 3.2-6 

Histogram of ML magnitudes from the revised catalog with GSC as the source for the time period 1928-1979 
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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. 
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Figure 3.3-1 

Illustration of equivalence of the M* and γ

2

 corrections to remove bias in earthquake 

recurrence relationships estimated from magnitudes with uncertainty, 

M

ˆ
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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 
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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 
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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 
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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 
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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.
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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. 
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Figure 3.3-8 

Residuals from offset fit shown on Figure 3.3-7 plotted against earthquake year 
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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.
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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. 
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Figure 3.3-11

Residuals from offset fit shown on Figure 3.3-10 plotted against earthquake year 
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Figure 3.3-12

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

year
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Figure 3.3-13

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

year
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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
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Figure 3.3-15

Difference between body-wave magnitudes reported by LDO and those by other sources 

as a function of year
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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.
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Figure 3.3-17

M-mb as a function of time for mb data from the GSC shown on Figure 3.3-16
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Figure 3.3-18

Plot of magnitude differences mbLg – m(3 Hz) for the OKO catalog 
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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.
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Figure 3.3-20

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

Spatial distribution of earthquakes in the CEUS SSC Project catalog with instrumental ML magnitudes and M magnitudes
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Figure 3.3-22

ML-M data from the CEUS SSC Project catalog and robust regression fit to the data 
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Figure 3.3-23

Relationship between MN and ML for the GSC data 
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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 
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Figure 3.3-25

Data from the northeastern portion of the study region with ML and M magnitudes from 

sources other than the GSC
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Figure 3.3-26

Spatial distribution of earthquakes in the CEUS SSC Project catalog with MS ≥ 3 magnitudes
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Figure 3.3-27

MS-M data from the CEUS SSC Project catalog and quadratic polynomial fit to the data 
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Figure 3.3-28

Spatial distribution of earthquakes in the CEUS SSC Project catalog with MC ≥ 2.5 magnitudes
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Figure 3.3-29

Spatial distribution of earthquakes in the CEUS SSC Project catalog with MC ≥ 2.5 and M magnitudes
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Figure 3.3-30

Spatial distribution of earthquakes in the CEUS SSC Project catalog with MD ≥ 3 magnitudes
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Figure 3.3-31

Spatial distribution of earthquakes in the CEUS SSC Project catalog with both MD and M magnitudes 
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Figure 3.3-32

MC-M data from the CEUS SSC Project catalog and linear regression fit to the data
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Figure 3.3-33

Spatial distribution of earthquakes with reported MC and MD magnitudes 
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Figure 3.3-34

Comparison of MC and MD magnitudes for the LDO and WES catalogs 
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Figure 3.3-35

Comparison of MC with MD for at least one of the two magnitude types reported in the OKO 

catalog 
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Figure 3.3-36

Comparison of MC with MD for at least one of the two magnitude types reported in the CERI 

catalog 
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Figure 3.3-37

Comparison of MC with MD for at least one of the two magnitude types reported in the 

SCSN catalog 
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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 
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Figure 3.3-39

Relationship between M and MC, MD, or ML for the Midcontinent portion of the study region 
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Figure 3.3-40

Comparison of MC and MD magnitudes with ML magnitudes for the region between 

longitudes 105°W and 100°W 
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Figure 3.3-41

Comparison of mb magnitudes with ML magnitudes for the region between longitudes 

105°W and 100°W 
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Figure 3.3-42

Comparison of mb magnitudes with MC and MD magnitudes for the region between 

longitudes 105°W and 100°W
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Figure 3.3-43

Spatial distribution of earthquake with ln(FA) in the CEUS SSC Project catalog
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Figure 3.3-44

Catalog ln(FA)–M data and fitted model
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Figure 3.3-45

Spatial distribution of earthquakes in the CEUS SSC Project catalog with reported values of I0 
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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). 
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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). 
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Figure 3.3-48

Categorical model fits of I0 as a function and M for earthquakes in the CEUS SSC Project 

catalog 
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Figure 3.3-49

Results from proportional odds logistic model showing the probability of individual 

intensity classes as a function of M 
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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 leastsquares fits to the two data sets are shown along with the relationship use to develop the 

EPRI (1988) catalog and the Sibol et al. (1987) relationship used in the NCEER91 catalog. 
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Figure 3.3-51

Linear fits to the data from Figure 3.3-50 for I0 ≥ V
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Figure 3.3-52

Comparison of I0 and mb data from the project, with mb adjusted for the difference in mb 

to M scaling 
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Figure 3.3-53

Linear fits to the data from Figure 3.3-52 for I0 ≥ V
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Figure 3.3-54

Composite I0–M data set used for assessment of I0 scaling relationship 
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Figure 3.3-55

Linear and inverse sigmoid models fit to the project data for I0 > IV 
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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 
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Figure 3.4-2 

Identification of secondary (dependent) earthquakes inside the cluster region through 

Poisson thinning (from EPRI, 1988, Vol. 1) 
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Figure 3.4-3 

Comparison of dependent event time and distance windows with results for individual 

clusters in the project catalog 

Note: Time windows represent the sum of the foreshock and aftershock windows for Grünthal 

(1985) and 1.5 times the aftershock window for Gardner and Knopoff (1974). 
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Figure 3.5-1 

Earthquake catalog and catalog completeness regions used in EPRI-SOG (EPRI, 1988) 
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Figure 3.5-2 

CEUS SSC Project earthquake catalog and modified catalog completeness regions 
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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. 
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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 
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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 
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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 
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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 
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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 
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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 
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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 

4-1

4

CHAPTER 4 

CONCEPTUAL SEISMIC SOURCE 

CHARACTERIZATION FRAMEWORK 

The conceptual SSC framework described in this section was developed early in the project to 

provide the entire TI Team with a consistent approach and philosophy to the identification and 

characterization of seismic sources for use in future PSHAs. The description of the conceptual 

SSC framework is included in the project report to help the reader understand the basic 

underpinnings of the SSC model developed for the project, and to show how the framework led 

to the basic structure and elements of the master logic tree for the SSC model. 

The TI Team, which consists of expert evaluators who are responsible for all the technical 

assessments, includes individuals and organizations with extensive experience in characterizing 

seismic sources in the CEUS for purposes of PSHA. The TI Team members have experience in 

PSHAs for nuclear facilities and a variety of other facilities throughout the region. This is a 

significant benefit to the project in that the team started with a high level of knowledge of the 

applicable databases for the evaluations, and of the various tools available to assist with the 

source characterization. Because of this knowledge and experience level, the TI Team was 

already familiar with the basic tools associated with SSC and uncertainty quantification (e.g., 

logic trees and probability distributions). So the conceptual SSC framework provided the TI team 

with the following guidance: 

Reminders of the advanced tools in the ―SSC toolbox‖ for characterizing sources and 

quantifying uncertainties. 

A systematic approach to use in identifying and documenting applicable data and evaluations 

of the data relative to its use in SSC. 

Systematic identification and application of various tectonic and seismologic criteria for 

defining seismic sources that exist within the larger technical community. 

The goal was to outline a logical, systematic, and complete framework for characterizing seismic 

sources within the context of a SSHAC process. To ensure consistency between this framework 

and the actual SSC effort, the framework was tied directly to the master logic tree of the SSC 

model.

Organized in this section are the concepts developed over the years for assessing seismic sources 

within stable continental regions (SCRs), including the CEUS. An early version of this section 

provided a useful tool to the team members during the course of their evaluations and to the peer 

reviewers, who sought to understand the framework within which the team worked. After the 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-2

actual SSC effort was completed, this section was refined to reflect the actual project 

implementation and it became a part of the project report documentation. 

4.1 Needs for a Conceptual SSC Framework 

In consideration of the purpose of the CEUS SSC Project, the TI Team identified three attributes 

that are needed for a conceptual SSC framework: 

1. A systematic and 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 and documented 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 that is based on defensible criteria for 

defining a seismic source, incorporates the lessons learned in SSC over the past two decades, 

and identifies the range of approaches and models that can be shown to be significant to 

hazard. 

The need for an SSC framework that would fulfill these needs was encouraged by the PPRP 

early in the project, and the PPRP provided valuable feedback during the course of developing 

the framework. Each of these needs has been addressed in the development of the framework for 

the project, as discussed in Sections 4.1.1 through 4.1.3 below. 

4.1.1 Logic Tree Approach to Representing Alternatives and 

Assessing Uncertainties 

Over the past 25 years, it has become clear that a significant contribution to epistemic 

uncertainties in SSC comes from uncertainty in alternative conceptual models. Logic trees 

provide an effective means of clearly representing the credible alternative models and assigning 

weights to the alternatives. Logic trees were originally defined in a probabilistic framework for 

use in PSHA (e.g., Kulkarni et al., 1984) with a specification that the values on the branches of 

the tree be mutually exclusive and that all branches at a node of the tree be collectively 

exhaustive. Some have called this assumption into question in common applications, because it 

is often not possible to prove that all branches have been included or that they are completely

mutually exclusive (Bommer and Scherbaum, 2008). Nevertheless, with these cautions in mind, 

logic trees provide a practical means of representing alternative hypotheses, expressing the 

relative weight for each hypothesis given the available data, and combining the hypotheses for 

use in the hazard analysis. 

Logic trees have become common tools for application in SSC and specifically for the modelbuilding or integration phase of a SSHAC project (Section 2.1), and the TI Team used them for 

expressing the epistemic uncertainties in alternative methods and approaches to characterizing 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-3

sources. For example, the first elements of the master logic tree (discussed in Section 4.2) define 

the basic alternative approaches to defining seismic sources as a function of the criteria used. 

Once these approaches are defined and the relative weight for each is assigned, the subsequent 

characterization will follow the approach defined for that branch. Thus the ―logic‖ that comes 

into play in a logic tree is defining the dependencies among the assessments on the branches, and 

the outcomes that derive from each branch. Therefore, logic trees typically begin with general 

assessments (e.g., alternative conceptual models) and proceed to more specific assessments that 

are conditional on the general assessments. The assessments found to the right on the logic tree 

are commonly the specific elements and parameter values that are associated with a particular 

conceptual model. For example, an assessment of alternative temporal models (e.g., Poisson 

versus renewal) would be to the left on the logic tree, and each model would then be defined by 

nodes to the right that define the required parameters for each model (e.g., mean recurrence, 

elapsed time, coefficient of variation of recurrence intervals). 

