Earthquakes continue to shake Stephens County

DUNCAN — Another earthquake shook Stephens County on Sunday night and multiple residents in the Duncan area reported feeling it.

Sunday’s earthquake happened around 7:40 p.m. and measured in with a 3.7 magnitude, according to a map from the United States Geological Survey (USGS). The quake happened 11 miles from the city seat in Stephens County, between Duncan and Velma-Alma.

Dr. Jake Walter, State Seismologist with the Oklahoma Geological Survey (OGS) — the organization that monitors and operates 90 seismometers around the state, reports Oklahoma earthquake data and works in partnership with USGS, but maintains authority for the state — confirmed the earthquake near Duncan and said the largest events and most frequent activity has been in the Stephens County area in the last five days.

“Toward the end of last week, there was several lightly felt earthquakes, in between Velma and Duncan,” Walter said. “We believe that those earthquakes are associated with hydraulic fracturing, which is going on right adjacent to that area. The operator actually paused operations as of Thursday, so there’s been no new injection going on into the subsurface since Thursday.”

Despite the operations going offline with Continental Resources, Walter said activity Stephens County has experienced can be quite frequent once it starts.

“They can continue. You can generate other earthquakes from earthquakes,” Walter said. “That’s why we have aftershocks, for example. So this has continued, but we believe that it should taper off naturally throughout the next several days.”

Walter said at this time, it remains unclear whether the operator will continue work in the area once seismic activity has stopped.

“We believe the seismicity should generally get smaller magnitude and less frequent, although there’s always a chance — sometimes there could be larger earthquakes,” Walter said. “So people should be prepared to duck, cover and hold on in the case (that should happen).”

Walter didn’t have reports of any damages in the area, but said people strongly felt it and even heard it.

“Some people have described it as feeling a little bit different than the smaller seismicity,” Walter said. “Somebody described that magnitude 3.7 as a concussive boom is one report we heard.”

The 3.7 is the largest that’s been seen in the last week. Others ranged from as low as 2.3 magnitude to as high as 3.0 magnitude last week, beginning on Tuesday, Sept. 19.

Aside from the “duck, cover and hold on” advice and protecting yourself first in the case of a larger earthquake, Walter also suggested securing personal belongings and valuables to avoid breakage.

“If you have things that are freestanding, you can sort of prevent those breaking by securing them with putty or putting them away in a safer place,” he said.

For more information about earthquakes or OGS, or to keep up with OGS’ monitoring of the state’s seismic activity, visit https://www.ou.edu/ogs/research/earthquakes/recentearthquakes. To report feeling an earthquake, visit https://www.ou.edu/ogs/research/earthquakes/report-an-earthquake.