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
Data files from simulations
Data Files for Ground-Motion Simulations of the 1906 San Francisco Earthquake and Scenario Earthquakes on the Northern San Andreas FaultUSGS Data Series 413
Software
PyLith crustal deformation modeling software, Computational Infrastructure for Geodynamics
Presentations
- USGS Public Lecture: Ground Shaking in the 1989 M6.9 Loma Prieta Earthquake: A view from 25 years later, September 25, 2014
Publications:
Cochran, E.S., Aagaard, B.T., Allen, R.M., Andrews, J., Baltay, A.S., Barbour, A.J., Bodin, P., Brooks, B.A., Chung, A., Crowell, B.W., Given, D.D., Hanks, T.C., Hartog, J.R., Hauksson, E., Heaton, T.H., McBride, S., Meier, M-A., Melgar, D., Minson, S.E., Murray, J.R., Strauss, J.A., and Toomey, D., 2018, Research to improve ShakeAlert earthquake early warning products and their utility: U.S. Geological Survey Open-File Report 2018–1131, 17 p., doi: 10.3133/ofr20181131.
Harris, R.A., M. Barall, B. Aagaard, S. Ma, D. Roten, K. Olsen, B. Duan, B. Luo, D. Liu, K. Bai, J.-P. Ampuero, Y. Kaneko, A.-A. Gabriel, K. Duru, T. Ulrich, S. Wollherr, Z. Shi, E. Dunham, S. Bydlon, Z. Zhang, X. Chen, S.N. Somala, C. Pelties, J. Tago, V.M. Cruz-Atienza, J. Kozdon, E. Daub, K. Aslam, Y. Kase, K. Withers, and L. Dalguer (2018), A suite of exercises for verifying dynamic earthquake rupture codes, Seism. Res. Lett., 89(3), 1146-1162, doi: 10.1785/0220170222.
Aagaard, Brad, Celebi, Mehmet, Gee, Lind, Graves, Robert, Jaiswal, Kishor, Kalkan, Erol, Knudsen, Keith, Luco, Nico, Smith, James, Steidl, Jamison, and Stephens, Christopher, 2017, U.S. Geological Survey National Strong-Motion Project strategic plan, 2017–22: U.S. Geological Survey Open-File Report 2017–1156, 14 p., doi: 10.3133/ofr20171156.
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 W. Graves, Brad Aagaard "Subsurface Geometry of the San Andreas Fault in Southern California: Results from the Salton Seismic Imaging Project (SSIP) and Strong Ground Motion Expectations," Bulletin of the Seismological Society of America Jul 2017, doi: 10.1785/0120160309
Aagaard, B.T., Blair, J.L., Boatwright, J., Garcia, S.H., Harris, R.A., Michael, A.J., Schwartz, D.P., and DiLeo, J.S., 2016, Earthquake outlook for the San Francisco Bay region 2014–2043 (ver. 1.1, August 2016): U.S. Geological Survey Fact Sheet 2016–3020, 6 p., doi: 10.3133/fs20163020.
Brocher, T.M., A. S. Baltay, J. L. Hardebeck, F. F. Pollitz, J. R. Murray, A. L. Llenos, D. P. Schwartz, J. L. Blair, D. J. Ponti, J. J. Lienkaemper, V. E. Langenheim, T. E. Dawson, K. W. Hudnut, D. R. Shelly, D. Dreger, J. Boatwright, B. T. Aagaard, D. J. Wald, R. M. Allen, W. D. Barnhart, K. L. Knudsen, B. A. Brooks, and K. M. Scharer, 2015, The M6.0 24 August 2014 South Napa Earthquake, Seism. Res. Lett., vol. 86, no. 2A, 309-326, doi:10.1785/0220150004.
Hudnut, K.W., Brocher, T.M., Prentice, C.S., Boatwright, J., Brooks, B.A., Aagaard, B.T., Blair, J.L., Fletcher, J., Erdem, J.E., Wicks, C.W., Murray, J.R., Pollitz, F.F., Langbein, J., Svarc, J., Schwartz, D.P., Ponti, D.J., Hecker, S., DeLong, S., Rosa, C., Jones, B., Lamb, R., Rosinski, A., McCrink, T.P., Dawson, T.E., Seitz, G., Rubin, R.S., Glennie, C., Hauser, D., Ericksen, T., Mardock, D., Hoirup, D.F., and Bray, J.D., 2014, Key recovery factors for the August 24, 2014, South Napa earthquake: U.S. Geological Survey Open-File Report 2014–1249, 51 p., doi: 10.3133/ofr20141249.
