William J Stephenson
Bill Stephensen is a scientist in the Earthquake Hazards Program.
Science and Products
Filter Total Items: 15
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Filter Total Items: 67
Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, part 1: Methodology and overall results Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, part 1: Methodology and overall results
We have produced a large set of broadband (0–10 Hz) synthetic seismograms for Mw 9.0 earthquakes on the Cascadia megathrust by combining synthetic seismograms derived from 3D finite‐difference simulations (≤1 Hz) with finite‐source, stochastic synthetics (≥1 Hz). We used a compound rupture model consisting of high stress drop Mw 8 subevents superimposed on large, shallower slip...
Authors
Arthur D. Frankel, Erin A. Wirth, Nasser A. Marafi, John Vidale, William J. Stephenson
Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia Megathrust based on 3D simulations and stochastic synthetics, Part 2: Rupture parameters and variability Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia Megathrust based on 3D simulations and stochastic synthetics, Part 2: Rupture parameters and variability
We used a combination of 3D finite‐difference simulations (>1 Hz) to generate broadband (0–10 Hz) synthetic seismograms for numerous Mw 9 earthquake rupture scenarios on the Cascadia megathrust. Slip consists of multiple high‐stress‐drop subevents (Mw 8) with short rise times on the deeper portions of the fault, superimposed on a background slip distribution with longer rise times. We...
Authors
Erin A. Wirth, Arthur D. Frankel, Nasser A. Marafi, John E. Vidale, William J. Stephenson
Integrate urban‐scale seismic hazard analyses with the U.S. National Seismic Hazard Model 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., MM 6.7 Northridge, California, Gao et al., 1996; MM 6.9 Kobe, Japan, Kawase, 1996; MM 6.8 Nisqually, Washington, Frankel, Carver, and Williams, 2002). Although this and other local‐scale features are critical to improving...
Authors
Morgan P. Moschetti, Nico Luco, Arthur D. Frankel, Mark D. Petersen, Brad T. Aagaard, Annemarie S. Baltay, Michael L. Blanpied, Oliver S. Boyd, Richard W. Briggs, Ryan D. Gold, Robert Graves, Stephen H. Hartzell, Sanaz Rezaeian, William J. Stephenson, David J. Wald, Robert A. Williams, Kyle B. Withers
P- and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, Version 1.6—Update for Open-File Report 2007–1348 P- and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, Version 1.6—Update for Open-File Report 2007–1348
In support of earthquake hazard studies and ground motion simulations in the Pacific Northwest, three-dimensional P- and S-wave velocity (VP and VS, respectively) models incorporating the Cascadia subduction zone were previously developed for the region encompassed from about 40.2°N. to 50°N. latitude, and from about 122°W. to 129°W. longitude. This report describes updates to the...
Authors
William J. Stephenson, Nadine G. Reitman, Stephen J. Angster
Geophysical characterization of seismic station sites in the United States – The importance of a flexible, multi-method approach Geophysical characterization of seismic station sites in the United States – The importance of a flexible, multi-method approach
Noninvasive geophysical site characterization methods were used in two recent projects to obtain shear-wave velocity (VS) profiles to a minimum depth of 30 m and the time-averaged VS of the upper 30 meters (VS30) at seismic station sites. These projects include the 2009 American Recovery and Reinvestment Act (ARRA) funded U.S. Geological Survey site characterization project for 191 sites...
Authors
Antony Martin, Alan Yong, William J. Stephenson, J. Boatwright, John Diehl
3D ground‐motion simulations of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone: Variability of long‐period (T≥1 s) ground motions and sensitivity to kinematic rupture parameters 3D ground‐motion simulations of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone: Variability of long‐period (T≥1 s) ground motions and sensitivity to kinematic rupture parameters
We examine the variability of long‐period (T≥1 s) earthquake ground motions from 3D simulations of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone, Utah, from a set of 96 rupture models with varying slip distributions, rupture speeds, slip velocities, and hypocenter locations. Earthquake ruptures were prescribed on a 3D fault representation that satisfies...
