Drilling Not Likely to Blame for Recent Quakes

Experts say it's possible drilling has an effect, but not likely

By SCOTT FRIEDMAN

Updated 6:30 PM CST, Mon, Jun 8, 2009

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North Texans are wondering if natural gas drilling is responsible for three minor earthquakes, but experts say it's much more likely that the tremors are just natural events.

Cleburne city officials held a news conference Monday to try to calm rattled nerves and address rumors that natural-gas wells in around town caused the quakes.

City officials said the U.S. Geological Survey had assured them the quakes were likely a natural phenomenon.

But seismologist Brian Stump, a professor at Southern Methodist University said last week that he couldn't rule out the possibility that gas drilling could be to blame.

"It's possible, but it can't be resolved with the kind of data we have at this point," he said.

The university's seismology lab detected the latest small quakes, which registered 2.6 and 2.3 in magnitude, Saturday and Sunday.

Stump said there are historical cases around the world where drilling has caused small earthquakes, but it's happened infrequently.

Most drilling in North Texas occurs at depths of around 5,000 feet. The U.S. Geological Survey estimates the Cleburne quakes were at a depth of several miles, much deeper than the drilling.

But the depths are only estimates, because the USGS' seismographs are located in Colorado. Stump said experts would need to place seismographs much closer to the quake sites to determine the exact depth and help answer the drilling question.

In the meantime, everyone in Cleburne seems to have a theory.

"Earth's changing, that's all I can say," said Patricia Turman, as she headed off to lunch at a local cafe in a town where she never dreamed she'd ever feel an earthquake.