HOUSTON (Reuters) - The U.S. Environmental Protection Agency will order wastewater disposal wells shut near the epicenter of a 5.6 magnitude earthquake that struck on Saturday around Pawnee, Oklahoma, local media reported on Tuesday.
The quake was one of the strongest ever to hit the state and prompted its oil and gas regulator, the Oklahoma Corporation Commission, to order 37 disposal wells shut in a 725-square-mile (1,878-sq-km) area around Pawnee.
It also asked the EPA to help shut disposal wells in a 211 square-mile (546.49-sq-km) area of Osage County because the OCC lacked jurisdiction there.
Local news website NewsOK reported that the EPA told the OCC in a letter on Sunday that it would order Osage County wastewater wells to be shut, but did not specify how many would be affected.
The EPA was not immediately available for comment.
Oklahoma has seen a massive spike in earthquakes in the past few years, registering 2-1/2 earthquakes daily of magnitude 3 or greater - a seismicity rate 600 times greater than before 2008, according to the Oklahoma Geological Survey.
Scientists have tied the quakes to the injection of saltwater, a normal byproduct of oil and gas drilling, into deep disposal wells and underground caverns.
Oklahoma has been putting new restrictions on some of its thousands of disposal wells for more than a year to curb seismic activity.