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Study links Oklahoma earthquake with fracking

Staff writer |
Researchers from Cornell University and the University of Colorado say a large swarm of earthquakes in central Oklahoma was probably caused by activity at a few highly active disposal wells.

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In those well wastewater from drilling operations, including hydraulic fracturing, is forced into deep geological formations for storage.

Four high-rate disposal wells in southeast Oklahoma City probably induced a group of earthquakes known as the Jones swarm, which accounted for 20% of the seismicity in the central and eastern United States between 2008 and 2013, the team rwrote in the journal Science.

The Jones swarm saw more than 100 earthquakes of magnitude 3 or greater during that five-year period. The four wells dispose of more than 4 million barrels of fluid monthly. Hydraulic fracturing involves shooting a high-pressure mixture of water, sand and chemicals deep underground to extract oil and natural gas. The resulting wastewater is often forced underground as well.

When fluid is injected into rock formations, it increases pressure in the pores of those formations, said study senior author Shemin Ge, a hydrogeology professor at the University of Colorado, Boulder. The increased pressure can trigger earthquakes in preexisting faults or other areas of geological weaknesses, she said.

"We view the expanding Jones earthquake swarm as a response to regionally increased pore pressure from fluids injected at the [southeast Oklahoma City] wells," the scientists concluded.

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