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
Filter Total Items: 48
The Mw6.0 24 August 2014 South Napa earthquake The Mw6.0 24 August 2014 South Napa earthquake
The Mw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike the greater San Francisco Bay area since the Mw 6.9 1989 Loma Prieta earthquake. The rupture from this right‐lateral earthquake propagated mostly unilaterally to the north and up‐dip, directing the strongest shaking toward the city of Napa, where peak ground accelerations...
Authors
Thomas M. Brocher, Annemarie S. Baltay Sundstrom, Jeanne L. Hardebeck, Fred F. Pollitz, Jessica R. Murray, Andrea L. Llenos, David P. Schwartz, J. Luke Blair, Daniel J. Ponti, James J. Lienkaemper, Victoria E. Langenheim, Timothy E. Dawson, Kenneth W. Hudnut, David R. Shelly, Douglas S. Dreger, John Boatwright, Brad T. Aagaard, David J. Wald, Richard M. Allen, William D. Barnhart, Keith L. Knudsen, Benjamin A. Brooks, Katherine M. Scharer
Key recovery factors for the August 24, 2014, South Napa Earthquake Key recovery factors for the August 24, 2014, South Napa Earthquake
Through discussions between the Federal Emergency Management Agency (FEMA) and the U.S. Geological Survey (USGS) following the South Napa earthquake, it was determined that several key decision points would be faced by FEMA for which additional information should be sought and provided by USGS and its partners. This report addresses the four tasks that were agreed to. These tasks are (1)
Authors
Kenneth W. Hudnut, Thomas M. Brocher, Carol S. Prentice, John Boatwright, Benjamin A. Brooks, Brad T. Aagaard, J. Luke Blair, Jon Peter B. Fletcher, Jemile Erdem, Charles W. Wicks, Jessica R. Murray, Fred F. Pollitz, John O. Langbein, Jerry L. Svarc, David P. Schwartz, Daniel J. Ponti, Suzanne Hecker, Stephen B. DeLong, Carla M. Rosa, Brenda Jones, Rynn M. Lamb, Anne M. Rosinski, Timothy P. McCrink, Timothy E. Dawson, Gordon G. Seitz, Craig Glennie, Darren Hauser, Todd Ericksen, Dan Mardock, Don F. Hoirup, Jonathan D. Bray, Ron S. Rubin
A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation
We employ a domain decomposition approach with Lagrange multipliers to implement fault slip in a finite-element code, PyLith, for use in both quasi-static and dynamic crustal deformation applications. This integrated approach to solving both quasi-static and dynamic simulations leverages common finite-element data structures and implementations of various boundary conditions...
Authors
Brad T. Aagaard, M.G. Knepley, C.A. Williams
Probabilistic estimates of surface coseismic slip and afterslip for Hayward fault earthquakes Probabilistic estimates of surface coseismic slip and afterslip for Hayward fault earthquakes
We examine the partition of long‐term geologic slip on the Hayward fault into interseismic creep, coseismic slip, and afterslip. Using Monte Carlo simulations, we compute expected coseismic slip and afterslip at three alinement array sites for Hayward fault earthquakes with nominal moment magnitudes ranging from about 6.5 to 7.1. We consider how interseismic creep might affect the...
Authors
Brad T. Aagaard, James J. Lienkaemper, David P. Schwartz
Testing long-period ground-motion simulations of scenario earthquakes using the Mw 7.2 El Mayor-Cucapah mainshock: Evaluation of finite-fault rupture characterization and 3D seismic velocity models Testing long-period ground-motion simulations of scenario earthquakes using the Mw 7.2 El Mayor-Cucapah mainshock: Evaluation of finite-fault rupture characterization and 3D seismic velocity models
Using a suite of five hypothetical finite-fault rupture models, we test the ability of long-period (T>2.0 s) ground-motion simulations of scenario earthquakes to produce waveforms throughout southern California consistent with those recorded during the 4 April 2010 Mw 7.2 El Mayor-Cucapah earthquake. The hypothetical ruptures are generated using the methodology proposed by Graves and...
Authors
Robert W. Graves, Brad T. Aagaard
Verifying a computational method for predicting extreme ground motion Verifying a computational method for predicting extreme ground motion
In situations where seismological data is rare or nonexistent, computer simulations may be used to predict ground motions caused by future earthquakes. This is particularly practical in the case of extreme ground motions, where engineers of special buildings may need to design for an event that has not been historically observed but which may occur in the far-distant future. Once the...
Authors
R.A. Harris, M. Barall, D.J. Andrews, B. Duan, S. Ma, E.M. Dunham, A.-A. Gabriel, Y. Kaneko, Y. Kase, Brad T. Aagaard, D. D. Oglesby, J.-P. Ampuero, Thomas C. Hanks, N. Abrahamson
Science and Products
Filter Total Items: 48
The Mw6.0 24 August 2014 South Napa earthquake The Mw6.0 24 August 2014 South Napa earthquake
The Mw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike the greater San Francisco Bay area since the Mw 6.9 1989 Loma Prieta earthquake. The rupture from this right‐lateral earthquake propagated mostly unilaterally to the north and up‐dip, directing the strongest shaking toward the city of Napa, where peak ground accelerations...
Authors
Thomas M. Brocher, Annemarie S. Baltay Sundstrom, Jeanne L. Hardebeck, Fred F. Pollitz, Jessica R. Murray, Andrea L. Llenos, David P. Schwartz, J. Luke Blair, Daniel J. Ponti, James J. Lienkaemper, Victoria E. Langenheim, Timothy E. Dawson, Kenneth W. Hudnut, David R. Shelly, Douglas S. Dreger, John Boatwright, Brad T. Aagaard, David J. Wald, Richard M. Allen, William D. Barnhart, Keith L. Knudsen, Benjamin A. Brooks, Katherine M. Scharer
Key recovery factors for the August 24, 2014, South Napa Earthquake Key recovery factors for the August 24, 2014, South Napa Earthquake
Through discussions between the Federal Emergency Management Agency (FEMA) and the U.S. Geological Survey (USGS) following the South Napa earthquake, it was determined that several key decision points would be faced by FEMA for which additional information should be sought and provided by USGS and its partners. This report addresses the four tasks that were agreed to. These tasks are (1)
Authors
Kenneth W. Hudnut, Thomas M. Brocher, Carol S. Prentice, John Boatwright, Benjamin A. Brooks, Brad T. Aagaard, J. Luke Blair, Jon Peter B. Fletcher, Jemile Erdem, Charles W. Wicks, Jessica R. Murray, Fred F. Pollitz, John O. Langbein, Jerry L. Svarc, David P. Schwartz, Daniel J. Ponti, Suzanne Hecker, Stephen B. DeLong, Carla M. Rosa, Brenda Jones, Rynn M. Lamb, Anne M. Rosinski, Timothy P. McCrink, Timothy E. Dawson, Gordon G. Seitz, Craig Glennie, Darren Hauser, Todd Ericksen, Dan Mardock, Don F. Hoirup, Jonathan D. Bray, Ron S. Rubin
A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation
We employ a domain decomposition approach with Lagrange multipliers to implement fault slip in a finite-element code, PyLith, for use in both quasi-static and dynamic crustal deformation applications. This integrated approach to solving both quasi-static and dynamic simulations leverages common finite-element data structures and implementations of various boundary conditions...
Authors
Brad T. Aagaard, M.G. Knepley, C.A. Williams
Probabilistic estimates of surface coseismic slip and afterslip for Hayward fault earthquakes Probabilistic estimates of surface coseismic slip and afterslip for Hayward fault earthquakes
We examine the partition of long‐term geologic slip on the Hayward fault into interseismic creep, coseismic slip, and afterslip. Using Monte Carlo simulations, we compute expected coseismic slip and afterslip at three alinement array sites for Hayward fault earthquakes with nominal moment magnitudes ranging from about 6.5 to 7.1. We consider how interseismic creep might affect the...
Authors
Brad T. Aagaard, James J. Lienkaemper, David P. Schwartz
Testing long-period ground-motion simulations of scenario earthquakes using the Mw 7.2 El Mayor-Cucapah mainshock: Evaluation of finite-fault rupture characterization and 3D seismic velocity models Testing long-period ground-motion simulations of scenario earthquakes using the Mw 7.2 El Mayor-Cucapah mainshock: Evaluation of finite-fault rupture characterization and 3D seismic velocity models
Using a suite of five hypothetical finite-fault rupture models, we test the ability of long-period (T>2.0 s) ground-motion simulations of scenario earthquakes to produce waveforms throughout southern California consistent with those recorded during the 4 April 2010 Mw 7.2 El Mayor-Cucapah earthquake. The hypothetical ruptures are generated using the methodology proposed by Graves and...
Authors
Robert W. Graves, Brad T. Aagaard
Verifying a computational method for predicting extreme ground motion Verifying a computational method for predicting extreme ground motion
In situations where seismological data is rare or nonexistent, computer simulations may be used to predict ground motions caused by future earthquakes. This is particularly practical in the case of extreme ground motions, where engineers of special buildings may need to design for an event that has not been historically observed but which may occur in the far-distant future. Once the...
Authors
R.A. Harris, M. Barall, D.J. Andrews, B. Duan, S. Ma, E.M. Dunham, A.-A. Gabriel, Y. Kaneko, Y. Kase, Brad T. Aagaard, D. D. Oglesby, J.-P. Ampuero, Thomas C. Hanks, N. Abrahamson