Brad Aagaard
Brad Aagaard is a research scientist in the Earthquake Hazards Program.
Ground-motion modeling
- Animations of ground shaking from computer simulations of earthquakes.
- 3D Geologic and Seismic Velocity Model of the San Francisco Bay Region
Software
PyLith crustal deformation modeling software, Computational Infrastructure for Geodynamics.
Professional Experience
Research Geophysicist, USGS, 2003-present
USGS Mendenhall Postdoctoral Scholar, 2001-2003
Education and Certifications
Ph.D., Civil Engineering, California Institute of Technology, 2000
M.S., Civil Engineering, California Institute of Technology, 1995
B.S., Engineering, Harvey Mudd College, 1994
Science and Products
Crustal Characterization
The geophysical structure of the Earth’s crust, from the surface to the Moho, plays a major role in seismic hazard by influencing earthquake source properties and wave propagation from the earthquake to the Earth’s surface. We make field measurements and create models to better characterize the crust and resulting earthquake ground motions.
Ground-motion records and basin depth models for Portland, Oregon, 2005-2022
This dataset includes processed ground-motion records and horizontal pseudospectral accelerations (5-percent-damped) from magnitude 3.0-6.8 earthquakes occurring in the vicinity of Portland, Oregon, between 2005 and 2022. The dataset includes 347 records from 134 earthquakes and 69 stations. Spectral values are provided at 21 periods (0.01-10 s). It also includes the basin depth models as GeoTiff
Ground-motion records and basin depth models for Reno, Nevada, 2008-2022
This dataset includes processed ground-motion records and horizontal pseudospectral accelerations (5-percent-damped) from magnitude 3.0-6.0 earthquakes occurring in the vicinity of Reno, Nevada, between 2008 and 2022. The dataset includes 592 records from 104 earthquakes and 42 stations. Spectral values are provided at 21 periods (0.01-10 s). Local basin depths as given by Z1.0 and Z2.5 (depths to
Ground-motion records and basin depth models for the Great Valley, California, 2000-2022
This dataset includes processed ground-motion records and horizontal pseudospectral accelerations (5-percent-damped) from magnitude 3.5-7.1 earthquakes occurring in the vicinity of the Great Valley, California, between 2000 and 2022. The dataset includes 12,044 records from 564 earthquakes and 254 stations. Spectral values are provided at 21 periods (0.01-10 s). It also includes the basin depth mo
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview
This data release contains data sets associated with the 2023 50-State National Seismic Hazard Model Update. The 2023 50-State National Seimsic Hazard Model (NSHM) Update includes an update to the NSHMs for the conterminous U.S (CONUS, last updated in 2018), Alaska (AK, last updated in 2007), and Hawaii (last updated in 2001). Data sets include inputs like seismicity catalogs used as input to the
San Francisco Bay region 3D seismic velocity model v21.0
This three-dimensional (3D) seismic velocity model includes a detailed domain covering the greater San Francisco Bay urban region and a regional domain at a coarser resolution covering a larger region. Version 21.0 is a re-release of v08.3.0 in a new storage scheme. The model was constructed by assigning elastic properties (density, Vp, Vs, Qp, and Qs) to grids of points based on the geologic unit
San Francisco Bay region 3D seismic velocity model v21.1
This three-dimensional (3D) seismic velocity model includes a detailed domain covering the greater San Francisco Bay urban region and a regional domain at a coarser resolution covering a larger region. Version 21.1 updates only the detailed domain with adjustments to the elastic properties east and north of the San Francisco Bay. There are no changes to the underlying 3D geologic model or the regi
Ground motions from the 2019 Ridgecrest, California, earthquake sequence
This project involves the compilation of ground motions, their derived parameters, and metadata for 133 earthquakes in the 2019 Ridgecrest, California, earthquake sequence. This dataset includes 22,991 records from 133 events from 4 July 2019 to 18 October 2019 with a magnitude range from 3.6 to 7.1.
