Advancing Geodesy in the U.S. Midcontinent: Workshop 

Report

By Michael W. Hamburger, Oliver S. Boyd, Eric Calais, Nancy E. King, and Seth A. Stein

Open-File Report 2014–1169

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014 

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit 

http://www.usgs.gov or call 1–888–ASK–USGS

For an overview of USGS information products, including maps, imagery, and publications,

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Suggested citation: 

Hamburger, M.W., Boyd, O.S., Calais, Eric, King, N.E., and Stein, S.A., 2014, Advancing geodesy in the U.S. 

Midcontinent—Workshop report: U.S. Geological Survey Open-File Report 2014–1169, 22 p., 

http://dx.doi.org/10.3133/ofr20141169. 

ISSN 2331-1258 (online)

Any use of trade, firm, or product names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Although this information product, for the most part, is in the public domain, it also may contain

copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be 

secured from the copyright owner. 
iii

Contents

Executive Summary....................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 2

Background and Motivation ........................................................................................................................................... 2

Geodetic Methods ......................................................................................................................................................... 4

Global Positioning System......................................................................................................................................... 5

Interferometric Synthetic Aperture Radar................................................................................................................... 5

Light Detection and Ranging...................................................................................................................................... 5

Anticipated Contribution to USGS Strategic Planning.................................................................................................... 6

The 2011 Norwood Workshop ....................................................................................................................................... 7

The 2012 Evanston Workshop ...................................................................................................................................... 8

Research and Modeling................................................................................................................................................. 9

Geodetic Research Targets and Network Design.......................................................................................................... 9

Proposed Network Design............................................................................................................................................10

Geodetic Data Analysis ................................................................................................................................................13

Long-Term Plan: Plate Interior Observatory .................................................................................................................13

Acknowledgments ........................................................................................................................................................13

References Cited..........................................................................................................................................................14

Appendix 1: List of Workshop Participants ...................................................................................................................19

Appendix 2: Workshop Agenda ....................................................................................................................................20

Figure

Figure 1. Proposed development of midcontinent geodetic networks..................................................................... 12
iv

List of Abbreviations and Acronyms

CEUS Central and Eastern United States

CGPS Continuous Global Positioning System 

CORS Continuously Operating Reference Stations

CUS Central United States

FAA Federal Aviation Administration

FEMA Federal Emergency Management Agency

GAMA Geodetic Array Studies for Mid America 

GPS Global Positioning System

InSAR Interferometric Synthetic Aperture Radar

lidar Light Detection and Ranging 

NGS National Geodetic Survey

NMSZ New Madrid Seismic Zone

NOAA National Oceanic and Atmospheric Administration

NWS National Weather Service

PBO Plate Boundary Observatory

PIO Plate Interior Observatory 

UCERF Uniform California Earthquake Rupture Forecast Model 

UNVACO University NAVSTAR Consortium 
1 

Advancing Geodesy in the U.S. Midcontinent: Workshop 

Report

By Michael W. Hamburger, Oliver S. Boyd, Eric Calais, Nancy E. King, and Seth A. Stein

Executive Summary 

The workshop on “Advancing Geodesy in the U.S. Midcontinent” was held from October 31 to 

November 1, 2012, at Northwestern University in Evanston, Illinois. The workshop included 28 

participants from academia, government, and private-sector organizations that are involved in research 

on geodesy and earthquake hazards in the seismically active areas of the U.S. midcontinent (the region 

of relatively undeformed crust roughly between the Great Plains and Appalachian Mountains). The 

workshop was intended to provide guidance to the U.S. Geological Survey’s (USGS) internal and 

external Earthquake Hazards research programs in the U.S. midcontinent. The 2012 workshop was 

developed as a follow-up to the “Workshop on New Madrid Geodesy and Understanding Intraplate 

Earthquakes,” held in Norwood, Massachusetts, in March 2011. The goal of the 2012 workshop was to 

provide specific recommendations to the USGS on priorities for infrastructure and research investments 

related to geodesy in the U.S. midcontinent. Participants were asked to share current research and 

proposals for future research plans, focusing on the following basic and applied science issues:

• Fundamental processes guiding earthquake generation in the New Madrid Seismic Zone and 

surrounding regions, 

• Application of geodetic measurements to assessment of earthquake hazards, 

• Optimization of geodetic monitoring networks to constrain crustal deformation, and 

• Critical approaches in data analysis, modeling, and interpretation of geodetic data. 

Among the outcomes of the workshop was a consensus recommendation for expanding the 

density, quality, and duration of geodetic observations in the New Madrid Seismic Zone and 

surrounding regions of active intraplate seismicity in order to better understand processes driving 

seismogenesis. The recommendations focus on short- and intermediate-term expansion of continuous 

Global Positioning System (GPS) monitoring of crustal deformation in the midcontinent region, 

developed in three principal approaches (fig. 1): 

Development of a roughly 10-station local continuous GPS (CGPS) network densified/extended across 

the New Madrid Seismic Zone

Expansion of the regional CGPS network by roughly 40 stations covering the seismically active areas 

outside the New Madrid Seismic Zone, including 

a. Expansion of geodetic observations into the Wabash Valley/Illinois Basin Seismic Zone, 

b. Expansion of geodetic observations into the southern New Madrid region, in and around 

Marianna, Arkansas, and

c. Development of a sparse regional network designed to capture regional deformation 

rates. 
2 

d. Development of a midcontinent-wide backbone network of highly reliable CGPS 

stations, drawing from existing Continuously Operating Reference Stations (CORS) and 

Plate Boundary Observatory (PBO) sites. This can be done at relatively low cost by 

leveraging existing efforts.

In addition to these short- and intermediate-term recommendations, the group recommends 

development of a long-term strategic plan directed toward a “Plate Interior Observatory” (PIO) that 

comprises over 100 stations and will be extended to include active deformation from the eastern 

seaboard to the Great Plains. This plan will leverage support from major funding agencies in 

collaboration with other earth science consortia (for example, EarthScope, UNAVCO). The networks 

may make use of existing CGPS networks (for example, navigation, transportation, or geodetic control 

networks) and may include transformation of existing campaign geodetic sites to CGPS observation, or 

development of new CGPS networks. Given the low rates of intraplate deformation in the central United 

States (CUS), a commitment to a long duration of observation will be required to ensure reliable 

detection of geodetic signals. Although the focus of the “Advancing Geodesy in the U.S. Midcontinent” 

workshop was primarily on GPS as a tool for measuring crustal deformation, this report briefly reviews 

other tools and their potential applicability to geodetic problems in the U.S. midcontinent. 

Introduction

This report summarizes discussions that took place at a community workshop on “Advancing 

Geodesy in the U.S. Midcontinent” that was held October 31 to November 1, 2012, at Northwestern 

University in Evanston, Illinois (Ill.). The workshop, which included 28 participants from academia, 

government, and private sector organizations involved in research on geodesy and earthquake hazards in 

the seismically active areas of the U.S. midcontinent, was convened to provide guidance to the U.S. 

Geological Survey’s (USGS) Earthquake Hazards Program for both its internal and external research 

programs on earthquake hazards in the U.S. midcontinent. This report summarizes those discussions and 

presents some specific recommendations for research priorities for research on active crustal 

deformation in the U.S. midcontinent. As a working definition, we take the “U.S. midcontinent” to 

include the relatively undeformed segment of the North American craton extending from the 

Appalachians to the Great Plains and from the Ouachita orogen to the Great Lakes. 

Background and Motivation

The August 2011 M5.8 Mineral, Virginia earthquake, which shook large areas of the east coast 

and damaged structures in Washington, D.C. (including the Washington Monument), demonstrated how 

little is known about the causes of earthquakes in the central and eastern United States and the hazards 

they pose. At present, no comprehensive model exists to explain such earthquakes. Taken at its simplest, 

the issue is how forces that we largely do not understand cause motion on faults that have not been 

identified and create hazards that we cannot easily assess. The earthquakes along these structures can be 

large. The best known in modern times, the 1929 M7.2 earthquake on the Grand Banks of 

Newfoundland, caused a large landslide of thick continental slope sediments, which cut trans-Atlantic 

telegraph cables and generated a tsunami. The resulting 28 fatalities include most of Canada’s known 

deaths from earthquakes. Other notable events include the 1933 M7.3 Baffin Bay earthquake, the 1755 

M~6 Cape Ann, Massachusetts (Mass.) earthquake, the 1811–1812 New Madrid sequence of three 

M~7+ earthquakes, and the 1886 M~7 Charleston, South Carolina earthquake. 

