Earthquake Shakes Swath of Midwest Where Wells Have Drawn Scrutiny
U.S. Geological Survey says 5.6-magnitude tremor centered in north-central Oklahoma; no major damage reported
A 5.6-magnitude earthquake rattled Oklahoma Saturday, damaging buildings and tying for the strongest temblor ever recorded in the state, which has experienced a rash of earthquake activity in the past decade that U.S. seismologists have tied to the underground disposal of wastewater from oil and gas drilling.
The earthquake took place around 7:02 a.m. central time near Pawnee, Okla., a town of about 2,200 people roughly 55 miles northwest of Tulsa, according to the U.S. Geological Survey. It was felt widely through the middle of the country, with reports coming from as far as Houston and Kansas City, according to the USGS.
There were no immediate reports of injuries, but local television reports showed damage to some buildings in Pawnee. People in other parts of Oklahoma reported cracked brick facades and other structural damage including in Stillwater, Okla., home to Oklahoma State University. It was not immediately clear whether the temblor was natural or triggered in part by human activity.
Officials in Pawnee are assessing damage in town, where the earthquake caused some building facades to crack and in some cases crumble. Chunks of a 100-year-old building fell two stories to litter the sidewalk near the city’s main street, officials said.
“That’s one of our historic buildings. But there have been no injuries, praise God,” said Lou Brock, a city councilman.
Mr. Brock said he was awake and was wishing a friend happy birthday when the rumbling started. “This was not the gift I wanted to give them,” he said. He felt the ground moving for over a minute.
“One of those incredible feelings,” he said.
The city asked residents to report any structural problems or smells of gas, he said.
“Right now the situation is that as long as we get the most information from our wonderful city people I think we’re going to be just fine,” Mr. Brock said.
Gov. Mary Fallin, a Republican, said on Twitter that state officials were asking structural engineers to assess bridges and building safety following the quake. Oklahoma Corporation Commission staffers were also reviewing oil and gas wastewater disposal wells in the vicinity of the quake area, she added.
Oklahoma has a history of seismic activity, and earthquakes in the state are not unheard of. But it has stepped up regulation of the wastewater injection wells after seeing a dramatic increase in seismic activity over the past decade. In 2015 the USGS recorded 2,500 quakes with a magnitude of 2.5 or higher in the state, up from just three in 2005.
The USGS in March released maps that for the first time show the potential risk of man-made as well as naturally occurring earthquakes, and they listed some parts of Texas and Oklahoma now at the same danger of temblors as California, due largely to the injection-well trend.
The strongest quake previously recorded in Oklahoma was also a 5.6 magnitude event, and took place near Prague, Okla. in 2011, buckling roads and destroying 14 homes. It spurred several lawsuits from homeowners who claimed energy companies burying wastewater nearby had helped trigger the quake.
When energy producers extract oil and gas from wells, thousands of barrels of salty water laced with heavy metals come up along with the fuel. The water often is injected back underground under high pressure into special disposal wells.
But government and academic researchers have found that the practice may help trigger movement along geologic fault lines. The oil-and-gas industry has acknowledged the validity of the studies and cooperated with regulators, but has said that more research is needed to link specific wells to specific incidents.
After Oklahoma’s Corporation Commission began taking stronger actions to police the location and volume of injection wells, the number of quakes in the state fell by roughly 25% compared with a year earlier, state officials said in June.
The quake’s epicenter was roughly 25 miles north of Cushing, Okla., one of the world’s major oil hubs. The town holds some 64 million barrels of crude in about 400 massive, aboveground tanks.
A representative of Enbridge Inc., one of the top pipeline and storage companies in Cushing, said no damage had been reported at its sites there.
“Following the earthquake, Enbridge employees were directed to conduct visual inspections of tanks, manifolds and other facilities. The Cushing Terminal is currently operating normally,” the company said.