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Early-morning earthquake rattles Oklahoma
Wastewater disposal raising risk of tremors
Kyndra Richards cleaned up at White’s Foodliner in Pawnee, Okla., on Saturday after the earthquake struck. (Paul Hellstern/Associated Press)
Associated Press

OKLAHOMA CITY — A record-tying earthquake in the edge of Oklahoma’s key energy-producing areas rattled the Midwest from Nebraska to North Texas on Saturday and will probably focus new attention to the practice of disposing oil and gas field wastewater deep underground.

The US Geological Survey said a 5.6 magnitude earthquake occurred at 7:02 a.m. in north-central Oklahoma, on the fringe of an area where regulators had stepped in to limit wastewater disposal. That temblor matches a November 2011 quake in the same region.

People in Kansas City and St. Louis, Mo.; Fayetteville and Little Rock, Ark.; Des Moines; and Norman, Okla., all reported feeling the earthquake. Dallas TV station WFAA tweeted that the quake shook its studios, too.

Pawnee County Emergency Management Director Mark Randell said no buildings collapsed in the town of 2,200 about 9 miles southeast of the epicenter, and there were no injuries. ‘‘We’ve got buildings cracked,’’ Randell said. ‘‘Most of it’s brick and mortar, old buildings from the early 1900s.’’

Pawnee furniture store owner Lee Wills said he first thought it was a thunderstorm.

‘‘Then it just . . . Everything went crazy after that. It just started shaking,’’ said Wills, who lives about 2½ miles outside of town. ‘‘It rocked my house like a rubber band. Threw stuff off cabinets and out of cabinets, broke glasses.’’

The office of Oklahoma Governor Mary Fallin tweeted that state highway crews were checking for bridge damage and the state Department of Emergency Management would assess damage and determine how to address it. Geologists say damage is not likely in earthquakes below magnitude 4.0.

The damage from Saturday’s quake was not as severe as that caused by the 2011 quake near Prague, Okla., about 60 miles south of Pawnee, despite being the same magnitude and approximately the same depth below the surface. Saturday’s was 3.7 miles deep, compared with 3.1 miles in 2011.

Hard bedrock beneath the surface in north-central Oklahoma is probably the reason for less damage, Oklahoma Geological Survey geophysicist Jefferson Chang said.

An increase in magnitude 3.0 or greater earthquakes in Oklahoma has been linked to underground disposal of wastewater from oil and natural gas production. State regulators have asked producers to reduce wastewater disposal volumes in earthquake-prone regions of the state.

Some parts of Oklahoma now match northern California for the nation’s most shake-prone, and one Oklahoma region has a 1 in 8 chance of a damaging quake in 2016, with other parts closer to 1 in 20.

Matt Skinner, the spokesman of the Oklahoma Corporation Commission, which regulates the energy industry, said members of its seismicity team were seeking more details.

The area where the quake was centered saw a magnitude 3.2 temblor earlier this week and is on the edge of a region covered by a ‘‘regional earthquake response plan’’ issued in March by the state Corporation Commission, whose goal was the cut the number of earthquakes by reducing wastewater injection volume by 40 percent from 2014 levels.