4.1.1.1 Examples of Logic Trees 

Examples of logic trees used in actual projects are shown on Figures 4.1.1-1 and 4.1.1-2. The 

first figure comes from the PEGASOS project in Switzerland (NAGRA, 2004). The SSC team 

evaluated the potential that Permo-Carboniferous troughs within the Molasse basin of 

Switzerland might be seismogenic and localizers of moderate to large earthquakes. The first node 

of the logic tree identifies this evaluation and the relative probabilities assigned to the alternative 

hypotheses (reactivated or inactive). A second example logic tree is given on Figure 4.1.1-2, 

which comes from the probabilistic volcanic hazard analysis for Yucca Mountain (SNL, 2008). 

This tree begins with the assessment of the relevant volcanic events to be considered for the 

analysis, then proceeds to the alternative spatial and temporal models identified to define the 

future distribution of volcanic events. In this case, the weights assigned to the alternative 

branches are expressed as percentages, with the branches at a particular node summing to 100 

percent. Regardless of the form—probabilities or percentages—the values on the branches are 

weights that represent an assessment of the relative credibility of the alternatives given on each 

branch. 

4.1.1.2 Assigning Weights to Logic Tree Branches 

In some cases, continuous parameter distributions can be accurately defined by a discrete set of 

logic tree branches and associated weights. However, in most cases in the CEUS SSC Project, 

the weights assigned to the branches are subjective and based on the TI Team’s assessment of the 

relative support for the alternative branches, given the available data. Although the final 

assignments of weights to logic tree branches are subjective, the weights represent assessments 

informed by the totality of the SSHAC evaluation process. Before weights were assigned, the TI 

Team heard from a properly wide range of resource and proponent experts, reviewed extensive 

technical information, created the Data Summary and Data Evaluation tables, and evaluated a 

wide range of issues with members of the knowledgeable broader technical community. In this 

way, the subjective weights are informed by the consideration of data, models, and methods in 

the evaluation phase of the SSHAC process. 
Chapter 4 

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4-4

Across all assessments in the SSC model, the total set of logic tree branches and weights 

represent the team’s assessment of the center, body, and range of technically defensible 

interpretations (see Section 2.1 for a discussion of this concept). Those assessed alternatives that 

are judged not to be credible should not be included in a logic tree. In some cases, it was deemed 

helpful in the project documentation to identify those alternatives that have not been included, 

and the basis for not including them, but there is no requirement to include the global set of 

noncredible alternatives. An example of a noncredible alternative might be a model that has been 

proposed in the literature but whose application to a particular seismic source would violate the 

available data. A recurrence model that would overpredict the observed seismicity by orders of 

magnitude after accounting for uncertainties in catalog completeness is an example of an 

alternative that can be assigned zero weight and not be included in the logic tree. A discussion in 

the report that such a model was considered and rejected assists the reader in understanding the 

full range of considerations made by the evaluation team. 

The weights applied to the branches of the logic trees reflect the TI Team’s assessment that the 

particular branch is the correct branch. It is important to note that the TI Team spent 

considerable effort identifying alternative logic tree branches to be included that are significantly 

different from one another—from a hazard point of view. For example, at an early point in the 

project, alternative source geometries were postulated for the Charlevoix zone. However, the 

differences between the alternatives were minor for use in a regional seismic hazard model and 

so did not warrant incorporation into the source logic tree as two separate branches. Commonly, 

for purposes of PSHA, the branches are used to represent data, models, and methods that have 

some level of credibility as the correct parameter value, model, or method. It is the available data 

and information that provide the basis for the TI Team’s assessment of the relative weights. If 

there is no basis in the available data for a preference from among the alternative branches, then 

the weights will be the same for all alternatives. For example, if the available data give equal 

support to two alternative positions of a seismotectonic zone boundary, then the alternatives are 

assessed equal weight. 

For purposes of illustration, assuming there are two alternative branches in a logic tree, a higher 

weight is assessed for one of the alternatives if there is a technical basis in the available data to 

do so. Moving from weights of 0.6/0.4 (slight preference) to 0.9/0.1 (strong preference), the 

relative preference for the alternatives is becoming more pronounced, reflecting the stronger 

technical support for one of the alternatives. Although numbers (weights) are being used, these 

are treated as subjective probabilities and there is rarely a quantitative basis for assigning these 

weights. Exceptions on the CEUS SSC Project are the five-point distributions to represent 

quantified continuous distributions of selected parameters (for example, see the description of 

recurrence parameters for RLME sources in Section 5.3.3.1.3). The TI Team evaluated the 

alternatives using available data and information and made its best attempt to represent the 

present uncertainty. The Team reviewed the positions of various proponents of the alternatives, if 

those positions have been taken, and considered the degree of support the alternatives would 

have if members of the technical community were aware of all the project databases and had 

gone through the interactive SSHAC process of evaluating the alternatives. Ultimately, the key 

to the use of logic trees is clear documentation of the models/parameters that are given on the 

branches of the tree and justification for the weights assessed for the various branches. For 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-5

example, the seismic source characteristics for the seismotectonic zones are given in Section 7, 

along with a discussion of the technical bases for all assessments and weights on the logic tree. 

4.1.2 Data Identification and Evaluation 

Documentation of SSC requires that the data be identified that were considered and used in the 

analyses. The term ―data‖ is used in a general sense to indicate all types of information that have 

potential use in defining and characterizing seismic sources for PSHA. By identifying the data, 

the reader will understand the technical bases for the assessments and, if some time has passed 

since the project was conducted, will have information about the data and references that were 

available and considered at the time of the project. Also, the documentation should preferably 

include an assessment of the quality of the data and the degree of reliance that was placed on 

various data sets. 

Data identification and evaluation occur at the earliest part of a PSHA project and continue until 

the model-building or integration process is complete. A distinction is made between data 

identification, which is the process of becoming aware of and compiling available information 

having relevance to SSC, and data evaluation, which is the process of assessing the quality and 

applicability of the information to SSC. The process by which the data were identified and 

evaluated for the CEUS SSC Project is discussed in Sections 4.1.2.1 and 4.1.2.2. 

4.1.2.1 ―Generic‖ Data Identification to Address Indicators of a Seismic Source 

For purposes of the CEUS SSC Project, the data identification process was informed by available 

guidance issued for this purpose, as well as by the experience of members of the TI Team in 

conducting SSC projects. Existing guidance documents provide recommendations as to the types 

of data that can be useful in defining seismic sources. For example, Table 4.1.2-1 is taken from 

the standard ANSI/ANS-2.27-2008, Criteria for Investigations of Nuclear Facility Sites for 

Seismic Hazard Assessments, and indicates the types of data that can be used to identify and 

characterize fault sources and areal source zones (American Nuclear Society, 2008a). Table 

4.1.2-2 provides another example taken from the SSHAC guidance (Budnitz et al., 1997). It 

includes a further specification of data that can be used for various source types, as well as an 

evaluation of the relative usefulness of various types of data for identifying and characterizing 

seismic sources. These types of summaries are useful at the outset of an SSC project in focusing 

the database identification and compilation efforts toward the data that are likely to be useful in 

characterizing seismic sources for PSHA. 

For the CEUS SSC Project, the data identification process is ―generic‖ in the sense that it applies 

to the entire CEUS study region and not to any particular seismic source or subregion. Rather 

than tie the data to particular types of sources (e.g., faults, source zones), the types of data are 

identified that can be used to address a variety of ―indicators‖ of a unique seismic source 

(Table 4.1.2-3). Table 4.1.2-3 documents the evaluation of the indicators of seismic sources and 

the relative usefulness of various types of data that can be used to address the indicators. This 

assessment is similar to that given in the examples in Tables 4.1.2-1 and 4.1.2-2, but provides 
Chapter 4 

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4-6

further evaluation of possible indicators of seismic sources and of the relative usefulness of 

various data in addressing those indicators. 

The assessment of possible indicators of seismic sources and their relative value is necessarily 

subjective and reflects the TI Team’s consideration of the current views of the SSC community. 

Also, the indicators are particularly pertinent to the CEUS, which is an SCR (Johnston et al., 

1994) in which the causative faults giving rise to seismicity are generally not known. Therefore, 

unlike an assessment of indicators of seismic sources in an active plate boundary region, the 

indicators within the CEUS are more uncertain and vary from evidence of geologically young 

deformation, to observed zones of earthquakes, to other types of geologic and geophysical 

evidence. The types of data that are potentially useful in addressing these indicators also vary. 

The generic data identification in Table 4.1.2-3 is intended to associate the types of data that may 

be useful for SSC with potential indicators of seismic sources. In this way, as the knowledge of 

the technical community evolves regarding the most important indicators of seismic sources in 

the CEUS, the table can be updated to reflect that evolution. Also, if particular data types emerge 

in the technical community as being more diagnostic in defining seismic sources, those data 

types can be assigned higher weight in the table. 

The various columns of Table 4.1.2-3 are defined and discussed below. 

The first column is a listing of possible indicators of a unique seismic source. If we assume 

that we start with a map of the entire CEUS, these are the indicators that could cause one to 

consider subdividing the region spatially to indicate a unique potential seismic source. 

Further, it is assumed for purposes of this table, which is a generic evaluation, that the 

indicator is known with certainty. In application to any particular region, there may be 

uncertainty as to whether the indicator exists. 

The second column is an evaluation by the TI Team of the relative usefulness of each of the 

indicators in identifying seismic sources. Note that the indicators and evaluation of their 

usefulness are snapshots of the knowledge at the time this table was made. It is expected that 

future scientific studies will provide additional insights into the causative factors related to 

CEUS seismicity. Accordingly, the relative usefulness of various indicators can be expected 

to change with time. 

The third column is a listing of the types of data that can be used to address the indicators. 

This list builds on previous efforts to identify the types of data that are potentially useful for 

characterizing seismic sources, including those shown in Tables 4.1.2-1 and 4.1.2-2.

The fourth column provides an evaluation of the relative usefulness of each data type in 

addressing the indicators. Because the evaluation of usefulness is a function of both data type 

and quality of the data, it is assumed for this assessment that high-quality data are available. 

For example, consider the indicator ―high strain rates.‖ This indicator is assigned a relatively 

high level of usefulness (a score of 4) for identifying a seismic source. Two types of data are 

identified for addressing this indicator: (1) tectonic geodetic strain data and (2) geologic 

indicators of recent strain. In evaluating the relative usefulness of the two data types, it 

should be assumed that good-quality geodetic data as well as geologic data are available. 