Filter Total Items: 43
2024 Crustal Deformation Modeling Workshop report
The 2024 Crustal Deformation Modeling Workshop was held June 10–14 at the Colorado School of Mines. The workshop included two days of tutorials on using PyLith for crustal deformation modeling, followed by three days of science talks and discussions. The workshop focused on four primary themes: ● Constraining long-term fault slip rates and their uncertainties using geodetic and geologic data; ● Ea
Authors
Brad T. Aagaard, Matthew Knepley, Eric Lindsey, Kathryn Materna, Hilary R Martens, Charles Williams
Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon
We assess how well the Next-Generation Attenuation-West 2 (NGA-West2) ground-motion models (GMMs), which are used in the US Geological Survey’s (USGS) National Seismic Hazard Model (NSHM) for crustal faults in the western United States, predict the observed basin response in the Great Valley of California, the Reno basin in Nevada, and Portland and Tualatin basins in Oregon. These GMMs rely on sit
Authors
Sean Kamran Ahdi, Brad T. Aagaard, Morgan P. Moschetti, Grace Alexandra Parker, Oliver S. Boyd, William J. Stephenson
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies
The U.S. Geological Survey is developing the National Crustal Model (NCM) for seismic hazard studies to facilitate modeling site, path, and source components of seismic hazard across the conterminous United States. The NCM is composed of a 1km grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a threedimensional (3D) geologic framework an
Authors
Oliver S. Boyd, James Andrew Smith, Morgan P. Moschetti, Brad T. Aagaard, Robert Graves, Evan Tyler Hirakawa, Sean Kamran Ahdi
The 2023 US 50-State National Seismic Hazard Model: Overview and implications
The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard (both increase
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Ned Field, Morgan P. Moschetti, Kishor S. Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur Frankel, Andrea L. Llenos, Andrew J. Michael, Jason M. Altekruse, Sean Kamran Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert E. Chase, Leah M. Salditch, Nico Luco, Kenneth S. Rukstales, Julie A Herrick, Demi Leafar Girot, Brad T. Aagaard, Adrian Bender, Michael L. Blanpied, Richard W. Briggs, Oliver S. Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Elise Hatem, Kirstie Lafon Haynie, Elizabeth H. Hearn, Kaj M. Johnson, Zachary Alan Kortum, N. Simon Kwong, Andrew James Makdisi, Henry (Ben) Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan T. Page, Frederick Pollitz, Justin Rubinstein, Bruce E. Shaw, Zheng-Kang Shen, Brian Shiro, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Jessica Ann Thompson Jobe, Erin Wirth, Robert C. Witter
Multiphysics modelling in PyLith: Poroelasticity
PyLith, a community, open-source code for modelling quasi-static and dynamic crustal deformation with an emphasis on earthquake faulting, has recently been updated with a flexible multiphysics implementation. We demonstrate the versatility of the multiphysics implementation by extending the code to model fully coupled continuum poromechanics. We verify the newly incorporated physics using standard
Authors
Robert L. Walker, Matthew G. Knepley, Brad T. Aagaard, Charles A. Williams
2023 PyLith Hackathon report
The 3rd Pylith Hackathon was held June 12–17, 2023, at the Colorado School of Mines in Golden, Colorado with funding from the Computational Infrastructure for Geodynamics (CIG). The hackathon involved 17 participants working on 5 different projects to implement new features and create new examples for the PyLith crustal deformation modeling software. The projects included (1) spontaneous rupture u
Authors
Brad T. Aagaard
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2
These 2 workshops were held in response to interest generated from sessions on the use of simulated earthquake ground motions at the 2020 and 2021 Consortium of Organizations for Strong Motion Observation Systems (COSMOS) Technical Sessions. The discussions at the Technical Sessions highlighted desires to promote the use of simulated earthquake ground motions for engineering applications and the n
Authors
Brad T. Aagaard, Aysegul Askan, Sanaz Rezaeian, Sean Kamran Ahdi, Alan Yong
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
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson
2022 Crustal Deformation Modeling Workshop Report
