Bill Stephensen is a scientist in the Earthquake Hazards Program.
Science and Products
Untangling Faults at Depth – What Lies Beneath Panamint Valley, California?
Release Date: APRIL 30, 2018 The eastern edge of Panamint Valley,CA has two types of faults that can be seen in the near-surface geology. 150 geophones and a seismic source will help reveal the subsurface picture.
Seismology in the City
Release Date: May 1, 2015 How seismologists can use noise to see under the ground.
Strike-slip in transtension: Complex crustal architecture of the Warm Springs Valley fault zone, northern Walker Lane
This data release contains field data for two P-wave seismic reflection profiles acquired across the Warm Springs Valley fault zone, part of the Northern Walker Lane, NV. The dataset consists of high-resolution seismic reflection field records in .segy format, shot coordinates in .csv format, and observers? logs in .pdf format. The high-resolution seismic profiles are approximately 4 km long. The
Seismic reflection imaging of the low-angle Panamint normal fault system, eastern California, 2018
A fundamental question in seismic hazard analysis is whether
Filter Total Items: 51
Implementation of basin models and sediment depth terms in the 2023 update of the U.S. National Seismic Hazard Model: Example from Reno, Nevada
We present a framework to evaluate the inclusion of candidate basin depth models in the U.S. Geological Survey National Seismic Hazard Model. We compute intensity measures (peak and spectral amplitudes) from uniformly processed earthquake ground motions in and around the basin of interest and compare these to ground-motion model (GMM) estimates over a range of oscillator periods. The GMMs use dept
Authors
Sean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. Stephenson
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. However, local
Authors
Alan Yong, Aysegul Askan, John Cassidy, Sebastiano D'Amico, Stefano Parolai, Marco Pilz, William J. Stephenson
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 field-bas
Authors
William J. Stephenson, Alan Yong, Antony Martin
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 to enable s
Authors
Koichi Hayashi, Michael W. Asten, William J. Stephenson, Cécile Cornou, Manuel Hobiger, Marco Pilz, Hiroaki Yamanaka
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 provides pra
Authors
James A. Hunter, Heather L. Crow, William J. Stephenson, André 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
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 administered perio
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, Cécile Cornou, Takumi Hayashida, Manuel Hobiger, Chun-Hsiang Kuo, Albert Macau, E. Diego Mercerat, Sheri Molnar, Passakorn Pananont, Marco Pilz, Nakhorn Poovarodom, Esteban Sáez, 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
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 zone (WSVFZ
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
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 acquired active
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
Shallowly dipping (
Authors
Ryan D. Gold, William J. Stephenson, Richard W. Briggs, Christopher 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
IntroductionTo understand the behavior of potentially damaging ground motions during earthquakes, seismic-site effects are routinely characterized by using the dispersion of surface waves. Many methods exist to measure dispersion; these methods have various advantages and disadvantages, but they all yield dispersion data that must be inverted for shear-wave velocity. This report presents a graphic
Authors
Devin McPhillips, Alan K. Yong, Antony Martin, William J. Stephenson
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 ∼6.2–0.4 ka∼6.2–0.4 ka. Interseismic recurrence ranges from 0.2 to 1.8 ky (mean 1.2 ky). We estimate 6.5±0.7 m6.5±0.7 m of cumulative vert
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
Science and Products
- Science
Untangling Faults at Depth – What Lies Beneath Panamint Valley, California?
