The 2011 Virginia M5.8 earthquake: Insights from seismic reflection imaging into the influence of older structures on eastern U.S. seismicity

Geological Society of America Special Papers
By: , and 

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Abstract

The Mineral, Virginia (USA), earthquake of 23 August 2011 occurred at 6– 8 km depth within the allochthonous terranes of the Appalachian Piedmont Province, rupturing an ~N36°E striking reverse fault dipping ~50° southeast. This study used the Interstate Highway 64 seismic refl ection profi le acquired ~6 km southwest of the hypocenter to examine the structural setting of the earthquake. The profi le shows that the 2011 earthquake and its aftershocks are almost entirely within the early Paleozoic Chopawamsic volcanic arc terrane, which is bounded by listric thrust faults dipping 30°–40° southeast that sole out into an ~2-km-thick, strongly refl ective zone at 7– 12 km depth. Refl ectors above and below the southward projection of the 2011 earthquake focal plane do not show evidence for large displacement, and the updip projection of the fault plane does not match either the location or trend of a previously mapped fault or lithologic boundary. The 2011 earthquake thus does not appear to be a simple reactivation of a known Paleozoic thrust fault or a major Mesozoic rift basin-boundary fault. The fault that ruptured appears to be a new fault, a fault with only minor displacement, or to not extend the ~3 km from the aftershock zone to the seismic profi le. Although the Paleozoic structures appear to infl uence the general distribution of seismicity in the area, Central Virginia seismic zone earthquakes have yet to be tied directly to specifi c fault systems mapped at the surface or imaged on seismic profiles.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The 2011 Virginia M5.8 earthquake: Insights from seismic reflection imaging into the influence of older structures on eastern U.S. seismicity
Series title Geological Society of America Special Papers
DOI 10.1130/2014.2509(16)
Volume 509
Year Published 2015
Language English
Publisher Geological Society of America
Contributing office(s) Earthquake Science Center
Description 9 p.
First page 285
Last page 294
Country United States
State Virginia
City Mineral
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