William J Stephenson
Bill Stephensen is a scientist in the Earthquake Hazards Program.
Science and Products
Comparisons between vs30 and spectral response for 30 sites in Newcastle, Australia from collocated seismic cone penetrometer, active- and passive-source vs data
High-resolution seismic reflection imaging of growth folding and shallow faults beneath the Southern Puget Lowland, Washington State
Compilation of VS30 Data for the United States
Kinematics of shallow backthrusts in the Seattle fault zone, Washington State
The use of wavenumber normalization in computing spatially averaged coherencies (KRSPAC) of microtremor data from asymmetric arrays
Site response in the eastern United States: A comparison of Vs30 measurements with estimates from horizontal:vertical spectral ratios
Modeling the effects of source and path heterogeneity on ground motions of great earthquakes on the Cascadia Subduction Zone Using 3D simulations
Ground-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia earthquake
Vs30 and spectral response from collocated shallow, active- and passive-source Vs data at 27 sites in Puerto Rico
Shear‐wave velocity (VS) and time‐averaged shear‐wave velocity to 30 m depth (VS30) are the key parameters used in seismic site response modeling and earthquake engineering design. Where VS data are limited, available data are often used to develop and refine map‐based proxy models of VS30 for predicting ground‐motion intensities. In this paper, we present shallow VS data from 27 sites in Puerto R
Quaternary extensional growth folding beneath Reno, Nevada, imaged by urban seismic profiling
Origin of the Blytheville Arch, and long-term displacement on the New Madrid seismic zone, central United States
Characterization of intrabasin faulting and deformation for earthquake hazards in southern Utah Valley, Utah, from high-resolution seismic imaging
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Comparisons between vs30 and spectral response for 30 sites in Newcastle, Australia from collocated seismic cone penetrometer, active- and passive-source vs data
Although the time‐averaged shear‐wave velocity down to 30 m depth (VS30) can be a proxy for estimating earthquake ground‐motion amplification, significant controversy exists about its limitations when used as a single parameter for the prediction of amplification. To examine this question in absence of relevant strong‐motion records, we use a range of different methods to measure the shear‐wave veAuthorsTheodora Volti, David Burbidge, Clive Collins, Michael W. Asten, Jackson K. Odum, William J. Stephenson, Chris Pascal, Josef HolzschuhHigh-resolution seismic reflection imaging of growth folding and shallow faults beneath the Southern Puget Lowland, Washington State
Marine seismic reflection data from southern Puget Sound, Washington, were collected to investigate the nature of shallow structures associated with the Tacoma fault zone and the Olympia structure. Growth folding and probable Holocene surface deformation were imaged within the Tacoma fault zone beneath Case and Carr Inlets. Shallow faults near potential field anomalies associated with the OlympiaAuthorsJackson K. Odum, William J. Stephenson, Thomas L. Pratt, Richard J. BlakelyCompilation of VS30 Data for the United States
VS30, the time-averaged shear-wave velocity (VS) to a depth of 30 meters, is a key index adopted by the earthquake engineering community to account for seismic site conditions. VS30 is typically based on geophysical measurements of VS derived from invasive and noninvasive techniques at sites of interest. Owing to cost considerations, as well as logistical and environmental concerns, VS30 data areAuthorsAlan Yong, Eric M. Thompson, David J. Wald, Keith L. Knudsen, Jack K. Odum, William J. Stephenson, Scott HaefnerKinematics of shallow backthrusts in the Seattle fault zone, Washington State
Near-surface thrust fault splays and antithetic backthrusts at the tips of major thrust fault systems can distribute slip across multiple shallow fault strands, complicating earthquake hazard analyses based on studies of surface faulting. The shallow expression of the fault strands forming the Seattle fault zone of Washington State shows the structural relationships and interactions between such fAuthorsThomas L. Pratt, K.G. Troost, Jackson K. Odum, William J. StephensonThe use of wavenumber normalization in computing spatially averaged coherencies (KRSPAC) of microtremor data from asymmetric arrays
