Rare earthquakes in Texas caused by gas mining
A wastewater reinjection well from natural gas mining is being blamed for a series of tremors in Texas, where earthquakes almost never happen.
Fri, Mar 12, 2010 at 05:53 PM
Seismologists working to discover the epicenter of 11 mysterious earthquakes occurring over the last two years in the Dallas/Fort Worth area in Texas have pinpointed their origin to a single wastewater reinjection well from a natural gas mining operation, according to USA Today. Earthquakes are extremely rare in Texas, where no human life within the state's borders has ever been lost due to a tremor.
"The earthquakes were right in our backyard, and quakes don't happen too often in Texas," said seismologist Brian Stump of Southern Methodist University in Dallas.
The mining operation being blamed for the quakes blasted 9,000 barrels of saltwater to depths of 10,000 to 14,000 feet daily, practically right over an old fault line which sits only about 1,000 feet under the reinjection well.
"The vast majority of wells don't have quakes associated with them," said Jim Dewey of the U.S. Geological Survey. This one, however, may have been ill-placed.
The well was created in part of the drilling process known as hydraulic fracturing, or "fracking", where shale is cracked by injections of high-pressure water, loaded with sand, to free natural gas trapped within. The process then causes salty water to "flowback" toward the surface, which is typically "reinjected" back down into deep rock layers instead of treating it for safety reasons.
"We are only saying a link to the well is 'plausible,' not definitive," said Stump. Even so, the tremors have curiously stopped ever since the saltwater reinjection was stopped at the site last June.
The largest of the recent quakes measured magnitude-3.3 , but it was felt widely over the densely populated Dallas/Forth Worth area. All of the earthquakes had an epicenter one tenth of a mile away from the Dallas/Fort Worth airport.
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