In the last few months, something unlikely happened—Oklahoma racked up more earthquakes in 2014 than California. And not by a little. As of June, the prairie state has had 190 earthquakes of magnitude 3 or greater, compared with only 71 in California. It’s almost certainly due to dewatering, a process associated with fracking.
Fracking works by injecting water, sand, and chemicals into a well at high pressure, fracturing the surrounding rock. Sand works its way into the cracks, holding them open and allowing the oil to seep out into the fluid. The fracking fluid is then pumped out and separated from the oil. Millions of gallons of water are left over, and it has to be disposed of. It’s often pumped back underground.
Eric Hand, reporting for Science:
The vast majority of Oklahoma’s more than 9000 injection wells cause no trouble whatsoever. Not so with four high-volume disposal wells used in a dewatering operation near Oklahoma City, the study suggests. The wells pump more than 4 million barrels (477,000 cubic meters) of water into the ground every month. Katie Keranen, a geophysicist at Cornell University, and colleagues found that the four wells are capable of triggering the earthquakes. By combining precise maps of Jones swarm earthquakes with a hydrogeologic model, they showed that an expanding underground wave of pressure from the wells (named Chambers, Flower Power, Deep Throat, and Sweetheart) closely matched the places and times of the quakes in the swarm.
While the main fault that runs through nearby Oklahoma City is unlikely to be affected by the high-volume disposal wells, which are run by energy company New Dominion, Keranen is still concerned that a magnitude-6 quake could strike the region should the practices continue. Some quakes linked to the New Dominion wells happened more than 20 miles away.
The state of Oklahoma, Hand reports, has recently been paying closer attention to scientific studies linking fracking practices with the rising number of earthquakes. After a magnitude-3.4 quake near the Oklahoma-Texas border was tied to fracking, a state regulator ordered the well operator to reduce the amount of waste water is was injecting. That same regulator is closely reading the new study by Keranen and her colleagues, Hand reports.