The 23 August 2011 M w (moment magnitude) 5.7 ± 0.1, Mineral, Virginia, earthquake was the largest and most damaging in the central and eastern United States since the 1886 M w 6.8–7.0, Charleston, South Carolina, earthquake. Seismic data indicate that the earthquake rupture occurred on a southeast-dipping reverse fault and consisted of three subevents that progressed northeastward and updip. U.S. Geological Survey (USGS) “Did You Feel It?” intensity reports from across the eastern United States and southeastern Canada, rockfalls triggered at distances to 245 km, and regional groundwater-level changes are all consistent with efficient propagation of high-frequency seismic waves (~1 Hz and higher) in eastern North America due to low attenuation. Reported damage included cracked or shifted foundations and broken walls or chimneys, notably in unreinforced masonry, and indicated intensities up to VIII in the epicentral area based on USGS “Did You Feel It?” reports. The earthquake triggered the first automatic shutdown of a U.S. nuclear power plant, located ~23 km northeast of the main shock epicenter. Although shaking exceeded the plant’s design basis earthquake, the actual damage to safety-related structures, systems, and components was superficial. Damage to relatively tall masonry structures 130 km to the northeast in Washington, D.C., was consistent with source directivity, soft-soil ground-motion amplification, and anisotropic wave propagation with lower attenuation parallel to the northeast-trending Appalachian tectonic fabric. The earthquake and aftershocks occurred in crystalline rocks within Paleozoic thrust sheets of the Chopawamsic terrane. The main shock and majority of aftershocks delineated the newly named Quail fault zone in the subsurface, and shallow aftershocks defined outlying faults. The earthquake induced minor liquefaction sand boils, but notably there was no evidence of a surface fault rupture. Recurrence intervals, and evidence for larger earthquakes in the Quaternary in this area, remain important unknowns. This event, along with similar events during historical time, is a reminder that earthquakes of similar or larger magnitude pose a real hazard in eastern North America.

The 2011 Mineral, Virginia, earthquake is one of the larger recorded seismic events occurring east of the Rocky Mountains since seismic instrumentation was first deployed. The operation of the North Anna nuclear power station (NANPS), located ~22 km northeast of the epicenter, was affected by the earthquake vibration. This moderate event caused the first incident in which a commercial U.S. nuclear power plant experienced a safe shutdown as a result of earthquake ground motion. Post-earthquake investigations confirmed that important safety-related structures, systems, and components (SSCs) at the NANPS did not have any detectable damage. Damage at the NANPS consisted of cracking and spalling of some of the non-safety-related ancillary structures, and the plant was restarted after three months of intensive inspections and reviews. Response spectra developed from the recorded ground motion at the NANPS showed a modest exceedance of the plant seismic design levels for safety-related SSCs, but these SSCs were not damaged and maintained their functionality. The NANPS performance, in combination with other global examples, shows that nuclear power plants have been able to function safely even when earthquake ground motions exceeded the design levels of the SSCs. In this paper we describe the observed earthquake effects at the NANPS and discuss the original geologic and seismic characterization of the plant site. We also discuss the impacts of other earthquakes on the performance of various nuclear power plants, and previous and current seismic hazard and risk evaluations for U.S. nuclear power plants.