Fracking Ruled Out as Contrubutor to East Coast Quake

Pittsburgh Tribune-Review
6 September 2011
By Timothy Puko

In recent years, gas drilling increased dramatically in the Mid-Atlantic States. Last month, a dramatic earthquake hit, unlike any in several decades.

That doesn't mean the two are connected.

Despite blog posts and Internet essays, expanded gas drilling had nothing to do with the Aug. 23 Virginia earthquake that shook the region, several scientists said. No one has connected the "hydraulic fracturing" drilling technique used in shale layers with strong, widespread earthquakes, they said.

"You've only got a very small volume of rock that you're taking out of there (with fracturing)," said Anthony Crone, a research geologist at the U.S. Geological Survey. "The only conceivable thing that could happen is that hole could close up, so it would only have a very narrow sphere of influence."

The epicenter of the Aug. 23 quake was in Mineral, Va., about 80 miles southwest of Washington.

Some people have tried to link shale drilling with earthquakes because of a few high-profile quake "swarms" in drilling areas over the past 18 months, including in Arkansas and West Virginia. But even in those cases scientists don't suspect the drilling as the trigger.

Researchers say a greater concern is deep-well injection of hazardous liquid waste thousands of feet underground by the drilling industry, chemical industry and other sources. There is a history -- although not an expansive one -- of disposal wells triggering earthquakes, scientists said. Repeatedly pumping fluid deep underground increases pressure on stressed layers of earth, which can cause a fault to slide if a well is nearby, they said.

State officials ruled out that process and any drilling industry activities in the West Virginia case. But researchers concluded disposal wells triggered the Arkansas quakes and four operations stopped, said Stephen Horton, a research scientist at the Center for Earthquake Research and Information at the University of Memphis. The quakes reached as high as 4.7 in magnitude and had potential to reach 6, Horton said.

"It was potentially a very dangerous situation," Horton said. "And, yes, there was a lot of controversy. The people who operated the businesses wanted no part of shutting down. And they still want no part of it because there are lawsuits. But the (state) did what was the politically and publicly responsible thing to do and balance those needs with public safety."

Pennsylvania has six active deep-injection disposal wells, in Somerset, Clearfield, Beaver and Erie counties. The Environmental Protection Agency reviews permits for disposal wells to ensure they aren't near faults or seismic zones, and prohibits pumping at high enough pressure to crack rocks underground, agency hydrogeologist Stephen Platt said.

Ohio has nearly 200 disposal wells and has become a popular place for fluid waste from Pennsylvania shale drilling.

It has not documented any cases of seismic activity near those wells. Tom Tomastik, the state official who oversees that program, is on an EPA work group that is studying data about such man-made earthquakes.

For Virginia officials, the conclusive proof that drilling did not cause last month's quake is that no well -- for natural gas extraction or fluid waste -- exists within at least 150 miles of the quake's epicenter. Pressure would have had to cross at least two major thrust faults and several smaller ones to travel from Marcellus shale drilling in the Appalachian Basin and affect the Central Virginia seismic zone in the Piedmont, said David B. Spears, Virginia's state geologist.

"There's just no way any kind of drilling or hydrofracturing in those wells could be physically transmitted through the Earth over such a great distance. It's just physically impossible," Spears said. "With eighth-grade physical science you can figure this out. It's just way, way, way too far and completely geologically isolated by multiple barriers."

The Marcellus formation lies in one of the least seismic zones in the world, said Helen L. Delano, a senior geologic scientist in Pennsylvania's Department of Conservation and Natural Resources. The risk for earthquakes is minimal, even without drilling.

"Man-made forces do not compare to earthquake forces," said Ricardo Taborda, a civil engineer who works at the Quake Project at Carnegie Mellon University. "There are many other things to be more concerned about with the Marcellus shale than this."

Timothy Puko can be reached at or 412-320-7991.