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Webinar: A Post-Earthquake Investigation in the Eastern United States
Thursday, May 21, 2020, 12:00 PM - 1:00 PM EDT
Category: Webinars

Speaker: David F. Fenster - Past President

At 1:51 pm on August 23, 2011, an Mw 5.8 earthquake occurred near the town of Mineral in Louisa County, Virginia. The earthquake caused both structural and non-structural damage in Mineral. The resulting ground motion was sufficient to cause the safe shutdown of a nuclear power plant at the North Anna site. The Mineral earthquake occurred within the Chopawamsic Terrane of the Virginia Piedmont, east of the Chopawamsic fault and west of the Spotsylvania fault. The Chopawamsic Terrane is comprised of the Chopawamsic Formation and the Ta River Metamorphic Suite – both interpreted as having formed in an island arc environment during the Ordovician. The earthquake occurred within the Central Virginia Seismic Zone, a cluster of seismicity that is not associated with known faults. Various geologic and seismologic investigations indicate that seismicity in the epicentral region is not associated with any of the known faults mapped at the surface. Aftershock hypocenters define a northeast striking, southeast dipping cluster of seismicity. When projected to the surface, this cluster of seismicity extends for a lateral distance of about 10 km. This investigation used interpretations of LiDAR imagery and published geologic maps to focus on locations of potential surface deformation. No surface faulting occurred, and all data and results were reported to the U.S. Nuclear Regulatory Commission as part of Dominion Power’s application for an additional nuclear power plant at the North Anna site.

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