We do not know whether the presently active zones are active for extended periods of time but 

lack clear geomorphic expression, or simply represent loci of activity that migrate (Stein and others,
3 

2009) with individual faults active for short intervals and dormant for long ones (Newman and others, 

1999; Crone and others, 2003). This question makes it particularly difficult to assess the extent to which 

the instrumental record for continents indicates the location of future damaging earthquakes. On one 

hand, the locations of past small earthquakes are good predictors of the locations of future ones (Kafka, 

2007). On the other hand, some models predict that aftershock sequences for large continental 

earthquakes should continue for hundreds of years (Stein and Liu, 2009). Thus, some present 

concentrations of seismicity may be “echoes” of large prehistoric earthquakes. However, in the case of 

the 1811–1812 New Madrid earthquakes, the study by Page and Hough (2014) argues that this is not the 

case.

Geodesy is a natural approach to exploring these issues. Because it provides an independent 

measurement of the accumulation of tectonic strain in continental interiors, geodesy may provide direct 

evidence of the basic cause of intracontinental earthquakes. The feasibility of capturing tectonic strain in 

continental interiors is illustrated by recent studies using GPS data to map the effects of glacial isostatic 

adjustment (GIA) (Calais and others, 2006; Sella and others, 2007). The results show that GIA is the 

predominant deformation process in eastern North America. GPS can resolve even the small motions 

south of the “hinge line” (approximately at the latitude of the Great Lakes) separating uplift to the north 

from subsidence to the south. This result also implies that a good knowledge of the GIA signal is 

necessary in order to extract tectonic deformation from a geodetic velocity field that reflects the 

combination of both GIA and tectonic deformation. Therefore, the search for regional tectonic signals in 

the eastern United States requires measurements over a much broader region in order to separate them 

from the GIA signal. 

Although there is general consensus about the recent history of large earthquakes in the U.S. 

midcontinent, there remains considerable debate about the level of future earthquake hazards facing 

residents of the CUS. The question of earthquake hazard relies on a fundamental understanding of the 

processes, observations, and implications of intraplate deformation in North America’s continental 

interior (for example, Newman and others, 1999; Petersen and others, 2014; Calais and Stein, 2009; 

Frankel and others, 2012). Critical issues that have fueled the debate include the question of the size 

(Johnston, 1996; Hough and others, 2000; Holzer and others, 2012) and return periods of earthquakes in 

the New Madrid Seismic Zone (NMSZ) (Newman and others, 1999; Tuttle and others, 2002; Calais and 

Stein, 2009), as well as the potential for large earthquakes in other areas of the CUS (Kelson and Swan, 

1990; Braile and others, 1982, Crone and others, 1997). Earthquake-magnitude estimates for the 

earthquakes in the 1811–1812 New Madrid sequence range from less than M7.0 to greater than M8.0; 

recurrence estimates range from as little as 160 to as many as 10,000 or more years (yr). Paleoseismic 

data from earthquake zones outside the NMSZ, such as the Wabash Valley Seismic Zone, record large 

past earthquakes (Obermeier and others, 1991; Munson and others, 1997), yet the size and recurrence 

intervals remain poorly constrained. These uncertainties have a profound effect on seismic-hazard

estimates (Petersen and others, 2014) and in turn affect the costs associated with adopting differing 

levels of earthquake-resistant construction and the potential loss of life and extent of economic hardship 

(Stein, 2010). 

Because the driving force of crustal seismicity—at least at plate boundaries—is the 

accumulation of tectonic strain along active faults, observations of geodetic strain are critical to 

understanding earthquake-generation processes and their manifestation in the earthquake record. 

Unfortunately, both the historical and paleoseismic record of seismicity remain insufficient to 

reasonably constrain fault slip rates and earthquake potential in many seismically active zones. For these 

reasons, we have seen considerable growth in the use of geodetic methods for improving earthquakehazard estimation. In other areas where geodetic techniques have been applied, zones of high crustal 
4 

strain rates are known to be associated with significant seismic energy release. Conversely, areas of low 

strain tend to have lower seismic potential (for example, Savage, 1983). Where the surface strain can be 

used to map strain on locked fault zones, these geodetic measurements can be specifically tied to 

earthquake strain accumulation and potential for future earthquakes (for example, Bürgmann and others, 

2000b; Fialko, 2006). However, the specific application of strain measurements to probabilistic seismichazard assessment remains controversial, largely because of the variability in quality and distribution of 

geodetic data and because its contribution to hazard estimation relies on specific mechanical models that 

remain poorly constrained. 

The USGS Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) (Field and 

others, 2009) and its successor, UCERF 3 (Working Group on California Earthquake Probabilities, 

2011) are now explicitly incorporating geodetically determined strain rates to constrain earthquakerecurrence intervals in the seismically and tectonically active plate boundary zone of California. The 

models generally rely on kinematic inversion of observed GPS velocities to infer both fault-related and 

off-fault strain accumulation. This approach is beginning to extend to other parts of the country, for 

instance in the Intermontane West and Wasatch fault regions of Utah and Nevada (M. Petersen, USGS, 

oral commun., 2013). 

The introduction of high-precision geodetic techniques to the CUS promises a powerful, 

independent observational tool to help address issues of earthquake hazard in the region. Yet, while 

geodetic observations and modeling are now widely used in plate-boundary environments, they have 

seen only limited application to intraplate environments, where strain rates are low and where, even 

under ideal conditions, signals may be exceeded by measurement errors for long periods of observation 

(Calais and Stein, 2009). 

Historically, application of geodetic methods to earthquake hazards in the CUS has been 

particularly problematic. Because the signals are relatively small, the geodetic noise (largely associated 

with near-surface noise and poor monumentation) relatively large, and the station spacing sparse, the 

history of geodetic analysis has been rife with conflicting conclusions. Initial estimates of high strain 

rate (albeit with large uncertainty) in the New Madrid Zone (Liu and others, 1992) were not supported 

by subsequent measurements (Weber and others, 1998; Newman and others, 1999). Measured regional 

surface strains have been exceptionally low, on the order of 10-9 per yr or less (Calais and Stein, 2009). 

More recent analysis of the same data, however, suggests that strains local to some areas within the 

NMSZ are an order of magnitude higher than seen regionally (Frankel and others, 2012). A decade of 

campaign-based GPS measurements in the Illinois Basin region (Galgana and Hamburger, 2010) 

suggests marginally significant strain rates, on the order of 1–2 × 10−9 yr −1

. 

Such low strains, coupled with moderate amounts of noise, require some combination of dense 

arrays, stable monumentation, and long periods of observation. Recent seismic studies of the NMSZ

indicate the existence of a pronounced mantle low-velocity zone (Bedle and van der Lee, 2006; Zhang 

and others, 2009; Pollitz and Mooney, 2013), suggesting a volume that is weaker than the surrounding 

mantle and thus may concentrate stresses. Hence, even low strains may be focused within the NMSZ, 

making the measurement of these strains an even higher priority. 

Geodetic Methods

The workshops described in this report addressed a number of issues critical to the success of 

geodetic research in the U.S. midcontinent. Although the focus of the discussions at the Norwood and 

Evanston workshops was primarily on GPS measurements and their implications for earthquake hazard 

research, we briefly review the predominant geodetic methods and their applicability to midcontinent 

geodynamic research.
5 

Global Positioning System 

For the past three decades, the GPS system has provided a reliable, low-cost approach for highprecision measurements of crustal deformation (for example, Dixon, 1991; Segall and Davis, 1997). The 

GPS system provides high-precision estimates of 3D surface site positions within a stable global 

reference frame. Because GPS relies on satellite-generated, microwave-frequency electromagnetic 

signals, it can be used under virtually any meteorological conditions and does not require inter-visibility 

of neighboring geodetic sites. The relatively low cost and high precision make it ideally suited for 

geodynamic studies of crustal strain. Measurement networks can be designed to maximize the number 

and spatial distribution of GPS stations (typically using episodic measurements at campaign-based 

networks of geodetic benchmarks) or to maximize GPS precision (typically at sparser networks of 

continuously operated GPS receivers). In some cases, GPS networks can balance precision and network 

density using a hybrid “semi-permanent” deployment model (Blewitt and others, 2009). Measurement 

precision depends strongly on the deployment strategy, but under ideal conditions, site positions can be 

estimated to an accuracy of 1–2 millimeters (mm) (horizontal), corresponding to velocity uncertainties 

(depending on network observation duration and monumentation) of fractions of a millimeter per year. 

