Research geophysicist with the U.S. Geological Survey studying various aspects of seismic hazard including ground motions and earthquake probabilities
I began with the National Seismic Hazards Modeling Project in Golden, CO in 2004 studying time-dependent seismic hazard in Alaska and producing a seismic hazard analysis of Afghanistan, the latter being done in conjunction with other U.S. Agency for International Development’s reconstruction efforts in Afghanistan. I moved to Memphis, TN in 2007 to focus on earthquake hazards in the central and eastern United States (CEUS) and returned to Golden in 2013 to work on issues related to earthquake hazards across the conterminous United States, specifically those related to earthquake ground motions as part of the Ground Motion Project. Much of my past research has centered on several aspects of earthquake hazards including time-dependent earthquake probabilities, declustering of foreshocks and aftershocks, and parameters related to earthquake sources. I helped update the CEUS source models for the 2008 and 2014 updates of the National Seismic Hazard Model (NSHM) and helped to incorporate basin models in the western United States for the 2018 update of the NSHM. More recently, I have been working on ground motion site amplification along the Atlantic and Gulf Coastal Plains and building a geology-based National Crustal Model for earthquake hazard studies. Prior to joining the Survey, I obtained my Ph.D. in Geophysics from the University of Colorado at Boulder where I performed laboratory experiments of seismic wave attenuation in artificial glass cracks and glass bead cylinders, produced and interpreted tomographic models of seismic wave attenuation and velocity beneath the western United States, and studied receiver functions in New Zealand.
Professional Experience
2004–present—Research Geophysicist, USGS
2004—Research Assistant—University of Colorado at Boulder
2000–2004—Graduate Research Assistant—University of Colorado at Boulder
1998–2000—Geophysicist, Western Geophysical
1996–1997—Technician, Geo-Insight
1995–1997—Graduate Research Assistant—University of Colorado at Boulder
1993–1995—Lab Research Assistant—University of Colorado at Boulder
Education and Certifications
2004—Ph.D. Geophysics, University of Colorado at Boulder
1997—M.S. Geology, University of Colorado at Boulder
1995—B.A. Geology, Emphasis in Geophysics, University of Colorado at Boulder
Affiliations and Memberships*
1995–present—American Geophysical Union, Member
2000–2015—Geological Society of America, Member
2004–present—Earthquake Engineering Research Institute, Associate Member
2004–present—Seismological Society of America, Member
2007–present—Eastern Section (ES) of the Seismological Society of America, Member
ES Secretary, 2011–2013
ES Vice President, 2013–2015
ES President, 2015–2017
ES Past President, 2017–2019
Science and Products
Data release for the lower seismogenic depth model of western U.S. earthquakes
A model of the lower seismogenic depth distribution of earthquakes in the western United States was developed to support models for seismic hazard assessment that will be included in the 2023 USGS National Seismic Hazard Model. This data release presents a recalibration using the hypocentral depths of events M>1 from the Advanced National Seismic System Comprehensive Earthquake Catalog from 198
Database of Central and Eastern North American Seismic Velocity Structure
The "Database of Central and Eastern North American Seismic Velocity Structure" involves the compilation of one-dimensional (1D) seismic velocity-depth functions for central and eastern North America (CENA). The present database is an update of the report by Chulick and Mooney (2002) who present a compilation and statistical analysis of 1D seismic velocity-depth functions for North Ameri
Database for the Central United States Velocity Model, v1.3
We have developed a new three-dimensional seismic velocity model of the central United States (CUSVM) that includes the New Madrid Seismic Zone (NMSZ) and covers parts of Arkansas, Mississippi, Alabama, Illinois, Missouri, Kentucky, and Tennessee. The model represents a compilation of decades of crustal research consisting of seismic, aeromagnetic, and gravity profiles; geologic mapping; geophysic
Ground motion Fourier and response spectra from Utah earthquakes, 2010--2020
Records from strong motion stations were downloaded from FDSN and CESMD data centers with a search radius of approximately 220 km from Salt Lake City. Waveforms were processed to deconvolve instrument response and for baseline corrections. Signal was separated from noise using an automated P-wave picker. The signal was then windowed to include the mean plus two standard deviations of the signal. A