Given this assumption, the geodetic data are assigned a moderately high usefulness (score 

of 4), and the recent geologic data are assigned a higher usefulness (score of 5) in addressing 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

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the high-strain-rate indicator. This is because the geologic data would span a longer period 

than the geodetic strain indicators. 

The fifth column is an identification of the part of the SSC model that would be affected by 

the indicator. The aspects of the model are the spatial component, which describes the 

location and geometry of seismic sources, or the temporal component, which describes the 

recurrence rate and magnitude distribution. One or the other or both components may be 

affected.

The assessments given in Table 4.1.2-3 provided a basis for the TI Team to identify the 

applicable data that should be compiled for purposes of SSC. The weights assigned to potential 

indicators of seismic sources and to the usefulness of various data types were not used in a 

quantitative way in the project. Rather, they provide a basis for documenting the current thinking 

regarding the relative importance of potential indicators and the relative usefulness of various 

types of data to address the indicators. They also provided a means of prioritizing the data 

compilation efforts toward those data that have the highest potential usefulness in the SSC 

process. For example, paleoseismic indicators of M > 5 earthquakes are judged to be highly 

diagnostic indicators of seismic sources, whereas zones of weakness in the crust or mantle are 

given a relatively low weight as an indicator. Spatially concentrated earthquakes are given a high 

weight. Consistent with these assessments, the TI Team turned the focus of the project database 

toward the development of a new earthquake catalog and devoted a major effort to compiling 

paleoliquefaction data. 

4.1.2.2 Data Evaluation for Particular Seismic Sources: Data Evaluation and 

Data Summary Tables 

The second part of the data identification and evaluation process is the identification of specific 

data that were considered and used to characterize particular seismic sources, including RLME 

sources or seismotectonic zones. The purpose of this evaluation is to identify the data used, 

evaluate the quality of the data, and specify the degree of reliance on each data set in 

characterizing seismic sources. Data Evaluation tables were developed for this purpose (Table 

4.1.2-4 is an example), and the tables for each source are included in Appendix C. The process 

also provides an opportunity to identify data sets that were considered in the evaluation even if 

they were not ultimately used to characterize seismic sources. Data Summary tables were 

developed for this purpose (Table 4.1.2-5 is an example), and those tables are included in 

Appendix D. 

The Data Evaluation tables include the following attributes (see Table 4.1.2-4):

The first column is a listing of the data, by data type, used in the evaluation for a particular 

RLME or seismotectonic source. 

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 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

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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. 

Data Summary tables (example in Table 4.1.2-5) provide information on the various data that 

were considered during the course of the characterization of various seismic sources. The tables 

provide the citations to the data and a description of the key conclusions and their potential 

relevance to SSC. The goal is to provide the reader with the TI Team’s view of the data set and 

how it might pertain to SSC. This can be particularly useful to other researchers—perhaps some 

years from now—in understanding what data sources were considered at the time of the CEUS 

SSC and how their relevance was assessed. 

The Data Evaluation and Data Summary tables are not intended to replace the documentation of 

an SSC effort, but rather to supplement it. The discussions in a project report of the data used in 

the evaluation are not always comprehensive and it can be difficult to gain a clear understanding 

of exactly which data sets were considered, which were actually used in the evaluation, and the 

degree of reliance that was placed on them. Therefore, these tables were designed to make the 

data evaluation process more transparent and reasonably complete. It should be noted that these 

tables in particular—and the documentation in general—are a snapshot of a particular point in 

time. That is, the types of data available and their quality and utility are a function of our present 

understanding of SSC for PSHA. It is likely that in the future, additional data will become 

available that will prove useful for identifying or characterizing seismic sources. 

Also, it is likely that the degree of reliance on any given data set will change in the future. For 

example, at the present time, GPS geodetic data are available for only a relatively limited part of 

the CEUS, and the period of observation is relatively short, such that errors in the data may 

exceed the signal. Moreover, it is not clear, given our present understanding of earthquake strain 

accumulation processes, exactly how geodetic strain rates provide direct constraints on seismic 

source characteristics. For example, the Independent Expert Panel on New Madrid Seismic Zone 

Earthquake Hazards (NEPEC, 2011) concluded that the observations of a lack of deformation 

based on the geodetic evidence were not sufficient to rule out the potential for future large 

earthquakes. Yet it is likely that uncertainties in the use of geodetic data will decrease with time 

and that this data set will become more valuable in the future for SSC. It is also possible that 
Chapter 4 

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4-9

entirely new types of data will become available in the future on which the SSC community will 

become increasingly reliant. 

Although the CEUS SSC Project placed a premium on compiling a wide variety of databases and 

placing many of the databases on a common GIS platform to facilitate their use, not all of the 

data were used directly in the characterization of seismic sources. This is simply because some 

data and references have been superseded by later studies or some types of data are viewed as 

having only a limited usefulness in meeting the criteria for defining seismic sources. 

Nevertheless, the documentation process followed in the data tables will allow the reader to 

understand which data were considered in the course of the evaluation process, as well as which 

data were relied on in the seismic source model. 

4.1.3 Methodology for Identifying Seismic Sources 

The methodology used in the CEUS SSC Project to identify seismic sources takes advantage of 

the experience gained over the past three decades in assessing SSCs for PSHAs. It incorporates 

the range of views in the scientific community regarding spatial stationarity of seismicity, and it 

is appropriate for a regional SSC assessment that can be applied on a consistent basis throughout 

the CEUS. A regional PSHA requires that the assessment include elements that are of sufficient 

specificity to include new thinking and contemporary data on seismic sources, yet is not reliant 

on site-specific information that cannot be applied systematically throughout the entire CEUS. 

Further, over time, new data are likely to be developed on a site-specific basis, thus calling for a 

stable regional model that can be refined for future new findings. For example, in recent years, 

paleoliquefaction data have been gathered and interpreted at particular locations, such as the 

New Madrid, Charleston, and Charlevoix seismic zones. For the vast majority of the CEUS, 

however, such features may not be present or data may not have been systematically gathered 

and evaluated; thus they are not available for incorporation into a hazard analysis. Accordingly, 

the SSC methodology advanced in this project can allow for the incorporation of such data in 

those cases where it is available, but given the incomplete distribution of the data across the 

region, the methodology should not assume or require that such data be available throughout the 

regional SSC model. 

Workshop #2 on Alternative Interpretations provided an opportunity for the TI Team to discuss 

with members of the technical community several important issues with potential relevance to 

the identification of seismic sources. For example, paleoseismic indicators of possible RLME 

sources were discussed, including locations with strong evidence and those with equivocal 

evidence. In particular, considerable discussion in the workshop centered on the evidence for the 

location, size, and timing of earthquakes based on paleoliquefaction evidence. Given the 

potentially high significance of these types of data and their increasing credibility within the 

technical community as indicators of seismic sources, the project and the TI Team were 

encouraged by the PPRP to place high priority on the identification and evaluation of 

paleoliquefaction data and to complete the paleoliquefaction database that culminated in 

Appendix E to this report. Another issue discussed was the degree to which the spatial patterns 

of observed earthquakes provide an indication of future patterns. Proponents dealt with the issue 

of observed geodetic strain rates and their consistency with the presence or absence of sources of 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-10

large earthquakes identified by other means. Likewise, alternative possible tectonic explanations 

were proposed to explain concentrations of observed seismicity, with the potential implications 

of using those explanations to define seismic sources. All of these issues have potential 

implications for defining the criteria for source identification in a meaningful way. That is, the 

criteria must take into account the technical community’s views of the important indicators of 

seismic sources and they must also be implementable across the study region given the available 

data. 

It is assumed that the methodology outlined in this section will provide the regional component 

of the SSC, which is subject to refinement with the consideration of site-specific data and 

information. For example, the output from this project will be a reasonably complete 

specification of the knowledge and uncertainty regarding the spatial and temporal aspects of 

seismic sources on a consistent basis throughout the CEUS study region. It can therefore be 

exercised in a PSHA (which will include ground motion characterization) at any location in the 

study region. If the results are to be used for purposes of licensing at a particular nuclear facility 

location, regulatory guidance (e.g., NRC Regulatory Guide 1.208) requires that a site-specific 

database be developed. Similar guidance for other nuclear facilities requires the consideration of 

local and site-specific information (e.g., ANSI/ANS-2.27-2008, ANSI/ANS-2.29-2008). Once it 

is developed, the applicant will need to evaluate whether the site-specific database includes 

information pertinent to SSC and, if it does, then the site-specific information will need to be 

incorporated into the CEUS SSC source model. Alternatively, the applicant might consider the 

hazard significance of the site-specific information and determine that it would not require a 

refinement to the CEUS SSC model (see Section 9.4.3 for a discussion of hazard significance). 

The concept of a ―regional‖ SSC model is easily understood, as is the type of ―site-specific‖ 

information that is commonly developed to support a regulatory license application under current 

regulatory guidance. However, the TI Team has considered whether further specification can be 

made of what is considered ―regional‖ and what is considered ―site-specific.‖ In other words, is 

there a ―scale cutoff‖ below which one would consider the data too local to be systematically 

characterized throughout the entire study region? Clearly, local tectonic features that lie entirely 

within the 8 km (5 mi.) radius site area, and likely the 40 km (25 mi.) radius site vicinity, as 

defined in NRC Regulatory Guide 1.208, would be too site-specific to be included on a 

systematic basis in the CEUS SSC source model. Unless special studies have been carried out 

that demonstrate the existence of tectonic features having a significant seismogenic potential, the 

consideration and potential incorporation of specific tectonic features would be part of the 

refinement of the CEUS SSC model for site-specific application. Thus the TI team is unable to 

specify a quantitative cutoff dividing regional from site-specific. 

A more reasonable criterion that was applied in the CEUS SSC Project is the following: the 

CEUS SSC model provides the regional characterization of sources on a consistent basis 

throughout the study region, including those special areas that have been the subject of 

considerable scrutiny in the past. Consideration of site-specific refinement of the CEUS SSC 

model would be required by current regulatory guidance and would occur only if such 

refinement would lead to significant differences in hazard. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-11

4.1.3.1 Hazard-Informed Approach 

Numerous PSHAs have been conducted within the CEUS and other SCRs over the past three 

decades. The experience gained over that time was used in defining the framework for 

identifying and characterizing seismic sources. The knowledge gained on the important SSC 

issues will likely contribute to the hazard results at annual frequencies of exceedance important 

to nuclear facilities. Likewise, the most important contributors to uncertainty can be anticipated. 

