Why Do East Coast Earthquakes Affect a Larger Area than West Coast Ones?

For those who have experienced earthquakes in California and their relatively small area of impact, a question arises concerning why such a moderate 5.9-magnitude east coast earthquake with a Virginia epicenter could be felt more than 300 miles away, in New York City?

As one might sense, there is a geological reason for this. The Earth's crust beneath the eastern U.S. is older and harder than the plates in the western U.S. The east coast also has fewer fault lines that are not as seismically active. However, when earthquakes do hit, that hard ground in the east coast literally carries seismic waves better than the west coast ground.

Eastern earthquakes affect areas 10 times larger than western quakes of the same magnitude, with some geologists estimating that figure may be as great as a 100 times, according to New Jersey's geological survey.

Tuesday's earthquake sent tremors from Washington to New York City at about 1:51 p.m. EDT, and U.S. geological officials and other authorities said it was a 5.9 magnitude earthquake based in Virginia. As of four p.m. EDT, there were no reports of any casualties.

The movement lasted no more than 30 seconds in downtown Washington, The New York Times reported. Several buildings in New York City were evacuated, with employees standing in the streets in Midtown Manhattan.

Officially, the quake lasted up to 45 seconds, according to the U.S. Geological Survey (USGS). It shook office buildings and homes and rattled residents. The USGS has warned of aftershocks.

Its epicenter was reported about four miles southwest of Mineral, Va., near Richmond, Va., and about 80 miles south of Washington, D.C.

NYC Mayor Bloomberg Felt Quake

New York City Mayor Michael Bloomberg, standing in front of the grand Renaissance-style building, said he had felt the tremors but assumed they stemmed from extensive renovations underway inside City Hall, The Times reported.

I did feel a little bit of shake, Bloomberg said.And then it got greater.

So far, Bloomberg said, we have no reports of any damage.

Meanwhile, farther south, in Lower Manhattan in the financial district, the tremor was felt at the 7 Hanover Square skyscraper office building, home to the International Business Times.

Employees in the newsroom felt the building move slightly, and detected a swaying sensation that affected their desks and work stations. Another IBTimes.com employee who was at home at the time in Greenwich Village, a Lower Manhattan neighborhood, said his television set was slightly jostled. Initially, he thought it was a problem related to the apartment building, but then realized it was a quake when others in the building and neighborhood experienced the same sensation.