One of the strongest earthquakes ever recorded in Oklahoma jolted one of the state's energy-producing areas Saturday, causing some local damage and shaking a large part of the central United States. Only one minor injury was reported.
The shallow earthquake had a magnitude of 5.6. The mayor of the town of Pawnee, closest to the quake's epicenter, said "right away you could tell this was something different" than other tremors felt in the area in recent years.
"This was a long, sustained, strong earthquake," Mayor Brad Sewell said. He estimated the shaking lasted for a full minute.
The quake was felt over a large area of the central United States, ranging from Texas to South Dakota, which are more than 930 miles (1,500 kilometers) apart. It fueled growing concerns about the link between industrial energy production and seismic tremors, and the state government ordered 35 wastewater disposal wells in the area around Pawnee to shut down until further notice.
Despite the strong shock, only one minor injury was reported in Pawnee, but cracks ran through many buildings in the north-central Oklahoma town. Pawnee, with a population of 2,200, and the surrounding area have a relatively large native American population from the Pawnee Nation, which has jurisdiction over three counties in the area.
Matched 2011 quake
The U.S. Geological Survey said Saturday's quake matched the magnitude of a jolt in November 2011, in the same region, that was the strongest in Oklahoma in modern times.
Parts of Oklahoma now rival Northern California as the nation's most earthquake-prone areas, and a dramatic rise in quakes in Oklahoma and neighboring Kansas has been linked to oil and natural gas producers' practice of digging deep underground wells to dispose of large quantities of wastewater.
Pumping water underground under pressure also is used in drilling operations to exploit deposits of oil and gas, in a process known as hydraulic fracturing, or fracking.
The Oklahoma Geological Survey ((http://www.ou.edu/ogs.html)) said fracking was a factor in the huge increase in earth tremors recorded in the state in recent years, but that a far greater volume of wastewater was injected underground by disposal wells.
The state agency said Oklahoma records an average of 2.5 tremors of magnitude 3.0 or less every day, a rate 600 times higher than existed before 2008.
