William J Stephenson
Bill Stephensen is a scientist in the Earthquake Hazards Program.
Science and Products
Filter Total Items: 16
A Bayesian Monte-Carlo Inversion of Spatial Auto-Correlation (SPAC) for Near-Surface Vs Structure Applied to Both Broadband and Geophone Data - Data Release A Bayesian Monte-Carlo Inversion of Spatial Auto-Correlation (SPAC) for Near-Surface Vs Structure Applied to Both Broadband and Geophone Data - Data Release
The datasets for this investigation consist of microtremor array data collected at: 1) 18 sites in Salt Lake and Utah valleys, Utah, and 2) two sites as part of the Frontier Observatory for Research in Geothermal Energy (FORGE) near Milford, Utah. Each of the 18 sites in the Salt Lake and Utah valleys were acquired with four-sensor arrays with three-component (3C) sensors having flat...
Shear-wave velocity in the Seattle basin to 2 km depth characterized with the krSPAC microtremor array method: insights for urban basin-scale imaging - Data Release Shear-wave velocity in the Seattle basin to 2 km depth characterized with the krSPAC microtremor array method: insights for urban basin-scale imaging - Data Release
The dataset for this investigation consists of microtremor array data collected at 11 sites in the Seattle basin, Washington State. Ten of the arrays consisted of seven Nanometrics Trillium Compact broadband sensors deployed in asymmetric nested triangles (sites ST01, BA02, SP04, LF05, UW06, SN07, RD08, EL09, CH10, and KG11) that recorded for up to six hours. The eleventh array, at site...
Data for Holocene fault reactivation in the eastern Cascades, WA Data for Holocene fault reactivation in the eastern Cascades, WA
Significant uncertainty remains in how and where crustal shortening occurs throughout the eastern Cascade Range in Washington State. Using lidar imagery, we identified a ~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 slope with an average of ~3 m of...
Data for P- and S-wave Seismic Velocity Models Incorporating the Cascadia Subduction Zone for 3D Earthquake Ground Motion simulations- Update for Open-File Report 2007-1348 Data for P- and S-wave Seismic Velocity Models Incorporating the Cascadia Subduction Zone for 3D Earthquake Ground Motion simulations- Update for Open-File Report 2007-1348
The data for this release is an ASCII file containing grid points of Cascadia P- and S-wave velocity models. The model volume was developed to include the Cascadia subduction zone for purposes of ground motion simulation. The description of the model and background of its development is provided in the associated Open-File Report. The grid points are given in Universal Transverse...
Filter Total Items: 69
Introduction to the special issue of the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) international guidelines for applying noninvasive geophysical techniques to characterize seismic site conditions Introduction to the special issue of the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) international guidelines for applying noninvasive geophysical techniques to characterize seismic site conditions
Knowledge about local seismic site conditions provides critical information to account for site effects that are commonly observed in strong motion recordings. Certainly, other wave propagation effects can influence these observations, which are attributable to variations in material properties of the paths traveled by the waves, as well as the characteristics of the seismic source...
Authors
Alan Yong, Aysegul Askan, John Cassidy, Sebastiano D’Amico, Stefano Parolai, Marco Pilz, William J. Stephenson
Flexible multimethod approach for seismic site characterization Flexible multimethod approach for seismic site characterization
We describe the flexible multimethod seismic site characterization technique for obtaining shear-wave velocity (VS) profiles and derivative information, such as the time-averaged VS of the upper 30 m (VS30). Simply stated, the multimethod approach relies on the application of multiple independent noninvasive site characterization acquisition and analysis techniques utilized in a flexible...
Authors
William J. Stephenson, Alan Yong, Antony Martin
Microtremor array method using spatial autocorrelation analysis of Rayleigh‑wave data Microtremor array method using spatial autocorrelation analysis of Rayleigh‑wave data
Microtremor array measurements (MAM) and passive surface wave methods in general, have been increasingly used to non-invasively estimate shear-wave velocity structures (Vs) for various purposes. The methods estimate dispersion curves and invert them for retrieving S-wave velocity profiles. This paper summarizes principles, limitations, data collection and processing methods. It intends...