Interferometric Synthetic Aperture Radar

Although less precise than GPS measurements, Interferometric Synthetic Aperture Radar 

(InSAR) provides a spatially continuous estimate of the surface deformation field (for example, 

Bürgmann and others, 2000a). InSAR has been widely used as one of a number of applications for noninvasive study of earthquake, volcanic, and anthropogenic surface deformation (Snieder and others, 

2007). Although it has traditionally been less applicable in areas of anthropogenic land use, a variety of 

new techniques, such as persistent scatterer analysis, allows high-precision measurements to be obtained 

even in areas of highly disrupted cultural land use. Because the precision of InSAR is nearly an order of 

magnitude lower than that of GPS, however, it is not widely applicable to the low signal-to-noise 

environment of intraplate tectonism. However, it has found significant value in analysis of coseismic 

surface deformation associated with moderate or large earthquakes in intraplate zones (for example, 

Schmidt and Bürgmann, 2007), and thus could have significant potential for future earthquakes in the 

U.S. midcontinent. InSAR may also be useful for separating deformation associated with regional 

tectonic processes from those associated with anthropogenic sources, such as groundwater withdrawal 

(Snieder and others, 2007). 

Light Detection and Ranging

Light Detection and Ranging (lidar) encompasses a suite of powerful new remote-sensing 

techniques that permit retrieval of surface topography, and in some cases, crustal deformation, even in 

the presence of significant vegetation. Both ground-based and airborne-based lidar methods have been 

applied to geodynamic research. Of particular interest is the ability to numerically remove vegetation 

from imagery to produce “bare-earth” ground models. It has found widespread application to the study 

of active fault zones (for example, Meigs, 2013), particularly in plate boundary environments (for 

example, Borsa and Minster, 2012; Salisbury and others, 2012; Duffy and others, 2013). Following 

identification of active faults in urban areas of the Pacific Northwest (for example, Haugerud and others, 

2001), similar applications have been developed in the CUS. The USGS funded and coordinated the 

acquisition of roughly 722 square kilometers of lidar data and derivative bare-earth ground models to 

support earthquake hazard studies in the NMSZ. The study area includes coverage of the Commerce 

Geophysical lineament, Crowley’s Ridge, and features in and near the St. Francis River 
6 

(http://opentopo.sdsc.edu/gridsphere). These data are in preliminary stages of analysis, and have not yet 

found their way into the scientific literature. 

Anticipated Contribution to USGS Strategic Planning 

The USGS Earthquake Hazards Program promotes research to improve our understanding of 

earthquake hazards. This can occur through internal research programs, and through funding of external 

research grants and cooperative monitoring networks. For example, the USGS Earthquake Hazards 

Program provided most of the support for the Geodetic Array Studies for Mid America GPS network in 

the NMSZ and has supported campaign-based GPS observations elsewhere in the U.S. midcontinent 

(for example, Illinois Basin geodetic network [Hamburger and others, 2002; Galgana and Hamburger, 

2010]). 

Each year, the USGS Earthquake Hazards Program requests research proposals to advance our 

state of understanding in specific geographic areas, such as the central and eastern United States

(CEUS), and in disciplines including earthquake effects and earthquake physics. Current significant 

research problems and recommendations by the research community form the basis for USGS strategic 

planning regarding earthquake hazards. For example, two themes for CEUS research that were a direct 

result of the 2011 and 2012 workshops are: 

• Proposals to improve the quality of geodetic data and networks in the CUS are encouraged, 

particularly if they are the outgrowth of a community-based plan for the New Madrid region and 

the CUS. These studies may include the development of a comprehensive set of precise geodetic 

measurements that could provide: (1) baseline measurements prior to any future earthquake in 

the region, (2) re-measurements of existing networks (for example, in New Madrid, Wabash 

Valley, and Charleston), (3) improvement of monumentation for existing networks (for example, 

CORS, National Geodetic Survey [NGS], and the Federal Aviation Administration [FAA]), and 

(4) continuous monitoring of data quality at existing GPS networks. 

• Development of synoptic, physical models of long-term deformation in intraplate areas including 

both onshore and offshore areas of the CEUS and the NMSZ are encouraged. Proposals may 

seek to address topics such as the cause of large earthquakes, regional migration of seismicity 

and earthquake clustering as suggested by paleoseismological results, and interaction of known 

geological structures within the tectonic stress field. Coordination with EarthScope research 

projects is particularly encouraged.

We envision that results from the 2012 workshop will lead to research and recommendations that 

will further shape USGS priorities with respect to geodetic monitoring and modeling, especially as they 

pertain to seismic hazards in the CEUS. Although the workshop was primarily focused on scientific 

targets of current and future midcontinent geodetic research, we recognize that there are many 

stakeholders, both within and outside the scientific community, for whom this research may make 

critical contributions. This includes other government agencies that directly or indirectly make use of 

geodetic data (National Geodetic Survey, Federal Aviation Administration, National Oceanic and 

Atmospheric Administration [NOAA], National Weather Service [NWS]), public- and private-sector 

organizations that make use of geodetic data for surveying (for example, government and commercial 

survey community), and organizations that will benefit from scientific results of geodetic research (for 

example, FEMA, state and local emergency management organizations, regional planning 

organizations, and insurance and engineering industry). We anticipate an increase in opportunities for 

research partnerships, funding opportunities, and public-private partnerships that can enhance future 

geodetic research.
7 

The 2011 Norwood Workshop

The controversy surrounding the question of New Madrid earthquake hazard and the potential 

for new approaches through geodetic data analysis led the scientific community to organize for a review 

of existing geodetic data and its meaning for continued New Madrid seismicity. In March 2011, a 

geodesy workshop, organized by Oliver Boyd, Eric Calais, John Langbein, Harold Magistrale, Seth 

Stein, and Mark Zoback, and funded by FM Global, took place in Norwood, Mass. A group of 26 

researchers met for a one-day workshop to discuss our current state of knowledge regarding earthquake 

return periods, seismic hazard, active tectonics, and geodetic infrastructure and models in the NMSZ. 

Specifically, the group addressed the challenge of reconciling present-day geodetic measurements with

paleoseismically derived earthquake rates. The workshop was summarized in an EOS article (Boyd and 

Magistrale, 2011) and a USGS Open-File Report (Boyd and others, 2013). 

Among the observations summarized at the workshop were: 

• There is a fundamental disagreement between paleoseismic estimates for recurrence of New 

Madrid earthquakes (roughly 500 yr, Tuttle and others [2002]) and estimates based on regional 

strain-rate accumulation, which imply a return period of at least 10,000 yr for M7 events with 2 

meters of average slip (Calais and Stein, 2009). 

• The relative motions between most of the 55 GPS station pairs in the NMSZ are less than 

roughly 0.2 mm/yr and that the uncertainties are probably on the order of 0.2 mm/yr (Calais and 

Stein, 2009). 

• Two baselines within the NMSZ show potentially significant relative motions of roughly 0.3–0.4 

mm/yr. There remains disagreement as to whether these signals reflect a physical process 

associated with strain accumulation on New Madrid faults (for example, Frankel and others, 

2012), or aberrant measurements that represent part of the statistically expected range of 

geodetic noise.

• There appears to be no difference in the orientation of principal stresses in the NMSZ with that 

of the surrounding region (Hurd and Zoback, 2012). Thus, the stress state in this region results 

from the same large-scale geologic processes stressing the central and eastern United States. 

• Active faults in the NMSZ appear to have frictional strength similar to faults throughout the 

region, and limited available heat flow data do not show the NMSZ to be warmer (and thus 

weaker) than its surroundings (McKenna and others, 2007). 

• There is evidence for marginally significant geodetic strain accumulation in the northern 

periphery of the NMSZ, including the southern Illinois Basin and the Wabash Valley seismic 

zone (Galgana and Hamburger, 2010). 

Models that relate low long-term strain to the occurrence of earthquakes in the NMSZ were 

presented and discussed and include those that invoke mantle convection (Forte and others, 2007), 

glacial isostatic adjustment (Grollimund and Zoback, 2001), crustal heterogeneity (Kenner and Segall,

2000; Pollitz and others, 2001), and erosion following retreat of the glaciers (Calais and others, 2010). 

These processes may be responsible for the continued triggering of, rather than restoring the energy 

needed for, repeated large earthquakes. Furthermore, some researchers hypothesize that the next large 

earthquakes could occur on other faults in the region based on observations of earthquake migration in 

China and models of stress evolution following the 1811–1812 earthquakes (Li and others, 2005; Liu 

and others, 2011). 