Aagaard, B. T., M. G. Knepley, and C. A. Williams (2013), A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation, Journal of Geophysical Research: Solid Earth, 118, 3059–3079, doi: 10.1002/jgrb.50217.
Aagaard, B. T., J. J. Lienkaemper, and D. P. Schwartz (2012, June), Probabilistic estimates of surface coseismic slip and afterslip for Hayward fault earthquakes, Bulletin of the Seismological Society of America, 103(3), 961-979, doi: 10.1785/0120110200.
Harris, R. A., M. Barall, D. J. Andrews, B. Duan, S. Ma, E. M. Dunham, A. A. Gabriel, Y. Kaneko, Y. Kase, B. T. Aagaard, D. D. Oglesby, J. P. Ampuero, T. C. Hanks, and N. Abrahamson (2011, September/October), Verifying a computational method for predicting extreme ground motion, Seismological Research Letters, 82(5), 638-644, doi: 10.1785/gssrl.82.5.638.
Graves, R. W. and B. T. Aagaard (2011, April), 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, Bulletin of the Seismological Society of America, 101(2), 895-907, doi: 10.1785/0120100233.
Aagaard, B. T., R. W. Graves, D. P. Schwartz, D. A. Ponce, and R. W. Graymer (2010, December), Ground-motion modeling of Hayward fault scenario earthquakes, Part I: Construction of the suite of scenarios, Bulletin of the Seismological Society of America 100(6), 2927-2944, doi: 10.1785/0120090324.
Aagaard, B. T., R. W. Graves, A. Rodgers, T. M. Brocher, R. W. Simpson, D. Dreger, N. A. Petersson, S. C. Larsen, S. Ma, and R. C. Jachens (2010, December), Ground motion modeling of Hayward fault scenario earthquakes, Part II: Simulation of long-period and broadband ground motions, Bulletin of the Seismological Society of America, 100(6), 2945-2977, doi: 10.1785/0120090379.
Graves, R. W., B. T. Aagaard, and K. W. Hudnut (2010, May), The ShakeOut earthquake source and ground motion simulations, Earthquake Spectra, 27(2), 273-291, doi: 10.1193/1.3570677.
Harris, R. A., M. Barall, R. Archuleta, E. Dunham, B. Aagaard, J. P. Ampuero, H. Bhat, V. Cruz-Atienza, L. Dalguer, P. Dawson, S. Day, B. Duan, G. Ely, Y. Kaneko, Y. Kase, N. Lapusta, Y. Liu, S. Ma, D. Oglesby, K. Olsen, A. Pitarka, S. Song, and E. Templeton (2009, January), The SCEC/USGS Dynamic Earthquake Rupture Code Verification Exercise, Seismological Research Letters, 80(1), 119-126, doi: 10.1785/gssrl.80.1.119.
Graves, R. W., B. T. Aagaard, K. W. Hudnut, L. M. Star, J. P. Stewart, and T. H. Jordan (2008, November 20), Broadband simulations for Mw 7.8 southern San Andreas earthquakes: Ground motion sensitivity to rupture speed, Geophysical Research Letters, 35, L22302,doi:10.1029/2008GL035750.
Aagaard, B. T., and T. H. Heaton (2008, April 8), Constraining fault constitutive behavior with slip and stress heterogeneity, Journal of Geophysical Research, 113, B04301, doi:10.1029/2006JB004793.
Aagaard, B. T. and G. C. Beroza (2008, April), The 1906 San Francisco Earthquake a Century Later: Introduction to the Special Section, Bulletin of the Seismological Society of America 98(2), 817--822, doi: 10.1785/0120060401.
Aagaard, B. T., T. M. Brocher, D. Dolenc, D. Dreger, R. W. Graves, S. Harmsen, S. Hartzell, S. Larsen, M. L. Zoback (2008, April), Ground-Motion Modeling of the 1906 San Francisco Earthquake, Part I: Validation Using the 1989 Loma Prieta Earthquake, Bulletin of the Seismological Society of America 98(2), 989-1011, doi: 10.1785/0120060409.
