June 29, 2009
By EVA-MARIE AYALA
Another small earthquake hit Cleburne late Friday night, and a city spokesman said it could be helpful to geologists trying to determine whether natural gas drilling is causing the seismic activity.
The quake was the sixth minor tremor to hit the city this month. A group of researchers from Southern Methodist University recently put four seismographs in the ground to measure the depth of the activity, said city spokesman Charles Hodges.
Hodges said city officials had worried that they wouldn’t be able to gather evidence from a live quake, making it impossible to find a cause. He likened the situation to a mechanic who can’t hear the clanging sound that a driver hears in his car.
"Well, our mechanics heard it," he said Saturday. "That’s a good thing. Now we will know how deep these go, how it’s affecting the earth beneath the city."
He said officials also would be able to tell whether any utility lines — such as gas, water or electrical — are being affected.
"The biggest question we have is: Is there any reason that this could be caused by natural gas drilling?" he said.
More than 200 wells have been permitted in the city as part of the Barnett Shale drilling boom in recent years. Geologists have said it’s possible that gas drilling could cause minor quakes, but it can be difficult to prove.
Chris Hayward, director of SMU’s geophysics research program, has said figuring out at what depth the quakes are occurring will help answer some questions.
"If the quakes are happening much deeper than the drilling, then we can probably rule it out," Hayward told the Star-Telegram earlier this month. "If the quakes are happening at the same depth or a shallower depth than the drilling, then we can’t rule out drilling as a possible cause."
The tremors began on June 2, when there were five within a week. Friday’s occurred around 10:30 p.m. and registered a 2.2 magnitude. There has been no damage reported from any of them.
The city was to hire a geologist to study the activity but then officials were contacted by the SMU researchers, Hodges said.
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