Although there remains considerable uncertainty as to the ultimate driving force of these 

intraplate earthquakes, it is reasonable to expect that processes responsible for strain accumulation prior 

to 1811–1812 are still active today. Attendees concurred that the current density of geodetic monitoring 
8 

is inadequate to address the apparent discrepancy between models inferred from geodetic and geologic 

data. There was general agreement on the need for densification of geodetic monitoring in key locations 

by a combination of continuous and less-expensive periodic campaign GPS deployments. Specific 

configurations were discussed by John Langbein in the 2013 Open-File Report detailing the 2011 

workshop (Boyd and others, 2013). In conjunction with improved geodetic monitoring, attendees argued 

that new physically based models of intraplate seismogenesis and data that constrain intraplate 

earthquake generation and recurrence are needed.

Although the Norwood workshop was highly successful in identifying critical scientific and 

technical issues, the short duration of the meeting proved to be insufficient to lead to consensus 

recommendations on implementation of geodetic infrastructure in the midcontinent region. It was this 

goal that led to the continuation workshop effort in Evanston, Ill., in October 2012. 

The 2012 Evanston Workshop

The U.S. Geological Survey provided support for a 2012 follow-up workshop, with a goal of 

providing guidance to the USGS National Earthquake Hazards Reduction Program for both its internal 

and external research programs on earthquake hazards in the Midwest. The workshop, entitled 

“Advancing Geodesy in the U.S. Midcontinent” was held October 31 to November 1, 2012, at 

Northwestern University in Evanston, Ill. The workshop was organized by Michael Hamburger (Indiana 

University), Oliver Boyd (USGS), Eric Calais (Purdue University), Nancy King (USGS), and Seth Stein 

(Northwestern University). The workshop included 28 participants from academia, government, and 

private-sector organizations involved in geodesy and earthquake hazards in the seismically active areas 

of the U.S. midcontinent. A list of participants is included in Appendix 1 and the workshop agenda in 

Appendix 2. 

Workshop participants were asked to share current research and proposals for future research 

plans, focusing on the following basic and applied science themes: 

• Fundamental processes guiding earthquake generation in New Madrid and surrounding regions, 

• Application of geodetic measurements to assessment of earthquake hazards, 

• Optimization of geodetic monitoring networks to constrain crustal deformation, and 

• Critical approaches in data analysis, modeling, and interpretation of geodetic data. 

The workshop was centered around four focused sessions addressing interconnected scientific 

themes associated with midcontinent geodesy and deformation; participants were asked to address a 

series of core scientific questions, as summarized below:

Session 1: Structural and Neotectonic Context

• What do we know about midcontinent geological evolution and structure that is 

relevant to current deformation in the midcontinent? 

• How does our knowledge about paleoearthquakes in the New Madrid and broader 

region inform models of crustal deformation? 

Session 2: Models for Intraplate Seismogenesis

• What drives midcontinent deformation and earthquakes? What do mechanical models 

tell us about intraplate deformation and earthquakes in the New Madrid and broader 

region? What additional constraints are needed?

Session 3: Geodetic infrastructure and observations 

• What do we know about spatial and temporal patterns of deformation in the 

midcontinent? What is needed to make progress?

Session 4: Geodetic Applications to Hazard Estimation
9 

• How do current data on deformation in the New Madrid and broader region inform 

earthquake hazard assessment and what additional information is needed to improve 

that assessment?

The structure of the workshop was designed to encourage short, provocative presentations and 

maximize time for informal group discussion of scientific and technical issues. Breakout sessions were 

focused on recommendations for geodetic infrastructure to address the scientific issues raised in the 

introductory sessions. 

Research and Modeling

The workshop addressed a number of issues critical to the success of geodetic research in the 

U.S. midcontinent. Research to better understand the link between processes driving seismogenesis and 

observed crustal deformation is needed to help guide the acquisition of data. Several synoptic models 

exist to explain ongoing earthquakes in the NMSZ (for example Kenner and Segall, 2000; Grollimund 

and Zoback, 2001; Pollitz and others, 2001; Forte and others, 2007; Calais and others, 2010), but 

additional research is needed to relate crustal deformation resulting from these models and observed 

motions. 

Geodetic Research Targets and Network Design 

The workshop also examined a number of issues critical to the success of geodetic experiments 

in the U.S. midcontinent. The focus of the discussions was on approaches to maximize the scientific 

value of future investments in GPS infrastructure and research. Given the primary emphasis on 

measurement of tectonic deformation as it relates to earthquake potential, two critical concerns are: (1) 

selection of geodetic measurement sites where one expects the greatest probability of measuring a 

tectonic deformation signal and (2) choosing a benchmark location and configuration that maximizes 

geodetic signal and minimizes noise. Tectonic deformation can result from several processes occurring 

within and beneath the crust. Forces acting from the sides and below, such as slab pull, ridge push, and 

mantle drag, can lead to broad continent-wide deformation (Zoback and others, 1989), which can be 

modulated by heterogeneities of crustal strength and heterogeneities in boundary forces. Viscous forces 

within the upper mantle, for example, caused by the sinking of remnant subducted lithosphere (Forte 

and others, 2007), can generate broad regional deformation signals on the Earth’s surface. Unstable 

density anomalies within the lithosphere, under appropriate conditions (Pollitz and others, 2001), can 

lead to relatively localized deformation at the Earth’s surface. Earth-surface processes, such as the 

melting of glaciers (Grollimund and Zoback, 2001) and rapid erosion of sediment (Calais and others, 

2010) can cause regional and relatively localized crustal strain that can persist for thousands of years. 

Lastly, the stressing of preexisting basement faults, formed as a result of late Precambrian and early 

Paleozoic tectonic activity, may be manifested as a complex of conjugate normal, reverse, and strikeslip structures at depth (Van Arsdale and Cupples, 2013). These faults may creep at depth yielding a 

measureable strain rate signal at the surface (Frankel and others, 2012). When the faults fail in an 

earthquake, the surrounding rock is stressed and will relax over time (Li and others, 2005). This leads to 

measureable surface strain.

Considering these geodynamic processes, the workshop examined a number of scenarios in 

which to place stations to maximize the success of geodetic experiments. Stations could be placed: (1) 

across boundaries of significant crustal heterogeneity and within regions of weak crust, (2) in broad 

transects across regions of proposed significant lateral deformation due to mantle-driven deformation, 
10

(3) in arrays that capture proposed deformation signals from Earth surface processes, and (4) across 

active faults.

Attendees concurred that the current density of high-quality stations in the NMSZ is inadequate 

to properly estimate motions on finite sections of faults that may be creeping at depth (see “Proposed 

Network Design” section). Other regions recognized as sites of prehistoric earthquakes, for example, 

Wabash Valley, southern New Madrid (near Marianna, Arkansas), have few or no geodetic stations of 

appropriate quality with which to analyze surface strain. Attendees suggested that CGPS stations could 

be added by adopting stations from CORS and upgrading the quality of the geodetic monumentation. 

Ideally, stations would be located on bedrock, but this is not possible within the Mississippi embayment. 

With evidence that high-frequency geodetic noise represents a combination of uncorrelated (white) and 

correlated (flicker and random-walk) noise (for example, Langbein and Johnson, 1997; Mao and others, 

1999), a combination of increased station density and extended observation periods is needed to yield 

more reliable estimates of long-term site velocities and spatial variations in surface strain (Boyd and 

others, 2013). 

Network design may also be informed by models of crustal heterogeneity based on newly 

available geophysical data sets. EarthScope’s USArray is providing an unprecedented volume of 

seismic data with which to image the lithosphere beneath the United States. For example, this data set 

could be used to estimate the depth of the Moho and lithosphere-asthenosphere boundaries from 

receiver functions (for example, Kumar and others, 2012) and seismic wavespeed and attenuation from 

tomographic methods (for example, Buehler and Shearer, 2012). In conjunction with existing 

aeromagnetic, gravity, and magnetotelluric data sets, a relatively detailed model of lithospheric strength 

could result. Given boundary forces, a model of expected crustal strain could then be developed, and, if 

warranted, stations placed to test and refine this model. Improved modeling of local sources of 

loading—including the role of deglaciation (Grollimund and Zoback, 2001), intracrustal heterogeneity 

(Kenner and Segall, 2000; Pollitz and others, 2001), erosion of surficial sediment (Calais and others, 

2010), and shorter term hydrological loading (for example, Costain and Bollinger, 2010)—are critically 

needed to inform the design of geodetic networks. Additional CGPS sites in the region are also of 

interest to study these loading processes. These observations can, in turn, be used to infer rheological 

properties of the lithosphere in the region. 

