Brad Aagaard
Biography
Research Geophysicist, USGS, 2003-present
USGS Mendenhall Postdoctoral Scholar, 2001-2003
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
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.
Science and Products
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...
Aagaard, Brad T.; Graymer, Russell W.; Thurber, Clifford H.; Rodgers, Arthur J.; Taira, Taka'aki; Catchings, Rufus D.; Goulet, Christine A.; Plesch, Andreas
The 2019 Ridgecrest, California, earthquake sequence ground motions: Processed records and derived intensity metrics
Following the 2019 Ridgecrest, California, earthquake sequence, we compiled ground‐motion records from multiple data centers and processed these records using newly developed ground‐motion processing software that performs quality assurance checks, performs standard time series processing steps, and computes a wide range of ground‐motion metrics....
Rekoske, John; Thompson, Eric M.; Moschetti, Morgan P.; Hearne, Mike; Aagaard, Brad T.; Parker, Grace Alexandra
Research to improve ShakeAlert earthquake early warning products and their utility
Earthquake early warning (EEW) is the rapid detection of an earthquake and issuance of an alert or notification to people and vulnerable systems likely to experience potentially damaging ground shaking. The level of ground shaking that is considered damaging is defined by the specific application; for example, manufacturing equipment may...
Cochran, Elizabeth S.; Aagaard, Brad T.; Allen, Richard M.; Andrews, Jennifer; Baltay, Annemarie S.; Barbour, Andrew J.; Bodin, Paul; Brooks, Benjamin A.; Chung, Angela; Crowell, Brendan W.; Given, Douglas D.; Hanks, Thomas C.; Hartog, J. Renate; Hauksson, Egill; Heaton, Thomas H.; McBride, Sara; Meier, Men-Andrin; Melgar, Diego; Minson, Sarah E.; Murray, Jessica R.; Strauss, Jennifer A.; Toomey, Douglas A suite of exercises for verifying dynamic earthquake rupture codes
We describe a set of benchmark exercises that are designed to test if computer codes that simulate dynamic earthquake rupture are working as intended. These types of computer codes are often used to understand how earthquakes operate, and they produce simulation results that include earthquake size, amounts of fault slip, and the patterns of...
Harris, Ruth A.; Barall, Michael; Aagaard, Brad T.; Ma, Shuo; Roten, Daniel; Olsen, Kim B.; Duan, Benchun; Liu, Dunyu; Luo, Bin; Bai, Kangchen; Ampuero, Jean-Paul; Kaneko, Yoshihiro; Gabriel, Alice-Agnes; Duru, Kenneth; Ulrich, Thomas; Wollherr, Stephanie; Shi, Zheqiang; Dunham, Eric; Bydlon, Sam; Zhang, Zhenguo; Chen, Xiaofei; Somala, Surendra N.; Pelties, Christian; Tago, Josue; Cruz-Atienza, Victor Manuel; Kozdon, Jeremy; Daub, Eric; Aslam, Khurram; Kase, Yuko; Withers, Kyle; Dalguer, Luis Integrate urban‐scale seismic hazard analyses with the U.S. National Seismic Hazard Model
For more than 20 yrs, damage patterns and instrumental recordings have highlighted the influence of the local 3D geologic structure on earthquake ground motions (e.g., M">MM 6.7 Northridge, California, Gao et al., 1996; M">MM 6.9 Kobe, Japan, Kawase, 1996; M">MM 6.8 Nisqually,...
Moschetti, Morgan P.; Luco, Nicolas; Frankel, Arthur; Petersen, Mark D.; Aagaard, Brad T.; Baltay, Annemarie S.; Blanpied, Michael; Boyd, Oliver S.; Briggs, Richard W.; Gold, Ryan D.; Graves, Robert; Hartzell, Stephen H.; Rezaeian, Sanaz; Stephenson, William J.; Wald, David J.; Williams, Robert A.; Withers, Kyle
U.S. Geological Survey National Strong-Motion Project strategic plan, 2017–22
The mission of the National Strong-Motion Project is to provide measurements of how the ground and built environment behave during earthquake shaking to the earthquake engineering community, the scientific community, emergency managers, public agencies, industry, media, and other users for the following purposes: Improving engineering evaluations...
Aagaard, Brad T.; Celebi, Mehmet; Gee, Lind; Graves, Robert; Jaiswal, Kishor; Kalkan, Erol; Knudsen, Keith L.; Luco, Nicolas; Smith, James; Steidl, Jamison; Stephens, Christopher D. 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...
Fuis, Gary S.; Bauer, Klaus; Goldman, Mark R.; Ryberg, Trond; Langenheim, Victoria; Scheirer, Daniel S.; Rymer, Michael J.; Stock, Joann M.; Hole, John A.; Catchings, Rufus D.; Graves, Robert; Aagaard, Brad T.
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...
Jacques, Kate; Donlin, Carolyn; Aagaard, Brad T.; Blair, James Luke; Boatwright, John; Garcia, Susan H.; Harris, Ruth A.; Michael, Andrew J.; Schwartz, David P.; DiLeo, Jeanne S. 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...
Brocher, Thomas M.; Baltay, Annemarie S.; Hardebeck, Jeanne L.; Pollitz, Fred F.; Murray, Jessica R.; Llenos, Andrea L.; Schwartz, David P.; Blair, James Luke; Ponti, Daniel J.; Lienkaemper, James J.; Langenheim, Victoria E.; Dawson, Timothy E.; Hudnut, Kenneth W.; Shelly, David R.; Dreger, Douglas S.; Boatwright, John; Aagaard, Brad T.; Wald, David J.; Allen, Richard M.; Barnhart, William D.; Knudsen, Keith L.; Brooks, Benjamin A.; Scharer, Katherine M.
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...
Hudnut, Kenneth W.; Brocher, Thomas M.; Prentice, Carol S.; Boatwright, John; Brooks, Benjamin A.; Aagaard, Brad T.; Blair, James Luke; Fletcher, Jon Peter B.; Erdem, Jemile; Wicks, Charles W.; Murray, Jessica R.; Pollitz, Fred F.; Langbein, John O.; Svarc, Jerry L.; Schwartz, David P.; Ponti, Daniel J.; Hecker, Suzanne; DeLong, Stephen B.; Rosa, Carla M.; Jones, Brenda; Lamb, Rynn M.; Rosinski, Anne M.; McCrink, Timothy P.; Dawson, Timothy E.; Seitz, Gordon G.; Glennie, Craig; Hauser, Darren; Ericksen, Todd; Mardock, Dan; Hoirup, Don F.; Bray, Jonathan D.; Rubin, Ron S. 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...
Aagaard, Brad T.; Knepley, M.G.; Williams, C.A. 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...
Aagaard, Brad T.; Lienkaemper, James J.; Schwartz, David P.