The 2022 Crustal Deformation Modeling Workshop was held June 20–24 at the Colorado School of Mines in Golden, Colorado. The workshop included two days of tutorials on the use of the open-source software PyLith for crustal deformation modeling followed by three days of science talks and discussions. The workshop focused on three primary themes: (1) Earthquake cycle modeling; (2) Inversions for faul
Authors
Brad T. Aagaard, Sylvain Barbot, Brittany Erickson, Matthew Knepley, Mark Simons, Charles Williams
Improving the Development Pipelines for USGS Earthquake Hazards Program Real-Time and Scenario Products
The real-time and scenario products of the U.S. Geological Survey (USGS) Earthquake Hazards Program, such as the ComCat catalog, Did You Feel It?, ShakeMap, ShakeCast, and PAGER, are highly visible and used by a wide variety of stakeholders. We propose two significant enhancements to the development pipelines for the Earthquake Hazards Program real-time and scenario products that have far-reaching
Authors
Brad T. Aagaard, David J. Wald, Eric M. Thompson, Mike Hearne, Lisa Sue Schleicher
2021 Computational Infrastructure for Geodynamics Developers Workshop
The CIG Developers Workshop resulted in a number of recommendations that we think will help expand the CIG developer community, make software more accessible to new users, and increase developer productivity through use of common infrastructure and best practices for software development. This includes building a broad user base with sufficient support through documentation, tutorials, user forums
Authors
Brad T. Aagaard, Jed Brown, Catherin Cooper, Rene Gassmoeller, Lorraine Hwang, Marc Spiegelman
Science plan for improving three-dimensional seismic velocity models in the San Francisco Bay region, 2019–24
This five-year science plan outlines short-term and long-term goals for improving three-dimensional seismic velocity models in the greater San Francisco Bay region as well as how to foster a community effort in reaching those goals. The short-term goals focus on improving the current U.S. Geological Survey San Francisco Bay region geologic and seismic velocity model using existing data. The long-t
Authors
Brad T. Aagaard, Russell W. Graymer, Clifford H. Thurber, Arthur J. Rodgers, Taka'aki Taira, Rufus D. Catchings, Christine A. Goulet, Andreas Plesch
USGS automated ground motion processing software
The goal of this project is to update, restructure, and consolidate existing USGS ground-motion processing software to incorporate recent advances from researchers at the USGS, PEER, and others. It will standardize tools for multiple USGS ground-motion products and enable scientists within the USGS and the external community to develop and expand ground-motion datasets used in many different appli
Science and Products
Crustal Characterization
The geophysical structure of the Earth’s crust, from the surface to the Moho, plays a major role in seismic hazard by influencing earthquake source properties and wave propagation from the earthquake to the Earth’s surface. We make field measurements and create models to better characterize the crust and resulting earthquake ground motions.
Ground-motion records and basin depth models for Portland, Oregon, 2005-2022
This dataset includes processed ground-motion records and horizontal pseudospectral accelerations (5-percent-damped) from magnitude 3.0-6.8 earthquakes occurring in the vicinity of Portland, Oregon, between 2005 and 2022. The dataset includes 347 records from 134 earthquakes and 69 stations. Spectral values are provided at 21 periods (0.01-10 s). It also includes the basin depth models as GeoTiff
Ground-motion records and basin depth models for Reno, Nevada, 2008-2022
This dataset includes processed ground-motion records and horizontal pseudospectral accelerations (5-percent-damped) from magnitude 3.0-6.0 earthquakes occurring in the vicinity of Reno, Nevada, between 2008 and 2022. The dataset includes 592 records from 104 earthquakes and 42 stations. Spectral values are provided at 21 periods (0.01-10 s). Local basin depths as given by Z1.0 and Z2.5 (depths to
Ground-motion records and basin depth models for the Great Valley, California, 2000-2022
This dataset includes processed ground-motion records and horizontal pseudospectral accelerations (5-percent-damped) from magnitude 3.5-7.1 earthquakes occurring in the vicinity of the Great Valley, California, between 2000 and 2022. The dataset includes 12,044 records from 564 earthquakes and 254 stations. Spectral values are provided at 21 periods (0.01-10 s). It also includes the basin depth mo
