Posted 2:57 am Friday, May 11, 2012
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3.7 Quake Shakes East Texas; Mount Enterprise Fault Suspected In Tremor
By TIM MONZINGO
Staff Writer
Staff Writer
Larry Burns and his work crew were at Timpson's Martin Luther King Park installing playground equipment when they heard the rumbling.
"I didn't feel the earthquake, but I head the rumble. I just thought it was a jet flying low," he said. "Then somebody called me and told me we had an earthquake."
The epicenter of the 3.7-magnitude earthquake that shook pictures off the walls of Timpson homes was about two kilometers, or about a mile, away from his town.
As of Thursday afternoon, Burns, who is the town's emergency management coordinator, said no structural damage or personal injuries were reported after the shakes, which started about 10:15 a.m.
Burns and emergency management and law enforcement officials in Shelby and Nacogdoches counties were taking assessments of their areas to see whether the quake could have caused any serious damage Thursday afternoon.
According to a news release issued by the Nacogdoches Unified Emergency Operations Center, no significant damage or injuries were found as a result form the quake.
East Texas isn't a hotspot for earthquakes the way California and the West coast, which sits on the Pacific tectonic plate, are, but in reality, the events aren't that rare, geologists said.
LaRell Neilson, a geology professor with Stephen F. Austin State University in Nacogdoches, said there's an active fault system that runs through East Texas, stretching from Mount Enterprise along Texas Highway 84 to Timpson. It's called the Mount Enterprise Fault.
"What you've got is probably activation of one of the faults along that fault system," he said. "It's not as active as the San Andreas Fault or some of the faults in California, but it's still fairly active."
The fault is active and delivers low-level quakes, such as Thursday's, fairly regularly. He said the last one he could recall struck the area around 1994 and measured between 3.5 and 4 on the United States Geological Survey's equipment.
"You've got to realize that we do have a fault system here that's active and we do have some scarps and other things that reflect that activity," he said.
Dr. John Ferguson, a geosciences professor and seismologist at The University of Texas at Dallas, agreed with Neilson's analysis and said the quake was likely from activity in the Mount Enterprise Fault system.
While Texas sits in toward the middle of the North American Plate, Ferguson said faults inland are actually pretty common, as are low-level quakes in the plate's interior.
The Mount Enterprise Fault is one of the major faults in the East Texas Basin, he said.
"That seems to be the thing that most quakes in that part of the state are associated with," he said. "There are faults everywhere. They're not a rare thing at all."
A contributing factor to the quakes in the region could be the natural gas boom, he said.
Natural gas and oil drilling creates large amounts of dirty water that is reinjected into the earth, he said. That reinjection changes the way the landscape reacts to geologic stresses.
In Dallas, a large water injection site created a series of quakes in the past, he said.
"The fracking itself does not cause earthquakes. What causes the earthquakes is other stuff that is associated with the production," he said. "And they are earthquakes occurring on natural faults, but they are stimulated by that injection. This is a very, very well-documented thing."
Ferguson said in all likelihood, there are probably small tremors and shakes going on beneath East Texas frequently, but it's unlikely they are anything significant. The Geologic Survey typically records events in East Texas that register as a 2 or higher on its equipment. Many, he said, are probably hitting a one, zero or less on the scale.
Local earthquakes likely will pose no threat for severe damage, he said, but one coming from the northeast could.
"In general terms, the most dangerous thing as far as seismic activity is concerned would be a big earthquake in Missouri," he said.
In the early 1800s, Missouri quakes registering higher than magnitude 7 were felt many states away, he said. A similar quake nowadays would have a much greater effect in East Texas, Louisiana, Arkansas and Tennessee than the common, low-magnitude quakes such as Thursday's, he said.
"If we were to have a similar event in Missouri, it would probably cause widespread, low-level damage all over Texas, or at least the eastern part of Texas," Ferguson said. "If there was a big one there, we'd certainly know about it here, but the local ones are likely to be very dangerous."
