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Shear-wave velocity structure and attenuation derived from aftershock data of the 2011 Mineral, Virginia, earthquake

Jennifer Dreiling and Walter D. Mooney
Shear-wave velocity structure and attenuation derived from aftershock data of the 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: 81-93

Abstract

A dense seismic array was deployed at a 2 km spacing to record the aftershocks of the M (sub w) (moment magnitude) 5.8 Mineral, Virginia (USA), earthquake in 2011. The three-component seismometers, installed on a 60-km-long profile, recorded 40 aftershocks over 9 days of deployment. Based on manual picking of P-wave (primary, compressional) and S-wave (secondary, shear) arrival times of 15 aftershocks, we find that the P-wave propagates with a velocity of 6.15 km/s through the upper crust, and the direct S-wave travels with a velocity of 3.66 km/s within the first 20 km (Vs (sub <20km) ) and decreases slightly to 3.54 km/s (Vs (sub >20km) ) for distances >20 km. Hence, the aftershock data show a Vp/Vs ratio of 1.68 within the first 20 km of hypocentral distance, and a ratio of 1.73 for distances >20 km. We attribute the small decrease in Vs with increased distance to the complex geologic setting: the recording array was deployed across the geologic boundary between the Quantico Formation and the Ta River Metamorphic Suite. Near-source attenuation of S-waves (amplitude decay with hypocentral distance R) was measured using approximately 1200 digital seismograms (north-south and east-west components) from 40 aftershocks. The decay of amplitude was extracted using a nonlinear least-squares regression for different frequency bands: 1-2, 2-4, 4-8, and 8-16 Hz. For 1-2 Hz the decay can be described as a function of distance (R) as R (super -0.8) , for 2-4 Hz as R (super -0.9) , for 4-8 Hz as R (super -1.05) , and for 8-16 Hz as R (super -1.15) . The decay exponents, or b values, increase approximately 9%-15% from a lower to the next higher analyzed frequency band. These values are valid to a distance of as much as approximately 45 km from the aftershocks.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 509
Title: Shear-wave velocity structure and attenuation derived from aftershock data of the 2011 Mineral, Virginia, earthquake
Title: The 2011 Mineral, Virginia, earthquake, and its significance for seismic hazards in eastern North America
Author(s): Dreiling, JenniferMooney, Walter D.
Author(s): Horton, J. Wright, Jr.editor
Author(s): Chapman, Martin C.editor
Author(s): Green, Russell A.editor
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Affiliation: U. S. Geological Survey, Reston, VA, United States
Pages: 81-93
Published: 2015
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 11
Accession Number: 2015-036161
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 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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