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Ground-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia, earthquake

William J. Stephenson, Jack K. Odum, Daniel E. McNamara, Robert A. Williams and Stephen J. Angster
Ground-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia, earthquake (in The 2011 Mineral, Virginia, earthquake, and its significance for seismic hazards in eastern North America, J. Wright Horton (editor), Martin C. Chapman (editor) and Russell A. Green (editor))
Special Paper - Geological Society of America (2015) 509: 47-65

Abstract

We characterize shear-wave velocity versus depth (Vs profile) at 16 portable seismograph sites through the epicentral region of the 2011 M (sub w) 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 multichannel analysis of surface waves (MASW) and passive-source refraction microtremor (ReMi) Rayleigh wave dispersion were interpreted separately. The time-averaged shear-wave velocity to a depth of 30 m (Vs30), interpreted bedrock depth, and site resonant frequency were estimated from the best-fit Vs profile of each method at each location for analysis. Using the median Vs30 value (270-715 m/s) as representative of a given site, we estimate that all 16 sites are National Earthquake Hazards Reduction Program (NEHRP) site class C or D. Based on a comparison of simplified mapped surface geology to median Vs30 at our sites, we do not see clear evidence for using surface geologic units as a proxy for Vs30 in the epicentral region, although this may primarily be because the units are similar in age (Paleozoic) and may have similar bulk seismic properties. We compare resonant frequencies calculated from ambient noise horizontal:vertical spectral ratios (HVSR) at available sites to predicted site frequencies (generally between 1.9 and 7.6 Hz) derived from the median bedrock depth and average Vs to bedrock. Robust linear regression of HVSR to both site frequency and Vs30 demonstrate moderate correlation to each, and thus both appear to be generally representative of site response in this region. Based on Kendall tau rank correlation testing, we find that Vs30 and the site frequency calculated from average Vs to median interpreted bedrock depth can both be considered reliable predictors of weak-motion site effects in the epicentral region.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 509
Title: Ground-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia, earthquake
Title: The 2011 Mineral, Virginia, earthquake, and its significance for seismic hazards in eastern North America
Author(s): Stephenson, William J.Odum, Jack K.McNamara, Daniel E.Williams, Robert A.Angster, Stephen J.
Author(s): Horton, J. Wright, Jr.editor
Author(s): Chapman, Martin C.editor
Author(s): Green, Russell A.editor
Affiliation: U. S. Geological Survey, Denver, CO, United States
Affiliation: U. S. Geological Survey, Reston, VA, United States
Pages: 47-65
Published: 2015
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 78
Accession Number: 2015-036159
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. 3 tables, geol. sketch maps
N37°53'60" - N37°53'60", W77°54'00" - W77°54'00"
Secondary Affiliation: Virginia Polytechnic Institute and State University, Department of Geosciences, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201517
Program Name: USGSOPNon-USGS publications with USGS authors
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