It is also possible to anticipate those technical issues that will have lesser or no significance to 

the hazard results. 

For example, SSC studies conducted in the 1980s, such as the EPRI-SOG project, focused on the 

issue of evaluating the probability for particular tectonic features to localize moderate to large 

(M ≥ 5) earthquakes within the contemporary tectonic regime. The evaluation of this probability 

of activity, Pa, was viewed as a fundamental part of the SSC process. Included in the evaluation 

were hypotheses related to the causative mechanisms of CEUS seismicity, the nature of the 

contemporary stress regime, and various data indicators that would provide insights into whether 

a tectonic feature—or class of features—might be seismogenic. These 1980s assessments 

provided valuable insights into the then-current state of knowledge and uncertainty about the 

causes of CEUS earthquakes. We can take advantage of these insights in outlining our SSC 

approach some 25 years later. 

One of the insights gained from experience on several PSHAs is that observed seismicity is 

perceived by the larger technical community as providing a fundamental constraint on estimates 

of the future spatial and temporal distribution of moderate to large earthquakes. This is despite 

the heavy emphasis placed on studies like the EPRI-SOG project on tectonic features and their 

potential to be seismogenic. Examples of the reliance on observed seismicity in these studies can 

be found in several source types. Within the more active zones, such as New Madrid, the 

seismicity data were used to define the spatial location of the seismic sources as well as the 

recurrence rates for the sources. Away from the more active zones, background zones were 

identified whose probability of activity was typically 1.0 and whose recurrence rate was defined 

by the diffuse seismicity within the zone. Seismicity within large background seismic source 

zones was also used to ―smooth‖ recurrence parameters (a- and b-values), providing for spatial 

variations based on seismicity. 

The assessment of maximum earthquake magnitudes for seismic sources within the CEUS is 

typically not constrained by physical characteristics of the source itself (e.g., fault rupture 

length); instead, it is estimated considering the largest earthquakes within the seismic source as 

well as analogues to other sources that are tectonically similar. Even in those cases where 

tectonic features were identified as candidates for localizing future M ≥ 5 earthquakes, the most 

diagnostic criterion for evaluating seismogenic potential was the spatial association of the feature 

with observed seismicity. Those tectonic features that were assessed to have a low probability of 

being spatially associated with seismicity (often due to low numbers of observed earthquakes) 

were assigned a low probability of being seismogenic, Pa, regardless of any existing evidence. In 

nearly all cases, conclusive geologic evidence for recent fault displacement—which would be a 

diagnostic criterion if it did exist—simply was not identified in the available data. As a result, in 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-12

nearly all cases, the hazard significance of individual tectonic features was assessed to be very 

low to negligible. 

We conclude from this experience that the characteristics of the observed seismicity record—

both the spatial and temporal distribution of earthquakes—are important constraints and have 

high hazard significance. Therefore, the SSC methodology advanced in the CEUS SSC Project 

appropriately places heavy emphasis on the systematic and consistent development of seismicity 

databases and on approaches to their use in defining and characterizing seismic sources. 

Conversely, less emphasis is placed on identifying and evaluating tectonic features that are not 

clearly associated with observed seismicity or that do not show geologic evidence of recent 

activity within the present tectonic regime. 

This should not be interpreted as suggesting that the earthquake community has discarded the 

search for associations between earthquakes and tectonic features within SCRs, or that observed 

seismicity provides an unequivocal description of future earthquakes. Earthquake research within 

SCRs continues to hypothesize a variety of possible mechanisms for the observed seismicity; 

spatial associations with deep crustal or mantle anomalies are such candidates. Rather, it reminds 

us that the purpose of the CEUS SSC Project is to develop a seismic source model to be used in a 

seismic hazard analysis, and not to answer research questions about SCR earthquake causative 

mechanisms. Postulated spatially and/or temporally clustered/episodic behavior of largemagnitude earthquakes at New Madrid is an example of a hypothesis that has potentially 

significant hazard implications and that is addressed directly in the seismic source model. 

An additional insight gained during the past 20 years, due largely to a number of geologic studies 

conducted over that period, is that paleoseismicity is important and its potential for hazard 

assessment is very significant. Beyond the observed historical and instrumental seismicity 

record, no single data set has had a more profound influence on matters of maximum size of SCR 

earthquakes, their spatial distribution over periods much longer than the historical record, and the 

rates and behavior of currently active seismic sources. With very few notable exceptions, such as 

the Meers fault, the paleoseismicity evidence has been based entirely on shaking effects rather 

than observed displacements along the causative fault. For this reason, the causative structures 

giving rise to the paleoearthquakes remain elusive in most cases. Likewise, significant 

uncertainties exist regarding the locations, magnitudes, and recurrence of the earthquakes based 

on the geologic record. Nevertheless, the existence of the paleoearthquakes is in most cases 

undeniable and, because of their potentially high hazard significance and the technical 

community’s general support, they must be incorporated explicitly into the seismic source 

model. Because the causative faults for these earthquakes are not known, the paleoearthquakes 

can be viewed as simply an extension of the observed seismicity catalog back in time. Of course, 

in doing so, care must be taken to properly evaluate the interpretation of paleoseismic evidence 

and assess the uncertainties in the size and timing of the earthquakes. 

To further identify and understand the issues of most hazard significance, seismic hazard 

calculations were conducted using the SSC sensitivity model prior to Workshop #3 for a series of 

sensitivity cases. The issues identified as having the most hazard significance were as follows: 

Large-magnitude sources (e.g., New Madrid, Charleston, Charlevoix) 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-13

o Magnitude of the ―characteristic‖ (repeated large-magnitude) earthquake 

o Recurrence rate 

o Location of the source 

Moderate-magnitude sources (e.g., Eastern Tennessee seismic zone, Central Virginia seismic 

zone, Wabash Valley) 

o Source geometries 

o Maximum earthquake magnitude 

o Recurrence rate 

o Smoothing (i.e., whether seismicity is distributed uniformly within the zone or smoothed 

locally) 

Background zones 

o Maximum earthquake magnitude 

o Smoothing 

o Probability of activity (i.e., whether the zone has a Pa less than 1.0) 

These findings reinforce the importance of focusing on the locales that have hosted moderate- to

large-magnitude earthquakes in the observed seismic record, and of using that record, along with 

other indicators such as paleoseismic information, to define the location/geometry, maximum 

size, and recurrence rates. Away from those locales, issues related to the seismogenic potential of 

the background regions were found to be important if the Pa was judged to be less than 1.0; that 

is, if there was some finite probability that the region was not capable of generating a M ≥ 5 

earthquake. However, with time and continued study of SCRs around the world, there is 

increasing consensus that any region within an SCR is capable of generating earthquakes of 

those magnitudes. Further, the uncertainties in this assessment can be readily addressed in the 

assessment of Mmax for the zones. Therefore, the Pa issue for background zones has much less 

hazard significance. 

4.1.3.2 Conclusions Regarding the Hazard Significance of Various SSC Issues 

Based on the experience of multiple PSHAs in the CEUS since the time that major studies were 

conducted in the 1980s, as well as sensitivity studies conducted for the CEUS SSC Project, the 

following conclusions can be drawn regarding the most important SSC issues and their 

implications in developing an SSC methodology. 

Despite continued study, the causative structures (faults) for the observed moderate- to largemagnitude earthquakes in the CEUS remain unknown, with very few exceptions. Thus a 

seismic source model comparable to those developed in the WUS (e.g., faults with 

background zones) is not possible. 

The observed record of seismicity, despite uncertainties in the locations and magnitudes of 

earthquakes, and the completeness of the record, is the fundamental means of assessing the 

future locations, sizes, and rates of earthquakes needed for a PSHA. Our tools for quantifying 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-14

the uncertainties in the record have become better developed, as have our tools for using the 

record (e.g., spatial smoothing). 

Evaluations of potential causative tectonic features, which include hypotheses about crustal 

loading mechanisms due to deeper mantle processes, remain an active area of seismologic 

research. But experience has shown that only those tectonic features/hypotheses having a 

significant probability of being seismogenic (Pa greater than about 0.5) will have hazard 

significance. Therefore, the evaluation of tectonic features/hypotheses with low Pa can only 

be represented in the regional characterization of seismotectonic source zones. Any 

consideration of local tectonic features would be part of a site-specific refinement to the 

regional SSC model. 

Geologic observations of paleoearthquakes are now largely accepted within the technical 

community and can be viewed as an extension of the observed seismicity record back in 

time. Further, these earthquakes have been shown to have a profound effect on hazard 

estimates for many sites within the CEUS. Therefore, they must be included explicitly in the 

seismic source model for the CEUS. However, the uncertainties in the location, magnitude, 

and recurrence of these earthquakes are evaluated differently from those of the historical and 

instrumental seismicity record. As a result, the CEUS SSC model should provide for 

paleoseismic earthquakes explicitly, but should also provide for addressing their uncertainties 

in a manner different from the rest of the observed seismicity catalog. 

The logic structure for the SSC model, represented by a master logic tree, should provide 

alternative approaches and conceptual models for our current understanding of the 

constraints on the location, size, and recurrence of future earthquakes. For clarity and 

efficiency, the logic tree should start with the most basic descriptions of seismic sources and 

should gain complexity only as needed to represent specific hypotheses and data sets that 

have hazard significance. In this way, unnecessarily complex source models will be avoided, 

such as those that depict a large number of tectonic features, none of which have a significant 

probability of being seismogenic. 

4.1.3.3 Criteria for Defining Seismic Sources 

Embarking on the development of a new SSC for the CEUS demanded that attention be given to 

the experience gained from similar efforts over the past few decades, in terms of both the 

development of new data and tools and the experience with issues of most significance to hazard 

at annual frequencies of interest for nuclear power plants. On the one hand, geologic and 

geophysical studies of the crust since the 1980s have provided little new information about 

tectonic features and the geologic history of the region that may have a bearing on evaluation of 

seismic hazards; a possible exception, however, is the improved understanding of the Illinois 

Basin Extended Basement and its features. On the other hand, paleoliquefaction studies have 

been useful in defining and characterizing seismic source zones. 