Authors
Koichi Hayashi, Michael W. Asten, William J. Stephenson, Cecile Cornou, Manuel Hobiger, Marco Pilz, Hiroaki Yamanaka
Seismic site characterization with shear wave (SH) reflection and refraction methods Seismic site characterization with shear wave (SH) reflection and refraction methods
Reflection and critically refracted seismic methods use traveltime measurements of body waves propagating between a source and a series of receivers on the ground surface to calculate subsurface velocities. Body wave energy is refracted or reflected at boundaries where there is a change in seismic impedance, defined as the product of material density and seismic velocity. This article...
Authors
James A. Hunter, Heather L. Crow, William J. Stephenson, Andre J.-M. Pugin, Robert Williams, James B. Harris, Jackson K. Odum, Edward W Woolery
An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials
Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site conditions of the local geology. Thus, a number of geophysical site characterization methods were developed to meet the demand for accurate and cost-effective results. As a consequence, a number of studies have been...
Authors
Michael W. Asten, Alan Yong, Sebastiano Foti, Koichi Hayashi, Antony J. Martin, William J. Stephenson, John F. Cassidy, Jacie Coleman, Robert L. Nigbor, Silvia Castellaro, Kosuke Chimoto, Ikuo Cho, Cecile Cornou, Takumi Hayashida, Manuel Hobiger, Chun-Hsiang Kuo, Albert Macau, E. Diego Mercerat, Sheri Molnar, Passakorn Pananont, Marco Pilz, Nakhorn Poovarodom, Esteban Saez, Marc Wathelet, Hiroaki Yamanaka, Toshiaki Yokoi, Don Zhao
Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA
The Walker Lane is a zone of distributed transtension where normal faults are overprinted by strike-slip motion. We use two newly-acquired high-resolution seismic reflection profiles and a reprocessed Consortium for Continental Reflection Profiling (COCORP) deep crustal reflection profile to assess the subsurface geometry of the Holocene-active, transtensional Warm Springs Valley fault...
Authors
Richard W. Briggs, William J. Stephenson, J.H. McBride, Jackson K. Odum, Nadine G. Reitman, Ryan D. Gold
Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction
We analyze multimethod shear (SH)‐wave velocity ( VS) site characterization data acquired at three permanent and 25 temporary seismograph stations in Oklahoma that recorded M 4+ earthquakes within a 50 km hypocentral distance of at least one of the 2016 M 5.1 Fairview, M 5.8 Pawnee, or M 5.0 Cushing earthquakes to better constrain earthquake ground‐motion modeling in the region. We...
Authors
William J. Stephenson, Jackson K. Odum, Stephen H. Hartzell, Alena L. Leeds, Robert Williams
Seismic reflection imaging of the low-angle Panamint normal fault system, eastern California Seismic reflection imaging of the low-angle Panamint normal fault system, eastern California
Shallowly dipping (
Authors
Ryan D. Gold, William J. Stephenson, Richard W. Briggs, Christopher B. DuRoss, Eric Kirby, Edward W Woolery, Jaime Delano, Jackson K. Odum
Graphical Dispersion Plot Editor (DPE) for seismic-site characterization by using multiple surface-wave methods Graphical Dispersion Plot Editor (DPE) for seismic-site characterization by using multiple surface-wave methods
Authors
Devin McPhillips, Alan K. Yong, Antony Martin, William J. Stephenson
Evidence for late Quaternary deformation along Crowley's Ridge, New Madrid seismic zone 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...
Authors
Jessica Thompson Jobe, Ryan D. Gold, Richard W. Briggs, Robert Williams, William J. Stephenson, Jaime E. Delano, Anjana K. Shah, Burke J. Minsley
Erratum to Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, Part 1: methodology and overall results Erratum to Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, Part 1: methodology and overall results
No abstract available.
Authors
Arthur D. Frankel, Erin A. Wirth, Nasser A. Marafi, John Vidale, William J. Stephenson
3-D Simulations of M9 earthquakes on the Cascadia Megathrust: Methodology and results 3-D Simulations of M9 earthquakes on the Cascadia Megathrust: Methodology and results
No abstract available.
