In June and July of 2009, seven quakes with magnitudes between 2.1 and 2.8 were reported in or around Cleburne, which is 50 miles southwest of Dallas.
Before last year, an earthquake had never hit the town of 22,000 people. That left some wondering whether natural gas drilling in the area could be a factor.
A study on what may be causing the earthquakes is not yet complete.
Earlier this year another study linked the wastewater disposal process done after natural gas extraction -- and not the drilling itself -- to some minor earthquakes in other Dallas-Fort Worth area cities.