Virginia Tech Seismological Observatory VTSO

Louisa County Aftershock: July 25, 2014

A small, shallow focus earthquake occurred on July 25, 2014 approximately 7.5 km to the southwest of Mineral, Virginia, in Louisa County. The earthquake occurred in the aftershock zone of the magnitude Mw 5.7 August 23, 2011 Mineral earthquake. The U.S. Geological Survey reported a magnitude of 2.1. The duration magnitude determined by VTSO is 2.5 +/- 0.2, based on 5 stations, and the mbLg magnitude estimate is 2.6 +/- 0.2, based on 9 observations in the distance range from 6 to 130 km. The VTSO magnitude estimate is more consistent with the felt reports provided by the public, and the magnitudes of many similar shocks recorded in the Central Virginia Seismic Zone since 1978. The VTSO hypocenter location is:

Latitude 37.9499 N, Longitude 77.9426 W. The horizontal location error estimate is 0.6 km (68% confidence interval).

Focal depth: 2.3 km. The error estimate for the focal depth is 3.7 km (68% confidence interval).

Origin time 16 Hr 54 Min 22.7 Sec, UTC, July 25, 2014 (12:54:22.7 PM EDT).

The earthquake was reported felt in Louisa County. No damage was reported.



seismogram for Louisa County aftershock July 2014

"Did You Feel It" Map