Mine activity likely cause of small Paonia quake

Scientists recorded a small earthquake early Thursday morning in coal country near Paonia, a tremor that doesn’t seem to have registered much with residents there.

The U.S. Geological Survey reported a magnitude 2.8 quake at 12:35 a.m., centered about four miles east of Paonia, a town surrounded by working coal mines that have been known to register small-scale quakes because of their mining operations.

“We don’t know for certain, but this is probably a coal bump, or a rock burst, in one of the coal mines there,” said Bruce Presgrave, a geophysicist with the USGS.

A coal bump happens when a pillar of coal suddenly fails, often violently. Rock bursts are caused by heavy pressure on brittle rocks deep in mines around an excavation.

Dave Wolny, an adjunct faculty member at Colorado Mesa University, said the school’s network of seismometers record these small-scale, man-caused seismic events all the time.

“This one is a little bigger than normal maybe, but it’s not out of the range of what we would expect,” Wolny said.

At 2.8 on the Richter scale, the Thursday quake near Paonia just barely made it over the 2.5 minimum threshold for the quake to be published by the USGS, according to Presgrave.

“What they do is, they mine the coal with a machine, and the miners stay off to the side,” Wolny explained. “As they remove the coal, all the weight from above, it just kind of collapses behind them. And every time it collapses it causes a little earthquake.”

Lindsey Leatherman, who manages the Rocky Mountain Inn in Paonia along with her fiancé, said she was up reading at about the time of the quake. She’s not sure she felt it, though.

“I heard some weird noises last night. I kept asking my fiancé, ‘Did you hear that?’ ” she said. “It might have been about that time.”


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