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The state of Oklahoma has seen a boom recently in oil and gas and also earthquakes. Not so long ago, you could count the number of earthquakes in a year in Oklahoma on one hand. But last year, the U.S. Geological Survey reported nearly 1,000 tremors in the seismic region centered in Oklahoma. And new research shows that surge is coming from areas where the oil and gas industry is pumping massive amounts of waste fluid underground. Joe Wertz of StateImpact Oklahoma reports.
(SOUNDBITE OF OIL FIELD WORK)
JOE WERTZ, BYLINE: In an oil field near the tiny town of Wakita near the Oklahoma-Kansas line, burly workers armed with sledgehammers are trying to unstick a steel fitting. Jay Storm of Eagle Energy Exploration is overseeing the efforts.
JAY STORM: Everything is a little bit seized up this morning, so we're having to manually try to get a couple of different components separated.
WERTZ: When the energy industry drills for oil and gas, it also strikes water. In Oklahoma, oil companies often get 50 barrels of water for every barrel of oil. That briny water is toxic and pumped into disposal wells like this one. Oklahoma's oil industry has boomed in recent years. It disposes of tens of millions of barrels of wastewater a month, and the earthquake rate has skyrocketed.
MARK ZOBACK: These hundreds and hundreds of wells that are injecting these enormous volumes is spreading out in the Arbuckle formation, penetrating potentially active faults at depth and triggering earthquakes.
WERTZ: That's Mark Zoback, a geophysics professor at Stanford University. The Arbuckle Zoback refers to is an underground formation. Until recently, Oklahoma averaged fewer than two magnitude 3.0 earthquakes a year. Last year, more than 580 were recorded.
ZOBACK: It's more than just a nuisance. It's a problem that has to be dealt with. So basically what's happening is, you know, thousands of years of earthquakes are occurring, you know, in just a few years in Oklahoma due to this massive injection of produced water.
WERTZ: Zoback says almost all of Oklahoma's recent earthquakes are coming from faults in granite located just below that popular wastewater injection spot. Scientists have known about this risk factor for a long time, but this new research reinforces the connection.
In their most aggressive action to date, Oklahoma regulators have started cracking down on wells that allow fluid to reach that granite rock.
Back in the oilfield, Jay Storm and his crew are pumping cement into the disposal well to make it shallower.
STORM: To be in compliance with the Corporation Commission, we're going to pull the casing out of it and the packer and run in and cement the zone below the Arbuckle that we're disposing in.
WERTZ: Oklahoma officials have been slow to formally tie the earthquakes to the oil and gas industry, the state's number one economic driver, but the state now publicly acknowledges the link. So far, more than 100 disposal wells like this one have been filled in to make them shallower and hopefully less likely to trigger earthquakes. For NPR News, I'm Joe Wertz in Oklahoma City. Transcript provided by NPR, Copyright NPR.