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May 2, 2014

Research suggests quake, wastewater injection are linked

OKLAHOMA CITY — New research suggests that the sharpest earthquake to strike Oklahoma may have been triggered in part by wastewater injection — which if true, would make the 2011 temblor the strongest ever linked to disposal practices within the oil and gas industry.

An industry spokesman said a cause-and-effect cannot be proven because work in the oil patch hasn’t changed much in generations. A study of the same quake last year noted that wastewater had been injected into abandoned oil wells nearby for 17 years without incident.

The magnitude 5.7 quake, centered near Prague, knocked over four spires at a university 17 miles away and shook a college football stadium that moments earlier had held more than 57,000 fans. Fourteen homes suffered significant damage and two people near the epicenter suffered minor injuries. The quake caused at least $4.5 million in damages.

A study published in March in the Journal of Geophysical Research, written by scientists from Brown and Cornell universities, the Lamont Doherty Earth Observatory at Columbia University, the University of Southern California and the U.S. Geological Survey, concentrated on Oklahoma quakes in the fall of 2011. The state has had thousands of smaller temblors since.

The lead researcher, Danielle Sumy, a postdoctoral student at Southern California and a former USGS geologist, said a magnitude-5.0 quake triggered by wastewater injection early on Nov. 6, 2011, set off subtle pressures that rolled along like dominoes before finding relief in the 5.7 temblor later that day.

“We found that this magnitude 5.0 earthquake did increase the stress in the region around the 5.7 magnitude earthquake, thus allowing a cascade of failure along the fault,” Sumy said.

A recent study linking hydraulic fracturing — the process in which water mixed with sand and chemicals is used to extract oil and gas — to quakes in Appalachia led Ohio agencies to issue new regulations. In Oklahoma, the focus is on the industry’s wastewater, which is often injected into old oil wells for disposal, not on fracking.

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