WASHINGTON, Aug. 23, 2011 — Operations continued at the Pentagon despite the magnitude 5.9 earthquake centered in Mineral, Va., today.
|A “shakemap” of the Aug. 23, 2011, central Virginia magnitude 5.9 earthquake. |
U.S. Geological Survey graphic
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The National Military Command Center in the building “maintained the watch, and there was no loss of communications,” said Navy Cmdr. Patrick McNally, a spokesman for the Joint Staff.
Some photos were knocked off walls in the building during the mid-afternoon quake, and a water pipe on the building’s third floor burst, but plant engineers were able to stop the deluge, Pentagon Force Protection Agency officials said.
Many offices did evacuate the building, but officials gave the all-clear to return after about 15 minutes.
The earthquake occurred at a depth of about 1 kilometer, about 27 miles east of Charlottesville, 34 miles southwest of Fredericksburg and 39 miles northwest of Richmond, all in Virginia.
The last time a magnitude 5.9 earthquake happened in Virginia was in Giles County, near Blacksburg, in May 1897, according to the U.S. Geological Survey.
Though it’s not as well known as the San Andreas seismic zone in California, there is a seismic zone in central Virginia. The nearest tectonic plate boundaries, which tend to generate large and more frequent earthquakes, are in the center of the Atlantic Ocean and in the Caribbean Sea, USGS officials said.
The central Virginia seismic zone has known faults, officials added, but probably has many undetected smaller and deeply buried faults. Because of these faults, people in central Virginia have felt small earthquakes and suffered damage from a few larger ones since at least 1774, according to the U.S. Geological Survey.
In 1875, a magnitude 4.8 earthquake struck in the central Virginia zone. Every year or two, smaller earthquakes happen in the region.
East Coast earthquakes are less frequent than West Coast temblors, but they tend to be shallower, and therefore, they can be felt over a larger region, USGS officials said.
East of the Rocky Mountains, an earthquake can be felt over an area as much as 10 times larger than a similar magnitude earthquake on the West Coast. Today’s magnitude 5.9 earthquake could be felt as far away as Georgia, the Carolinas, Tennessee, Ohio, Illinois, New York and Massachusetts.
U.S. Department of Defense
Office of the Assistant Secretary of Defense (Public Affairs)