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
San Francisco Bay region 3D seismic velocity model v21.1 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...
Ground motions from the 2019 Ridgecrest, California, earthquake sequence 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.
USGS automated ground motion processing software 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...
Filter Total Items: 48
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies 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...
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 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...
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Edward H. Field, Morgan P. Moschetti, Kishor S. Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur D. 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 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 A. Wirth, Robert C. Witter
Multiphysics modelling in PyLith: Poroelasticity 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...
Authors
Robert L. Walker, Matthew G. Knepley, Brad T. Aagaard, Charles A. Williams
2023 PyLith Hackathon report 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...
Authors
Brad T. Aagaard
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2 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...
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 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...
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson
Science and Products
San Francisco Bay region 3D seismic velocity model v21.1 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...
Ground motions from the 2019 Ridgecrest, California, earthquake sequence 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.
USGS automated ground motion processing software 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...
Filter Total Items: 48
Recent applications of the USGS National Crustal Model for Seismic Hazard Studies 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...
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 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...
Authors
Mark D. Petersen, Allison Shumway, Peter M. Powers, Edward H. Field, Morgan P. Moschetti, Kishor S. Jaiswal, Kevin R. Milner, Sanaz Rezaeian, Arthur D. 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 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 A. Wirth, Robert C. Witter
Multiphysics modelling in PyLith: Poroelasticity 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...
Authors
Robert L. Walker, Matthew G. Knepley, Brad T. Aagaard, Charles A. Williams
2023 PyLith Hackathon report 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...
Authors
Brad T. Aagaard
COSMOS Ground-Motion Simulation Working Group workshops #1 and #2 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...
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 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...
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson