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: 50
Subsurface geometry of the San Andreas fault in southern California: Results from the Salton Seismic Imaging Project (SSIP) and strong ground motion expectations Subsurface geometry of the San Andreas fault in southern California: Results from the Salton Seismic Imaging Project (SSIP) and strong ground motion expectations
The San Andreas fault (SAF) is one of the most studied strike‐slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton Seismic Imaging Project (SSIP) was undertaken to image the structure surrounding the SAF and also its subsurface geometry. We present SSIP studies at two locations in the Coachella Valley of the northern Salton trough. On our...
Authors
Gary S. Fuis, Klaus Bauer, Mark R. Goldman, Trond Ryberg, Victoria E. Langenheim, Daniel S. Scheirer, Michael J. Rymer, Joann M. Stock, John A. Hole, Rufus D. Catchings, Robert Graves, Brad T. Aagaard
Earthquake outlook for the San Francisco Bay region 2014–2043 Earthquake outlook for the San Francisco Bay region 2014–2043
Using information from recent earthquakes, improved mapping of active faults, and a new model for estimating earthquake probabilities, the 2014 Working Group on California Earthquake Probabilities updated the 30-year earthquake forecast for California. They concluded that there is a 72 percent probability (or likelihood) of at least one earthquake of magnitude 6.7 or greater striking...
Authors
Brad T. Aagaard, J. Luke Blair, John Boatwright, Susan H. Garcia, Ruth A. Harris, Andrew J. Michael, David P. Schwartz, Jeanne S. DiLeo
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
Science and Products
Filter Total Items: 50
Subsurface geometry of the San Andreas fault in southern California: Results from the Salton Seismic Imaging Project (SSIP) and strong ground motion expectations Subsurface geometry of the San Andreas fault in southern California: Results from the Salton Seismic Imaging Project (SSIP) and strong ground motion expectations
The San Andreas fault (SAF) is one of the most studied strike‐slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton Seismic Imaging Project (SSIP) was undertaken to image the structure surrounding the SAF and also its subsurface geometry. We present SSIP studies at two locations in the Coachella Valley of the northern Salton trough. On our...
Authors
Gary S. Fuis, Klaus Bauer, Mark R. Goldman, Trond Ryberg, Victoria E. Langenheim, Daniel S. Scheirer, Michael J. Rymer, Joann M. Stock, John A. Hole, Rufus D. Catchings, Robert Graves, Brad T. Aagaard
Earthquake outlook for the San Francisco Bay region 2014–2043 Earthquake outlook for the San Francisco Bay region 2014–2043
Using information from recent earthquakes, improved mapping of active faults, and a new model for estimating earthquake probabilities, the 2014 Working Group on California Earthquake Probabilities updated the 30-year earthquake forecast for California. They concluded that there is a 72 percent probability (or likelihood) of at least one earthquake of magnitude 6.7 or greater striking...
Authors
Brad T. Aagaard, J. Luke Blair, John Boatwright, Susan H. Garcia, Ruth A. Harris, Andrew J. Michael, David P. Schwartz, Jeanne S. DiLeo
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