Proposed Network Design

The primary outcome of the workshop was a consensus recommendation for expanding geodetic 

observations in the New Madrid and surrounding regions of active intraplate seismogenesis. The 

recommendations focus on expansion of CGPS monitoring of crustal deformation in the midcontinent 

region, developed in three principal approaches (fig. 1): 

1. Development of a roughly 10-station CGPS network densified/extended across the NMSZ.

2. Expansion of the regional CGPS network by roughly 40 continuous stations expanded to 

seismically active areas outside the NMSZ, including: 

• Expansion of geodetic observations into the Wabash Valley/Illinois Basin seismic 

zone, 

• Expansion of geodetic observations into the southern New Madrid region, and 

• Development of a sparse regional network designed to capture regional deformation 

rates. 
11

3. Development of a midcontinent-wide backbone network of highly reliable CGPS stations, 

drawing from existing CORS and PBO sites, and augmenting with new sites where necessary. 

This can be done at very low cost by leveraging existing efforts.

In addition to these short- and intermediate-term recommendations, the group recommends 

collaborative development of a long-term strategic plan directed toward a PIO that comprises over 100 

stations and will be extended to include active deformation from the Eastern Seaboard to the Great 

Plains, leveraging support from major funding agencies in collaboration with other earth science 

consortia (for example, EarthScope and UNAVCO). 

High priority was given to expansion of the current New Madrid GPS network (Approach 1 

above). Additional, high-quality CGPS sites are needed to help confirm or refute the presence of 

significant geodetic signals associated with strain accumulation along the New Madrid fault system.

Particular attention will need to be paid to monumentation to minimize near-surface geodetic noise. The 

networks may also benefit by maximizing use of existing CGPS networks (for example, navigation, 

transportation, or geodetic control networks), upgrading existing CGPS networks, and transforming 

existing geodetic monuments to CGPS observation. 

An expansion of GPS networks should be designed to address earthquake potential in areas 

adjacent to the NMSZ. The primary focus of this expansion would be to provide improved geodetic 

coverage of areas of current seismic activity (for example, Wabash Valley Seismic Zone), areas of 

proposed recurrent basement faulting (for example, Reelfoot South Fault Zone [Csontos and others,

2008; Van Arsdale and Cupples, 2013), Meeman-Shelby Fault Zone (Odum and others, 2010; Hao and 

others, 2013]), and areas with demonstrated history of paleoseismic events (for example, Wabash Valley 

Seismic Zone [Munson and others, 1997], Marianna, Arkansas zone [Tuttle and others, 2006], and 

Saline River Fault Zone [Cox and others, 2010]). Because the records of both basement faulting and 

paleoseismicity are incomplete, the group also recommended inclusion of a sparse, regional network to 

capture background regional strain and possible localized strain outside of known target areas. The 

group recommended, as a lower priority, continued monitoring of existing campaign GPS networks (for 

example, New Madrid and Illinois Basin networks) and exploration of ‘hybrid’ networks that 

incorporate the benefits of high-quality monumentation and the flexibility and low-cost of episodic or 

‘semi-permanent’ GPS observations (for example, Blewitt and others, 2009). Improvements in analysis 

of stability of geodetic monumentation in areas of thick unconsolidated sediment (for example, Mattioli 

and Jansma, 2007) are critically needed to advance the reliability of geodetic measurements in the New 

Madrid region. Taking advantage of the expertise attained through the PBO project, a partnership with 

the UNAVCO consortium could play a key role in ensuring quality in installation, status monitoring, 

data integrity, and data processing. An example of a possible configuration of an expanded midcontinent 

GPS network, including a 10-station New Madrid network and a 40-station regional GPS network, is 

shown in figure 1. 
12

Figure 1. Proposed development of midcontinent geodetic networks. Solid blue and red triangles show existing 

continuous GPS (CGPS) stations operated as part of the Continually Operating Reference Stations (CORS) 

and Geodetic Array Studies for Mid America (GAMA) networks, respectively. Red and yellow stars show 

generalized distribution of proposed sites for CGPS in Phase I (New Madrid densification) and Phase II 

(regional strain monitoring) respectively. Ellipses show generalized areas proposed for network expansion: red 

= New Madrid region; blue = Wabash Valley Seismic Zone; yellow = southern New Madrid extension; green = 

regional strain monitoring network. Base-map is 3-arc second topography available from the USGS at 

http://ned.usgs.gov/index.html. 
13

Geodetic Data Analysis

An essential component of any future expansion of geodetic networks in the U.S. midcontinent 

is a plan for geodetic data archiving and analysis. Because the signal of intraplate deformation is so 

small, the introduction of systematic errors in GPS data processing could have significant potential 

impact on the results and interpretation (for example, Stein, 2007). For that reason, it would be 

beneficial to subject all midcontinent geodetic data to multiple streams of analysis. Large-scale dataprocessing centers offer the benefit of consistent data processing, in the same reference frame, and 

potentially provide daily time series, short-term kinematic results, and average station velocities in 

numerical and graphical form. Among the data-analysis centers that could potentially provide this 

service are the USGS Earthquake Hazards Program (http://earthquake.usgs.gov/monitoring/gps/), the 

UNAVCO PBO data processing facility (http://pbo.unavco.org/data/gps), the Scripps Orbit and 

Permanent Array Center (http://sopac.ucsd.edu/processing/), and the Nevada Geodetic Laboratory 

(http://geodesy.unr.edu/). Any of these network processing centers could be easily adapted to add new 

stations to the system and process them at minimal cost. In addition, it is important that a rigorous 

comparison of complementary data-analysis products be performed, with a thorough investigation of 

position time series, in order to reduce ambiguity in identifying the signals of tectonic origin. This postprocessing stage should benefit from solutions from the large-scale data-processing centers mentioned 

above as well as from solutions from individual investigators. The end product would be a verified, 

combined, velocity solution expressed in a well-defined geodetic frame.

Long-Term Plan: Plate Interior Observatory

A long-term strategy that was supported by participants at the Evanston Workshop is a goal to 

develop a CGPS PIO that comprises over 100 stations (comparable to the EarthScope PBO) which 

would provide the necessary infrastructure to study active deformation from the eastern seaboard to the 

Great Plains. Such an effort could leverage support from major funding agencies in collaboration with 

other earth science consortia (for example, EarthScope and UNAVCO) and NOAA/NGS. The resulting 

data would have much better resolution of the anticipated slow deformation than possible with present 

NOAA CORS sites. PIO and CORS data could be processed as part of the PBO data analysis, providing 

a publicly available, consistent velocity field. CORS and PBO sites will give insight into the quality of 

CORS data. As the GIA studies show, using careful quality control to reject poor data yields high 

quality velocity fields from the CORS data.

The velocity field, together with earthquake, geological, and geomorphological data (for 

example, Pazzaglia and others, 2010) would be analyzed using a new generation of tectonic models (for 

example, Ghosh and Holt, 2012) to constrain the dynamics of short- and long-term local and regional 

deformation processes. The practicality of doing so is shown by the fact that the GPS velocities are 

already being used to improve models of mantle viscosity (Peltier and Drummond, 2008), which 

controls the response to ice loads. We believe that such a large-scale effort is essential to provide both 

the spatial coverage and geodetic resolution necessary to resolve fundamental scientific problems 

associated with the generation of earthquakes in North America’s continental interior. 

Acknowledgments

We gratefully acknowledge the reviews of Bill Leith, Ed Nissen, and Rob Williams, and the 

constructive input from workshop participants. Indiana University Department of Geological Sciences 

and Northwestern University Department of Earth and Planetary Sciences provided various types of 
14

support that helped make this workshop a success. The workshop was funded by USGS Grant 

#G12AC20026.

References Cited

Bedle, Heather, and van der Lee, Suzan, 2006, Fossil flat-slab subduction beneath the Illinois Basin, 

USA: Tectonophysics, v. 424, p. 53–68. 

Blewitt, Goeffrey, Hammond, W.C., and Kreemer, Corné, 2009, Geodetic observation of contemporary 

deformation in the northern Walker Lane—1. Semipermanent GPS strategy: Geologic Society of

America Special Paper 447, p. 1–15. 

Borsa, A.A., and Minster, J.B., 2012, Rapid determination of near-fault earthquake deformation using 

differential LiDAR: Bulletin of the Seismological Society of America, v. 102, no. 4, p. 1,335–1,347, 

doi:/10.1785/0120110159. 

Boyd, O.S., and Magistrale, Harold, 2011, Studying geodesy and earthquake hazard in and around the 

New Madrid Seismic Zone—Meeting report: Eos Transactions American Geophysical Union, v. 92, 

no. 38, p. 317. 

Boyd, O.S., Calais, Eric, Langbein, John, Magistrale, Harold, Stein, S.A., and Zoback, Mark, 2013, 

Workshop on New Madrid geodesy and the challenges of understanding intraplate earthquakes: U.S. 

