Earthquake's effects felt in Tri-State area

July 16, 2010

TRI-STATE -- An aftershock could follow the 3.6-magnitude earthquake that struck the Washington, D.C., area Friday morning, but the strength likely would be weaker than the original, according to a federal official.

Paul Caruso, a geophysicist with the U.S. Geological Survey, said the magnitude of aftershocks typically averages about one point less than the earthquake.

The mid-Atlantic doesn't get hit with large earthquakes because it's too far away from major fault lines, Caruso said. The nearest major fault line is about 1,500 miles away in the middle of the Atlantic Ocean.

"We can still have earthquakes, but we don't see large ones," Caruso said.

The solid rock structure along the East Coast also helps to minimize the severity of earthquakes, he said.

Caruso said earthquakes typically don't cause damages and casualties unless the magnitude reaches at least 5.5.

Thursday's quake hit at 5:04 a.m. with a magnitude of 3.6, The Associated Press reported. The quake was centered near Rockville, Md., according to Randy Baldwin, a physicist with U.S. Geological Survey's National Earthquake Information Center.

Susan Potter, a geophysicist at the U.S. Geological Survey, said it was the strongest to hit within 30 miles of the nation's capital since they began keeping records in 1974.

Police in Washington and in nearby Montgomery County, Md., said there were no immediate reports of injuries or damage, according to The Associated Press.

On the federal agency's website, by mid-morning more than 11,000 people had reported feeling the quake, some from Pennsylvania and West Virginia.

The agency said earthquakes east of the Rocky Mountains can be felt over an area as much as 10 times larger than a similar magnitude earthquake on the West Coast.

A dispatcher with Washington County Emergency Services said two calls were received Friday morning, one from Funkstown and one from Sharpsburg.

In Berkeley County, W.Va., "three or four" calls related to the quake were received, according to a dispatcher. The calls came from the west end of Martinsburg, and from Showers Lane and Lost Road west of the city, she said.

A resident of the west end of Martinsburg told The Herald-Mail that vibrations from the earthquake caused items on shelves inside her home to rattle.

Barb Miller of the Office of Homeland Security in Jefferson County, W.Va., said the county's 911 center received several calls beginning at 5:13 a.m., "mostly from people who wondered what was going on." Miller said there were no reports of damage.

A dispatcher at the Franklin County (Pa.) Department of Emergency Services said the office received no calls Friday morning about the earthquake.

"All we know is what we saw on television," he said.

The Washington area has had small, infrequent earthquakes over the years, including a 2.5-magnitude quake in 1997 that was within 25 to 30 miles of Friday's quake and a 2.3-magnitude quake in 1996 that was within 15 miles, Baldwin said.

"The thing that makes this (Friday's) earthquake distinctive is that it was felt widely over the region," he said.

Staff members Dan Dearth and Bob Fleenor contributed to this story.

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