Digitized datasets of the structure of Cenozoic and late Cretaceous strata along the Atlantic and Gulf Coastal Plains from Texas to New Jersey
This dataset consists of shapefiles that are digitized contours of the structure of Cenozoic and late Cretaceous strata along the Gulf and Atlantic Coastal plains from Texas to New Jersey, not including Maryland and Delaware. Well depths and seismic profiles indicating depth to or elevation of subsurface geologic contacts present in some datasets have also been digitized. Metadata files (.xml) des
Calibration Coefficients for the U.S. Geological Survey National Crustal Model and Depth to Water Table
The U.S. Geological Survey National Crustal Model (NCM) is being developed to include spatially varying estimates of site response in seismic hazard assessments. Primary outputs of the NCM are continuous velocity and density profiles from the Earth's surface to the mantle transition zone at 410 km depth for each location on a 1-kilometer grid across the conterminous United States. Datasets used to
3D Geologic Framework for use with the U.S. Geological Survey National Crustal Model, Phase 1: Western United States
A 3D geologic framework is presented here as part of the U.S. Geological Survey National Crustal Model for the western United States, which will be used to improve seismic hazard assessment. The framework is based on 1:250,000 to 1:1,000,000-scale state geologic maps and depths of multiple subsurface unit boundaries. The geology at or near the Earth’s surface is based on published maps with modifi
Grids in support of the U.S. Geological Survey Thermal Model for Seismic Hazard Studies
A 3D temperature model is constructed in order to support the estimation of physical parameters within the USGS National Crustal Model. The crustal model is defined by a geological framework consisting of various lithologies with distinct mineral compositions. A temperature model is needed to calculate mineral density and bulk and shear modulus as a function of position within the crust. These pro
An updated stress map of the continental U.S. reveals heterogeneous intraplate stress
Earthquake focal mechanisms and stress inversion results for the conterminous United States.
Petrologic and Mineral Physics Database for use with the USGS National Crustal Model - Data Release
We present a petrologic and mineral physics database as part of the USGS National Crustal Model (NCM) for the western United States. Each of 209 geologic units, 134 of which are currently part of the geologic framework within the NCM, is assigned a mineralogical composition according to generalized classifications with some refinement for specific geologic formations. The mineral physics database
Thickness of unconsolidated sediments for the USGS National Crustal Model
We present a numeric grid containing estimates of the thickness of unconsolidated sediments for the western United States. Values for these grids were combined and integrated from previous studies or derived directly from gravity analyses. The grids are provided with 1-km grid-node spacing in WGS84 latitude-longitude coordinates. Detailed information regarding the derivation of these estimates is
Depth to Mesozoic basement for the USGS National Crustal Model
We present a numeric grid containing estimates of the depth to the pre-Cenozoic basement for the western United States. Values for these grids were combined and integrated from previous studies or derived directly from gravity analyses. The grids are provided with 1-km grid-node spacing in WGS84 latitude-longitude coordinates. Detailed information regarding the derivation of these estimates is pro
Filter Total Items: 47
Lower seismogenic depth model of western U.S. Earthquakes
We present a model of the lower seismogenic depth of earthquakes in the western United States (WUS) estimated using the hypocentral depths of events M > 1, a crustal temperature model, and historical earthquake rupture depth models. Locations of earthquakes are from the Advanced National Seismic System Comprehensive Earthquake Catalog from 1980 to 2021 supplemented with seismicity in southern Cali
Implementation of basin models and sediment depth terms in the 2023 update of the U.S. National Seismic Hazard Model: Example from Reno, Nevada
We present a framework to evaluate the inclusion of candidate basin depth models in the U.S. Geological Survey National Seismic Hazard Model. We compute intensity measures (peak and spectral amplitudes) from uniformly processed earthquake ground motions in and around the basin of interest and compare these to ground-motion model (GMM) estimates over a range of oscillator periods. The GMMs use dept
