The epicenter was about 10 miles west of Whitesburg, in the heart of Kentucky’s coal country, where underground mining and surface blasting are common.
Zhenming Wang, the head of UK’s Geologic Hazards Section, says Saturday’s quake occurred about 12 miles below the surface, far too deep for underground mining to have been a factor.
Wang says the earthquake occurred near the Eastern Tennessee Seismic Zone, which receives a four-magnitude quake every five to 10 years.
“If the earthquake had been close to the surface, then we might think it was mining-related,” said Stephen Horton, a research scientist at the University of Memphis Center for Earthquake Research and Information. “The depth is the giveaway really.”
Mining and hydraulic fracturing, a practice used by the natural gas industry, can possibly be a contributor to earthquakes, but the quakes would not be as deep under the surface as the one that occurred in Kentucky, Horton said.
Hydraulic fracturing, also known as fracking, involves pumping water, sand and chemicals into the ground to cause subterranean fractures that in turn release gas or oil. Wang said he is not aware of fracking operations in the area where the earthquake originated.
“We try to monitor that pretty closely,” Wang said.
The Saturday quake just after noon caused little damage but was felt in West Virginia, Tennessee, North Carolina, South Carolina, Indiana, Ohio and Georgia.
The strongest earthquake recorded in Kentucky occurred in 1980 in Bath County and had a magnitude of 5.2, according to the U.S. Geological Survey.