Data Release for the 2023 U.S. 50-State National Seismic Hazard Model - Overview
This data release contains data sets associated with the 2023 50-State National Seismic Hazard Model Update. The 2023 50-State National Seimsic Hazard Model (NSHM) Update includes an update to the NSHMs for the conterminous U.S (CONUS, last updated in 2018), Alaska (AK, last updated in 2007), and Hawaii (last updated in 2001). Data sets include inputs like seismicity catalogs used as input to the
San Francisco Bay region 3D seismic velocity model v21.0
This three-dimensional (3D) seismic velocity model includes a detailed domain covering the greater San Francisco Bay urban region and a regional domain at a coarser resolution covering a larger region. Version 21.0 is a re-release of v08.3.0 in a new storage scheme. The model was constructed by assigning elastic properties (density, Vp, Vs, Qp, and Qs) to grids of points based on the geologic unit
San Francisco Bay region 3D seismic velocity model v21.1
This three-dimensional (3D) seismic velocity model includes a detailed domain covering the greater San Francisco Bay urban region and a regional domain at a coarser resolution covering a larger region. Version 21.1 updates only the detailed domain with adjustments to the elastic properties east and north of the San Francisco Bay. There are no changes to the underlying 3D geologic model or the regi
Ground motions from the 2019 Ridgecrest, California, earthquake sequence
This project involves the compilation of ground motions, their derived parameters, and metadata for 133 earthquakes in the 2019 Ridgecrest, California, earthquake sequence. This dataset includes 22,991 records from 133 events from 4 July 2019 to 18 October 2019 with a magnitude range from 3.6 to 7.1.
Filter Total Items: 43
2024 Crustal Deformation Modeling Workshop report
The 2024 Crustal Deformation Modeling Workshop was held June 10–14 at the Colorado School of Mines. The workshop included two days of tutorials on using PyLith for crustal deformation modeling, followed by three days of science talks and discussions. The workshop focused on four primary themes: ● Constraining long-term fault slip rates and their uncertainties using geodetic and geologic data; ● Ea
Authors
Brad T. Aagaard, Matthew Knepley, Eric Lindsey, Kathryn Materna, Hilary R Martens, Charles Williams
Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon
We assess how well the Next-Generation Attenuation-West 2 (NGA-West2) ground-motion models (GMMs), which are used in the US Geological Survey’s (USGS) National Seismic Hazard Model (NSHM) for crustal faults in the western United States, predict the observed basin response in the Great Valley of California, the Reno basin in Nevada, and Portland and Tualatin basins in Oregon. These GMMs rely on sit
Authors
Sean Kamran Ahdi, Brad T. Aagaard, Morgan P. Moschetti, Grace Alexandra Parker, Oliver S. Boyd, William J. Stephenson
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies
The U.S. Geological Survey is developing the National Crustal Model (NCM) for seismic hazard studies to facilitate modeling site, path, and source components of seismic hazard across the conterminous United States. The NCM is composed of a 1km grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a threedimensional (3D) geologic framework an
Authors
Oliver S. Boyd, James Andrew Smith, Morgan P. Moschetti, Brad T. Aagaard, Robert Graves, Evan Tyler Hirakawa, Sean Kamran Ahdi
The 2023 US 50-State National Seismic Hazard Model: Overview and implications
The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard (both increase
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Ned Field, Morgan P. Moschetti, Kishor S. Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur Frankel, Andrea L. Llenos, Andrew J. Michael, Jason M. Altekruse, Sean Kamran Ahdi, Kyle Withers, Charles Mueller, Yuehua Zeng, Robert E. Chase, Leah M. Salditch, Nico Luco, Kenneth S. Rukstales, Julie A Herrick, Demi Leafar Girot, Brad T. Aagaard, Adrian Bender, Michael L. Blanpied, Richard W. Briggs, Oliver S. Boyd, Brandon Clayton, Christopher DuRoss, Eileen L. Evans, Peter J. Haeussler, Alexandra Elise Hatem, Kirstie Lafon Haynie, Elizabeth H. Hearn, Kaj M. Johnson, Zachary Alan Kortum, N. Simon Kwong, Andrew James Makdisi, Henry (Ben) Mason, Daniel McNamara, Devin McPhillips, P. Okubo, Morgan T. Page, Frederick Pollitz, Justin Rubinstein, Bruce E. Shaw, Zheng-Kang Shen, Brian Shiro, James Andrew Smith, William J. Stephenson, Eric M. Thompson, Jessica Ann Thompson Jobe, Erin Wirth, Robert C. Witter