Authors
Morgan P. Moschetti, Stephen H. Hartzell, Leonardo Ramirez-Guzman, Arthur D. Frankel, Stephen J. Angster, William J. Stephenson
The story of a Yakima fold and how it informs Late Neogene and Quaternary backarc deformation in the Cascadia subduction zone, Manastash anticline, Washington, USA The story of a Yakima fold and how it informs Late Neogene and Quaternary backarc deformation in the Cascadia subduction zone, Manastash anticline, Washington, USA
The Yakima folds of central Washington, USA, are prominent anticlines that are the primary tectonic features of the backarc of the northern Cascadia subduction zone. What accounts for their topographic expression and how much strain do they accommodate and over what time period? We investigate Manastash anticline, a north vergent fault propagation fold typical of structures in the fold...
Authors
Harvey M. Kelsey, Tyler C. Ladinsky, Lydia M. Staisch, Brian L. Sherrod, Richard J. Blakely, Thomas L. Pratt, William J. Stephenson, Jackson K. Odum, Elmira Wan
3-D simulations of M9 earthquakes on the Cascadia Megathrust: Key parameters and uncertainty 3-D simulations of M9 earthquakes on the Cascadia Megathrust: Key parameters and uncertainty
Geologic and historical records indicate that the Cascadia subduction zone is capable of generating large, megathrust earthquakes up to magnitude 9. The last great Cascadia earthquake occurred in 1700, and thus there is no direct measure on the intensity of ground shaking or specific rupture parameters from seismic recordings. We use 3-D numerical simulations to generate broadband (0-10...
Authors
Erin Wirth, Arthur D. Frankel, John Vidale, Nasser A. Marafi, William J. Stephenson
Continuity of the Reelfoot fault across the Cottonwood Grove and Ridgely faults of the New Madrid Seismic Zone Continuity of the Reelfoot fault across the Cottonwood Grove and Ridgely faults of the New Madrid Seismic Zone
Previous investigators have argued that the northwest-striking Reelfoot fault of northwest Tennessee and southeastern Missouri is segmented. One segment boundary is at the intersection of the northeast-striking Cottonwood Grove and Ridgely strike-slip faults with the Reelfoot fault. We use seismic reflection and geologic mapping to locate and determine the history of the Reelfoot South...
Authors
M.L. Greenwood, Edward W Woolery, R. B. Van Arsdale, William J. Stephenson, Gary L. Patterson
The Evergreen basin and the role of the Silver Creek fault in the San Andreas fault system, San Francisco Bay region, California The Evergreen basin and the role of the Silver Creek fault in the San Andreas fault system, San Francisco Bay region, California
The Evergreen basin is a 40-km-long, 8-km-wide Cenozoic sedimentary basin that lies mostly concealed beneath the northeastern margin of the Santa Clara Valley near the south end of San Francisco Bay (California, USA). The basin is bounded on the northeast by the strike-slip Hayward fault and an approximately parallel subsurface fault that is structurally overlain by a set of west-verging...
Authors
Robert C. Jachens, Carl M. Wentworth, Russell W. Graymer, Robert Williams, David A. Ponce, Edward A. Mankinen, William J. Stephenson, Victoria E. Langenheim
Seismic imaging beneath an InSAR anomaly in eastern Washington State: Shallow faulting associated with an earthquake swarm in a low-hazard area Seismic imaging beneath an InSAR anomaly in eastern Washington State: Shallow faulting associated with an earthquake swarm in a low-hazard area
In 2001, a rare swarm of small, shallow earthquakes beneath the city of Spokane, Washington, caused ground shaking as well as audible booms over a five‐month period. Subsequent Interferometric Synthetic Aperture Radar (InSAR) data analysis revealed an area of surface uplift in the vicinity of the earthquake swarm. To investigate the potential faults that may have caused both the...
Authors
William J. Stephenson, Jackson K. Odum, Charles W. Wicks, Thomas L. Pratt, Richard J. Blakely
Preliminary assessment of a previously unknown fault zone beneath the Daytona Beach sand blow cluster near Marianna, Arkansas Preliminary assessment of a previously unknown fault zone beneath the Daytona Beach sand blow cluster near Marianna, Arkansas
We collected new high‐resolution P‐wave seismic‐reflection data to explore for possible faults beneath a roughly linear cluster of early to mid‐Holocene earthquake‐induced sand blows to the south of Marianna, Arkansas. The Daytona Beach sand blow deposits are located in east‐central Arkansas about 75 km southwest of Memphis, Tennessee, and about 80 km south of the southwestern end of the...
