Over the past few years, the number of earthquakes in the
usually seismically calm central United States has
skyrocketed. Now scientists are pointing the finger at
hydraulic fracturing, better known as "fracking," as the
Fracking is a method of extracting natural gas, the cleanest
fossil fuel, from underground rocks. Proponents of natural gas
say it could reduce the country's dependence on foreign oil since
vast majority of it comes from within the country. Natural gas is
also more plentiful and cheaper than oil.
Workers use high-pressure fluids to create fractures in rocks
such as sandstone and shale to allow natural gas to flow out. The
injection of these high-pressure fluids, a combination of water
sand and chemicals, are suspected of
"We've been watching the seismicity across most of the country
very carefully for a number of years now," Bill Ellsworth, a
seismologist at the U.S. Geological Survey and coauthor of the
, "One thing we had begun to notice was there was an unusual
number of earthquakes occurring in the middle of the
On average, the central U.S. experienced 21 earthquakes per
year between 1970 and 2000. However, the numbers jumped suddenly
in 2009, when the area was hit by 50 quakes -- and it has been
rising every year.
The area was hit by 87 quakes in 2010 and 134 in 2011,
according to the U.S. Geological Survey. Officials concluded that
the earthquakes are being caused by wastewater from fracking,
according to research that will be presented at the Seismological
Society of America conference next week.
"Our scientists cite a series of examples for which an uptick
in seismic activity is observed in areas where the disposal of
wastewater through deep-well injection increased significantly,"
David Hayes, the deputy secretary of the U.S. Department of
Interior, said in a
Researchers found clusters of wastewater wells where the
majority of the earthquakes occurred. As fracking became more
popular more and larger wells were created, which led to more
disturbances and more earthquakes.
"[An increase of earthquakes] of this magnitude is
unprecedented outside of volcanic settings or in the absence of a
main shock, of which there were neither in this region," the
Steve Horton, a seismologist at the University of Memphis who
has been tracking earthquakes in Arkansas, said there is too
strong a link between fracking and earthquakes for it to be
"The earthquakes started after the injection at the two wells
started, and they stopped after the injection stopped," he told
Geologists aren't sure exactly how fracking is causing the
earthquakes, but say it doesn't take much to trigger one.
"Small perturbations can tip the scales, allowing an
earthquake that might not otherwise happen for a very long time,"
There is no way to predict if a well site will produce an
earthquake, researchers said, but they plan
more studies to determine what exactly is
The geologists published the
of their study online on Thursday, but are holding off on
releasing any more information until they present the research
next Wednesday at the conference.
Earthquakes Linked To Natural Gas Drilling's
Waste Water Wells, Says USGS