The methodology needed to be consistent with the seismotectonic setting of the CEUS and our 

current knowledge base for assessing the locations, sizes, and rates of future earthquakes. For 

example, we currently lack a clear definition of the causative faults giving rise to the observed 

seismicity, so applying a methodology that relies on knowledge of fault location and behavior 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-15

would not be appropriate. Similarly, geodynamic data on contemporary crustal strain are 

currently limited in their duration and spatial extent; in addition, available physical models are 

unable to make a unique association between geodetic strain and earthquake processes (NEPEC, 

2011). Therefore, although such data may be useful in assisting with the evaluation of seismic 

source characteristics, the methodology should not rely on knowledge of the relationship 

between short-term crustal strain data and future earthquake characteristics. 

Various authors over time have defined seismic sources for purposes of PSHA in different ways. 

For example: 

―Sources are explicitly defined as being of uniform earthquake potential; that is, the chance 

of an earthquake of a given size is the same throughout the source.‖ (Reiter, 1990)

―[A seismic source is] a region of the earth’s crust that is assumed for PSHA to have 

relatively uniform seismic source characteristics.‖ (Budnitz et al., 1997) 

―A seismic source is a volume of the earth’s crust that has the same earthquake potential as 

defined by the size of events that may be generated.‖ (BC Hydro, 2008) 

A common theme in these definitions is a degree of ―uniform‖ earthquake potential or 

characteristics, although exactly what this means is not clear or varies with the application. Early 

in the history of PSHA, the Mmax (and associated uncertainty) and recurrence rates (expressed 

as a- and b-values) within identified seismic sources were assumed to be ―uniform.‖ ―Uniform‖

in this case meant the same throughout the source without spatial variation. Since then, a number 

of approaches have been developed to express the spatial variation of recurrence parameters. For 

example, the EPRI-SOG project provided for spatial variation of a- and b-values at the scale of 

one-degree cells (~100 km [~62 mi.] dimensions), and the USGS national hazard maps utilize a 

Gaussian smoothing kernel to express spatial variations in a-values. Thus far, the spatial 

variation in Mmax has only been expressed by the identification of separate sources (including 

fault sources within areal source zones), and a strong technical basis for spatial variations of 

Mmax within source zones has not been established. 

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. Their sequence represents their relative 

significance to seismic hazard results, with earthquake recurrence rate being most important and 

the probability of activity having lesser impact on calculated hazard results. Further, because 

each criterion adds complexity to the seismic source model, it is applied only if its application 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-16

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. 

Examples will assist in illustrating the notion of progressively applying the seismic source 

criteria. To begin, consider the entire CEUS study region and the first criterion of differences in 

earthquake recurrence rate. In general, the record of past earthquakes is obtained from the 

historical/instrumental catalog and from the paleoseismic record of prehistoric earthquakes. For 

the CEUS SSC Project, RLME sources are the locations of repeated (more than one) largemagnitude (M ≥ 6.5) earthquakes, and paleoseismic evidence is used to define the source’s 

recurrence rate (see Section 4.4.1.1 for further discussion of RLME sources). This is an example 

of identifying distinct seismic sources based on differences in recurrence. 

Spatial smoothing of the recurrence rate (a- and b-values) based on observed seismicity accounts 

for the spatial variation in rate. The approach used in the CEUS SSC is a refinement of that used 

in the EPRI-SOG project. Conceptually, the smoothed seismicity model is the least complex 

seismic source representation. Embedded within the concept of spatial smoothing is the notion of 

spatial stationarity; that is, the pattern of past earthquakes is a predictor of the pattern of future 

earthquakes. Studies of seismicity in the CEUS have concluded that this is a reasonable 

interpretation (Kafka, 2007, 2009). Further, because the historical record of observed 

earthquakes is relatively short (about 200 years in most of the CEUS) relative to the recurrence 

intervals for large-magnitude earthquakes, there is an assumption that the spatial distribution of 

observed smaller-magnitude earthquakes constrains the spatial distribution of larger-magnitude 

earthquakes. The use of spatial smoothing to represent earthquake recurrence, together with 

RLME sources, means that there may not be a need to identify seismic source boundaries within 

a region due to recurrence differences. 

After spatial variations in rate have been established using smoothing, then the CEUS can be 

subdivided to account for differences in Mmax. Current approaches to assessing Mmax within 

SCRs such as the CEUS are based on analogies to domains having similar tectonic 

characteristics. The EPRI Mmax project (Johnston et al., 1994) presented a Bayesian approach to 

assessing Mmax that establishes prior distributions of Mmax for two domains: extended crust 

(defined as having undergone major extension in Paleozoic and younger time) and non-extended 

crust. These prior distributions are modified by a likelihood function that reflects the earthquake 

counts within a seismic source and is truncated at the low-magnitude end by the largest observed 

earthquake within the source of interest. The SCR database and analysis of the data given in 

Johnston et al. (1994) were updated as part of the CEUS SSC Project (see the discussion in 

Section 5.2.1.1).

The results of the data reanalysis suggest that there is only a weak statistical basis for separation 

of the SCR data to establish a prior distribution on Mmax. As a result, the CEUS SSC model 

invokes either a single prior distribution that is applicable to the entire CEUS SSC study region, 

or two prior distributions: one that is based on Mesozoic-and-younger extension and one that is 

based on non-extended regions or older extended regions. In the latter case, a seismic source 

boundary is drawn (including uncertainty) to separate the regions of Mesozoic-and-younger 

extension from the remainder of the study area. This is an example of a seismic source being 

defined on the basis of Mmax differences. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-17

From variations in recurrence and Mmax, the next criterion for subdividing the CEUS is 

expected significant differences in future earthquake characteristics, such as their depth 

distribution, style of faulting, and expected orientation of earthquake ruptures (strike and dip). In 

seismic hazard models, future earthquakes are modeled as having finite dimension, magnitudedependent rupture dimensions, orientations, and depth extent. This is because these 

characteristics are important to modern ground-motion prediction equations, including those that 

will be developed for the CEUS region as part of the ongoing Next Generation Attenuation East 

(NGA-East) project (PEER, 2010). To accommodate these assessments, the CEUS study region 

was subdivided into seismotectonic zones having comparable characteristics. These subdivisions 

may also have implications for Mmax assessments in that the likelihood function varies with the 

size of the largest observed earthquake for the source of interest. Within these subdivisions, 

spatial smoothing of seismicity is carried out to express the variation of recurrence rate spatially. 

A final assessment that can be considered is the identification of particular tectonic features that 

have significant potential to localize seismicity; that is, they are assessed to have a Pa that is 

greater than about 0.5. These might be associated with a paleoearthquake, smaller-magnitude 

earthquakes, or they might have geologic indicators of activity. In the cases where potentially 

seismogenic tectonic features are identified, it is necessary to consider the relationship between 

the feature and the local background within which the feature lies. For example, if the feature has 

a Pa less than 1.0, then there is a finite probability (1–Pa) that the feature is not seismogenic and 

does not localize seismicity. In that case, the background zone would need to be identified. 

Likewise, in the case where the feature is judged to be seismogenic, the earthquakes that should 

be assumed to be associated with the feature need to be identified so that recurrence rate for the 

feature and the background zone can be calculated. The CEUS SSC Project identified very few 

local tectonic features with clear and compelling reported evidence of activity and these are the 

RLME fault sources (e.g., the Meers fault and Cheraw fault). However, because the CEUS SSC 

model is a regional model, any site-specific use of the model will need to consider whether any 

local evidence for tectonic feature activity might exist and, if so, refine the model locally. 

The basis for the assessment of the recency of fault displacement and the potential for 

Quaternary activity is the comprehensive study conducted by Crone and Wheeler (2000), who 

place each feature into Classes A through D depending on what is known about the feature’s 

geologic evidence for Quaternary activity. The inclusion of faults that only have a high 

probability of activity in the CEUS SSC model does not preclude, however, the need to consider 

local site-specific data and evidence for the potential activity of tectonic features on a local scale. 

It is anticipated that the required site-specific data collection studies for a nuclear facility will 

provide the basis for identifying potential local seismic sources and, if necessary, local 

refinements to the CEUS SSC model. 

The application of the criteria for identifying seismic sources results in the suite of seismic 

sources given in the CEUS SSC model. A summary of the criteria that resulted in the 

identification of each of the seismic sources is given in Table 4.1.3-1. A detailed description of 

the application of the criteria to each source is given in the ―Basis for Defining Seismotectonic 

Zone‖ sections in Chapter 7 (e.g., Sections 7.3.6.2 and 7.3.7.2). In addition, the bases for 

defining the RLME sources and the Mmax zones are given in applicable sections of Chapter 6 

(e.g., Section 6.2.1). In those cases where alternative source geometries are included in the SSC 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-18

model, a discussion of the alternatives and the basis for the weights assigned to each alternative 

are also given in the applicable sections of Chapters 6 and 7. 

To represent the uncertainties in the seismic source identification process, both a master logic 

tree and individual seismic source logic trees were constructed. These are discussed below. 

4.2 Master Logic Tree 

The master logic tree establishes the framework for the entire seismic source model. It identifies 

the alternative approaches and conceptual models that will be used and establishes the relative 

weights assigned to the main alternatives. By laying out the alternatives at the start, the 

subsequent detailed source evaluations will each be conducted within a framework that ensures 

consistency across all sources. Likewise, the sum total of the source evaluations will be logically 

combined in such a way as to avoid double-counting and provide for meaningful weighted 

combinations. In this section, the discussion of the master logic tree is followed by a description 

of the major elements of the logic trees that describe the various seismic sources. The detailed 

discussions of the individual seismic sources and the characterizations in their logic trees are 

given in Sections 6 and 7 of this report. 

4.2.1 Description of Logic Tree Elements 

Using the criteria given in Section 4.1.3.3 and the associated conceptual basis, a master logic tree 

was developed that provides a framework for all of the seismic source evaluations in the CEUS 

SSC (Figure 4.2.1-1). The basic structure of the logic tree has been developed to include the 

simplest representation of seismic sources (smoothing of observed seismicity with subdivisions 

of the CEUS related to recurrence and Mmax) as well as more complex subdivisions to account 

for differences in the characteristics of future earthquakes. Accordingly, the first-order branches 

of the tree address the basic conceptual models related to the approaches; these are followed by 

branches that represent the uncertainties in the implementation of each approach. 

The first assessment on the master logic tree (Figure 4.2.1-1), represented by the first node, is the 

choice between two conceptual models used to assess the spatial and temporal distribution of 

future seismicity. The application of the seismic source criteria given in Section 4.1.3.3 leads to 

the identification of RLME sources based on differences in earthquake recurrence (from 

paleoseismic evidence) from the ―background‖ zones within which they lie. RLME sources are 

identified based on well-defined evidence for Late Quaternary or Holocene RLMEs. Thus the 

RLME sources are present for all seismic source interpretations. 

