A computer screen displays real-time monitoring of seismic activity throughout the state at the Oklahoma Geological Survey at the University of Oklahoma in Norman. Credit: Sue Ogrocki/Associated Press

Oklahomans were jolted out of bed this morning by the strongest earthquake there since 2011.

The quake’s epicenter was 8 miles northwest of Pawnee, according to the U.S. Geological Survey. Pawnee has about 2,000 residents.

Oklahoma has been trying to slow down an explosion of earthquakes that seismologists blame on the disposal of wastewater from oil and gas exploration. Reveal from The Center for Investigative Reporting found last year that Oklahoma had three times as many earthquakes as California in 2014.

The Associated Press quoted county officials as saying no injuries had been reported, but journalists and emergency personnel have reported damage to buildings in Pawnee, in northeastern Oklahoma.

People as far away as Iowa reported feeling the shaking just after 7 a.m.

Today’s magnitude 5.6 quake is nearly the same size as the magnitude 5.7 one near Prague in 2011, which was the state’s largest recorded earthquake. That earthquake injured several people and damaged numerous buildings.

The quake was centered about 20 miles north of Stillwater, the site of Oklahoma State University and home to 45,000 people, and 20 miles south of Ponca City, population 25,000.

Pawnee and the earthquake’s epicenter are inside one of the “areas of interest” targeted by the Oklahoma Corporation Commission for reductions in the amount of water injected underground because of concerns about earthquakes.

The epicenter also is about 30 miles north of Cushing, the site of a large strategic oil storage facility that has raised seismic concerns.

Michael Corey can be reached at mcorey@cironline.org. Follow him on Twitter: @mikejcorey.

Michael Corey is Reveal's senior data editor. He leads a team of data journalists who seek to distill large datasets into compelling and easily understandable stories using the tools of journalism, statistics and programming. His specialties include mapping, the U.S.-Mexico border, scientific data and working with remote sensing. Corey's work has been honored with an Online Journalism Award, an Emmy Award, a Polk Award, an IRE Medal and other national awards. He previously worked for the Des Moines Register and graduated from Drake University. He is based in Reveal's Emeryville, California, office.