Most U.S. States Have Earthquake Risk; Major Fault Lines Cross Country

Jan. 18, 2010— -- As the outpouring of support for earthquake-ravaged Haiti continues, seismologists say a similar catastrophe can happen thoughout the United States.

"Earthquakes are a national hazard," David Applegate, a seismologist with the U.S. Geological Survey, told "Good Morning America."

People usually associate earthquakes with the West Coast, the Pacific Northwest and Alaska but 39 of the 50 states -- including New York and Tennessee -- have moderate to high seismic hazard risk, Applegate said.

The New Madrid fault in the central United States is particularly dangerous. The fault is among the most active in the country, running from St. Louis to Memphis.

The New Madrid fault line is best known for some of the most violent earthquakes to ever hit the United States: a series of four in 1811 and 1812. The quakes were estimated at magnitude 7.5 to 8.0, so strong the Mississippi River reportedly flowed backward. Damage occurred as far away as Washington, D.C., and Charleston, S.C.

Some New Madrid, Mo., residents saw large cracks open in the ground. The crew of a steamboat mooring overnight along a Mississippi River island reportedly awoke to find the island had disappeared below the water.

"We have about 200 small earthquakes per year that we record," said Gary Patterson of the University of Memphis Center for Earthquake Research and Information. "Compared to California, you're getting two to three thousand smaller quakes like that, but for eastern North America, this is a hot spot, the most active seismic area east of the Rockies in the United States."

As for whether there is a big earthquake on the way for the zone, Patterson said there have been major earthquakes in the area about every 500 years in the past 1,500 years. The earthquakes happened as a part of a sequence of events, not just one main shock, he said.