Geological Survey Open-File Report 2013–1004, 184 p. 

Braile, Larry, Hinze, W.J., Keller, G.R., and Lidiak, E.G., 1982, The northeastern extension of the New

Madrid Seismic Zone, in Investigations of the New Madrid, Missouri, Earthquake Region, McKeown,

F.A., and Pakiser, L.C., eds.: U.S. Geological Survey Professional Paper 1236, p. 175–184. 

Buehler, J.S., and Shearer, P.M., 2012, Localized imaging of the uppermost mantle with USArray Pn

data: Journal of Geophysical Research, v. 117, B09305, doi:10.1029/2012JB009433.

Bürgmann, Roland, Rosen, P.A., and Fielding, E.J., 2000a, Synthetic aperture radar interferometry to 

measure earth’s surface topography and its deformation: Annual Review of Earth and Planetary

Sciences, v. 28, p. 169–209. 

Bürgmann, Roland, Schmidt, Dominic, Nadeau, R.M., d’Alessio, M.A., Fielding, E.J., Manaker, D.M., 

McEvilly, T.V., and Murray, M.H., 2000b, Earthquake potential along the northern Hayward fault, 

California: Science, v. 289, no. 5482, p. 1,178–1,182. 

Calais, Eric, Han, J.Y., DeMets, Chris, and Nocquet, J.M., 2006, Deformation of the North American 

plate interior from a decade of continuous GPS measurements: Journal of Geophyical Research, 

v. 111, doi:10.1029/2005JB004253. 

Calais, Eric, and Stein, S.A., 2009, Time-variable deformation in the New Madrid Seismic Zone: 

Science, v. 323, no. 5920, p. 1,442–1,442. 

Calais, Eric, Freed, A.M., Arsdale, R.V. ,and Stein, S.A., 2010, Triggering of New Madrid seismicity by 

late-Pleistocene erosion: Nature, v. 466, p. 608–611. 

Costain, J.K., and Bollinger, G.A., 2010, Review—Research results in hydroseismicity from 1987 to 

2009: Bulletin of the Seismological Society of America, v. 100, p. 1,841–1,858. 

Cox, R.T., Gordon, Joshua, Forman, S.L., Brezina, Thomas, Negrau, Mircea, Hill, Arleen, Gardner, 

Christopher, and Machin, Sarah, 2010, Paleoseismic sand blows in north Louisiana and south 

Arkansas: Seismological Research Letters, v. 81, p. 1,032–1,047. 

Crone, A.J., Machette, M.N., Bradley, L-A., and Mahan, S.A., 1997, Late Quaternary surface faulting 

on the Cheraw fault, southeastern Colorado: U.S. Geological Survey Miscellaneous Geologic 

Investigations I-2591, 7 p. pamphlet, 1 plate. 
15

Crone, A.J., De Martini, P.M., Machette, M.N., Okumura, Koji, and Prescott, J.R. 2003, Paleoseismicity 

of two historically quiescent faults in Australia—Implications for fault behavior in stable continental 

regions: Bulletin of the Seismological Society of America, v. 93, p. 1,913–1,934. 

Csontos, Ryan, Van Arsdale, R., Cox, R.T., and Waldron, Brian, 2008, The Reelfoot Rift and its impact 

on Quaternary deformation in the central Mississippi River Valley: Geosphere, v. 4, p. 145–158. 

Dixon, T.H., 1991, An introduction to the global positioning system and some geological applications: 

Reviews of Geophysics, v. 29, no. 2, p. 249–276, doi:10.1029/91RG00152. 

Duffy, Brendan, Quigley, Mark, Barrell, D.J.A., Van Dissen, Russ, Stahl, Timothy, Leprince, Sébastien, 

McInnes, Craig, and Bilderback, Eric, 2013, Fault kinematics and surface deformation across a 

releasing bend during the 2010 MW7.1 Darfield, New Zealand, earthquake revealed by differential 

lidar and cadastral surveying: Geological Society of America Bulletin, v. 125, no. 3-4, p. 420–431, 

doi:10.1130/B30753.1. 

Fialko, Yuri, 2006, Interseismic strain accumulation and the earthquake potential on the southern San 

Andreas Fault system: Nature, v. 441, p. 968–971. 

Field, E.H., Dawson, T.E., Felzer, K.R., Frankel, A.D., Gupta, V., Jordan, T.H., Parsons, 

Thomas, Petersen, M.D., Stein, R.S., Weldon, R.J., Wills, C.J., 2009, Uniform California 

earthquake rupture forecast, version 2 (UCERF 2): Bulletin of the Seismological Society of 

America, v. 99, p. 2053–2107. 

Forte, A.M., Mitrovica, J.X., Moucha, Robert, Simmons, N.A., and Grand, S.P., 2007, Descent of the 

ancient Farallon slab drives localized mantle flow below the New Madrid Seismic Zone: Geophysical

Research Letters, v. 34, doi:10.1029/2006GL027895. 

Frankel, Art, Smalley, Robert, and Paul, John, 2012, Significant motions between GPS sites in the New 

Madrid region: Implications for seismic hazard: Bulletin of the Seismological Society of America, 

v. 102, p. 479–489. 

Galgana, G.A., and Hamburger, M.W., 2010, Geodetic observations of active intraplate crustal 

deformation in the Wabash Valley seismic zone and the southern Illinois Basin: Seismological 

Research Letters., v. 81, p. 699–714. 

Ghosh, Attreyee, and Holt, W.E., 2012, Plate motions and stresses from global dynamic models:

Science, v. 335, p. 839–843. 

Grollimund, Balz, and Zoback, M.D., 2001, Did deglaciation trigger intraplate seismicity in the New 

Madrid Seismic Zone?: Geology, v. 29, p. 175–178. 

Michael W.H., Vladimir Rybakov, Anthony Lowry, Bingming Shen-Tu, 2002, Preliminary Results 

from a GPS Geodetic Network in the Southern Illinois Basin: Seismological Research Letters., v. 73, 

p. 762–775. 

Hao, Yanjun, Magnani, M.B., McIntosh, Kirk, Waldron, Brian, and Guo, Lei, 2013, Quaternary 

deformation along the Meeman-Shelby fault, near Memphis, Tennessee imaged by high-resolution 

marine and land seismic reflection profiles: Tectonics, v. 32, p. 1–15. 

Haugerud, R.A., Weaver, C.S., and Harless, Jerry, 2001, Finding faults with LIDAR in the Puget 

Lowland: Seismological Research Letters, v. 72, no. 2, p. 253. 

Holzer, T.L., Noce, Thomas, and Bennett, M.J., 2012, Liquefaction evidence for large magnitudes of the 

1811–1812 New Madrid earthquakes [abstract]: Geological Society of America Absracts with 

Program, v. 44, no. 7, p. 291. 

Hough, S.E., Armbruster, J.G., Seeber, Leonardo, and Hough, J.F., 2000, On the Modified Mercalli 

intensities and magnitudes of the 1811–1812 New Madrid earthquakes: Journal of Geophysical

Research, v. 105, 23,839–23,864. 
16

Hurd, Owen, and Zoback, M.D., 2012, Regional stress orientations and slip compatibility of earthquake 

focal planes in the New Madrid Seismic Zone: Seismological Research Letters, v. 83, p. 672–679, 

doi:10.1785/0220110122 . 

Johnston, A.C., 1996, Seismic moment assessment of earthquakes in stable continental regions—III. 

New Madrid 1811–1812, Charleston 1886 and Lisbon 1755: Geophysical Journal International, v. 

126, p. 314–344. 

Kafka, Alan, 2007, Does seismicity delineate zones where future large earthquakes are likely to occur in 

intraplate environments?, in Continental intraplate earthquakes—Science, hazard, and policy issues, 

Stein, S., and Mazzotti, S., eds: Geological Society of America Special Paper 425, p. 35–48. 

Kelson, K.I., and Swan, F.H., 1990, Paleoseismic history of the Meers fault, southwestern Oklahoma, 

and implications for evaluations of earthquake hazards in the Central and Eastern United States, in 

Seventeenth water reactor safety information meeting, Weiss, A.J., ed.,: Proceedings of the U.S. 

Nuclear Regulatory Commission NUREG/CP-0105, v. 2, p. 341–365. 

Kenner, S.J., and Segall, Paul, 2000, A mechanical model for intraplate earthquakes—Application to the 

New Madrid Seismic Zone: Science, v. 289, p. 2,329–2,332. 

