There has been a lot of seismic activity in Arkansas the last few days, specifically at Guy, AR about 40 miles north of Little Rock.  There is speculation that this is an extension of the New Madrid fault line.  Today there was a M 4.0 followed by a M 3.6.  There have been 48 quakes of magnitude 1.0 or greater during the last week.

http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/US2/34.36.-93.-91.php