Trevor Hughes

USA TODAY

A swarm of more than 70 small earthquakes has rattled Oklahoma in the past week, raising concerns that the state’s quake problem is getting worse.

The largest quake measured magnitude-4.8 and struck around midnight Wednesday near the town of Fairview. No significant damage has been reported, although it shook pictures and crockery.

“It was felt all over the county, pretty much all over the state,” Major County Undersherrif Darin Reams said. "This one rattled a little bit.”

Smaller quakes continued Thursday.

Oklahoma in 2014 had at least 5,415 earthquakes; 585 of them were magnitude-3 or greater. In comparison, the state had just 109 magnitude-3 quakes in 2013, according to the Oklahoma Geologic Survey. Statistics for 2015 are still being compiled.

A state report last year noted a connection between hydraulic fracturing and some earthquake "swarms," and state officials say there's a potential risk to the public due to the increase in quakes. Experts say the quakes are likely being caused by injection wells, which are particularly deep wells into which drilling byproducts and wastewater are injected, rather than wells drilled to extract oil or gas.

"The OGS considers it very likely that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, are triggered by the injection of produced water in disposal wells," the agency said.

It added: “The seismicity rate is now about 600 times greater than the background seismicity rate and is very unlikely the result of a natural process."

Earthquakes have been linked to oil and gas activity for more than five decades, but in recent years the rate of tremors has shot up across the United States in areas where drilling and waste from the production occur, said Bill Ellsworth, a Stanford University geophysics professor and a former longtime geologist at the U.S. Geological Survey.

Kansas, Oklahoma, Colorado, Texas and Arkansas all have seen steep upticks in earthquakes suspected to be linked to oil and gas activity, he said. The injected water changes the friction of naturally occurring fault lines, uncorking the quakes. “Over the past few years, there has been a growing recognition within the industry and within regulators that this is an issue that needs to be considered very carefully,” Ellsworth said.

State regulators have ordered well companies operating in the area to either scale back or halt injection operations. One of the companies, Pedestal Oil Co. has been ordered to cut the amount of water it’s injecting for disposal by 50%, while Devon Energy Production, Grayhorse Operating, New Dominion and Taylor R.C. have all be ordered to reduce injection volumes by 25%. The Sierra Club is preparing to sue some of the companies that operate injection wells, among them SandRidge Exploration and Production, New Dominion, Devon Energy Production and Chesapeake Operating.

SandRidge has been struggling financially as low gas and oil prices keep profits low. The company’s stock is being delisted from the New York Stock Exchange, it announced Jan. 7, and the company has said it will ignore the state’s requests that it shut down its injections wells, setting up a potential court battle.

'Swarms' of earthquakes strike Oklahoma

For many Oklahoma residents, the quakes have become a way of life, in much the way they have for those living in North Texas, which has seen similar quake swarms. Oklahoma’s frequent quakes prompted composer Edward Knight to create a 15-minute musical piece called Rumble, which debuts Saturday with a performance by the 2016 Central Oklahoma Directors Association All-Region High School Symphonic Honor Band.

“I started noticing the house shaking several years ago,” said Knight, who is composer-in-residence and director of composition at Oklahoma City University. “I literally thought a bulldozer or a truck hit the house. There was a loud bang and the house started to shake.”

Today's Earthquakes in Oklahoma, United States

Knight said his piece features usual instruments and sounds, along with Latin chanting, to portray the Earth awakening. Members of the concert band are drawn from across the state, and the quakes are something they — and their parents and the audience — can relate to, Knight said.

“It’s this ominous sort of tone that starts the piece,” he said.

The earthquakes represent a challenge for Oklahoma, which depends heavily on the oil and gas industry for employment and tax revenue. Reams said many Major County residents, including himself, believe the quakes are an unfortunate but understandable byproduct of extracting the oil and gas the country needs.

“As long as they’re staying in the four-point-whatever range, I think we’ll be OK,” he said.