Earthquake rattles Mid-Atlantic area

It wasn’t much of an earthquake Thursday, but it was unusual, centered in the normally quiescent state of Delaware. It could be felt as far as the nation’s capital and its Virginia suburbs.

The tremor occurred at 4:47 p.m., centered about 6miles northeast of Dover, Delaware, and about 5 miles deep. The U. S. Geological Survey gave varying estimates of the earthquake’s magnitude, at one point rating it as high as a 5.1 but later downgrading it to a 4.1. The Delaware Emergency Management Agency told the Dover Post that there were no reports of damage or injuries.

Geophysicist Dale Grant of the USGS told The Washington Post that an earthquake in Delaware is “exceptionally rare.”

The earthquake was felt across a broad swath of the Washington-New York corridor, and into the Hudson River Valley and parts of Connecticut and Long Is- land, according to the USGS “Did You Feel It?” page.

In comments posted to The Post’s Capital Weather Gang blog, people in and around Washington noted rattling windows or the sense that a big truck had just passed down the street.

There is no known fault associated with this earthquake. The hazard maps produced by the USGS do not show Delaware as a place with a seismic hazard.

The East Coast has a limited history of major earthquakes, but experts say that citizens should not assume they are free of seismic hazard. Charleston, S.C., was hit by a devastating quake in 1886, killing 110 people. New York City is considered highly vulnerable over the long term because so many masonry structures lack reinforced steel.