Oklahoma’s governor declared a state of emergency and state regulators ordered oil and gas wastewater disposal operations shut down after a record-tying 5.6 earthquake rattled much of the Midwest Saturday morning.
“The earthquake was felt in multiple states and was the strongest the state has experienced since November 2011 when a magnitude 5.6 earthquake occurred in Lincoln County,” Gov. Mary Fallin said Saturday night.
“This emergency declaration will start the process to helping individuals, families and businesses impacted by the earthquakes and serves as a precursor to requesting any necessary assistance.”
In the past decade, Oklahoma has experienced an alarming increase of earthquake activity, which seismologists have linked to the underground, high-pressure injection of wastewater by the oil and gas industry.
Thousands of barrels of salty water mixed with heavy metals are churned up from wells deep below the earth’s surface when energy producers extract oil and gas. This wastewater is usually forced back underground through special disposal wells. A small portion of the water is injected to fracture underground shale, a process more commonly known as fracking.
Seismic activity used to be relatively rare in Oklahoma. In 2005, there were just three quakes with a magnitude of 2.5 or higher in the state. In 2015, the U.S. Geological Survey recorded 2,500 earthquakes of a 2.5 magnitude or higher – a dramatic increase proportionate to the rise in energy drilling activity.
The increase in seismic activity puts some parts of Oklahoma and Texas at the same earthquake risk as California, USGS maps show.
Saturday’s earthquake occurred at 7:02 a.m. in the northwestern part of the state near Pawnee, Okla., about 55 miles northwest of Tulsa. The quake was felt as far away as central Tennessee, Houston, Missouri, Iowa, and Arizona.
One injury was reported. According to News On 6 Tulsa, a man protecting his child in the quake suffered a head injury when bricks from a chimney fell on his head.
Several buildings in Pawnee and the surrounding area were damaged, with most of the reports involving cracked or crumbled facades. People in other cities, including Stillwater, home to Oklahoma State University, reported structural damages.
The Oklahoma Corporation Commission continues to inspect bridges and buildings for signs of damage. The agency is also reviewing oil and gas wastewater disposal wells in areas in the northeastern part of the state.
The Commission ordered wastewater disposal wells within a 500-square-mile radius to cease operations as a precaution. There are 4,200 wastewater disposal wells within the state.
Amid the increase in earthquake activity, Oklahoma’s Corporation Commission started policing wastewater well operations more closely and the number of quakes in the state fell by roughly 25 percent. It is unclear what measures the state plans to take to protect people and property from drilling-induced earthquakes over the long term.