Tremors induced by wastewater disposal are larger and harder to predict than previously thought.
Underground disposal of wastewater from fracking may pose a much greater risk of causing dangerous earthquakes than previously believed, particularly in areas of the U.S. Southwest and Midwest where earthquake faults have not been mapped extensively, seismology researchers are warning, in a story by Patrick Kiger for National Geographic Daily News.
The warning comes as evidence continues to accumulate that the activities associated with the North American oil and gas boom can lead to unintended, man-made tremors, or “induced seismicity,” as researchers call it.
Fracking itself has been linked to quakes. More often, though, the cause is injection of fracking wastewater into disposal wells.
A paper published in the scientific journal Geology in 2013 found that the tip of the Oklahoma quake’s initial rupture plane was less than 200 meters (656 feet) away from injection wells, and concluded that years of injecting fluid into them had altered the pressure on the fault.
That paper’s lead author, Cornell University geophysicist Katie Keranen, released a new paper at the conference, which found that four high-volume wastewater injection wells in Oklahoma had triggered a swarm of small earthquakes about 9.3 miles (15 kilometers) away. It’s not necessary for wastewater in an underground reservoir to actually reach an earthquake fault directly, because “the pressure can travel,” Keranen explained.
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