Multiphysics modelling in PyLith: Poroelasticity
PyLith, a community, open-source code for modelling quasi-static and dynamic crustal deformation with an emphasis on earthquake faulting, has recently been updated with a flexible multiphysics implementation. We demonstrate the versatility of the multiphysics implementation by extending the code to model fully coupled continuum poromechanics. We verify the newly incorporated physics using standard
Authors
Robert L. Walker, Matthew G. Knepley, Brad T. Aagaard, Charles A. Williams
2023 PyLith Hackathon report
The 3rd Pylith Hackathon was held June 12–17, 2023, at the Colorado School of Mines in Golden, Colorado with funding from the Computational Infrastructure for Geodynamics (CIG). The hackathon involved 17 participants working on 5 different projects to implement new features and create new examples for the PyLith crustal deformation modeling software. The projects included (1) spontaneous rupture u
Authors
Brad T. Aagaard
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2
These 2 workshops were held in response to interest generated from sessions on the use of simulated earthquake ground motions at the 2020 and 2021 Consortium of Organizations for Strong Motion Observation Systems (COSMOS) Technical Sessions. The discussions at the Technical Sessions highlighted desires to promote the use of simulated earthquake ground motions for engineering applications and the n
Authors
Brad T. Aagaard, Aysegul Askan, Sanaz Rezaeian, Sean Kamran Ahdi, Alan Yong
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
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson
2022 Crustal Deformation Modeling Workshop Report
The 2022 Crustal Deformation Modeling Workshop was held June 20–24 at the Colorado School of Mines in Golden, Colorado. The workshop included two days of tutorials on the use of the open-source software PyLith for crustal deformation modeling followed by three days of science talks and discussions. The workshop focused on three primary themes: (1) Earthquake cycle modeling; (2) Inversions for faul
Authors
Brad T. Aagaard, Sylvain Barbot, Brittany Erickson, Matthew Knepley, Mark Simons, Charles Williams
Improving the Development Pipelines for USGS Earthquake Hazards Program Real-Time and Scenario Products
The real-time and scenario products of the U.S. Geological Survey (USGS) Earthquake Hazards Program, such as the ComCat catalog, Did You Feel It?, ShakeMap, ShakeCast, and PAGER, are highly visible and used by a wide variety of stakeholders. We propose two significant enhancements to the development pipelines for the Earthquake Hazards Program real-time and scenario products that have far-reaching
Authors
Brad T. Aagaard, David J. Wald, Eric M. Thompson, Mike Hearne, Lisa Sue Schleicher
2021 Computational Infrastructure for Geodynamics Developers Workshop
The CIG Developers Workshop resulted in a number of recommendations that we think will help expand the CIG developer community, make software more accessible to new users, and increase developer productivity through use of common infrastructure and best practices for software development. This includes building a broad user base with sufficient support through documentation, tutorials, user forums
Authors
Brad T. Aagaard, Jed Brown, Catherin Cooper, Rene Gassmoeller, Lorraine Hwang, Marc Spiegelman
Science plan for improving three-dimensional seismic velocity models in the San Francisco Bay region, 2019–24
This five-year science plan outlines short-term and long-term goals for improving three-dimensional seismic velocity models in the greater San Francisco Bay region as well as how to foster a community effort in reaching those goals. The short-term goals focus on improving the current U.S. Geological Survey San Francisco Bay region geologic and seismic velocity model using existing data. The long-t
Authors
Brad T. Aagaard, Russell W. Graymer, Clifford H. Thurber, Arthur J. Rodgers, Taka'aki Taira, Rufus D. Catchings, Christine A. Goulet, Andreas Plesch
USGS automated ground motion processing software
The goal of this project is to update, restructure, and consolidate existing USGS ground-motion processing software to incorporate recent advances from researchers at the USGS, PEER, and others. It will standardize tools for multiple USGS ground-motion products and enable scientists within the USGS and the external community to develop and expand ground-motion datasets used in many different appli