Oklahomans ask: What’s causing these quakes?

Reporting from Meeker, Okla. —  Geophysicist Katie Keranen was burying a seismometer on a farm in what is supposed to be tornado, not earthquake, country when a trio of figures came striding across the misty cow pasture, all dressed in camouflage.

Ashley Gilbreth, 33, and her two children had been hunting when yet another earthquake hit, a magnitude 3.6 temblor accompanied by a thunderous boom.

Bowdie Gilbreth, 13, whose school was closed this day for quake-induced ceiling repairs, had been perched in a deer stand 17 feet high in the trees. Bowdie and his 11-year-old sister, Megan, clung to the rails as if they were riding a roller coaster.

What, they asked Keranen, is going on in Oklahoma?

It’s what everyone here wants to know.

Keranen, an assistant professor at the University of Oklahoma in Norman, was among scientists dispatched by the Oklahoma Geological Survey, Oklahoma State University, the U.S. Geological Survey and other research groups after the Meeker area was rocked by a magnitude 5.6 quake on Nov. 5, the strongest in state history.

In a state that’s home to 185,000 drilling wells, where oil derricks dot the landscape, a pressing question is whether industrial drilling has been triggering the quakes.

Mike Terry, president of the Oklahoma Independent Petroleum Assn., dismissed any connection between the two. “To try to blame it on an industry that’s been around for hundreds of years is pretty far-fetched,” Terry said.

Geologists have traced the quakes to the Wilzetta fault, also known as the Seminole uplift. Ashley Gilbreth, like many in the area, had never heard of it until last weekend, when the earthquakes led her to comb through the Oklahoma Geological Survey website. There she saw a long black line representing the fault running right under the property where she and her husband plan to build their new home.

“My husband thinks it’s the drilling, all the holes they left behind,” she said.

“They draw so much out of the earth,” said Gene Gilbreth, 65, her father-in-law, who owns the farm and has leased land to an oil company. “Something’s got to give.”

Keranen told the Gilbreths it was unlikely that drilling caused the latest quakes, but that researchers would ask that question as they compiled readings from the seismometers.

Meeker, with a population of fewer than 1,000, lies at the center of the state, one of the small towns strung along U.S. 62. Oil and gas drilling operations are not evident here. Instead, one can see herds of Limousin cattle, farm equipment and insurance offices unaccustomed to issuing earthquake policies.

At the crossroads in town, old men in bib overalls claim seats at the Conoco station and confer about the quakes, which caused no major injuries but damaged scores of homes, leading some to move out in despair. As of Monday, the area had seen 22 quakes of magnitude 3 or greater since the record quake and more than 200 smaller aftershocks.

Some researchers claim recent earthquakes in Arkansas, California, Texas, England, Germany and Switzerland were caused by drilling or injection wells, underground pipes that are used to dispose of wastewater. Of particular interest to some is active hydraulic fracturing, or fracking, which involves shooting water infused with chemicals and sand at high pressure into the ground to fracture rock and extract oil and gas. It produces waste that may be deposited in injection wells.

Accompanying Keranen to the farm was another geophysicist from the university, Austin Holland. Earlier this year, Holland examined possible connections between earthquakes and drilling in Garvin County to the south. While he found some correlation, he said it was impossible to say drilling caused the quakes, a study the oil and gas industry has seized on.

Jean Antonides, a geologist and vice president of exploration at New Dominion, a Tulsa-based oil and gas producer with wells near the recent quakes’ epicenters, said the latest temblors were more likely caused by the complex underlying fault system.

“It’s like a system of underground mountains. A lot of people don’t realize that. They just see flat Oklahoma,” Antonides said. “If people really saw the structures under their feet that they drive across every day, they’d be shocked. It’s anything from flat. There were volcanoes here at one time.”

Before the weekend quakes, the Oklahoma Geological Survey had three seismometers in the field. By Monday, researchers had 34 seismometers in the field and planned to install more, Holland said.

About a mile up Highway 62 from the Gilbreth’s, a USGS paleoseismologist last week examined a 90-foot-long crack in a pasture where Black Angus cattle grazed under an autumn canopy of golden and auburn oaks.

“So is the earth going to spread there?” said Justin Armitage, 32, whose family owns the land.

Armitage said he had read online that Oklahoma had an average of two to six earthquakes a year until 2009, when suddenly there were 50. Last year there were 1,047.

Brian Sherrod, the Seattle-based paleoseismologist, nodded. He said he saw at least 10 wastewater injection wells nearby.

“That may be a factor,” Sherrod said. “That’s something they’re just beginning to look at.”

An industry-funded study released this month linked drilling activity to two recent quakes in northwestern England. Scientists have also traced quake swarms at the Dallas-Fort Worth airport in 2008 and 2009 to an injection well near a fault, said USGS geophysicist William Ellsworth.

“We’ve known for quite a long time that by changing the pressure of water underground, it’s possible to trigger earthquakes,” said Ellsworth, who is based at the Earthquake Science Center in Menlo Park, Calif., but he added: “From what we have seen, fracking has not been related to any earthquakes of significant magnitude. Where we have seen larger earthquakes, they have been related to deeper well injection.”

After an earthquake swarm shook north-central Arkansas last year, state leaders issued a temporary moratorium on new injection wells. State investigators found that three wells near an unknown fault had likely contributed to the earthquakes; the state shut the wells and banned future wells near the fault.

Holland reviewed the Arkansas quake studies, but he said they did not convince him that injection wells were to blame.

Back at the Gilbreth spread, Bowdie said he had noticed that wild animals didn’t seem to mind the earthquakes — while hunting, he watched some wild turkeys eating, oblivious to the rattle and boom. But the shaking bothers his mother, who has taken down the deer heads from the walls but still has to replace the contents of her spice rack and medicine cabinet every time the house shakes them out onto the floor.

Her father-in-law’s house is so quake-damaged that he was living in his RV last week. She wondered whether the next quake would be the big one.

“Everyone’s saying we’ll take the tornadoes,” Ashley Gilbreth said. “At least you know they’re coming.”

molly.hennessy-fiske@latimes.com