Authors
Jackson K. Odum, Robert Williams, William J. Stephenson, Martitia P. Tuttle, Hadar Al-Shukri
Science and Products
Filter Total Items: 15
No Result Found
Filter Total Items: 67
Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, part 1: Methodology and overall results Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, part 1: Methodology and overall results
We have produced a large set of broadband (0–10 Hz) synthetic seismograms for Mw 9.0 earthquakes on the Cascadia megathrust by combining synthetic seismograms derived from 3D finite‐difference simulations (≤1 Hz) with finite‐source, stochastic synthetics (≥1 Hz). We used a compound rupture model consisting of high stress drop Mw 8 subevents superimposed on large, shallower slip...
Authors
Arthur D. Frankel, Erin A. Wirth, Nasser A. Marafi, John Vidale, William J. Stephenson
Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia Megathrust based on 3D simulations and stochastic synthetics, Part 2: Rupture parameters and variability Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia Megathrust based on 3D simulations and stochastic synthetics, Part 2: Rupture parameters and variability
We used a combination of 3D finite‐difference simulations (>1 Hz) to generate broadband (0–10 Hz) synthetic seismograms for numerous Mw 9 earthquake rupture scenarios on the Cascadia megathrust. Slip consists of multiple high‐stress‐drop subevents (Mw 8) with short rise times on the deeper portions of the fault, superimposed on a background slip distribution with longer rise times. We...
Authors
Erin A. Wirth, Arthur D. Frankel, Nasser A. Marafi, John E. Vidale, William J. Stephenson
Integrate urban‐scale seismic hazard analyses with the U.S. National Seismic Hazard Model 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., MM 6.7 Northridge, California, Gao et al., 1996; MM 6.9 Kobe, Japan, Kawase, 1996; MM 6.8 Nisqually, Washington, Frankel, Carver, and Williams, 2002). Although this and other local‐scale features are critical to improving...
Authors
Morgan P. Moschetti, Nico Luco, Arthur D. Frankel, Mark D. Petersen, Brad T. Aagaard, Annemarie S. Baltay, Michael L. Blanpied, Oliver S. Boyd, Richard W. Briggs, Ryan D. Gold, Robert Graves, Stephen H. Hartzell, Sanaz Rezaeian, William J. Stephenson, David J. Wald, Robert A. Williams, Kyle B. Withers
P- and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, Version 1.6—Update for Open-File Report 2007–1348 P- and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, Version 1.6—Update for Open-File Report 2007–1348
In support of earthquake hazard studies and ground motion simulations in the Pacific Northwest, three-dimensional P- and S-wave velocity (VP and VS, respectively) models incorporating the Cascadia subduction zone were previously developed for the region encompassed from about 40.2°N. to 50°N. latitude, and from about 122°W. to 129°W. longitude. This report describes updates to the...
Authors
William J. Stephenson, Nadine G. Reitman, Stephen J. Angster
Geophysical characterization of seismic station sites in the United States – The importance of a flexible, multi-method approach Geophysical characterization of seismic station sites in the United States – The importance of a flexible, multi-method approach
Noninvasive geophysical site characterization methods were used in two recent projects to obtain shear-wave velocity (VS) profiles to a minimum depth of 30 m and the time-averaged VS of the upper 30 meters (VS30) at seismic station sites. These projects include the 2009 American Recovery and Reinvestment Act (ARRA) funded U.S. Geological Survey site characterization project for 191 sites...
Authors
Antony Martin, Alan Yong, William J. Stephenson, J. Boatwright, John Diehl
3D ground‐motion simulations of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone: Variability of long‐period (T≥1 s) ground motions and sensitivity to kinematic rupture parameters 3D ground‐motion simulations of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone: Variability of long‐period (T≥1 s) ground motions and sensitivity to kinematic rupture parameters
We examine the variability of long‐period (T≥1 s) earthquake ground motions from 3D simulations of Mw 7 earthquakes on the Salt Lake City segment of the Wasatch fault zone, Utah, from a set of 96 rupture models with varying slip distributions, rupture speeds, slip velocities, and hypocenter locations. Earthquake ruptures were prescribed on a 3D fault representation that satisfies...