U.S. Geological Survey coastal plain amplification virtual workshop
In early October of 2020, the U.S. Geological Survey (USGS) held a virtual workshop to discuss Gulf and Atlantic Coastal Plains site-response models. Earthquake researchers came together to assess (1) research related to proposed Coastal Plains amplification models and (2) USGS plans for implementing these models. Presentations spanned a broad range of topics from Atlantic and Gulf Coastal Plains
Updates to and applications of the USGS National Crustal Model for seismic hazard studies
The U.S. Geological Survey (USGS) National Crustal Model (NCM) is being developed to assist in the modeling of seismic hazards across the conterminous United States. The NCM is composed of a grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a 3D geologic framework and geophysical rules defined by: (1) a petrologic and mineral physics dat
Crustal seismic attenuation of the central United States and Intermountain West
Seismic attenuation is generally greater in the western United States (WUS) than the central and eastern United States (CEUS), but the nature of this transition or location of this boundary is poorly constrained. We conduct crustal seismic (Lg) attenuation tomography across a region that stretches from the CEUS across the Rocky Mountains to the Basin and Range using a total of 115,870 amplitude me
Seismic wave propagation and basin amplification in the Wasatch Front, Utah
Ground‐motion analysis of more than 3000 records from 59 earthquakes, including records from the March 2020 Mw 5.7 Magna earthquake sequence, was carried out to investigate site response and basin amplification in the Wasatch Front, Utah. We compare ground motions with the Bayless and Abrahamson (2019; hereafter, BA18) ground‐motion model (GMM) for Fourier amplitude spectra, which was developed on
The 2018 update of the US National Seismic Hazard Model: Ground motion models in the western US
The U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous U.S. NSHM includes significant changes to the underlying ground motion models (GMMs), most of which are necessary to enable the new multi-p
The 2018 update of the US National Seismic Hazard Model: Where, why, and how much probabilistic ground motion maps changed
The 2018 US Geological Survey National Seismic Hazard Model (NSHM) incorporates new data and updated science to improve the underlying earthquake and ground motion forecasts for the conterminous United States. The NSHM considers many new data and component input models: (1) new earthquakes between 2013 and 2017 and updated earthquake magnitudes for some earlier earthquakes; (2) two updated smoothe
Calibration of the U.S. Geological Survey National Crustal Model
The U.S. Geological Survey National Crustal Model (NCM) is being developed to include spatially varying estimates of site response in seismic hazard assessments. Primary outputs of the NCM are continuous velocity and density profiles from the Earth’s surface to the mantle transition zone at 410-kilometer (km) depth for each location on a 1-km grid across the conterminous United States. Datasets us
Temperature model in support of the U.S. Geological Survey National Crustal Model for seismic hazard Ssudies
The U.S. Geological Survey National Crustal Model (NCM) is being developed to assist with earthquake hazard and risk assessment by supporting estimates of ground shaking in response to an earthquake. The period-dependent intensity and duration of shaking depend upon the three-dimensional seismic velocity, seismic attenuation, and density distribution of a region, which in turn is governed to a lar
The 2018 update of the US National Seismic Hazard Model: Overview of model and implications
During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated
Code to access the Central United States Velocity Model, v1.3
We have developed a new three-dimensional seismic velocity model of the central United States (CUSVM) that includes the New Madrid Seismic Zone (NMSZ) and covers parts of Arkansas, Mississippi, Alabama, Illinois, Missouri, Kentucky, and Tennessee (Ramirez Guzman et al, 2012). The model represents a compilation of decades of crustal research consisting of seismic, aeromagnetic, and gravity profiles
GeoPhys
This set of utilities is used to extract geophysical information from the NCM (Boyd, 2020) including, for example, S-wave, P-wave, and density profiles, as well as attributes for ground motions models including VS30, Z1.0, and Z2.5. Running the code in either MATLAB or Python requires all of the NCM databases (https://doi.org/10.5066/P9T96Q67).
