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 Brocher, Annemarie Baltay Sundstrom, Jeanne Hardebeck, Fred F. Pollitz, Jessica Murray, Andrea L. Llenos, David Schwartz, J. Blair, Daniel Ponti, James J. Lienkaemper, Victoria E. Langenheim, Timothy Dawson, Kenneth Hudnut, David Shelly, Douglas Dreger, John Boatwright, Brad Aagaard, David Wald, Richard Allen, William Barnhart, Keith Knudsen, Benjamin Brooks, Katherine 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 Hudnut, Thomas Brocher, Carol Prentice, John Boatwright, Benjamin Brooks, Brad Aagaard, J. Blair, Jon Fletcher, Jemile Erdem, Charles Wicks, Jessica Murray, Fred F. Pollitz, John Langbein, Jerry Svarc, David Schwartz, Daniel Ponti, Suzanne Hecker, Stephen DeLong, Carla Rosa, Brenda Jones, Rynn Lamb, Anne Rosinski, Timothy McCrink, Timothy Dawson, Gordon G. Seitz, Craig Glennie, Darren Hauser, Todd Ericksen, Dan Mardock, Don Hoirup, Jonathan Bray, Ron 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 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 Aagaard, James Lienkaemper, David 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 Graves, Brad 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 Aagaard, D. D. Oglesby, J.-P. Ampuero, Thomas Hanks, N. Abrahamson
Ground-motion modeling of Hayward fault scenario earthquakes, part I: Construction of the suite of scenarios Ground-motion modeling of Hayward fault scenario earthquakes, part I: Construction of the suite of scenarios
We construct kinematic earthquake rupture models for a suite of 39 Mw 6.6-7.2 scenario earthquakes involving the Hayward, Calaveras, and Rodgers Creek faults. We use these rupture models in 3D ground-motion simulations as discussed in Part II (Aagaard et al., 2010) to provide detailed estimates of the shaking for each scenario. We employ both geophysical constraints and empirical...
Authors
Brad Aagaard, Robert Graves, David Schwartz, David Ponce, Russell Graymer
Ground-motion modeling of Hayward fault scenario earthquakes, part II: Simulation of long-period and broadband ground motions Ground-motion modeling of Hayward fault scenario earthquakes, part II: Simulation of long-period and broadband ground motions
We simulate long-period (T>1.0–2.0 s) and broadband (T>0.1 s) ground motions for 39 scenario earthquakes (Mw 6.7–7.2) involving the Hayward, Calaveras, and Rodgers Creek faults. For rupture on the Hayward fault, we consider the effects of creep on coseismic slip using two different approaches, both of which reduce the ground motions, compared with neglecting the influence of creep...
Authors
Brad Aagaard, Robert Graves, Arthur Rodgers, Thomas Brocher, Robert Simpson, Douglas Dreger, N. Anders Petersson, Shawn Larsen, Shuo Ma, Robert Jachens
Data files for ground-motion simulations of the 1906 San Francisco earthquake and scenario earthquakes on the Northern San Andreas Fault Data files for ground-motion simulations of the 1906 San Francisco earthquake and scenario earthquakes on the Northern San Andreas Fault
This data set contains results from ground-motion simulations of the 1906 San Francisco earthquake, seven hypothetical earthquakes on the northern San Andreas Fault, and the 1989 Loma Prieta earthquake. The bulk of the data consists of synthetic velocity time-histories. Peak ground velocity on a 1/60th degree grid and geodetic displacements from the simulations are also included. Details...
Authors
Brad Aagaard, Michael Barall, Thomas Brocher, David Dolenc, Douglas Dreger, Robert Graves, Stephen Harmsen, Stephen Hartzell, Shawn Larsen, Kathleen McCandless, Stefan Nilsson, N. Anders Petersson, Arthur Rodgers, Bjorn Sjogreen, Mary Lou Zoback
The SCEC/USGS dynamic earthquake rupture code verification exercise The SCEC/USGS dynamic earthquake rupture code verification exercise
Numerical simulations of earthquake rupture dynamics are now common, yet it has been difficult to test the validity of these simulations because there have been few field observations and no analytic solutions with which to compare the results. This paper describes the Southern California Earthquake Center/U.S. Geological Survey (SCEC/USGS) Dynamic Earthquake Rupture Code Verification...