Release Date: APRIL 30, 2018 The eastern edge of Panamint Valley,CA has two types of faults that can be seen in the near-surface geology. 150 geophones and a seismic source will help reveal the subsurface picture.Seismology in the City
Release Date: May 1, 2015 How seismologists can use noise to see under the ground. - Data
Strike-slip in transtension: Complex crustal architecture of the Warm Springs Valley fault zone, northern Walker Lane
This data release contains field data for two P-wave seismic reflection profiles acquired across the Warm Springs Valley fault zone, part of the Northern Walker Lane, NV. The dataset consists of high-resolution seismic reflection field records in .segy format, shot coordinates in .csv format, and observers? logs in .pdf format. The high-resolution seismic profiles are approximately 4 km long. TheSeismic reflection imaging of the low-angle Panamint normal fault system, eastern California, 2018
A fundamental question in seismic hazard analysis is whether - Publications
Filter Total Items: 51
Implementation of basin models and sediment depth terms in the 2023 update of the U.S. National Seismic Hazard Model: Example from Reno, Nevada
We present a framework to evaluate the inclusion of candidate basin depth models in the U.S. Geological Survey National Seismic Hazard Model. We compute intensity measures (peak and spectral amplitudes) from uniformly processed earthquake ground motions in and around the basin of interest and compare these to ground-motion model (GMM) estimates over a range of oscillator periods. The GMMs use deptAuthorsSean Kamran Ahdi, Morgan P. Moschetti, Brad T. Aagaard, Kaitlyn Abernathy, Oliver S. Boyd, William J. StephensonIntroduction 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. However, localAuthorsAlan Yong, Aysegul Askan, John Cassidy, Sebastiano D'Amico, Stefano Parolai, Marco Pilz, William J. StephensonFlexible 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 field-basAuthorsWilliam J. Stephenson, Alan Yong, Antony MartinMicrotremor 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 to enable sAuthorsKoichi Hayashi, Michael W. Asten, William J. Stephenson, Cécile Cornou, Manuel Hobiger, Marco Pilz, Hiroaki YamanakaSeismic 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 provides praAuthorsJames A. Hunter, Heather L. Crow, William J. Stephenson, André J.-M. Pugin, Robert Williams, James B. Harris, Jackson K. Odum, Edward W WooleryAn 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 administered perioAuthorsMichael 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, Cécile Cornou, Takumi Hayashida, Manuel Hobiger, Chun-Hsiang Kuo, Albert Macau, E. Diego Mercerat, Sheri Molnar, Passakorn Pananont, Marco Pilz, Nakhorn Poovarodom, Esteban Sáez, Marc Wathelet, Hiroaki Yamanaka, Toshiaki Yokoi, Don ZhaoGeophysical 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 zone (WSVFZAuthorsRichard W. Briggs, William J. Stephenson, J.H. McBride, Jackson K. Odum, Nadine G. Reitman, Ryan D. GoldShear-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 acquired activeAuthorsWilliam J. Stephenson, Jackson K. Odum, Stephen H. Hartzell, Alena L. Leeds, Robert WilliamsSeismic reflection imaging of the low-angle Panamint normal fault system, eastern California
Shallowly dipping (AuthorsRyan D. Gold, William J. Stephenson, Richard W. Briggs, Christopher Duross, Eric Kirby, Edward W Woolery, Jaime Delano, Jackson K. OdumGraphical Dispersion Plot Editor (DPE) for seismic-site characterization by using multiple surface-wave methods
IntroductionTo understand the behavior of potentially damaging ground motions during earthquakes, seismic-site effects are routinely characterized by using the dispersion of surface waves. Many methods exist to measure dispersion; these methods have various advantages and disadvantages, but they all yield dispersion data that must be inverted for shear-wave velocity. This report presents a graphicAuthorsDevin McPhillips, Alan K. Yong, Antony Martin, William J. StephensonEvidence 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 seismAuthorsJessica Thompson Jobe, Ryan D. Gold, Richard W. Briggs, Robert Williams, William J. Stephenson, Jaime E. Delano, Anjana K. Shah, Burke J. MinsleyPaleoseismic 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 ∼6.2–0.4 ka∼6.2–0.4 ka. Interseismic recurrence ranges from 0.2 to 1.8 ky (mean 1.2 ky). We estimate 6.5±0.7 m6.5±0.7 m of cumulative vertAuthorsScott 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 - News