TherMod
This set of utilities is used to extract temperature profiles and maps from the NCM thermal model (Boyd, 2019). Running the code requires the NCM thermal model, NCM_TemperatureGrids.nc (https://doi.org/10.5066/P935DT1G), and the NCM spatial grid, NCM_SpatialGrid.nc (https://doi.org/10.5066/P9SBQENM). These codes and datasets are part of an effort to produce a three dimensional national crustal mod
GeoFram
This set of utilities is used to extract geologic profiles from the NCM geologic framework (Boyd, 2019). Running the code in either MATLAB or Python requires the NCM geologic framework and related databases, NCM_GeologicFrameworkVolume.nc, NCM_GeologicFrameworkGrids.nc, and NCM_SpatialGrid.nc (https://doi.org/10.5066/P9SBQENM). These data and codes are part of an effort to produce a three dimensio
MinVel
This program is used to calculate anharmonic p- and s-wave velocity and density for zero-porosity mineral aggregates. It is based on the work of Hacker and Abers (2004, updated in 2016) with additional minerals and optimized for related work. Running the code in either MATLAB or Python requires a mineral physics database, MineralPhysicsDatabase.nc (https://doi.org/10.5066/P9HN170G). Combined with
Science and Products
- Data
Data release for the lower seismogenic depth model of western U.S. earthquakes
A model of the lower seismogenic depth distribution of earthquakes in the western United States was developed to support models for seismic hazard assessment that will be included in the 2023 USGS National Seismic Hazard Model. This data release presents a recalibration using the hypocentral depths of events M>1 from the Advanced National Seismic System Comprehensive Earthquake Catalog from 198Database of Central and Eastern North American Seismic Velocity Structure
The "Database of Central and Eastern North American Seismic Velocity Structure" involves the compilation of one-dimensional (1D) seismic velocity-depth functions for central and eastern North America (CENA). The present database is an update of the report by Chulick and Mooney (2002) who present a compilation and statistical analysis of 1D seismic velocity-depth functions for North AmeriDatabase for the Central United States Velocity Model, v1.3
We have developed a new three-dimensional seismic velocity model of the central United States (CUSVM) that includes the New Madrid Seismic Zone (NMSZ) and covers parts of Arkansas, Mississippi, Alabama, Illinois, Missouri, Kentucky, and Tennessee. The model represents a compilation of decades of crustal research consisting of seismic, aeromagnetic, and gravity profiles; geologic mapping; geophysicGround motion Fourier and response spectra from Utah earthquakes, 2010--2020
Records from strong motion stations were downloaded from FDSN and CESMD data centers with a search radius of approximately 220 km from Salt Lake City. Waveforms were processed to deconvolve instrument response and for baseline corrections. Signal was separated from noise using an automated P-wave picker. The signal was then windowed to include the mean plus two standard deviations of the signal. ADigitized datasets of the structure of Cenozoic and late Cretaceous strata along the Atlantic and Gulf Coastal Plains from Texas to New Jersey
This dataset consists of shapefiles that are digitized contours of the structure of Cenozoic and late Cretaceous strata along the Gulf and Atlantic Coastal plains from Texas to New Jersey, not including Maryland and Delaware. Well depths and seismic profiles indicating depth to or elevation of subsurface geologic contacts present in some datasets have also been digitized. Metadata files (.xml) desCalibration Coefficients for the U.S. Geological Survey National Crustal Model and Depth to Water Table
The U.S. Geological Survey National Crustal Model (NCM) is being developed to include spatially varying estimates of site response in seismic hazard assessments. Primary outputs of the NCM are continuous velocity and density profiles from the Earth's surface to the mantle transition zone at 410 km depth for each location on a 1-kilometer grid across the conterminous United States. Datasets used to3D Geologic Framework for use with the U.S. Geological Survey National Crustal Model, Phase 1: Western United States
A 3D geologic framework is presented here as part of the U.S. Geological Survey National Crustal Model for the western United States, which will be used to improve seismic hazard assessment. The framework is based on 1:250,000 to 1:1,000,000-scale state geologic maps and depths of multiple subsurface unit boundaries. The geology at or near the Earth’s surface is based on published maps with modifiGrids in support of the U.S. Geological Survey Thermal Model for Seismic Hazard Studies
