| West Virginia officials say they've found no link between minor earthquakes that rattled central West Virginia last year and natural gas drilling.
Eight earthquakes with magnitudes between 2.2 and 3.4 were reported in Braxton County last year, with some residents and officials expressing concern that the tremors were related to drilling.
Michael Hohn with the West Virginia Geological and Economic Survey said the earthquakes were probably more of a coincidence.
This week, Arkansas officials said a swarm of quakes in that state appear to be linked to drilling operations.
Steve Horton, an earthquake specialist at the University of Memphis and hydrologic technician with the U.S. Geological Survey, is warning there could be a correlation between the Arkansas earthquakes swarm as a side effect of drilling.
At issue is a practice called hydraulic fracturing, or "fracking," in which water is injected into the ground at high pressure to fracture rock and release natural gas trapped within it.
"Ninety percent of these earthquakes that have happened since 2009 have been within 6 kilometers of these salt water disposal wells," Horton told FoxNews. He says the timing is too coincidental to ignore.
"They started doing these injection wells in the area that we're talking about in April of 2009. Since that time, there has been an increase in the rate of seismicity," he said.
Scientists are slow to draw conclusions on any subject, and despite years of speculation, there is still little consensus about whether the practice is contributing to the quakes.
Horton also pointed to quakes in West Virginia, noting the same pattern of unusual seismic activity where previously there had been none.
"That isn't a place where you usually have earthquakes," he told FoxNews.
When the West Virginia Oil and Gas Commission forced the disposal companies to cut back on their injection rate and pressure, the professor said, the earthquakes there seem to have dissipated.
Hundreds of earthquakes have been recorded in Arkansas, most in areas where quakes have never been recorded.
The U.S. Geological Survey recorded a 4.7-magnitude quake at 11 p.m. Sunday, centered just northeast of Greenbrier, about 40 miles north of Little Rock.
It was the largest of more than 800 quakes to strike the area since September.
Nearly two dozen small quakes have been recorded in Arkansas in a single day.
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