The 5.6 magnitude earthquake that hit nine miles northwest of Pawnee Saturday morning was the largest in the state’s history, damaging buildings and prompting Governor Mary Fallin to issue a state of emergency for Pawnee County., according to Tulsa World.
Saturday’s earthquake matched a previous record set in 2011, when a 5.6 magnitude earthquake struck near Prague in Lincoln County. There were six aftershocks after Saturday’s quake, one registering 3.6. According to the U.S. Geological Survey, the earthquake struck at 7:02 a.m.
Saturday’s earthquake prompted the Oklahoma Corporation Commission to issue orders shutting down indefinitely 37 oil and gas disposal wells in a 725-square-mile area near Pawnee County. “This is a mandatory directive,” Fallin said, according to CNN.
The commission, which regulates fuel, oil, gas, public utilities and transportation industries, is investigating to determine the epicenter of the quake said commission spokesman Matt Skinner. The Environmental Protection Agency is also investigating.
There is growing evidence that hydraulic fracking operations are responsible for the growing number of Oklahoma earthquakes. Oklahoma has seen a 160-fold spike in quakes, many of them causing injuries and damaging buildings and highways. In 2014 the state’s earthquake rate surpassed California’s.
Hydraulic injections, the process of pumping millions of gallons of water and other toxic chemicals into the ground under high pressure, can alter the stresses that hold geological fault lines in place. Skinner insists Oklahoma’s earthquakes are not directly caused by fracking, but he does agree that the pressure from the disposal wells used to get rid of toxic wastewater from fracking may be the problem.
“The disposal wells dispose into the state’s deepest formation, the Arbuckle formation, which is right above what we call the basement,” Skinner said. The basement is above where the critical faults lie that shift and make earthquakes.” Fallin added that all wells within 5 to 10 miles of the fault in question need to be shut down within seven days and the other wells within 10 days.
