Earthquake may be strongest in central Virginia history
"It's an unusually large event for the eastern U.S.," said Ken Hudnut, a geophysicist with the U.S. Geological Survey in Pasadena. "There have been earthquakes in the area before, but not this large."
About 200 earthquakes have been recorded in the area since 1977, but none as strong as Tuesday's, he told The Times.
Previously, the largest earthquake recorded in the area, known to seismologists as the Central Virginia Seismic Zone, was a 4.8-magnitude quake that occurred outside Richmond in 1875, according to a 2006 publication by the USGS. The largest in the state's history was a 5.9-magnitude quake that hit western Virginia's Giles County, near the border with West Virginia in 1897. Smaller earthquakes that cause little or no damage are felt each year or two.
Although earthquakes are much less common on the East Coast than in California, differences in the Earth's crust mean that in the eastern U.S., shaking can be felt in an area about 10 times as wide, the USGS report said. A magnitude 5.5 earthquake in the eastern U.S. usually can be felt as far as 300 miles from its origin and sometimes causes damage in a 25-mile radius
The largest earthquake recorded in the wider region was the 1886 Charleston, S.C., earthquake, with a magnitude of 6.6 or more. That was felt as far north as Canada, as far west as Missouri, and as far south as Cuba.
At one point, Tuesday's earthquake was reported by the USGS to be a 5.9 magnitude earthquake. That was later revised to a 5.8 magnitude earthquake.
-- Tony Barboza in Los Angeles
Photo: Civilians and military personnel evacuate the Pentagon in Washington after an earthquake was felt about 2 p.m. (AP Photo/U.S. Navy, Mass Communication Specialist 2nd Class Jason Graham)