Oklahomans feel first strong quake of 2022 as 4.5M event shakes Medford

MEDFORD — A strong earthquake near here Monday morning caught the attention of people across Oklahoma and from as far away as Salina, Kansas, and Springfield, Missouri.

While no reports of significant damage from Monday's temblor at 11:10 a.m. (estimated as being a 4.5-magnitude event) had been reported by later in the day, its occurrence didn't escape the attention of Oklahoma's state seismologist or oil and gas regulators.

Monday's earthquake, near Clyde, is the first they have seen that strong inside of the state in nearly three years.

By 2 p.m. Monday, the Oklahoma Corporation Commission's Induced Seismicity Department instructed operators of three saltwater injection wells putting water into the Arbuckle formation within 6 miles of the temblor's epicenter northwest of Medford to cease operating.

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The department also limited saltwater injection rates for other disposal wells using the Arbuckle formation within 10 miles of the earthquake's location to 500 barrels a day.

Inspectors on Monday afternoon were going site to site to ensure the directives were being carried out, corporation commission spokesman Matt Skinner said.

On Tuesday, the division updated its order to note it had ordered seven injection wells within 6 miles of the earthquake's epicenter to cease operating (four were injecting at the time of the event), and restricted others within 10 miles of the earthquake's epicenter to limit their injections to their 30-day reported average volume or 500 barrels a day, whichever is less. 

Recent trends

By 2017, data showed Oklahoma seemed to be getting past the worst effects from a massive swarm of earthquakes that had been impacting its residents over the prior eight years.

Data provided Monday by Jake Walter, Oklahoma's state seismologist, showed the number of 3.0 magnitude or stronger temblors observed in Oklahoma that year was 302, down from 624 the previous year.

In subsequent years, the numbers declined to 195 in 2018, 65 in 2019, 39 in 2020 and 29 last year.

Monday's temblor is the first strong event for the current year, Walter said.

Walter attributes reductions in Oklahoma's statewide numbers to aggressive enforcement of injection restrictions developed by the independent Coordinating Council on Seismic Activity, the corporation commission's induced seismicity department and the Oklahoma Geological Survey.

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Across much of Oklahoma, disposal well operators using the Arbuckle have been facing increased scrutiny for nearly a decade, with some being required to permanently reduce their injection rates and others having to plug back their wells to use other, more shallow formations as alternative disposal zones research has found are less likely to cause seismic shifts.

The overall volume of wastewater disposed within the Arbuckle formation across the state within the corporation commission's identified area of interest has plateaued at about 20 million barrels per month, Walter said Monday.

Still, the Mississippian Lime play in northern Oklahoma (where Monday's earthquake was centered) continues to be a major producer of saltwater that is reinjected underground to protect fresh water tables depended upon by people, livestock and wildlife.

Across other parts of the state, produced saltwater rates have fallen as producers have moved their efforts to pull oil and gas out of the ground into shale plays that contain less saltwater and are more profitable to produce.

But even in those areas, seismic events continue to be a concern.

Protocols developed in recent years have required oil and gas operators completing shale wells to use either contracted seismic monitoring systems or the one operated by the geological survey to monitor ground shakes and to pause or completely end those completion activities when a nearby temblor with a magnitude of 2 or greater is observed.

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Walter, meanwhile, said Oklahoma continues to work with industry and scientific partners to enhance the capabilities of its permanent seismic monitoring system (most of the state's 90 monitors in use today currently are being furnished by academic or governmental partners).

On Monday, he warned northern Oklahoma residents they could expect to see continued shaking for weeks to come.

"They could expect to see several aftershocks, and in some circumstances, those aftershocks could be as strong as or even stronger than Monday's event," Walter said. "People who live in that part of the state should plan appropriately and should drop to the floor, take cover under sturdy furniture and hold on to something during prolonged periods of shaking."

Oklahoma's strongest earthquakes:

1.  A 5.8 magnitude earthquake northwest of Pawnee on Nov. 7, 2016, with people reportedly feeling the ground move as far away as San Antonio Texas, Little Rock, Arkansas, Kansas City, Missouri, and Minneapolis, Minnesota.
2.  A 5.7 magnitude earthquake that happened 4 miles east of Sparks in November 5, 2011.
3.  A 5.5 magnitude earthquake that happened near El Reno in 1952. The event interrupted phone services in Oklahoma City and El Reno, due to a sudden overload in use by alarmed state residents at the time.
4.  A 5.0 magnitude earthquake that happened near Cushing on Nov. 6, 2016, causing exterior damage to many of its historic downtown buildings.
5.  An estimated 4.8 magnitude earthquake that happened near Fort Gibson on Oct. 22, 1882. The Cherokee Advocate reported "the trembling and vibrating were so severe as to cause door and window shutters to open and shut, hogs in pens to fall and squeal, poultry to run and hide, the tops of weeds to dip, [and] cattle to lowe."
6.  A 4.8-magnitude earthquake that happened near Prague on Nov. 8, 2011.
7.  A second 4.8-magnitude earthquake that happened near Prague, also on Nov. 8, 2011.
8.  Monday's 4.5 magnitude temblor near Medford.
9.  A 4.5-magnitude earthquake near Pond Creek in May, 2019 in Grant County.
10.  A 4.5-magnitude earthquake near Marshall that happened March 30 2014.

Business Writer Jack Money covers Oklahoma’s energy and agricultural beats for the newspaper and Oklahoman.com. Contact him at jmoney@oklahoman.com. Please support his work and that of other Oklahoman journalists by subscribing to The Oklahoman.