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Record-tying magnitude 5.6 quake in Oklahoma oil country rattles Midwest

OKLAHOMA CITY — A record-tying earthquake in the edge of Oklahoma's key energy-producing areas rattled the Midwest as far north as Chicago and reached into part of Texas on Saturday, and likely will bring fresh attention to the practice of disposing oil and gas field wastewater deep underground.

The United States Geological Survey said a 5.6 magnitude earthquake happened at 7:02 a.m. Saturday in north-central Oklahoma near the town of Pawnee, 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.

An increase in magnitude 3.0 or greater quakes in the state has been linked to underground disposal of wastewater from oil and natural gas production.

The Oklahoma Corporation Commission, which since 2013 has asked wastewater-well owners to reduce disposal volumes in parts of the state, is now requiring 37 wells in a 514-square-mile area around the epicenter of the quake to shut down within seven to 10 days because of previous connections between the injection of wastewater and quakes.

Pawnee County Emergency Management director Mark Randell said no buildings collapsed in Pawnee, a town of 2,200 about nine miles southeast of the epicenter. "We've got buildings cracked," Randell said. "Most of it's brick and mortar, old buildings from the early 1900s."

Randell also said a man suffered a minor head injury when part of a fireplace fell on him as he protected a child. The man was treated and released.

Oklahoma Gov. Mary Fallin has declared a state of emergency for the county.

People in Kansas City and St. Louis, Mo.; Chicago; Gilbert, Ariz.; Fayetteville and Little Rock, Ark.; Des Moines, Iowa; Memphis; and Big Lake in southwest Texas, all reported feeling the earthquake. Dallas TV station WFAA tweeted that the quake also shook its studios.