The SPAC method of processing microtremor noise observations for estimation of Vs profiles has a limitation that the array has circular or triangular symmetry in order to allow spatial (azimuthal) averaging of inter-station coherencies over a constant station separation. Common processing methods allow for station separations to vary by typically ±10% in the azimuthal averaging before degradationAuthorsM.W. Asten, William J. Stephenson, Stephen H. HartzellSite response in the eastern United States: A comparison of Vs30 measurements with estimates from horizontal:vertical spectral ratios
Earthquake damage is often increased due to local ground-motion amplification caused by soft soils, thick basin sediments, topographic effects, and liquefaction. A critical factor contributing to the assessment of seismic hazard is detailed information on local site response. In order to address and quantify the site response at seismograph stations in the eastern United States, we investigate theAuthorsDaniel E. McNamara, William J. Stephenson, Jackson K. Odum, Robert Williams, Lind GeeModeling the effects of source and path heterogeneity on ground motions of great earthquakes on the Cascadia Subduction Zone Using 3D simulations
We ran finite‐difference earthquake simulations for great subduction zone earthquakes in Cascadia to model the effects of source and path heterogeneity for the purpose of improving strong‐motion predictions. We developed a rupture model for large subduction zone earthquakes based on a k−2 slip spectrum and scale‐dependent rise times by representing the slip distribution as the sum of normal modesAuthorsAndrew Delorey, Arthur Frankel, Pengcheng Liu, William J. StephensonGround-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia earthquake
We characterize shear-wave velocity versus depth (Vs profile) at 16 portable seismograph sites through the epicentral region of the 2011 Mw 5.8 Mineral (Virginia, USA) earthquake to investigate ground-motion site effects in the area. We used a multimethod acquisition and analysis approach, where active-source horizontal shear (SH) wave reflection and refraction as well as active-source multichanneAuthorsWilliam J. Stephenson, Jackson K. Odum, Daniel E. McNamara, Robert A. Williams, Stephen J AngsterVs30 and spectral response from collocated shallow, active- and passive-source Vs data at 27 sites in Puerto Rico
Shear‐wave velocity (VS) and time‐averaged shear‐wave velocity to 30 m depth (VS30) are the key parameters used in seismic site response modeling and earthquake engineering design. Where VS data are limited, available data are often used to develop and refine map‐based proxy models of VS30 for predicting ground‐motion intensities. In this paper, we present shallow VS data from 27 sites in Puerto R
AuthorsJack K. Odum, William J. Stephenson, Robert A. Williams, Christa von Hillebrandt-AndradeQuaternary extensional growth folding beneath Reno, Nevada, imaged by urban seismic profiling
We characterize shallow subsurface faulting and basin structure along a transect through heavily urbanized Reno, Nevada, with high‐resolution seismic reflection imaging. The 6.8 km of P‐wave data image the subsurface to approximately 800 m depth and delineate two subbasins and basin uplift that are consistent with structure previously inferred from gravity modeling in this region of the northern WAuthorsWilliam J. Stephenson, Roxy N. Frary, John Louie, Jackson K. OdumOrigin of the Blytheville Arch, and long-term displacement on the New Madrid seismic zone, central United States
The southern arm of the New Madrid seismic zone of the central United States coincides with the buried, ~110 km by ~20 km Blytheville Arch antiform within the Cambrian–Ordovician Reelfoot rift graben. The Blytheville Arch has been interpreted at various times as a compressive structure, an igneous intrusion, or a sediment diapir. Reprocessed industry seismic-reflection profiles presented here showAuthorsThomas L. Pratt, Robert Williams, Jackson K. Odum, William J. StephensonCharacterization of intrabasin faulting and deformation for earthquake hazards in southern Utah Valley, Utah, from high-resolution seismic imaging
We conducted active and passive seismic imaging investigations along a 5.6-km-long, east–west transect ending at the mapped trace of the Wasatch fault in southern Utah Valley. Using two-dimensional (2D) P-wave seismic reflection data, we imaged basin deformation and faulting to a depth of 1.4 km and developed a detailed interval velocity model for prestack depth migration and 2D ground-motion simuAuthorsWilliam J. Stephenson, Jack K. Odum, Robert A. Williams, John H. McBride, Iris Tomlinson - News