Authors
R.A. Harris, M. Barall, R. Archuleta, E. Dunham, Brad Aagaard, J.-P. Ampuero, H. Bhat, Victor M. Cruz-Atienza, L. Dalguer, P. Dawson, S. Day, B. Duan, G. Ely, Y. Kaneko, Y. Kase, N. Lapusta, Yajing Liu, S. Ma, D. Oglesby, K. Olsen, A. Pitarka, S. Song, E. Templeton
The 1906 San Francisco earthquake a century later: Introduction to the special section The 1906 San Francisco earthquake a century later: Introduction to the special section
The great 1906 San Francisco earthquake is perhaps the landmark event in the history of earthquake science. It began with a foreshock at 5:12 a.m. local time in the morning of 18 April 1906. Some 30 sec later, the main event initiated on the San Andreas fault, just off the San Francisco coast (Lawson, 1908). Within 90 sec, nearly 480 km of the San Andreas fault ruptured (see Fig. 1)...
Authors
Brad Aagaard, Gregory Beroza
Broadband simulations for Mw 7.8 southern san andreas earthquakes: Ground motion sensitivity to rupture speed Broadband simulations for Mw 7.8 southern san andreas earthquakes: Ground motion sensitivity to rupture speed
Using the high-performance computing resources of the Southern California Earthquake Center, we simulate broadband (0-10 Hz) ground motions for three Mw 7.8 rupture scenarios of the southern San Andreas fault. The scenarios incorporate a kinematic rupture description with the average rupture speed along the large slip portions of the fault set at 0.96, 0.89, and 0.84 times the local...
Authors
R.W. Graves, Brad Aagaard, K.W. Hudnut, L.M. Star, J.P. Stewart, T.H. Jordan
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 Brocher, Annemarie Baltay Sundstrom, Jeanne Hardebeck, Fred F. Pollitz, Jessica Murray, Andrea L. Llenos, David Schwartz, J. Blair, Daniel Ponti, James J. Lienkaemper, Victoria E. Langenheim, Timothy Dawson, Kenneth Hudnut, David Shelly, Douglas Dreger, John Boatwright, Brad Aagaard, David Wald, Richard Allen, William Barnhart, Keith Knudsen, Benjamin Brooks, Katherine 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 Hudnut, Thomas Brocher, Carol Prentice, John Boatwright, Benjamin Brooks, Brad Aagaard, J. Blair, Jon Fletcher, Jemile Erdem, Charles Wicks, Jessica Murray, Fred F. Pollitz, John Langbein, Jerry Svarc, David Schwartz, Daniel Ponti, Suzanne Hecker, Stephen DeLong, Carla Rosa, Brenda Jones, Rynn Lamb, Anne Rosinski, Timothy McCrink, Timothy Dawson, Gordon G. Seitz, Craig Glennie, Darren Hauser, Todd Ericksen, Dan Mardock, Don Hoirup, Jonathan Bray, Ron 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 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 Aagaard, James Lienkaemper, David 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 Graves, Brad 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 Aagaard, D. D. Oglesby, J.-P. Ampuero, Thomas Hanks, N. Abrahamson
Ground-motion modeling of Hayward fault scenario earthquakes, part I: Construction of the suite of scenarios Ground-motion modeling of Hayward fault scenario earthquakes, part I: Construction of the suite of scenarios
We construct kinematic earthquake rupture models for a suite of 39 Mw 6.6-7.2 scenario earthquakes involving the Hayward, Calaveras, and Rodgers Creek faults. We use these rupture models in 3D ground-motion simulations as discussed in Part II (Aagaard et al., 2010) to provide detailed estimates of the shaking for each scenario. We employ both geophysical constraints and empirical...
