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 tpuko@tribweb.com or 412-320-7991.