Kumar, Prakash, Kind, Rainer, Yuan, Xiaohui, and Mechie, James, 2012, 

USArray receiver function images of the lithosphere-asthenosphere boundary: Seismological

Research Letters, v. 83, p. 486–491, doi:10.1785/gssrl.83.3.486. 

Langbein, John, and Johnson, Hadley, 1997, Correlated errors in geodetic time series—Implications for

time-dependent deformation: Journal of Geophysical Research, v. 102, p. 591–603. 

Li, Qingsong, Liu, Mian, and Sandvol, Eric, 2005, Stress evolution following the 1811–1812 large

earthquakes in the New Madrid Seismic Zone: Geophysical Research Letters, v. 32, 

doi:10.1029/2004GL022133. 

Liu, Lanbo, Zoback, M.D., and Segall, Paul, 1992, Rapid intraplate strain accumulation in the New 

Madrid Seismic Zone: Science, v. 257, p. 1,666–1,669. 

Liu, Mian, Stein, S.A., and Wang, Hui, 2011, 2000 years of migrating earthquakes in North China—

How earthquakes in midcontinents differ from those at plate boundaries: Lithosphere, v. 3, p. 128–

132. 

Mao, Ailin, Harrison, C.G., and Dixon, T.H., 1999, Noise in GPS coordinate time series: Journal of 

Geophysical Research, v. 104, p. 2,797–2,816. 

Mattioli, G.S., and Jansma, P.E., 2007, Evaluation of monument stability and noise associated with 

campaign and continuous GPS geodesy in the New Madrid Seismic Zone and other areas of 

unconsolidated sediment: U.S. Geological Survey Final Technical Report, v. 2, p. 19, HQGR0107. 

McKenna, Jason, Stein, S.A., and Stein, C.A., 2007, Is the New Madrid Seismic Zone hotter and weaker 

than its surroundings?, in Continental intraplate earthquakes, Stein, S., and Mazzotti, S., eds.,: 

Boulder, Colo., Geological Society of America Special Paper 425, p. 167–175. 

Meigs, Andrew, 2013, Active tectonics and the lidar revolution: Lithosphere, v. 5, no. 2, p. 226–229, 

doi:10.1130/RF.L004.1. 

Munson, P.J., Obermeier, S.F., Munson, C.A., and Hajic, E.R., 1997, Liquefaction evidence for 

Holocene and latest Pleistocene seismicity in the southern halves of Indiana and Illinois—A 

preliminary overview: Seismological Research Letters, v. 68, p. 521–536. 

Newman, Andrew, Stein, S.A., Weber, John, Engeln, Joseph, Mao, Ailin, and Dixon, Timothy, 1999, 

Slow deformation and lower seismic hazard at the New Madrid Seismic Zone: Science, v. 284, p. 622. 

Obermeier, S.F., Bleuer, N.K., Munson, C.A., Munson, P.J., Martin, W.S., McWilliams, K.M., 

Tabaczynski, D.A., Odum, J.K., Rubin, E.M., and Eggert, D.L., 1991, Evidence of strong earthquake 
17

shaking in the lower Wabash Valley from prehistoric liquefaction features: Science, v. 251, 

p. 1,061–1,063. 

Odum, J.K., Stephenson, W.J., and Williams, R.A., 2010, Multisource, high-resolution seismicreflection imaging of Meeman-Shelby fault and a possible tectonic model for a Joiner Ridge–Manila 

High stepover structure in the upper Mississippi Embayment region: Seismological Research Letters, 

v. 81, p. 647–663. 

Page, Morgan, and Hough, Susan, 2014, The New Madrid Seismic Zone—Not dead yet: Science, 

v. 343, p. 762–764. 

Pazzaglia, Frank, Zeitler, P.K., Idleman, B.D., McKeon, R., Berti, Claudio, Enkelmann, E., Laucks, J., 

Ault, A., Elasmar, M., and Becker, T., 2010, Tectonics and topography of the Cenozoic Appalachians, 

in Tectonics of the Susquehanna Piedmont, Wise, D., and Fleeger, G., eds.: Lancaster, Penn., Field 

Conference of Pennsylvania Geologists, Guidebook for the Annual Field Conference of Pennsylvania 

Geologists, v. 75, p. 111–126. 

Peltier, W.R., and Drummond, Rosemarie, 2008, Rheological stratification of the lithosphere—A direct 

inference based upon the geodetically observed pattern of the glacial isostatic adjustment of the North 

American continent: Geophysical Research Letters, v. 35, doi:10.1029/2008GL034586. 

Petersen, Mark D., Moschetti, Morgan P., Powers, Peter M., Mueller, Charles S., Haller, Kathleen M., 

Frankel, Arthur D., Zeng, Yuehua, Rezaeian, Sanaz, Harmsen, Stephen C., Boyd, Oliver S., Field, 

Ned, Chen, Rui, Rukstales, Kenneth S., Luco, Nico, Wheeler, Russell L., Williams, Robert A., Olsen, 

Anna H., 2014, Documentation for the 2014 update of the United States national seismic hazard 

maps: U.S. Geological Survey Open-File Report 2014–1091, 243 p., 

http://pubs.usgs.gov/of/2014/1091/.

Pollitz, F.F., Kellogg, Louise, and Bürgmann, R., 2001, Sinking mafic body in a reactivated lower 

crust—A mechanism for stress concentration at the New Madrid Seismic Zone: Bulletin of the 

Seismological Society of America, v. 91, p. 1,882–1,897. 

Pollitz, F.F., and Mooney, W.D., 2013, Seismic structure of the Central US crust and shallow upper 

mantle—Uniqueness of the Reelfoot Rift: Earth and Planetary Science Letters, 

doi:10.1016/j.epsl.2013.05.042 

Salisbury, J.B., Rockwell, T.K., Middleton, T.J., and Hudnut, K.W., 2012, LiDAR and field 

observations of slip distribution for the most recent surface ruptures along the central San Jacinto 

Fault: Bulletin of the Seismological Society of America, v. 102, no. 2, p. 598–619, 

doi:10.1785/0120110068. 

Savage, J.C., 1983, Strain accumulation in western United States: Annual Review of Earth and 

Planetary Sciences, v. 11, p. 11–43. 

Schmidt, D.A., and Bürgmann, Roland, 2006, InSAR constraints on the source parameters of the 2001 

Bhuj earthquake: Geophysical Research Letters, v. 33, no. 2, doi:10.1029/2005GL025109. 

Segall, Paul, and Davis, J.L., 1997, GPS applications for geodynamics and earthquake studies: Annual 

Review of Earth and Planetary Sciences, v. 25, p. 301–336. 

Sella, Giovanni, Stein, S.A., Dixon, Timothy, Craymer, Michael, James, T.S., Mazzotti, Stephane, and 

Dokka, R.K., 2007, Observations of glacial isostatic adjustment in stable North America with GPS: 

Geophysical Research Letters, v. 34, doi:10.1029/2006GL027081. 

Snieder, Roel, Hubbard, Susan, Haney, Matthew, Bawden, Gerald, Hatchell, Paul, Revil, Andre, and 

DOE Geophysical Monitoring Working Group, 2007, Advanced noninvasive geophysical monitoring 

techniques: Annual Review of Earth and Planetary Sciences, v. 35, p. 653–683. 

doi:10.1146/annurev.earth.35.092006.145050 
18

Stein, S.A., 2007, New Madrid GPS—Much ado about nothing?: EOS Transactions American 

Geophysical Union, v. 88, no.5, p. 59.

Stein, S.A., 2010, Disaster deferred—How new science is changing our view of earthquake hazards in 

the Midwest: New York, Columbia University Press, 275 p. 

Stein, S.A., and Liu, Mian, 2009, Long aftershock sequences within continents and implications for 

earthquake hazard assessment: Nature, v. 462, p. 87–89. 

Stein, S.A., Liu, Mian, Calais, Eric, and Li, Qingsong, 2009, Midcontinent earthquakes as a complex 

system: Seismological Research Letters, v. 80, p. 551–553. 

Tuttle, M.P., Schweig, E.S., Sims, J.D., Lafferty, R.H., Wolf, L.W., and Haynes, M.L., 2002, The 

earthquake potential of the New Madrid Seismic Zone: Bulletin of the Seismological Society of 

America, v. 92, p. 2,080–2,089. 

Tuttle, M. P., Al-Shukri, Haydar, and Mahdi, Hanan, 2006, Very large earthquakes centered southwest 

of the New Madrid Seismic Zone 5,000–7,000 years ago: Seismological Research Letters, v. 77, p. 

755–770. 

Van Arsdale, Roy, and Cupples, William, 2013, Late Pliocene and Quaternary deformation of the 

Reelfoot Rift: Geosphere, v. 9, p. 1,819–1,831. 