A 3D temperature model is constructed in order to support the estimation of physical parameters within the USGS National Crustal Model. The crustal model is defined by a geological framework consisting of various lithologies with distinct mineral compositions. A temperature model is needed to calculate mineral density and bulk and shear modulus as a function of position within the crust. These proAn updated stress map of the continental U.S. reveals heterogeneous intraplate stress
Earthquake focal mechanisms and stress inversion results for the conterminous United States.Petrologic and Mineral Physics Database for use with the USGS National Crustal Model - Data Release
We present a petrologic and mineral physics database as part of the USGS National Crustal Model (NCM) for the western United States. Each of 209 geologic units, 134 of which are currently part of the geologic framework within the NCM, is assigned a mineralogical composition according to generalized classifications with some refinement for specific geologic formations. The mineral physics databaseThickness of unconsolidated sediments for the USGS National Crustal Model
We present a numeric grid containing estimates of the thickness of unconsolidated sediments for the western United States. Values for these grids were combined and integrated from previous studies or derived directly from gravity analyses. The grids are provided with 1-km grid-node spacing in WGS84 latitude-longitude coordinates. Detailed information regarding the derivation of these estimates isDepth to Mesozoic basement for the USGS National Crustal Model
We present a numeric grid containing estimates of the depth to the pre-Cenozoic basement for the western United States. Values for these grids were combined and integrated from previous studies or derived directly from gravity analyses. The grids are provided with 1-km grid-node spacing in WGS84 latitude-longitude coordinates. Detailed information regarding the derivation of these estimates is pro - Publications
Filter Total Items: 47
Lower seismogenic depth model of western U.S. Earthquakes
We present a model of the lower seismogenic depth of earthquakes in the western United States (WUS) estimated using the hypocentral depths of events M > 1, a crustal temperature model, and historical earthquake rupture depth models. Locations of earthquakes are from the Advanced National Seismic System Comprehensive Earthquake Catalog from 1980 to 2021 supplemented with seismicity in southern CaliImplementation of basin models and sediment depth terms in the 2023 update of the U.S. National Seismic Hazard Model: Example from Reno, Nevada
We present a framework to evaluate the inclusion of candidate basin depth models in the U.S. Geological Survey National Seismic Hazard Model. We compute intensity measures (peak and spectral amplitudes) from uniformly processed earthquake ground motions in and around the basin of interest and compare these to ground-motion model (GMM) estimates over a range of oscillator periods. The GMMs use deptU.S. Geological Survey coastal plain amplification virtual workshop
In early October of 2020, the U.S. Geological Survey (USGS) held a virtual workshop to discuss Gulf and Atlantic Coastal Plains site-response models. Earthquake researchers came together to assess (1) research related to proposed Coastal Plains amplification models and (2) USGS plans for implementing these models. Presentations spanned a broad range of topics from Atlantic and Gulf Coastal PlainsUpdates to and applications of the USGS National Crustal Model for seismic hazard studies
The U.S. Geological Survey (USGS) National Crustal Model (NCM) is being developed to assist in the modeling of seismic hazards across the conterminous United States. The NCM is composed of a grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a 3D geologic framework and geophysical rules defined by: (1) a petrologic and mineral physics datCrustal seismic attenuation of the central United States and Intermountain West
Seismic attenuation is generally greater in the western United States (WUS) than the central and eastern United States (CEUS), but the nature of this transition or location of this boundary is poorly constrained. We conduct crustal seismic (Lg) attenuation tomography across a region that stretches from the CEUS across the Rocky Mountains to the Basin and Range using a total of 115,870 amplitude meSeismic wave propagation and basin amplification in the Wasatch Front, Utah
