A 3.6-magnitude earthquake was recorded about 9 miles east of Wright on Tuesday afternoon.
No injuries or damage has been reported as of Wednesday morning, said Robby Gallob, emergency management coordinator for the town of Wright.
The modest earthquake is the 12th recorded in Campbell County since records began being kept in 1967, said Campbell County Emergency Management Coordinator David King.
The largest earthquake in the county was a 5.1 temblor that was centered 27 miles west of Gillette in 1984, King said.
From all of the earthquakes to happen in Campbell County, ranging from magnitude 2.1 to 5.1, he said there have never been any reported injuries or damage.
Although the recent quake happened in the vicinity of coal mines, because of its 9-mile deep epicenter and acknowledgement from the U.S. Geological Survey, it is unlikely that it was a coal blast mistaken for an earthquake, King said.
Coal blasts are executed in the mines in different areas of the county and can sometimes be felt in surrounding areas.
Gary Mills lives about 12 miles northeast of Wright and close to the Coal Creek mine. He was home at the time of the earthquake and said he and his wife thought that it was a coal blast at first.
He said it felt “no different from mine blasts because I live between two coal mines, and that’s what I thought it was. It was a low, minor shake, kind of like a sway for about 5 seconds and that was it.”
Having experienced multiple coal blasts throughout his years living near mines, Mills said he did not second-guess what he felt Tuesday.
“(It) didn’t move any structures in the house, just a slight movement, no different from mine blasts that we’ve had in years past," Mill said. "We’ll get them periodically anyways and that’s what I just assumed."
Another earthquake was recorded near the same area in 1993, about 10 miles east of Wright, King said.
Unlike the western part of Wyoming, where seismic activity is more common, the Powder River Basin between the Black Hills and Big Horn Mountains is relatively tame.
“We do have some fault lines and so forth, but they’re not seismically active, nothing like the western part of the state is,” King said.
The fault lines that have been active in Campbell County are relatively minor and unnamed, he said.
Aftershocks or other successive occurrences may be hallmarks of larger, more active fault lines elsewhere, but that has not been the case in Campbell County, King said.
“We’ve never had any of those reported in any of the earthquakes we’ve had in Campbell County,” he said. “Almost all of them have been single events.”
Campbell County’s last earthquake was in 2011, marking nearly a decade between them and is evidence there is no established trend to the frequency or intensity of the quakes, other than that they seldom occur and tend to be minor, he said.
“We’ve gone nine years, so it’s not something I’d be sitting up late at night using a flashlight to watch the seismograph,” King said. “It’s not going to happen that often.”