The ―Mmax zones‖ model involves identifying alternative configurations based on differences in 

the prior distribution of Mmax using the Bayesian Mmax approach (see Section 5.2.1.1). 

Accordingly, the CEUS SSC study region is either subdivided according to evidence of 

Mesozoic and younger extension (with associated uncertainties in the location of the boundary) 

or not subdivided. In this model, the spatial variation of recurrence parameters is based on spatial 

smoothing of observed earthquakes. The ―seismotectonic zones‖ model also includes the concept 

of subdividing the region according to differences in the prior Mmax distributions, and identifies 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-19

seismic sources based on spatial variations in the characteristics of future earthquakes (the third 

criterion identified in Section 4.1.3.3).

In addition to the RLME sources, the region is divided into seismotectonic zones that provide for 

differences in expected future earthquake characteristics. For example, differences in the style of 

faulting, strike of ruptures, and depth distribution of future earthquakes can be accommodated in 

the ―seismotectonic zones‖ model. The model also accommodates any differences in Mmax 

among the seismotectonic zones due to differences in the size of the largest observed 

earthquakes; Sections 5.2.1.1 and 5.2.1.2 describe the influence of the largest observed 

earthquakes on the Mmax estimates. 

The weights assigned to the ―Mmax zones‖ and ―seismotectonic zones‖ branches reflect the 

relative preference for the alternative approaches for characterizing the future spatial and 

temporal distribution of earthquakes and their characteristics, given the available data for the 

CEUS. The two models are quite similar in many respects. They both include RLME sources as 

independent sources defined by paleoseismic evidence for the size and recurrence rate for the 

RLME earthquakes. Moreover, both allow spatial variation of recurrence parameters by 

smoothing within seismic source zones (see Section 5.3.2 for a discussion of spatial smoothing). 

The key difference between the two models is in their ability to include and represent 

information related to the characteristics of future earthquakes. The ―Mmax zones‖ model is 

based on average or ―default‖ characteristics that are representative of the the entire study region 

(Table 5.4-1), whereas the ―seismotectonic zones‖ model can include information that allows for 

an assessment of spatial variations of future earthquake characteristics at a scale that is 

appropriate to a regional SSC model (see Table 5.4-2 for the characteristics of each 

seismotectonic zone). A higher weight (0.6) is assigned to the seismotectonic zones branch than 

to the Mmax zones branch (0.4) because the seismotectonic zones approach allows for more 

relevant information on the characteristics of future earthquakes to be included in the model. 

While many of the characteristics of the seismotectonic zones are uncertain, such as the locations 

of the source boundaries and the characteristics of future earthquake ruptures, they are still 

judged to provide a better description of the applicable source characteristics. 

Early in the project, as part of the SSC sensitivity model, a third conceptual model was 

considered that would be even simpler conceptually than the Mmax zones model. This model 

was called the ―zoneless‖ model and it postulated that all earthquakes—both those defined from 

the historical record and those defined from paleoseismic evidence—would be subject to spatial 

smoothing. As such, the model would not need to invoke any source zone boundaries, including 

those that identify RLME sources. With further consideration, however, it was found that the 

model cannot be applied with confidence given our present knowledge. This is because the 

spatial smoothing approach is actually smoothing the recurrence parameters a and b, which 

require that the record be complete over a given time interval. Completeness adjustments can 

readily be made for the historical record, but there is not sufficient information in the 

paleoseismic record to make the same type of completeness adjustments. The current spatial 

distribution of paleoseismic investigations is decidedly non-uniform. Some areas have been 

investigated in detail, and estimates of the completeness of the record locally are possible, but 

other areas have not been subject to searches for paleoseismic evidence at all. Until systematic 

searches for paleoseismic evidence are conducted such that the completeness of the record can be 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-20

assessed and corrected for, it is not possible to exercise the ―zoneless‖ model, and it has been 

dropped from the CEUS SSC model. It is mentioned here, however, in anticipation that future 

work will allow its incorporation into SSC models. 

Given either the Mmax zones or seismotectonic zones branches of the master logic tree, certain 

source characteristics are defined in the subsequent parts of the logic tree. A detailed discussion 

is given in Section 5 of the various approaches used in the CEUS SSC Project to characterize the 

Mmax (Section 5.2), earthquake recurrence (Section 5.3), and future earthquake characteristics 

(Section 5.4). Here we present the major elements of the master logic tree and discuss why they 

are included. The discussion in this section also includes the relative weights assigned to 

assessments that are not source-specific. The source-specific assessments for RLME sources are 

given in Section 6.1, for Mmax zones in Section 6.2, and for seismotectonic zones in Section 7.3. 

4.2.2 RLME Source Logic Tree

RLME sources are identified and characterized in either the Mmax zones or the seismotectonic 

zones branches. The logic tree that describes the RLME source characteristics is given on Figure 

4.2.2-1, which shows an example tree for the Marianna RLME source. Figure 4.2.2-2 identifies 

the RLME sources, which are listed in Table 4.2.2-1. In this section of the report, the 

characteristics are described generically without reference to any particular RLME source. 

Individual RLME source characteristics are described in Section 6.1. 

The first node of the logic tree for RLME sources (Figure 4.2.2-1) deals with the issue of 

temporal clustering of large-magnitude earthquakes. Many seismic sources, especially those 

within SCRs, display evidence of clustering through time such that the recurrence rates may be 

elevated for several seismic cycles during a cluster, followed by much longer time intervals. This 

behavior can be modeled by identifying two rates: the within-cluster rate and the out-of-cluster 

rate. The SSC model resulting from the CEUS SSC Project will be useful for engineering 

applications that will entail up to approximately the next 50 years;1for this reason, it is important 

to assess whether the source is currently (i.e., over approximately the next 50 years) within or out 

of a cluster such that the within-cluster or out-of-cluster rate is applicable. This is the first 

assessment in the RLME source logic tree. 

The second node of the logic tree is the assessment of the nature of the localizing tectonic feature 

for the RLMEs. In some cases the source will be modeled as a fault source; in other cases the 

existing data will not allow for a clear definition of causative faults, and some type of areal 

source zone will be used. Alternative geometries are then defined at the third node of the tree for 

the localizing tectonic feature(s). 

The fourth and fifth nodes of the tree provide information regarding the rupture characteristics 

for future earthquakes within the RLME source. As discussed in Section 5.4 and shown in Table 

5.4-1, a ―default‖ set of characteristics were developed for the entire study region, and the 

 

1

 Note that 50 years is the approximate lifetime of nuclear facilities and is used in this context as the time period of 

interest for assessing within-cluster or out-of-cluster rates. There is no implication that the lifetime of the CEUS 

SSC model is 50 years. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-21

assessments made by the TI Team for individual seismic sources could either adopt the default 

characteristics or, if sufficient data were available to do so, specify source-specific 

characteristics. Source-specific characteristics are included on the logic tree and are shown in 

Table 5.4-2. Shown are seismogenic crustal thickness, rupture orientation, and source boundary 

characteristics. Seismogenic crustal thickness can be important in the assessment of distance 

from ruptures for ground-motion prediction equations, as well as in calculations of seismic 

moment rate from geologic slip rates. Also, the dimensions of rupture are magnitude dependent 

(Section 5.4), and finite ruptures, using the assessed rupture orientations and downdip 

dimensions, are modeled for purposes of the hazard calculations. The hazard model assumes that 

the epicenters of all earthquakes will occur within the seismic source, although the seismic 

source boundary characteristics are assessed for whether the rupture can cross the source 

boundary (termed a ―leaky‖ boundary) or must remain within the boundary (―strict‖ boundary).

Not shown on the tree is the assessment of the style of faulting for the source. 

The sixth node of the logic tree expresses the estimates of the RLME magnitudes. Because most 

of the evidence for the RLMEs in the CEUS comes from paleoseismic data, there can be 

significant uncertainty in the size of the earthquakes. There are two components to this 

assessment: an aleatory component that expresses the variations in the size of the RLME eventto-event, and an epistemic component that expresses the uncertainty in the average size of the 

RLME. The epistemic component is given in the logic tree, and the aleatory component is 

assumed to be plus or minus 0.25 magnitude units about the mean unless there is source-specific 

information that suggests otherwise. The value of 0.25 magnitude is judged to be appropriate 

based on observations of the repeated sizes of paleoearthquakes in well-studied areas. 

The seventh node of the logic tree is the recurrence method and differs depending on whether the 

―in-cluster‖ or ―out-of-cluster‖ branch is being followed. Given the ―in-cluster‖ branch, 

approaches to estimating recurrence include either interevent times (recurrence intervals) or slip 

rates. In either case, the data should be those that are applicable to the present cluster and that 

would apply for the future period of interest of about 50 years. Given the ―out-of-cluster‖ branch, 

the assessments of recurrence should again focus on the applicable recurrence information that 

would apply to the future period of interest. 

The eighth ―events/data‖ node of the logic tree expresses the data that are used in the recurrence 

assessment for the RLME source. In most cases, this is an assessment of the dates of past 

earthquakes, which includes the uncertainty in the timing of earthquakes given the available 

paleoseismic data. In other cases, an assessment is made of the number of events that have 

occurred over a particular time interval. The approaches taken in the estimation of RLME 

recurrence are described in Section 5.3.3. 

The earthquake occurrence model in the ninth node of the logic tree expresses the approach that 

is used to model the temporal occurrence of earthquakes. Two alternative models are considered, 

depending on the availability of data for the RLME source of interest. A Poisson model assumes 

that earthquakes occur in a temporally random way that is defined simply by a mean recurrence 

rate without regard to the time elapsed since the last earthquake. The Poisson model is the most 

commonly used in PSHA because of the minimal number of parameters that must be 

constrained. An alternative model is the renewal model (strictly, a Brownian passage time, or 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-22

BPT, model is used [see Section 5.3.3.2]), which requires information not only on the mean 

recurrence rate, but also on the aperiodicity factor (alpha) and the time elapsed since the most 

recent earthquake. The model is based on a strain accumulation and release physical model that 

is most applicable to a fault source. To be compatible with common PSHA models, the resulting 

recurrence rates for both the Poisson and renewal models are expressed as equivalent annual 

frequencies, as shown in the last node of the RLME source logic tree. 