Ground‐motion analysis of more than 3000 records from 59 earthquakes, including records from the March 2020 Mw 5.7 Magna earthquake sequence, was carried out to investigate site response and basin amplification in the Wasatch Front, Utah. We compare ground motions with the Bayless and Abrahamson (2019; hereafter, BA18) ground‐motion model (GMM) for Fourier amplitude spectra, which was developed onThe 2018 update of the US National Seismic Hazard Model: Ground motion models in the western US
The U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous U.S. NSHM includes significant changes to the underlying ground motion models (GMMs), most of which are necessary to enable the new multi-pThe 2018 update of the US National Seismic Hazard Model: Where, why, and how much probabilistic ground motion maps changed
The 2018 US Geological Survey National Seismic Hazard Model (NSHM) incorporates new data and updated science to improve the underlying earthquake and ground motion forecasts for the conterminous United States. The NSHM considers many new data and component input models: (1) new earthquakes between 2013 and 2017 and updated earthquake magnitudes for some earlier earthquakes; (2) two updated smootheCalibration of the U.S. Geological Survey National Crustal Model
The U.S. Geological Survey National Crustal Model (NCM) is being developed to include spatially varying estimates of site response in seismic hazard assessments. Primary outputs of the NCM are continuous velocity and density profiles from the Earth’s surface to the mantle transition zone at 410-kilometer (km) depth for each location on a 1-km grid across the conterminous United States. Datasets usTemperature model in support of the U.S. Geological Survey National Crustal Model for seismic hazard Ssudies
The U.S. Geological Survey National Crustal Model (NCM) is being developed to assist with earthquake hazard and risk assessment by supporting estimates of ground shaking in response to an earthquake. The period-dependent intensity and duration of shaking depend upon the three-dimensional seismic velocity, seismic attenuation, and density distribution of a region, which in turn is governed to a larThe 2018 update of the US National Seismic Hazard Model: Overview of model and implications
During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated - Software
Code to access the Central United States Velocity Model, v1.3
We have developed a new three-dimensional seismic velocity model of the central United States (CUSVM) that includes the New Madrid Seismic Zone (NMSZ) and covers parts of Arkansas, Mississippi, Alabama, Illinois, Missouri, Kentucky, and Tennessee (Ramirez Guzman et al, 2012). The model represents a compilation of decades of crustal research consisting of seismic, aeromagnetic, and gravity profilesGeoPhys
This set of utilities is used to extract geophysical information from the NCM (Boyd, 2020) including, for example, S-wave, P-wave, and density profiles, as well as attributes for ground motions models including VS30, Z1.0, and Z2.5. Running the code in either MATLAB or Python requires all of the NCM databases (https://doi.org/10.5066/P9T96Q67).TherMod
This set of utilities is used to extract temperature profiles and maps from the NCM thermal model (Boyd, 2019). Running the code requires the NCM thermal model, NCM_TemperatureGrids.nc (https://doi.org/10.5066/P935DT1G), and the NCM spatial grid, NCM_SpatialGrid.nc (https://doi.org/10.5066/P9SBQENM). These codes and datasets are part of an effort to produce a three dimensional national crustal modGeoFram
This set of utilities is used to extract geologic profiles from the NCM geologic framework (Boyd, 2019). Running the code in either MATLAB or Python requires the NCM geologic framework and related databases, NCM_GeologicFrameworkVolume.nc, NCM_GeologicFrameworkGrids.nc, and NCM_SpatialGrid.nc (https://doi.org/10.5066/P9SBQENM). These data and codes are part of an effort to produce a three dimensioMinVel
This program is used to calculate anharmonic p- and s-wave velocity and density for zero-porosity mineral aggregates. It is based on the work of Hacker and Abers (2004, updated in 2016) with additional minerals and optimized for related work. Running the code in either MATLAB or Python requires a mineral physics database, MineralPhysicsDatabase.nc (https://doi.org/10.5066/P9HN170G). Combined with
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government