Tuesday, August 23, 2011

Source of Virginia's M5.9 quake

The Virginia Division of Geology and Mineral Resources issued this statement on the magnitude 5.9 earthquake that occurred today, shaking large areas of the Eastern U.S.:

Virginia experienced a widely-felt earthquake at 1:51 p.m. eastern daylight time on Tuesday, August 23, 2011. According to the U.S. Geological Survey, the epicenter of the quake was located near Mineral, in Louisa County. With a preliminary magnitude of 5.9, this is the
largest Virginia earthquake in historic times. A few small aftershocks have been reported.

The epicenter falls within the Central Virginia Seismic Zone, a cluster of dozens of earthquakes that have occurred within the past 120 years, centered about halfway between Richmond and Charlottesville. Several known faults are present in the area: the Chopawamsic Fault, the Lakeside Fault, and the Spotsylvania Fault. These are old faults, related to plate tectonic events that closed and then reopened the Atlantic Ocean about 150 million years ago. Even though these faults are quite old and considered to be inactive, occasional earthquakes continue to occur.

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