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That 4.1-magnitude earthquake is one of the latest to hit the Timpson area in the last year.
A 3.9-magnitude earthquake occurred on May 10, and on May 17, there was a 4.8-magnitude earthquake, according to the U.S. Geological Survey. Those were followed by a 2.7-magnitude on May 20; a 2.5-magnitude on May 26; a 2.1-magnitude on June 16; a 2.8-magnitude on Dec. 7; a 2.6-magnitude on Dec. 22; and Friday's earthquake. The most recent earthquake — a 2.8-magnitude — occurred about 6:30 a.m. Tuesday.
Timpson court clerk Paula Mullins said Tuesday's earthquake wasn't as bad as Friday's.
“It just kind of felt like a sonic boom,” she recalled.
She said residents discuss earthquakes when they come, and everybody wonders why.
“Everybody's got their own idea of fracking or God giving us a wake-up call,” she said. “It's just happening, and we don't know (why).”
Cliff Frohlich, associate director at The University of Texas at Austin Institute for Geophysics, said Tuesday there is a fault system in East Texas called the Mount Enterprise fault system, which has been known for a long time.
He said faults there can get reactivated by stresses of various kinds, and some people say the fault system may be related to a 1981 Center earthquake and an 1891 Rusk earthquake.
Frohlich said there's been a lot of interest in human causes of Texas earthquakes in relation to the injection of fluids into the ground.
He said there are wells near where Timpson earthquakes were the strongest, and it's possible that the injection of disposable fluids played a role.
“Sometimes when you inject fluids you get earthquakes, (and) in Texas there are (numerous) disposable wells,” he said.
Frohlich noted that faults are also everywhere, and some might be as small as a football field or garage.
He said there is friction to help prevent faults from slipping, but if fluids are pumped in, it can become “like an air hockey table.”
“If mankind is causing them, it's triggering faults that were stuck…,” he said. “If conditions are right for a fault to move, it moves.”
He said it is also possible that earthquakes are natural.
Typically, if one earthquake occurs in an area, more are likely there, Frohlich said.
He said small earthquakes also are more common than big earthquakes. According to a U.S. Geological Survey earthquake calculator, a 4.1-magnitude earthquake is nearly 20 times bigger than a 2.8-magnitude but more than 89 times stronger.
Frohlich said he's never heard of a 2.8-magnitude earthquake like Tuesday's doing much damage.
“Something might fall off a shelf or a window might be cracked, but you're not getting chimneys falling down,” he said.
Shelby County Sheriff Willis Blackwell said there were no reports of damage Tuesday morning. He said there was some structural damage to maybe two or three homes on the fault line last week, but other than that, there were only minor things such as items falling off the wall.
Frohlich said the Timpson area could have more earthquakes in the near future, but he would be surprised if they were much different than the earthquakes that already have occurred.
(Updated Wednesday, January 30, 2013 at 1:14 p.m. CST)