Delaware and surrounding areas experienced an earthquake event on the afternoon of Tuesday, August 23, 2011. According to the US Geological Survey, a magnitude 5.8 earthquake struck at 1:51 p.m. in central Virginia, in an area referred to as “the Central Virginia Seismic Zone” because of its relatively active earthquake activity for the region. The epicenter was located five miles south-southwest of Mineral, Virginia, with the quake was focused at a depth of 6 km (3.7 miles) below the surface (http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/se082311a.html). The Virginia Geological Survey reports that this is the largest Virginia earthquake known in historic times. A few small aftershocks have occurred in the hours afterward.
Delaware is not in a seismically active region but, even here, earthquakes occur because of sudden adjustments in the earth's crust. Even though such movements can be startling they yield important information about the behavior of the earth and the potential for future events. The Delaware Geological Survey continually monitors seismicity in the State because of both the scientific value of the information and to help address the concern of residents and other agencies over possible effects.