William J Stephenson
Bill Stephensen is a scientist in the Earthquake Hazards Program.
Science and Products
Filter Total Items: 53
Evidence for late Quaternary deformation along Crowley's Ridge, New Madrid seismic zone
The New Madrid seismic zone has been the source of multiple major (M ~7.0–7.5) earthquakes in the past 2 ka, yet the surface expression of recent deformation remains ambiguous. Crowleys Ridge, a linear ridge trending north‐south for 300+ km through the Mississippi Embayment, has been interpreted as either a fault‐bounded uplift or a nontectonic erosional remnant. New and previously published seism
Authors
Jessica Thompson Jobe, Ryan D. Gold, Richard W. Briggs, Robert Williams, William J. Stephenson, Jaime E. Delano, Anjana K. Shah, Burke J. Minsley
Paleoseismic results from the Alpine site, Wasatch fault zone: Timing and displacement data for six holocene earthquakes at the Salt Lake City–Provo segment boundary
To improve the characterization of Holocene earthquakes on the Wasatch fault zone (WFZ), we conducted light detection and ranging (lidar)‐based neotectonic mapping and excavated a paleoseismic trench across an 8‐m‐high fault scarp near Alpine, Utah, located <1 km<1 km south of the boundary between the Salt Lake City and Provo segments (SLCS and PS). We document evidence for six paleoearthquakes
Authors
Scott E. K. Bennett, Christopher DuRoss, Ryan D. Gold, Richard W. Briggs, Stephen Personius, Nadine G. Reitman, Joshua Devore, Adam Hiscock, Shannon A. Mahan, Harrison J. Gray, Sydney Gunnarson, William J. Stephenson, Elizabeth Pettinger, Jackson K. Odum
Holocene fault reactivation in the eastern Cascades, Washington
Significant uncertainty remains concerning how and where crustal shortening occurs throughout the eastern Cascade Range in Washington State. Using light detection and ranging (lidar) imagery, we identified an ∼5‐km‐long lineament in Swakane canyon near Wenatchee, roughly coincident with a strand of the Entiat fault. Topographic profiles across the lineament reveal a southwest‐side‐up break in slop
Authors
Benjamin L. Carlson, Elizabeth R. Schermer, Colin B. Amos, William J. Stephenson, Brian Sherrod, Shannon A. Mahan
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) and 1D stochastic synthetics (>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
Authors
Erin A. Wirth, Arthur Frankel, Nasser A. Marafi, John E. Vidale, William J. Stephenson
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 seismic ha
Authors
Morgan P. Moschetti, Nicolas Luco, Arthur Frankel, Mark D. Petersen, Brad T. Aagaard, Annemarie S. Baltay, Michael 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 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
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 Cascadia velocit
Authors
William J. Stephenson, Nadine G. Reitman, Stephen J. Angster
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 geologic constra
Authors
Morgan P. Moschetti, Stephen H. Hartzell, Leonardo Ramirez-Guzman, Arthur 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 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 province. F
Authors
Harvey M. Kelsey, Tyler C. Ladinsky, Lydia M. Staisch, Brian Sherrod, Richard J. Blakely, Thomas Pratt, William Stephenson, Jackson K. Odum, Elmira Wan
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 Hz) synthe
Authors
Erin Wirth, Arthur 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
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 fault acros
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 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 reverse-o
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
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 earthquakes and th
Authors
William J. Stephenson, Jackson K. Odum, Charles W. Wicks, Thomas L. Pratt, Richard J. Blakely
Science and Products
Filter Total Items: 53
Evidence for late Quaternary deformation along Crowley's Ridge, New Madrid seismic zone
The New Madrid seismic zone has been the source of multiple major (M ~7.0–7.5) earthquakes in the past 2 ka, yet the surface expression of recent deformation remains ambiguous. Crowleys Ridge, a linear ridge trending north‐south for 300+ km through the Mississippi Embayment, has been interpreted as either a fault‐bounded uplift or a nontectonic erosional remnant. New and previously published seism
Authors
Jessica Thompson Jobe, Ryan D. Gold, Richard W. Briggs, Robert Williams, William J. Stephenson, Jaime E. Delano, Anjana K. Shah, Burke J. Minsley
Paleoseismic results from the Alpine site, Wasatch fault zone: Timing and displacement data for six holocene earthquakes at the Salt Lake City–Provo segment boundary
To improve the characterization of Holocene earthquakes on the Wasatch fault zone (WFZ), we conducted light detection and ranging (lidar)‐based neotectonic mapping and excavated a paleoseismic trench across an 8‐m‐high fault scarp near Alpine, Utah, located <1 km<1 km south of the boundary between the Salt Lake City and Provo segments (SLCS and PS). We document evidence for six paleoearthquakes
Authors
Scott E. K. Bennett, Christopher DuRoss, Ryan D. Gold, Richard W. Briggs, Stephen Personius, Nadine G. Reitman, Joshua Devore, Adam Hiscock, Shannon A. Mahan, Harrison J. Gray, Sydney Gunnarson, William J. Stephenson, Elizabeth Pettinger, Jackson K. Odum
Holocene fault reactivation in the eastern Cascades, Washington
Significant uncertainty remains concerning how and where crustal shortening occurs throughout the eastern Cascade Range in Washington State. Using light detection and ranging (lidar) imagery, we identified an ∼5‐km‐long lineament in Swakane canyon near Wenatchee, roughly coincident with a strand of the Entiat fault. Topographic profiles across the lineament reveal a southwest‐side‐up break in slop
Authors
Benjamin L. Carlson, Elizabeth R. Schermer, Colin B. Amos, William J. Stephenson, Brian Sherrod, Shannon A. Mahan
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) and 1D stochastic synthetics (>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
Authors
Erin A. Wirth, Arthur Frankel, Nasser A. Marafi, John E. Vidale, William J. Stephenson
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 seismic ha
Authors
Morgan P. Moschetti, Nicolas Luco, Arthur Frankel, Mark D. Petersen, Brad T. Aagaard, Annemarie S. Baltay, Michael 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 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
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 Cascadia velocit
Authors
William J. Stephenson, Nadine G. Reitman, Stephen J. Angster
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 geologic constra
Authors
Morgan P. Moschetti, Stephen H. Hartzell, Leonardo Ramirez-Guzman, Arthur 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 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 province. F
Authors
Harvey M. Kelsey, Tyler C. Ladinsky, Lydia M. Staisch, Brian Sherrod, Richard J. Blakely, Thomas Pratt, William Stephenson, Jackson K. Odum, Elmira Wan
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 Hz) synthe
Authors
Erin Wirth, Arthur 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
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 fault acros
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 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 reverse-o
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
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 earthquakes and th
Authors
William J. Stephenson, Jackson K. Odum, Charles W. Wicks, Thomas L. Pratt, Richard J. Blakely