Oil-Rich Oklahoma Has Been Hit by Nearly Three Dozen Earthquakes Since Wednesday

Nearly three dozen small to mid-sized earthquakes have rocked northern Oklahoma towns since Wednesday, rattling windows and nerves in a region where scientists have linked seismic activity to oil wells.

The quakes included a magnitude 4.4 and a magnitude 4.8 that struck about two miles apart and within a minute of each other Wednesday night, the US Geological Survey (USGS) reported. They kept going into Friday, with two 4.0s on Thursday and a 4.1 on Friday morning. At least 15 more were in the 3 range — and all were centered within a few miles of each other, in a patch of prairie about 100 miles northwest of Oklahoma City, according to the USGS.

Wednesday night's quakes were the first "that really made me nervous," said Paul Southwick, the city manager of Fairview, Oklahoma, about 20 miles southeast of the quakes' epicenters.

"It started out with a rumble and then it got louder and louder and louder," Southwick said. "Then I felt this wave go under the house. The house lifted and went down and started shaking. I could feel it with my feet on the floor until it was just about gone, and then we got hit with another one."

More than 25 people reported feeling Wednesday night's quakes as far away as Kansas City, Missouri, nearly 350 miles away, according the USGS. Before Wednesday night, there had been four or five noticeable recent quakes in the area, Woods County Sheriff's Deputy William Barnum said.

"We've had quite a few of them lately. This one just shook a little longer," said Barnum, who lives in Waynoka, about 20 miles west of where the quake cluster was centered. "In my house, it shook my chair and shook the windows."

In less than a decade, Oklahoma has gone from having one or two small earthquakes a year to nearly three a day. The Sooner State saw more than 900 quakes of magnitude 3.0 or above in 2015, with 29 of them in the 4-range, said Jeremy Boak, the head of the Oklahoma Geological Survey.

"It's the first time we've seen three magnitude 4s in less than 24 hours, and all three in the same area," Boak said. "And those come on the heels of two that were only two days apart."

Scientists say the seismic surge stems from the salty wastewater that gets pumped up from oil wells in the petroleum-rich state, separated from crude oil, and shot back deep underground, where it lubricates the faults that crisscross the state. There are no injection wells operating in the immediate vicinity of the Fairview-area quakes, said Matt Skinner, a spokesman for the Oklahoma Corporation Commission, which regulates the oil industry — but go about 30 miles further out, and there are a lot of them.

"That region has seen an enormous increase in disposal activity over the past couple of years," Skinner said. And most of those wells handle high volumes of wastewater, he said.

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State officials have responded to previous quake swarms by ordering wastewater injection wells in nearby areas to reduce their depth or volumes — most recently around the Oklahoma City suburb of Edmond, which was hit with a magnitude 4.2 quake on January 1. Skinner said some action would be taken in response to the latest quakes, but officials are still studying what to do.

Boak said state seismologists put Wednesday night's biggest quake at 4.6 instead of the 4.8 that the USGS recorded. But he said seismic activity in the area has grown sharply as more oil companies have begun drilling there.

"That's on the edge of an area that has been slowly but steadily lighting up more and more over a larger and larger area," Boak said. "I'm presuming that's partly about the development of this particular play out there."

The oil and gas industry is the bedrock of Oklahoma's economy, and the industry has argued that there's not enough evidence to blame the quakes on injection wells. But even the petro-friendly state government has said it considers the issue settled, even if industry critics say their recognition came too late. Even small quakes have been adding up to big bills for some homeowners, most of whom don't have earthquake insurance.

And for others, the quakes are starting to give them the creeps.

"We've felt some others, but again, not to this intensity," Southwick said. "This was to that level that really wakes you up and you say, 'What are we getting into here? Are we going to have something that's going to be worse?' This is concerning."

Related: A Big Earthquake Just Hit Oklahoma — And It Might Be the Oil Industry's Fault

Follow Matt Smith on Twitter: @mattsmithatl