Earthquake 'swarm' rattles Arkansas town and its residents - CNN.com

http://www.cnn.com/2010/US/12/13/arkansas.earthquakes/index.html?eref=mrss_igoogle_cnn
(CNN) -- The Arkansas Geological Survey is trying to unravel a mystery: What is causing earthquakes in the town of Guy, Arkansas?
Since September 20, the community of 549 residents north of Little Rock has experienced an almost constant shaking from 487 measurable earthquakes.
"We've had 15 today including a 3.1 (magnitude) from this morning," Scott Ausbrooks, geohazards supervisor for the Geological Survey, said Monday. "These are shallow quakes between two and eight kilometers (between one-and-a-quarter and five miles) below the surface."
While earthquakes aren't unusual in the Southeast state, the frequency is.
"This time last year we had 39 quakes total for the entire state," said Ausbrooks.
Most of the quakes in the swarm -- a localized surge of earthquakes with all of them about the same magnitude, according to the United States Geological Survey -- are so small they go unnoticed. The largest, a 4.0 on October 11, caused the only documented damage, cracking a window at a visitor's center to a state park.

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