4.2.3 Mmax Zones Logic Tree 

As implied by the name, the Mmax zones model considers possible subdivisions of the CEUS 

based on considerations of Mmax. As discussed in Section 5.2, two approaches to estimating 

Mmax are used in the CEUS SSC Project: 

The Bayesian approach (Johnston et al., 1994), in which prior distributions are based on 

statistical analyses of tectonically analogous domains to the CEUS worldwide, and likelihood 

functions are derived from the number and size of earthquakes that occur within the seismic 

source of interest. 

The Kijko (2004) approach, in which the statistics of observed earthquakes within the source 

of interest are used to estimate Mmax. 

The two approaches are similar in the use of observed seismicity data within the source of 

interest, but they differ in the use of a prior distribution in the Bayesian approach. For the CEUS 

SSC Project, the global database of tectonically analogous earthquakes was updated from the 

Johnston et al. (1994) study and the prior distributions from that study were reassessed. As 

discussed in Section 5.2, the statistics do not strongly define the prior distributions. This means 

that there are no unique tectonic characteristics that strongly correlate with maximum earthquake 

size. Past studies using the database have suggested that a difference exists between sources 

having Paleozoic and younger extension and those that do not. However, the analysis conducted 

for this project does not support that view, but suggests that the only potentially significant 

difference is between sources having Mesozoic and younger extension and those that do not. 

Based on the analyses conducted for Mmax, two alternative models define the first branch of the 

Mmax zones logic tree (Figure 4.2.3-1): a branch that represents the entire CEUS SSC study 

region by a single prior distribution, and a branch that calls for the separation of Mesozoic and 

younger extended regions from those that do not display such evidence. The available evidence 

and statistical analyses of the global SCR database (Section 5.2) carried out as part of the CEUS 

SSC Project suggests that the separation into Mesozoic and younger sources is significant, but 

only marginally so. Therefore, the approach that uses the separation is preferred (0.6) over the 

approach that does not recognize a separation (0.4), although the preference is not large, given 

the marginal statistical significance. 

The second node of the Mmax zones logic tree, which applies only to the Mesozoic and younger 

separation branch, considers the uncertainty in the location of the boundary between Mesozoic 

and younger regions and those that do not show evidence of such extension. As discussed in 

Section 6.2, there is stronger technical support for the ―narrow‖ interpretation in the available 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-23

data than the ―wide‖ interpretation.Two alternative locations are considered, with higher weight 

(0.8) given to the narrow interpretation than the wide interpretation (0.2). These two alternative 

locations of the boundary are shown on Figures 4.2.3-2 and 4.2.3-3. 

The third node addresses the issue of the weight assigned to various magnitudes in the estimation 

of seismicity parameters for the seismic source zones. The three alternatives, Cases A, B, and E 

are discussed in Section 5.3.2.2.1, along with the bases for the weights assigned to the 

alternatives. 

The remaining assessments of the logic tree are a function of the region that is being 

characterized, which is either the entire study region, the Mesozoic extended-wide, the Mesozoic 

extended-narrow, or the non-Mesozoic extended regions. 

Similar to the RLME sources, the next assessments in the logic tree are related to the 

characteristics of future earthquake ruptures. The first assessment is seismogenic crustal 

thickness, which controls the downdip extent of ruptures, and the second is rupture orientation 

and boundary characteristics. Given the large extent of the regions of interest in the Mmax zones 

model, the characteristics of future ruptures are those given in the ―default‖ set of characteristics 

for the entire study region (see Section 5.4). 

The next level of the logic tree addresses the approach used for assessing seismicity rates and 

their spatial distribution. Allowing both the a-value and the b-value to vary spatially is the 

selected approach. Seismicity parameters are estimated for 1⁄4° × 1⁄4° cells using an update of the 

approach developed in EPRI-SOG. 

The ―degree of smoothing‖ level of the logic tree addresses the degree of smoothing applied in 

the seismicity parameter estimation in each source region. An ―objective‖ approach is used to 

select the degree of smoothing, as discussed in Section 5.3.2.4. 

The next level of the logic tree addresses the seismicity parameter epistemic uncertainty. The 

seismicity parameter distributions for the ―variable a and b‖ approach are represented by eight 

alternative spatial distributions developed by simulation from the fitted parameter distributions 

(Section 5.3.2.5). 

The final level of the logic tree addresses the uncertainty in the maximum magnitude for each 

region. This assessment includes uncertainty in the basic approach to estimating Mmax as well 

as uncertainties with a given approach. The two alternative approaches estimating Mmax are the 

Bayesian approach developed in Johnston et al. (1994) with updated prior distributions 

developed in this project, and the Kijko (2004) approach that uses the numbers and magnitudes 

of observed earthquakes directly without a prior distribution. As discussed in Section 5.2.1.3, the 

relative weights applied to the two approaches are source-specific and region-specific and are 

related directly to the p-value derived from the Kijko approach. Given the Bayesian approach, 

two prior distributions are considered, depending on the assessment in the first node of the logic 

tree. If the region is not subdivided (the ―no‖ branch on the first node), then a single composite 

prior distribution is used. If a separation is made between Mesozoic and younger extension and 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-24

non-Mesozoic extension, then the appropriate prior distributions for those regions are used for 

the Mmax estimates. 

4.2.4 Seismotectonic Zones Branch 

The seismotectonic zones identified for the CEUS SSC model are listed in Table 4.2.4-1. The 

logic tree for the seismotectonic zones branch of the master logic tree is shown on Figure 

4.2.4-1, and the maps of the seismotectonic zones are shown on Figures 4.2.4-2 through 4.2.4-5. 

Following the ―seismotectonic zones‖ branch of the master logic tree, the first assessment is the 

uncertainty in the western boundary of the Paleozoic Extended Crust seismotectonic zone. The 

two alternatives are the narrow interpretation (0.8) and the wide interpretation (0.2). As 

discussed in Section 7.3.4, there is significantly more technical support for the location of the 

boundary in the narrow case. 

The second node of the logic tree addresses the uncertainty in the eastern extent of the Reelfoot 

Rift zone—whether or not it includes the Rough Creek Graben. These two logic tree branches 

lead to the four alternative seismotectonic zonation configurations shown on Figures 4.2.4-2 

through 4.2.4-5. The discussion of this assessment and the associated weights is given in Section 

7.3.6.3.

The third node of the logic tree represents the uncertainty in the issue of the weight assigned to 

various magnitudes in estimating seismicity parameters for the seismotectonic zones. The 

assessment is the same as that given in the Mmax zones branch and is discussed in Section 

5.3.2.2.1 

The next element of the tree (which is not a node but a listing) identifies the various 

seismotectonic zones included in the CEUS SSC model, which are given in Table 4.1.3-1.

Similar to the RLME sources, the next assessments in the logic tree are related to the 

characteristics of future earthquake ruptures. The first assessment is seismogenic crustal 

thickness, which controls the downdip extent of ruptures, and the second is rupture orientation 

and boundary characteristics. The characteristics of future ruptures are discussed in the ―default‖ 

set of characteristics for the entire study region (see Section 5.4); each seismotectonic zone is 

assigned a set of characteristics based on the applicable data specific to that zone. 

The next level of the logic tree addresses the approach used for assessing seismicity rates and 

their spatial distribution. Allowing both the a-value and the b-value to vary spatially is the 

selected approach. Seismicity parameters are estimated for 1⁄4° × 1⁄4° cells using an update of the 

approach developed in EPRI-SOG. 

The ―degree of smoothing‖ level of the logic tree addresses the degree of smoothing applied in 

the seismicity parameter estimation in each seismotectonic zone. An ―objective‖ approach is 

used to select the degree of smoothing, as discussed in Section 5.3.2.4. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-25

The next level of the logic tree addresses the seismicity parameter epistemic uncertainty. The 

seismicity parameter distributions for the ―variable a and b‖ approach are represented by eight 

alternative spatial distributions developed by simulation from the fitted parameter distributions 

(Section 5.3.2.5). 

The final level of the logic tree addresses the uncertainty in the maximum magnitude for each 

seismotectonic zone. This assessment includes uncertainty in the basic approach to estimating 

Mmax as well as uncertainties for a given approach. The two alternative approaches estimating 

Mmax are the Bayesian approach developed by Johnston et al. (1994) with updated prior 

distributions developed in this project, and the Kijko (2004) approach that uses the numbers and 

magnitudes of observed earthquakes directly without a prior distribution. As discussed in Section 

5.2, the relative weights applied to the two approaches are source-specific and region-specific 

and are related directly to the p-value derived from the Kijko approach. Given the Bayesian 

approach, two options are available regarding prior distributions: a ―composite‖ prior that is 

based on the entire SCR data set, or two priors that are based on Mesozoic or younger extension 

and non-Mesozoic or younger extension. As discussed in Section 5.2, the relative weight 

assigned to the composite distribution is 0.4 and the relative weight of the two-prior option is 

0.6. These relative weights are assigned to each seismotectonic source, but given the two-prior 

option, a source-specific assessment must be made as to whether the zone lies within a Mesozoic 

or younger extended region. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-26

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)
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-27

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) 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-28

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. 

Indicators of a Potential

Seismic Source

Usefulness 

of Indicator 

in Defining 

Seismic 

Sources

5 = High

1 = Low Data to Address Indicator

Relative 

Usefulness 

of Data in 

Addressing

Indicator

5 = High

1 = Low

Notes: 

Source 

Aspect

(Temporal, 

Spatial)

Paleoseismic indicators of M > 5 

earthquakes

5

Paleoliquefaction evidence 4

Temporal, 

spatial Quaternary faulting 5

Quaternary deformation 3

High strain rates in contemporary tectonic 

setting 4

Tectonic geodetic strain data 4 Temporal, 

perhaps 

Geologic indicators of recent strain (e.g., Quaternary) 5 spatial

Variations in stress/strain orientations 3 Tectonic geodetic strain data 3 Spatial

Zones of weakness, including both crustal 

and mantle (including hotspot tracks and 

lithospheric upwelling)

1

Tectonic geodetic strain data/modeling 1

Spatial

Geophysical evidence of mantle anomalies (e.g., 

tomography, heat flow, concentration of heatproducing elements)

3

Consideration of rheology based on rock 

types/petrology 2

Geologic mapping 3

Evidence for recent and/or repeated 

reactivation of preexisting structures

(Note: General types of structures should 

be identified with a focus on those that 

may contain faults of sufficient dimension 

(see below) (see below) (see below) (see below)
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-29

Indicators of a Potential

Seismic Source

Usefulness 

of Indicator 

in Defining 

Seismic 

Sources

5 = High

1 = Low Data to Address Indicator

Relative 

Usefulness 

of Data in 

Addressing

Indicator

5 = High

1 = Low

Notes: 

Source 

Aspect

(Temporal, 

Spatial)

to cause M > 5 earthquakes.)