Authors
Arthur D. Frankel, Erin Wirth Moriarty, J. Vidale, William J. Stephenson, Nasser A. Marafi
Science and Products
Filter Total Items: 16
A Bayesian Monte-Carlo Inversion of Spatial Auto-Correlation (SPAC) for Near-Surface Vs Structure Applied to Both Broadband and Geophone Data - Data Release A Bayesian Monte-Carlo Inversion of Spatial Auto-Correlation (SPAC) for Near-Surface Vs Structure Applied to Both Broadband and Geophone Data - Data Release
The datasets for this investigation consist of microtremor array data collected at: 1) 18 sites in Salt Lake and Utah valleys, Utah, and 2) two sites as part of the Frontier Observatory for Research in Geothermal Energy (FORGE) near Milford, Utah. Each of the 18 sites in the Salt Lake and Utah valleys were acquired with four-sensor arrays with three-component (3C) sensors having flat...
Shear-wave velocity in the Seattle basin to 2 km depth characterized with the krSPAC microtremor array method: insights for urban basin-scale imaging - Data Release Shear-wave velocity in the Seattle basin to 2 km depth characterized with the krSPAC microtremor array method: insights for urban basin-scale imaging - Data Release
The dataset for this investigation consists of microtremor array data collected at 11 sites in the Seattle basin, Washington State. Ten of the arrays consisted of seven Nanometrics Trillium Compact broadband sensors deployed in asymmetric nested triangles (sites ST01, BA02, SP04, LF05, UW06, SN07, RD08, EL09, CH10, and KG11) that recorded for up to six hours. The eleventh array, at site...
Data for Holocene fault reactivation in the eastern Cascades, WA Data for Holocene fault reactivation in the eastern Cascades, WA
Significant uncertainty remains in how and where crustal shortening occurs throughout the eastern Cascade Range in Washington State. Using lidar imagery, we identified a ~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 slope with an average of ~3 m of...
Data for P- and S-wave Seismic Velocity Models Incorporating the Cascadia Subduction Zone for 3D Earthquake Ground Motion simulations- Update for Open-File Report 2007-1348 Data for P- and S-wave Seismic Velocity Models Incorporating the Cascadia Subduction Zone for 3D Earthquake Ground Motion simulations- Update for Open-File Report 2007-1348
The data for this release is an ASCII file containing grid points of Cascadia P- and S-wave velocity models. The model volume was developed to include the Cascadia subduction zone for purposes of ground motion simulation. The description of the model and background of its development is provided in the associated Open-File Report. The grid points are given in Universal Transverse...
Filter Total Items: 69
Introduction to the special issue of the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) international guidelines for applying noninvasive geophysical techniques to characterize seismic site conditions Introduction to the special issue of the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) international guidelines for applying noninvasive geophysical techniques to characterize seismic site conditions
Knowledge about local seismic site conditions provides critical information to account for site effects that are commonly observed in strong motion recordings. Certainly, other wave propagation effects can influence these observations, which are attributable to variations in material properties of the paths traveled by the waves, as well as the characteristics of the seismic source...
Authors
Alan Yong, Aysegul Askan, John Cassidy, Sebastiano D’Amico, Stefano Parolai, Marco Pilz, William J. Stephenson
Flexible multimethod approach for seismic site characterization Flexible multimethod approach for seismic site characterization
We describe the flexible multimethod seismic site characterization technique for obtaining shear-wave velocity (VS) profiles and derivative information, such as the time-averaged VS of the upper 30 m (VS30). Simply stated, the multimethod approach relies on the application of multiple independent noninvasive site characterization acquisition and analysis techniques utilized in a flexible...
Authors
William J. Stephenson, Alan Yong, Antony Martin
Microtremor array method using spatial autocorrelation analysis of Rayleigh‑wave data Microtremor array method using spatial autocorrelation analysis of Rayleigh‑wave data
Microtremor array measurements (MAM) and passive surface wave methods in general, have been increasingly used to non-invasively estimate shear-wave velocity structures (Vs) for various purposes. The methods estimate dispersion curves and invert them for retrieving S-wave velocity profiles. This paper summarizes principles, limitations, data collection and processing methods. It intends...