Authors
Morgan P. Moschetti, Stephen H. Hartzell, Leonardo Ramirez-Guzman, Arthur D. Frankel, Stephen J. Angster, William J. Stephenson
The story of a Yakima fold and how it informs Late Neogene and Quaternary backarc deformation in the Cascadia subduction zone, Manastash anticline, Washington, USA The story of a Yakima fold and how it informs Late Neogene and Quaternary backarc deformation in the Cascadia subduction zone, Manastash anticline, Washington, USA
The Yakima folds of central Washington, USA, are prominent anticlines that are the primary tectonic features of the backarc of the northern Cascadia subduction zone. What accounts for their topographic expression and how much strain do they accommodate and over what time period? We investigate Manastash anticline, a north vergent fault propagation fold typical of structures in the fold...
Authors
Harvey M. Kelsey, Tyler C. Ladinsky, Lydia M. Staisch, Brian L. Sherrod, Richard J. Blakely, Thomas L. Pratt, William J. Stephenson, Jackson K. Odum, Elmira Wan
3-D simulations of M9 earthquakes on the Cascadia Megathrust: Key parameters and uncertainty 3-D simulations of M9 earthquakes on the Cascadia Megathrust: Key parameters and uncertainty
Geologic and historical records indicate that the Cascadia subduction zone is capable of generating large, megathrust earthquakes up to magnitude 9. The last great Cascadia earthquake occurred in 1700, and thus there is no direct measure on the intensity of ground shaking or specific rupture parameters from seismic recordings. We use 3-D numerical simulations to generate broadband (0-10...
Authors
Erin Wirth, Arthur D. Frankel, John Vidale, Nasser A. Marafi, William J. Stephenson
Continuity of the Reelfoot fault across the Cottonwood Grove and Ridgely faults of the New Madrid Seismic Zone Continuity of the Reelfoot fault across the Cottonwood Grove and Ridgely faults of the New Madrid Seismic Zone
Previous investigators have argued that the northwest-striking Reelfoot fault of northwest Tennessee and southeastern Missouri is segmented. One segment boundary is at the intersection of the northeast-striking Cottonwood Grove and Ridgely strike-slip faults with the Reelfoot fault. We use seismic reflection and geologic mapping to locate and determine the history of the Reelfoot South...
Authors
M.L. Greenwood, Edward W Woolery, R. B. Van Arsdale, William J. Stephenson, Gary L. Patterson
The Evergreen basin and the role of the Silver Creek fault in the San Andreas fault system, San Francisco Bay region, California The Evergreen basin and the role of the Silver Creek fault in the San Andreas fault system, San Francisco Bay region, California
The Evergreen basin is a 40-km-long, 8-km-wide Cenozoic sedimentary basin that lies mostly concealed beneath the northeastern margin of the Santa Clara Valley near the south end of San Francisco Bay (California, USA). The basin is bounded on the northeast by the strike-slip Hayward fault and an approximately parallel subsurface fault that is structurally overlain by a set of west-verging...
Authors
Robert C. Jachens, Carl M. Wentworth, Russell W. Graymer, Robert Williams, David A. Ponce, Edward A. Mankinen, William J. Stephenson, Victoria E. Langenheim
Seismic imaging beneath an InSAR anomaly in eastern Washington State: Shallow faulting associated with an earthquake swarm in a low-hazard area Seismic imaging beneath an InSAR anomaly in eastern Washington State: Shallow faulting associated with an earthquake swarm in a low-hazard area
In 2001, a rare swarm of small, shallow earthquakes beneath the city of Spokane, Washington, caused ground shaking as well as audible booms over a five‐month period. Subsequent Interferometric Synthetic Aperture Radar (InSAR) data analysis revealed an area of surface uplift in the vicinity of the earthquake swarm. To investigate the potential faults that may have caused both the...
Authors
William J. Stephenson, Jackson K. Odum, Charles W. Wicks, Thomas L. Pratt, Richard J. Blakely
Preliminary assessment of a previously unknown fault zone beneath the Daytona Beach sand blow cluster near Marianna, Arkansas Preliminary assessment of a previously unknown fault zone beneath the Daytona Beach sand blow cluster near Marianna, Arkansas
We collected new high‐resolution P‐wave seismic‐reflection data to explore for possible faults beneath a roughly linear cluster of early to mid‐Holocene earthquake‐induced sand blows to the south of Marianna, Arkansas. The Daytona Beach sand blow deposits are located in east‐central Arkansas about 75 km southwest of Memphis, Tennessee, and about 80 km south of the southwestern end of the...
Authors
Jackson K. Odum, Robert Williams, William J. Stephenson, Martitia P. Tuttle, Hadar Al-Shukri