Aagaard, B. T., T. M. Brocher, D. Dolenc, D. Dreger, R. W. Graves, S. Harmsen, S. Hartzell, S. Larsen, K. McCandless, S. Nilsson, N. A. Petersson, A. Rogers, B. Sjogreen, M. L. Zoback (2008, April), Ground-Motion Modeling of the 1906 San Francisco Earthquake, Part II: Ground-Motion Estimates for the 1906 Earthquake and Scenario Events, Bulletin of the Seismological Society of America 98(2), 1012-1046, doi: 10.1785/0120060410.
McPhee, D. K., V. E. Langenheim, S. Hartzell, R. J. McLaughlin, B. T. Aagaard, R. C. Jachens, and C. McCabe (2007, October), Basin Structure beneath the Santa Rosa Plain, Northern California: Implications for Damage Caused by the 1969 Santa Rosa and 1906 San Francisco Earthquakes, Bulletin of the Seismological Society of America 97(5), 1449-1457, doi: 10.1785/0120060269.
Bakun, W. H., B. Aagaard, B. Dost, W. L. Ellsworth, J. L. Hardebeck, R. A. Harris, C. Ji, M. J. S. Johnston, J. Langbein, J. J. Lienkaemper, A. J. Michael, J. R. Murray, R. M. Nadeau, P. A. Reasenberg, M. S. Reichle, E. A. Roeloffs, A. Shakal, R. W. Simpson and F. Waldhauser (2005, October 13), Nature 437, 969--974, doi: 10.1038/nature04067.
Smith, D. E., B. T. Aagaard, and T. H. Heaton (2005, June), Teleseismic body waves from dynamically rupturing shallow thrust faults: Are they opaque for surface-reflected phases?, Bulletin of the Seismological Society of America 95(3), 800-817, doi: 10.1785/0120030171.
B. T. Aagaard, G. Anderson, and K. Hudnut (2004, December), Dynamic Rupture Modeling of the Transition from Thrust to Strike-Slip Motion in the 2002 Denali Fault, Alaska, Earthquake, Bulletin of the Seismological Society of America 94(6B), S190-S201, doi: 10.1785/0120040614.
B. T. Aagaard and T. H. Heaton (2004, December), Near-Source Ground Motions From Simulations of Sustained Intersonic and Supersonic Fault Ruptures, Bulletin of the Seismological Society of America 94(6), 2064-2078.
B. T. Aagaard, J. F. Hall, and T. H. Heaton (2004, February), Effects of Fault Dip and Slip Rake Angles on Near-Source Ground Motions: Why Rupture Directivity Was Minimal in the 1999 Chi-Chi, Taiwan, Earthquake, Bulletin of the Seismological Society of America 94(1), 155-170, doi: 10.1785/0120030053.
Anderson, G., B. T. Aagaard, and K. Hudnut (2003, December 12), Fault Interactions and Large Complex Earthquakes in the Los Angeles Area, Science 302(5652), 1946-1949, doi: 10.1126/science.1090747.
B. T. Aagaard, T. H. Heaton, and J. F. Hall (2001, December), Dynamic earthquake ruptures in the presence of lithostatic normal stresses: Implications for friction models and heat production, Bulletin of the Seismological Society of America 91(6), 1765-1796, doi: 10.1785/0120000257
B. T. Aagaard, J. F. Hall, and T. H. Heaton (2001, May), Characterization of near-source ground motion with earthquake simulations, Earthquake Spectra 17(2), 177-207, doi: 10.1193/1.1586171.
Duron, Z. H., B. Aagaard, and D. K. Ostrom (1994, December), Spectral estimates of ambient and transient responses of a concrete dam using the maximum entropy method, Dam Engineering 5(4), 31-42.
Duron, Z. H., D. K. Ostrom, B. Aagaard (1994, May), Measured steady state, ambient, and transient responses of a small arch dam, Dam Engineering 5(1), 43-62.
Duron, Z. H., D. K. Ostrom, B. Aagaard, and B. Fischer (1994, April), Evaluating the behavior of dams during earthquakes, Hydro Review 13(2), 54-52.
Ph.D. Thesis
B. T. Aagaard (1999, October 13), Finite-element simulations of earthquakes, Technical Report 99-03, California Institute of Technology, Earthquake Engineering Research Laboratory, Pasadena, California. Caltech Earthquake Engineering Research Laboratory Technical Reports.
Technical Reports
B. T. Aagaard, J. F. Hall, and T. H. Heaton (2001), Effect of fault dip and slip rake on near-source ground motions: Why Chi-Chi was a relatively mild M 7.6 earthquake, University of California, Berkeley, Pacific Earthquake Engineering Research Center, Berkeley, California.
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.