(1) Cratons 1

Geologic mapping 2

Spatial

Potential field geophysics (magnetic, gravity) 2

Historical and instrumental seismicity 2

Deep crustal seismic profiles 3

Compilations of historical analogues 2

(2) Extended Margins—and age 

(Mesozoic and younger) 1

Geologic mapping 2

Spatial

Potential field geophysics (magnetic, gravity) 2

Historical and instrumental seismicity 2

Deep crustal seismic profiles 3

Compilations of historical analogues 2

(3) Rifted Margins—and age (Mesozoic 

and younger) 2

Geologic mapping 2

Spatial

Potential field geophysics (magnetic, gravity) 2

Historical and instrumental seismicity 2

Deep crustal seismic profiles 3

Compilations of historical analogues 2

(4) Rift Basins 2

Geologic mapping 2

Spatial

Potential field geophysics (magnetic, gravity) 2
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-30

Indicators of a Potential

Seismic Source

Usefulness 

of Indicator 

in Defining 

Seismic 

Sources

5 = High

1 = Low Data to Address Indicator

Relative 

Usefulness 

of Data in 

Addressing

Indicator

5 = High

1 = Low

Notes: 

Source 

Aspect

(Temporal, 

Spatial)

Historical and instrumental seismicity 2

Deep crustal seismic profiles 3

Compilations of historical analogues 2

(5) Failed Rift (Paleozoic and younger) 1

Geologic mapping 2

Spatial

Potential field geophysics (magnetic, gravity) 2

Historical and instrumental seismicity 2

Deep crustal seismic profiles 3

Compilations of historical analogues 2

Cold strong crust 1

Heat flow 2

Spatial Geophysical modeling of mantle processes (e.g., 

tomography) 3

Geologic evidence for potential zones of 

stress concentration/amplification 2–3

Analysis of instrumental seismicity data (depths, focal 

mechanisms) 2

Spatial Consideration of rheological contrasts based on 

geologic mapping and modeling (mafic plutons, 

intersecting faults)

2

Orientation of structures relative to 

underlying stress field (either favorable or 

unfavorable)

2

Analysis of instrumental seismicity data (depths, focal 

mechanisms) 2

Spatial

Geologic mapping and geophysical interpretations of 

structures at depth 2
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-31

Indicators of a Potential

Seismic Source

Usefulness 

of Indicator 

in Defining 

Seismic 

Sources

5 = High

1 = Low Data to Address Indicator

Relative 

Usefulness 

of Data in 

Addressing

Indicator

5 = High

1 = Low

Notes: 

Source 

Aspect

(Temporal, 

Spatial)

Local loading mechanisms (as stress 

concentrators) 1

Geologic mapping 2

Spatial Detailed topographic analysis 2

Isostatic analyses (sediment load/denudation, glacial 

forebulge, or rebound) 3

Evidence of geologically recent fault 

displacement 5

Mapped fault with historical rupture 5

Spatial, 

temporal

Mapped Quaternary fault at surface 5

Mapped localized Quaternary deformation, inferred 

fault at depth 4

High-resolution seismic reflection or borehole 

evidence for fault, especially in young units 3

Fault having significant dimensions 1

Geophysical evidence (e.g., seismic reflection) of 

fault at depth 3

Spatial

Map of pre-Quaternary faults 3

Concentrated zone of observed seismicity 4

Well-located instrumental seismicity 5

Spatial, 

Temporal

Fault(s) mapped at surface or subsurface in proximity 

to seismicity; alignments parallel to structure 3

Historical seismicity 3

Focal mechanisms/stress orientation 2

Rapid lateral changes in 

structures/tectonic features/observed 

seismicity

3–4

Historical and instrumental seismicity showing 

changes in spatial distribution/concentration/density 

of seismicity

3 Spatial
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-32

Indicators of a Potential

Seismic Source

Usefulness 

of Indicator 

in Defining 

Seismic 

Sources

5 = High

1 = Low Data to Address Indicator

Relative 

Usefulness 

of Data in 

Addressing

Indicator

5 = High

1 = Low

Notes: 

Source 

Aspect

(Temporal, 

Spatial)

Geologic/tectonic maps showing regions of 

genetically related tectonic history; similar structural 

styles

3

Geophysical maps showing changes in crustal 

thickness or crustal composition 3

Regions of different geophysical signature 3

Stress indicators showing changes in regional 

stresses (e.g., compressional to tensional; orientation 

of horizontal stress directions)

2

Changes in regional physiography (e.g., fall line) 2

Regional or local strain energy buildup 

following larger (M > 7) earthquakes (e.g., 

New Madrid earthquakes trigger 

earthquakes to the north)

Note: The occurrence of the M > 7 earthquake would 

define the unique seismic source; current temporal 

methods do not account for triggering of adjacent 

earthquakes.

Temporal

Stress shadows following large 

earthquakes

Note: Occurrence of large earthquakes would be 

considered in defining seismic source; real-time 

model would be needed to account for timedependent temporal behavior; this indicator has more 

applicability for modeling of stress interactions among 

faults in WUS.

Spatial, 

temporal

Regional variations in expected Mmax or 

recurrence (background zones)

Note: These are applicable criteria, but they are 

based on a derivative product (Mmax or recurrence) 

and not data per se.

Spatial, 

temporal

1. Each indicator is assumed to be known with certainty. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-33

2. It is assumed that high-quality data exist of the type identified. 

3. Could be accounted for using spatial smoothing, thus not requiring a source boundary. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-34

Table 4.1.2-4 

Example of Data Evaluation Table for the Illinois Basin–Extended Basement Zone (IBEB) 

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

Note: Only a portion of the table is shown as an example. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-35

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 

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 degrees of 

counterclockwise rotation (160–150 Ma). This was followed by a further 20

degrees 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:
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-36

Citation Title Description and Relevance to SSC

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.

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. 

Note: Only a portion of the table is shown as an example.
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-37

Table 4.1.3-1 

Criteria Used to Define the Seismotectonic Zones and Mmax Zones 

Zone

Criteria Used for Defining Source Zone2

Earthquake

Recurrence Rate Mmax

Future Earthquake Characteristics

Style of 

Faulting

Rupture 

Orientation

Seismogenic 

Depth

Seismotectonic Zones

Atlantic Highly Extended Crust (AHEX) X X

Extended Continental Crust–Atlantic Margin (ECC-AM) X X

Extended Continental Crust–Gulf Coast (ECC-GC) X X X

Gulf Coast Highly Extended Crust (GHEX) X

Great Meteor Hotspot (GMH) X X X X X

Illinois Basin Extended Basement (IBEB) X X X

Midcontinent-Craton (MidC-A, B, C, D) X X

Northern Appalachian (NAP) X X X

Oklahoma Aulacogen (OKA) X X

Paleozoic Extended Crust (PEZ-N, PEZ-W) X

Reelfoot Rift (RR, RR-RCG) X X X X

St. Lawrence Rift (SLR) X X X X

Mmax Zones

Mesozoic-and-Younger Extension (MESE) X

Non-Mesozoic-and-Younger Extension (NMESE) X

 

2

 The criteria that have been used to define the seismic source zones are indicated with an ―X.‖ Note that none of the seismic source zones are defined based on 

the criterion of the probability of activity. However, this criterion was used to define the RLME fault sources. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-38

Table 4.2.2-1 

RLME Sources 

Source Alternatives Report Section

Charlevoix Charlevoix 6.1.1

Charleston

Charleston—local

Charleston—narrow 6.1.2

Charleston—regional

Cheraw Fault

Cheraw fault

6.1.3

Cheraw fault—extended

Meers Fault

Meers fault—Quaternary

Meers fault—extended 6.1.4

Oklahoma Aulacogen

Reelfoot Rift Central Fault 

System–New Madrid North

New Madrid North—short

New Madrid North—extended

6.1.5 Reelfoot Rift Central Fault 

System–New Madrid South

New Madrid South: Blytheville fault zone

New Madrid South: Bootheel lineament

Reelfoot Rift Central Fault 

System–Reelfoot Thrust

Reelfoot thrust—short

Reelfoot thrust—extended

Reelfoot Rift–Eastern Rift Margin

Eastern rift margin—north

6.1.6

Eastern rift margin—south/Crittenden 

County

Eastern rift margin—south/river (fault) 

picks

Reelfoot Rift–Marianna Marianna 6.1.7

Reelfoot Rift–Commerce Fault 

Zone Commerce fault zone 6.1.8

Wabash Valley Wabash Valley 6.1.9
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-39

Table 4.2.4-1 

Seismotectonic Zones

Zone Acronym Seismotectonic Source Zone

AHEX Atlantic Highly Extended Crust

ECC-AM Extended Continental Crust—Atlantic Margin

ECC-GC Extended Continental Crust—Gulf Coast

GHEX Gulf Coast Highly Extended Crust

GMH Great Meteor Hotspot

IBEB Illinois Basin Extended Basement

MidC-A, B, C, D Midcontinent-Craton (various geometries depending on PEZ 

and RR geometries)

NAP Northern Appalachian

OKA Oklahoma Aulacogen

PEZ-N and PEZ-W Paleozoic Extended Crust narrow and Paleozoic Extended 

Crust wide

RR and RR-RCG Reelfoot Rift, Reelfoot Rift with Rough Creek Graben

SLR St. Lawrence Rift, including the Ottawa and Saguenay grabens
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-40

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. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-41

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
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-42

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
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-43

Figure 4.2.2-1 

Example of a logic tree for RLME sources. Shown is the tree for the Marianna RLME source. 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-44

Figure 4.2.2-2 

Map showing RLME sources, some with alternative source geometries (discussed in Section 6.1).
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-45

Figure 4.2.3-1 

Logic tree for the Mmax zones branch of the master logic tree 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-46

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.
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-47

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.
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-48

Figure 4.2.4-1(a) 

Logic tree for the seismotectonic zones branch of the master logic tree 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-49

Figure 4.2.4-1(b) 

Logic tree for the seismotectonic zones branch of the master logic tree 
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-50

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)
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-51

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)
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-52

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)
Chapter 4 

Conceptual Seismic Source Characterization Framework 

4-53

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)

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. 1

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 1: Chapters 1 to 4

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