Two Years After Oklahoma Earthquake Officials Warn More to Come

Reader Contribution by Stan Cox
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Two years ago this week, a magnitude 5.7 earthquake struck near Prague, Okla., destroying fourteen houses and shaking the ground as far away as Wisconsin. The November 5, 2011, quake was the biggest ever recorded in a state where tornadoes rather than seismic disasters are the familiar hazard; therefore, it naturally drew the attention of researchers. And now federal and state geologists are warning Oklahomans that the risk of new quakes has risen significantly.

This new state of affairs is apparently connected to the activities of natural gas companies. Five months

ago, a paper appeared in the journal Geology showing how injection of wastewater from oil and gas mining operations into the earth had led to the disaster. Wastewater injection has been practiced near Prague since 1993, but in the report, scientists at the University of Oklahoma, Columbia University, and the U.S. Geological Survey (USGS) noted that the volume of waste being injected into deep holes had increased dramatically with the increasing use of hydraulic fracturing, or “fracking” to free natural gas from tight formations. Waste injection, they found, had caused subterranean fluid pressure to built up to the point at which it set off a cascade of small quakes that eventually triggered the record quake.

Fracking itself was not the direct cause. But the controversial gas-mining process uses vast quantities of fluids, the bulk of which return to the surface as a salty, toxic stew that requires safe disposal. Therefore, the scale-up of fracking has brought a dramatic escalation in the quantity of wastes being reinjected into old wells. (The conventional oil and gas operations that have long been a familiar feature of the Oklahoma landscape also inject wastewater, but in much smaller quantities.)

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