Three weekend tremors in shale-rich Oklahoma

OKLAHOMA CITY, Feb. 22 (UPI) -- Seismic activity in shale-rich Oklahoma was apparent again, with the U.S. Geological Survey recording three minor events in less than 24 hours as of Monday.

Three tremors of magnitude-3 or less were recorded in Oklahoma since Sunday. A magnitude-2.8 tremor was reported Sunday in Kansas about six miles from the northern border of Oklahoma.

The state reported one of its largest earthquakes in recorded history with a mid-February magnitude-5.1 earthquake near Fairview, about 100 miles north of Oklahoma City. The USGS reported last year the increase in seismic activity in Oklahoma since 2009 may be in part related to activity associated with oil production. The agency said the disposal by the energy industry of wastewater in deep underground wells is potentially leading to more earthquakes.

Oil and gas regulators with the Oklahoma Corporation Commission called on operators last week to reduce the volume of waste water disposed from oil and gas wells in western Oklahoma in response to increased seismic activity. That followed reductions already in place for other parts of the state prone to tremors.

Division chief Tim Baker said the new plans cover areas "not yet" recording earthquakes.

"This plan is aimed not only at taking further action in response to past activity, but also to get out ahead of it and hopefully prevent new areas from being involved," he said.

In January, Oklahoma Gov. Mary Fallin authorized the use of $1.4 million from state emergency funds to help drive earthquake research at state agencies.

Last week, the Sierra Club and Public Justice filed a federal lawsuit against energy companies New Dominion, Chesapeake Operating and Devon Energy Production Co., for waste-water disposal activity. Johnson Bridgwater, director of the Oklahoma chapter of the Sierra Club, said the lawsuit was filed in part in response to the dangers "associated" with hydraulic fracturing, a drilling practice more commonly known as fracking.