Oil and gas regulators investigating swarm of earthquakes near Oklahoma City overnight, early Saturday; largest a 4.3 magnitude

Editor's note: Some of the recorded magnitudes of these earthquakes have changed from their initial listings.

Several earthquakes, the largest a magnitude 4.3, shook the Oklahoma City metro late Friday and early Saturday morning.

State regulators and the Oklahoma Geological Survey are investigating the swarm of quakes, which centered around the Arcadia area northeast of Edmond.

According to the U.S. Geological Survey, the following earthquakes were reported late Friday into Saturday.

• 3.2 magnitude: Recorded at 9:37 p.m. near Arcadia

• 4.3 magnitude: Recorded at 9:46 p.m. near Arcadia

• 2.5 magnitude: Recorded at 10:04 p.m. near Arcadia

• 2.7 magnitude: Recorded at 10:43 p.m. near Arcadia

• 4.1 magnitude: Recorded at 5:36 a.m. near Edmond

• 2.7 magnitude: Recorded at 6:55 a.m. Northeast of Edmond

State seismologist Jake Walter said Edmond and Arcadia area residents could continue to feel seismic activity through the weekend and into next week.

“We expect there to be an order of magnitude more earthquakes, or aftershocks, from a main shock at lower magnitude. So that means if you have a magnitude 4.0 earthquake, you can expect about 10 magnitude 3 aftershocks and then possibly 100 magnitude 2 aftershocks,” Walter said.

Severe earthquakes tied to oil and gas operations in Oklahoma have fallen in recent years

Severe earthquakes once were rare in Oklahoma.

But by 2015 the state had become one of the most earthquake-prone areas in the world, with the number of quakes magnitude 3.0 or greater skyrocketing to 800 from a few dozen in 2012.

The increases in both frequency and severity of earthquakes have widely been blamed on saltwater disposal operations associated with oil and natural gas production.

Many of the earthquakes were occurring in swarms in areas where injection wells were pumping salty wastewater — a byproduct of oil and gas production — deep into the earth.

The increase in seismic activity has lead to a series of lawsuits and regulatory actions. In February of 2021, the Oklahoma Corporation Commission directed operators of five saltwater disposal wells near Covington to cease operations after a 4.2-magnitude earthquake.

On Saturday, a corporation commission spokesman said Oklahoma’s 3.0 magnitude and greater earthquake activity has dropped by more than 98 percent since 2017 since the commission initiated large-scale actions in 2015.

In a statement, the commission said:

"Our OCC Induced Seismicity Dept is researching these quakes. The quakes that occurred years ago (2014-2017) in the area were linked to oil and gas wastewater disposal wells that used the deep Arbuckle formation. They were shut down by the OCC years ago. Hydraulic fracturing has been linked to quakes in other areas, but there are no such activities in the Arcadia area."

OKC metro area residents should take precautions

Walter said OKC area residents should take reasonable safety precautions like securing valuables and familiarizing themselves with the concept of “Drop, Cover and Hold On.”

“That's what we teach for protecting yourself in the event from strong shaking from earthquakes is drop down wherever you're at, try to get under a table or a piece of furniture and then hold on until the shaking subsides,” Walter said.

“There's no guarantee that the aftershock isn't going to be bigger than the main shock. So, that’s why it's a particularly tense time after any type of earthquake.”

A series of smaller temblors, magnitude 1.0 to 1.6, struck the same area between Dec. 29 and Jan. 6. Walter said the quakes this weekend could be a continuation of that sequence.

“We believe that that's a fault zone, previously unmapped until now we know that it's there, because of the seismicity that we've observed in the last year, but also going back at least eight or nine years.”

Walter said, “We don't necessarily really know the direct cause of the seismicity today. But a lot of the earthquake activity was sort of kicked off by wastewater disposal when it was higher several years ago.”

While wastewater disposal is down statewide significantly, Walter said the Oklahoma Geological Survey has "seen a number of different fault segments around the state that still have smaller earthquakes going on within those faults."

"This particular sequence, too, even though it's been since 2017 since any kind of magnitude 4s that would be felt widely across the metro area, there has been smaller seismicity from time to time. … We don't necessarily understand why it's become active all of a sudden.”

More: The Oklahoman's earthquake tracker

Social media reaction to the earthquakes in Oklahoma

Residents in and around Oklahoma City took to social media to report the rumbling and shaking.

Oklahoman staff reporter Brandy McDonnell and The Associated Press contributed to this story.

This article originally appeared on Oklahoman: U.S. Geological Survey reports multiple earthquakes near Oklahoma City, oil and gas regulators investigating