Authors
Koichi Hayashi, Michael W. Asten, William J. Stephenson, Cecile Cornou, Manuel Hobiger, Marco Pilz, Hiroaki Yamanaka
Seismic site characterization with shear wave (SH) reflection and refraction methods Seismic site characterization with shear wave (SH) reflection and refraction methods
Reflection and critically refracted seismic methods use traveltime measurements of body waves propagating between a source and a series of receivers on the ground surface to calculate subsurface velocities. Body wave energy is refracted or reflected at boundaries where there is a change in seismic impedance, defined as the product of material density and seismic velocity. This article...
Authors
James A. Hunter, Heather L. Crow, William J. Stephenson, Andre J.-M. Pugin, Robert Williams, James B. Harris, Jackson K. Odum, Edward W Woolery
An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials
Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site conditions of the local geology. Thus, a number of geophysical site characterization methods were developed to meet the demand for accurate and cost-effective results. As a consequence, a number of studies have been...
Authors
Michael W. Asten, Alan Yong, Sebastiano Foti, Koichi Hayashi, Antony J. Martin, William J. Stephenson, John F. Cassidy, Jacie Coleman, Robert L. Nigbor, Silvia Castellaro, Kosuke Chimoto, Ikuo Cho, Cecile Cornou, Takumi Hayashida, Manuel Hobiger, Chun-Hsiang Kuo, Albert Macau, E. Diego Mercerat, Sheri Molnar, Passakorn Pananont, Marco Pilz, Nakhorn Poovarodom, Esteban Saez, Marc Wathelet, Hiroaki Yamanaka, Toshiaki Yokoi, Don Zhao
Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA Geophysical constraints on the crustal architecture of the transtensional Warm Springs Valley fault zone, northern Walker Lane, western Nevada, USA
The Walker Lane is a zone of distributed transtension where normal faults are overprinted by strike-slip motion. We use two newly-acquired high-resolution seismic reflection profiles and a reprocessed Consortium for Continental Reflection Profiling (COCORP) deep crustal reflection profile to assess the subsurface geometry of the Holocene-active, transtensional Warm Springs Valley fault...
Authors
Richard W. Briggs, William J. Stephenson, J.H. McBride, Jackson K. Odum, Nadine G. Reitman, Ryan D. Gold
Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction
We analyze multimethod shear (SH)‐wave velocity ( VS) site characterization data acquired at three permanent and 25 temporary seismograph stations in Oklahoma that recorded M 4+ earthquakes within a 50 km hypocentral distance of at least one of the 2016 M 5.1 Fairview, M 5.8 Pawnee, or M 5.0 Cushing earthquakes to better constrain earthquake ground‐motion modeling in the region. We...
Authors
William J. Stephenson, Jackson K. Odum, Stephen H. Hartzell, Alena L. Leeds, Robert Williams
Seismic reflection imaging of the low-angle Panamint normal fault system, eastern California Seismic reflection imaging of the low-angle Panamint normal fault system, eastern California
Shallowly dipping (
Authors
Ryan D. Gold, William J. Stephenson, Richard W. Briggs, Christopher B. DuRoss, Eric Kirby, Edward W Woolery, Jaime Delano, Jackson K. Odum
Graphical Dispersion Plot Editor (DPE) for seismic-site characterization by using multiple surface-wave methods Graphical Dispersion Plot Editor (DPE) for seismic-site characterization by using multiple surface-wave methods
Authors
Devin McPhillips, Alan K. Yong, Antony Martin, William J. Stephenson
Evidence for late Quaternary deformation along Crowley's Ridge, New Madrid seismic zone 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...
Authors
Jessica Thompson Jobe, Ryan D. Gold, Richard W. Briggs, Robert Williams, William J. Stephenson, Jaime E. Delano, Anjana K. Shah, Burke J. Minsley
Erratum to Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, Part 1: methodology and overall results Erratum to Broadband synthetic seismograms for magnitude 9 earthquakes on the Cascadia megathrust based on 3D simulations and stochastic synthetics, Part 1: methodology and overall results
No abstract available.
Authors
Arthur D. Frankel, Erin A. Wirth, Nasser A. Marafi, John Vidale, William J. Stephenson
3-D Simulations of M9 earthquakes on the Cascadia Megathrust: Methodology and results 3-D Simulations of M9 earthquakes on the Cascadia Megathrust: Methodology and results
No abstract available.
Authors
Arthur D. Frankel, Erin Wirth Moriarty, J. Vidale, William J. Stephenson, Nasser A. Marafi