WHEELING - Alhough some remain concerned that fracking may lead to water pollution, experts do not believe the process causes earthquakes.
The magnitude-5.6 quake that rocked Oklahoma over the weekend had the power of 3,800 tons of TNT, which is nearly 2,000 times stronger than the 1995 Oklahoma City bombing.
This energy is far greater than the amount released by fracking.
The typical energy produced in tremors triggered by fracking "is the equivalent to a gallon of milk falling off the kitchen counter," said Stanford University geophysicist Mark Zoback.
In Oklahoma, home to 185,000 drilling wells and hundreds of injection wells, the question of man-made seismic activity comes up quickly. But so far, federal, state and academic experts say readings show the Oklahoma quakes were natural, following the lines of a long-known fault.
"There's a fault there," said U.S. Geological Survey seismologist Paul Earle. "You can have an earthquake that size anywhere east of the Rockies. You don't need a huge fault to produce an earthquake that big. It's uncommon, but not unexpected."
In the past, earthquakes have been linked to energy exploration and production, including from injections of enormous amounts of drilling wastewater or injections of water for geothermal power, experts said.
In addition to all of the drilling and fracking activities in West Virginia and eastern Ohio, similar injection wells are also located in the local region. Tim Carr, West Virginia University's Marshall Miller Professor of Energy, previously said there is no evidence that fracking or fluid injection into underground wells leads to earthquakes.
Noting the action does cause some "micro-seismic" shifting, Carr said, "These are much, much less than having a large truck go by. They are measured with sophisticated downhole tools and are used to map fracture stimulation treatments. No one could ever feel or even detect these events at the surface."
In April 2010, a 3.4 magnitude earthquake hit Braxton County, W.Va. In a span of several months the area was hit by five more such quakes.
The quakes were small - about 2.7 magnitude - but large enough to catch the attention of state officials. Carr attributes the West Virginia tremors to natural activity.
Oil and gas production can lead to tremors another way: When drillers suck all the oil from underground and leave nothing to fill the gap where the oil was, the emptying reservoir can collapse.
If this happens at all, it usually happens slowly over decades.
Oklahoma Geological Survey seismologist Austin Holland, who has documented some of the biggest shaking associated with fracking, compared a man-made earthquake to a mosquito bite.
"It's really quite inconsequential," he said.