Unusual Dallas Earthquakes Linked to Fracking, Expert Says

Unusual Dallas Earthquakes Linked to Fracking, Expert Says

By Eli MacKinnon, Life's Little Mysteries Staff Writer

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  Operating Officer of Wellsboro & Corning Railroad Bill Myles
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Three unusual earthquakes that shook a suburb west of Dallas over the
weekend appear to be connected to the past disposal of wastewater from
local hydraulic fracturing operations, a geophysicist who has studied
earthquakes in the region says.

Preliminary data from the U.S. Geological Survey (USGS) show the first
quake, a magnitude 3.4, hit at 11:05 p.m. CDT on Saturday a few miles
southeast of the Dallas-Fort Worth (DFW) International Airport. It was
followed 4 minutes later by a 3.1-magnitude aftershock that originated
nearby.

A third, magnitude-2.1 quake trailed Saturday's rumbles by just under
24 hours, touching off at 10:41 p.m. CDT on Sunday from an epicenter a
couple miles east of the first, according to the USGS. The tremors set
off a volley of 911 calls, but no injuries have been reported.

Not a coincidence

Before a series of small quakes on Halloween 2008, the Dallas area had
never recorded a magnitude-3 earthquake, said Cliff Frohlich, associate
director and senior research scientist at the University of Texas at
Austin's Institute for Geophysics. USGS data show that, since then, it
has felt at least one quake at or above a magnitude 3 every year except
2010.

Frohlich said he doesn't think it's a coincidence that an intensification in seismic activity in the Dallas area came the year after a pocket of ground just south of
(and thousands of feet below) the DFW airport began to be inundated
with wastewater from hydraulic fracturing[/url].

During hydraulic fracturing, or "fracking," millions of gallons of
high-pressure, chemical-laden water are pumped into an underground
geologic formation (the Barnett Shale, in the case of northern Texas) to
free up oil. But once fractures have been opened up in the rock and the
water pressure is allowed to abate, internal pressure from the rock
causes fracking fluids to rise back to the surface, becoming what the
natural gas industry calls "flowback," according to the Environmental
Protection Agency.

"That's dirty water you have to get rid of," said Frohlich. "One way people do that is to pump it back into the ground."

In a study he recently published
in the journal Proceedings of the National Academy of Sciences,
Frohlich analyzed 67 earthquakes recorded between November 2009 and
September 2011 in a 43.5-mile (70 kilometers) grid covering northern
Texas' Barnett Shale formation. He found that all 24 of the earthquakes
with the most reliably located epicenters originated within 2 miles (3.2
km) of one or more injection wells for wastewater disposal.

The injection well just south of DFW airport has been out of use since
September 2011, according to Frohlich, but he says that doesn't rule it
out as a cause of the weekend's quakes. He explained that, though water
is no longer being added, lingering pressure differences from wastewater
injection could still be contributing to the lubrication of long-stuck
faults.

"Faults are everywhere. A lot of them are stuck, but if you pump water
in there, it reduces friction and the fault slips a little," Frohlich
told Life's Little Mysteries. "I can't prove that that's what happened,
but it's a plausible explanation."

History of human-induced earthquakes

Oliver Boyd, a USGS seismologist and an adjunct professor of geophysics
at the University of Memphis, agrees that, in general, links between
wastewater injection and seismic activity are plausible.

"Most, if not all, geophysicists expect induced earthquakes to be more
likely from wastewater injection rather than hydrofracking," Boyd wrote
in an email to Life's Little Mysteries. "This is because the wastewater
injection tends to occur at greater depth where earthquakes are more
likely to nucleate. I also agree [with Frohlich] that induced
earthquakes are likely to persist for some time (months to years) after
wastewater injection has ceased."

For past examples of likely human-induced earthquakes,
Boyd points to the story of the Rocky Mountain Arsenal, a now-closed
U.S. Army chemical weapons manufacturing center that operated just
outside of Denver until the early '90s.

In 1961, the Rocky Mountain Arsenal drilled a 12,000-foot-deep (3,658
meters) waste fluid disposal well near Denver. According to the USGS,
"an unusual series of earthquakes erupted in the area soon after."

Use of the well was discontinued in February 1966. A year and a half
later, on Aug. 9, 1967, a 5.3-magnitude earthquake, the most powerful in
Denver's history, struck. It was followed by a 5.2-magnitude quake in
the region that November, according to the USGS.


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