Authors
Brad Aagaard, Robert Graves, David Schwartz, David Ponce, Russell Graymer
Ground-motion modeling of Hayward fault scenario earthquakes, part II: Simulation of long-period and broadband ground motions Ground-motion modeling of Hayward fault scenario earthquakes, part II: Simulation of long-period and broadband ground motions
We simulate long-period (T>1.0–2.0 s) and broadband (T>0.1 s) ground motions for 39 scenario earthquakes (Mw 6.7–7.2) involving the Hayward, Calaveras, and Rodgers Creek faults. For rupture on the Hayward fault, we consider the effects of creep on coseismic slip using two different approaches, both of which reduce the ground motions, compared with neglecting the influence of creep...
Authors
Brad Aagaard, Robert Graves, Arthur Rodgers, Thomas Brocher, Robert Simpson, Douglas Dreger, N. Anders Petersson, Shawn Larsen, Shuo Ma, Robert Jachens
Data files for ground-motion simulations of the 1906 San Francisco earthquake and scenario earthquakes on the Northern San Andreas Fault Data files for ground-motion simulations of the 1906 San Francisco earthquake and scenario earthquakes on the Northern San Andreas Fault
This data set contains results from ground-motion simulations of the 1906 San Francisco earthquake, seven hypothetical earthquakes on the northern San Andreas Fault, and the 1989 Loma Prieta earthquake. The bulk of the data consists of synthetic velocity time-histories. Peak ground velocity on a 1/60th degree grid and geodetic displacements from the simulations are also included. Details...
Authors
Brad Aagaard, Michael Barall, Thomas Brocher, David Dolenc, Douglas Dreger, Robert Graves, Stephen Harmsen, Stephen Hartzell, Shawn Larsen, Kathleen McCandless, Stefan Nilsson, N. Anders Petersson, Arthur Rodgers, Bjorn Sjogreen, Mary Lou Zoback
The SCEC/USGS dynamic earthquake rupture code verification exercise The SCEC/USGS dynamic earthquake rupture code verification exercise
Numerical simulations of earthquake rupture dynamics are now common, yet it has been difficult to test the validity of these simulations because there have been few field observations and no analytic solutions with which to compare the results. This paper describes the Southern California Earthquake Center/U.S. Geological Survey (SCEC/USGS) Dynamic Earthquake Rupture Code Verification...
Authors
R.A. Harris, M. Barall, R. Archuleta, E. Dunham, Brad Aagaard, J.-P. Ampuero, H. Bhat, Victor M. Cruz-Atienza, L. Dalguer, P. Dawson, S. Day, B. Duan, G. Ely, Y. Kaneko, Y. Kase, N. Lapusta, Yajing Liu, S. Ma, D. Oglesby, K. Olsen, A. Pitarka, S. Song, E. Templeton
The 1906 San Francisco earthquake a century later: Introduction to the special section The 1906 San Francisco earthquake a century later: Introduction to the special section
The great 1906 San Francisco earthquake is perhaps the landmark event in the history of earthquake science. It began with a foreshock at 5:12 a.m. local time in the morning of 18 April 1906. Some 30 sec later, the main event initiated on the San Andreas fault, just off the San Francisco coast (Lawson, 1908). Within 90 sec, nearly 480 km of the San Andreas fault ruptured (see Fig. 1)...
Authors
Brad Aagaard, Gregory Beroza
Broadband simulations for Mw 7.8 southern san andreas earthquakes: Ground motion sensitivity to rupture speed Broadband simulations for Mw 7.8 southern san andreas earthquakes: Ground motion sensitivity to rupture speed
Using the high-performance computing resources of the Southern California Earthquake Center, we simulate broadband (0-10 Hz) ground motions for three Mw 7.8 rupture scenarios of the southern San Andreas fault. The scenarios incorporate a kinematic rupture description with the average rupture speed along the large slip portions of the fault set at 0.96, 0.89, and 0.84 times the local...
Authors
R.W. Graves, Brad Aagaard, K.W. Hudnut, L.M. Star, J.P. Stewart, T.H. Jordan