US Geological Survey geophysicist Bruce Presgrave told Colorado newspaper the Daily Sentinel that the quake, which was recorded at about 12.35am local time Thursday, was likely caused by a coal bump or rock burst.
Both events are more common in the western US coalfields, which often have more overburden than their Appalachian counterparts.
The USGS said the event was centered about 4 miles east of Paonia, Delta County.
The immediate area is home to at least three underground coal mines, including Bowie, Oxbow and West Elk.
However, Presgrave did not indicate which specific mine could have suffered the burst and no public statement was made by any of the mine owners – Bowie Resources, Oxbow Mining and Arch Coal – on Monday.
In all, a dozen coal operations operate in the state, including nine underground mines in Delta, Garfield, Gunnison, La Plata, Las Animas, Rio Blanco and Routt counties and three surface mines in Moffat and Montrose counties.
An ILN request seeking confirmation of the event and more details from the US Mine Safety and Health Administration was not returned by press time.
A November 2012 earthquake measuring 4.3 magnitude that rocked eastern Kentucky was found to be unrelated to the region’s mining operations.
In that event, hydraulic fraccing was also ruled out as a contributing factor.