Weber, John, Stein, S.A., and Engeln, Joseph, 1998, Estimation of strain accumulation in the New 

Madrid Seismic Zone from GPS geodesy: Tectonics, v. 17, p. 250–266. 

Working Group on California Earthquake Probabilities (WGCEP), 2011, The Uniform California 

Earthquake Rupture Forecast, version 3 (UCERF3) project plan: Working Group on California 

Earthquake Probabilities, accessed July, 28 2014, at http://www.wgcep.org.

Zhang, Qie, Sandvol, E., and Liu, Mian, 2009, Lithospheric velocity structure of the New Madrid 

Seismic Zone: A joint teleseismic and local P tomographic study: Geophysical Research Letters, 

v. 36, doi:10.1029/2009GL037687. 

Zoback, M.L., Zoback, M.D., Adams, J., Assumpcao, M., Bell, S., Bergman, E.A., Blumling, P., 

Brereton, N.R., Denham, D., Ding, J., Fuchs, K., Gay, N., Gregersen, S., Gupta, H.K., Gvishiani, A., 

Jacob, K., Klein, R., Knoll, P., Magee, M., Mercier, J. L., Muller, B.C., Paquin, C., Rajendran, K., 

Stephansson, O., Suarez, G., Suter, M., Udias, A., Xu, Z.H., Zhizhin, M., 1989, Global patterns of 

tectonic stress: Nature, v. 341, p. 291–298. ISSN 2331-1258

http://dx.doi.org/10.3133/ofr20141169
19

Appendix 1: List of Workshop Participants

Participant Name Institution

Michael Blanpied U.S. Geological Survey—Reston 

Oliver Boyd U.S. Geological Survey—Memphis

Eric Calais Purdue University 

Ksenia Dmitrieva Stanford University 

Michael Hamburger Indiana University 

Bill Hammond University of Nevada

Eric Hetland University of Michigan 

*William Holt Stony Brook University 

Susan Hough U.S. Geological Survey—Pasadena

Nancy King U.S. Geological Survey—Pasadena

John Langbein U.S. Geological Survey—Menlo Park

Mian Liu University of Missouri–Columbia 

Harold Magistrale FM Global 

Steve Marshak University of Illinois – Urbana-Champaign

*Stephane Mazzotti University of Montpelier

Jill McCarthy U.S. Geological Survey—Golden

Chuck Meertens UNAVCO Consortium

Miguel Merino Northwestern University

Walter Mooney U.S. Geological Survey—Menlo Park

Fred Pollitz U.S. Geological Survey—Menlo Park

John Puchakayala University of Memphis 

Paul Segall Stanford University 

*Giovanni Sella National Oceanic and Atmospheric Administration–

National Geodetic Survey

Bob Smalley University of Memphis 

Seth Stein Northwestern University

Roy Van Arsdale University of Memphis 

Rob Williams U.S. Geological Survey—Golden

Yuehua Zeng U.S. Geological Survey—Golden

*

Unable to participate due to weather-related travel interruption.
20

Appendix 2: Workshop Agenda

Advancing Geodesy in the U.S. Midcontinent 

October 31 – November 1, 2012 

Northwestern University, Evanston, Illinois

Workshop Agenda 

October 30

Afternoon/Evening: Participants arrive, check in at Orrington 

8:30 – 10:00 PM Informal Icebreaker Globe Café Den, 

Cash bar at Globe Café Orrington Hotel 

October 31

7:30 – 8:30 AM Continental Breakfast Norris Center, Room 202 

Meeting registration Northwestern Room 

8:30 AM Workshop begins Norris Center Room 202 

Northwestern Room 

8:30 – 8:45 AM Introduction: Meeting organization and goals 

• Welcome from organizing committee, USGS

• Review meeting agenda and logistics

• Large-scale goals of workshop 

8:45 – 9:15 Organizational Context 

• USGS goals for geodetic research and infrastructure (Blanpied/King) 

• Role of NSF in Midcontinent Geodesy Research (Chuck Estabrook) 

• Review of Boston workshop findings (Boyd) 

8:45 – 9:30 Session 1: Structural and Neotectonic Context

• What do we know about midcontinent geological evolution and structure 

that is relevant to current deformation in the midcontinent? 

• How does our knowledge about paleoearthquakes in the New Madrid and 

broader region inform models of crustal deformation? 

Introduction: Rob Williams

Steve Marshak - Basement Topography of the Midcontinent, USA: A Visual 

Signature of Fault-Related and Epeirogenic Crustal Displacement

Walter Mooney: Continental Intra-Plate Earthquakes: Correlation with 

Lithospheric Structure. 

Roy Van Arsdale: Structure and Paleoseismology of the New Madrid Seismic 

Zone 
21

Fred Pollitz: Mantle Origin for Stress Concentration at the New Madrid 

Seismic Zone?

Michael Hamburger: Could the next New Madrid earthquake be in the 

Wabash Valley Seismic Zone?

9:30 – 10:15 Discussion – Leaders: Miguel Merino, Rob Williams 

10:15 -10:30 Break

10:30 – 11:15 Session 2: Models for Intraplate Seismogenesis

• What drives midcontinent deformation and earthquakes? What do 

mechanical models tell us about intraplate deformation and earthquakes 

in the New Madrid and broader region? What additional constraints are 

needed?

Introduction: Paul Segall

1

William Holt: Intraplate stress and strain in the North American plate 

inferred from global dynamic models.

Susan Hough: Moment accrual versus moment release: the NMSZ and 

Beyond. 

Stephane Mazzotti: Can we constrain maximum strain rates and seismicity 

rates in midcontinent US from rheology models? 

Eric Hetland: Reloading of non-plate boundary faults: the potential role of 

stress reservoirs.

Oliver Boyd: Relaxation and creep in the New Madrid Seismic Zone. 

11:15 – 12:00 Discussion – Leaders: Main Liu, Paul Segall 

12:00 – 1:30 Lunch Norris Center Room 202 

Northwestern Room 

1:30 – 2:15 Session 3: Geodetic infrastructure and observations

• What do we know about spatial and temporal patterns of deformation in the 

midcontinent? What is needed to make progress? 

Introduction: Eric Calais

Chuck Meertens: EarthScope Geodesy in the midcontinent and eastern U.S. 

1

Giovanni Sella: CORS Network and its contribution to assessing the stability 

of the North American Plate. 

Bob Smalley: Examining deformation of plate interiors with GPS: Application 

to the Central US.

Bill Hammond: Using GPS Geodesy to Assess Very Low Strain Rates in the 

North American Mid-Continent. 

Ksenia Dmitrieva: Network Noise Estimator (NENE) for time-dependent 

noise in GPS velocities in Intraplate regions. 

 

1

Giovanni Sella and Bill Holt were unable to attend the meeting due to weather-related delays (Hurricane Sandy). 

These presentations were not given but are retained in the agenda to show that they were considered in the 

workshop planning. 
22

John Langbein: Improving geodetic infrastructure to test models of 

deformation in the New Madrid Seismic Zone 

2:15 – 3:00 Discussion – Leaders: Nancy King, Eric Calais 

3:00 – 3:15 Break

3:15 – 3:45 Session 4: Geodetic Applications to Hazard Estimation 

• How does current data on deformation in the New Madrid and broader 

region inform earthquake hazard assessment and what additional 

information is needed to improve that assessment? 

Introduction: Michael Blanpied

Yuehua Zeng: Western US GPS observation and application to the national 

seismic hazard mapping project.

Main Liu: Roaming earthquakes with long aftershock sequences in China 

highlight earthquake hazard in mid–continents. 

Seth Stein: Using GPS to improve New Madrid hazard mitigation and tectonic 

investigations.

3:45 – 4:30 Discussion – Leaders: Harold Magistrate, Michael Blanpied

4:30-5:00 Summary Discussion 

6:30 – 8:00 Dinner Dave’s Italian Kitchen

 

November 1

7:30 – 8:30 AM Continental Breakfast Norris Center Room 202 

Northwestern Room 

8:30 – 8:45 AM Morning Logistics 

Organization of breakout session 

8:45 – 10:00 AM Breakout sessions Room 103 Chicago Room 

• Geodetic targets: location and density Room 207 Rock Room 

• Infrastructure recommendations: 

Continuous/campaign GPS 

• Analysis/Modeling

• Hazard Assessment applications

10:00 -10:15 Break

10:15 – 11:15 Report from breakout groups/discussion

11:15 – 12:00 Closing discussion/recommendations

12:00 – 1:00 Box lunch; participants depart

1:00 – 2:30 Organizing committee drafts outline for report