Does fracking cause earthquakes?

Posted on December 16, 2011 

Forgive the pun, but there has recently been a seismic shift in the fracking debate.

Earthquakes have been reported in areas where hydraulic fracturing has been used to extract oil and gas from shale deposits, from Arkansas to Oklahoma to the United Kingdom.

In England last month, Cuadrilla Resources unleashed a shock on the industry when it issued a press release admitting it was "highly probable" its hydrofracturing of a natural gas shale formation had caused earthquakes ranging from 1.9 and 2.8 on the Richter scale.

The earthquakes haven't just been felt abroad. In Arkansas, around 100 earthquakes were reported in a week before the state government shut down the operations of Chesapeake Energy and Clarita Operating in the Fayetteville Shale -- a formation similar to the Marcellus Shale. The companies had been disposing of wastewater by pumping deep underground, but their operations were shut down until further studies could shine more light on the matter. The Arkansas Oil and Gas Commission said operations at the injection wells might have caused up to 1,000 quakes in the region in a six-month period.

A 5.6 magnitude earthquake hit Oklahoma, the heart of the natural gas industry's U.S. operations on Nov. 5. It was the largest earthquake ever felt in the state, according to Scientific American. Though gas industry officials said the quake was too large to be associated with drilling activity, according to that publication, from 1972 to 2008 only two to six earthquakes were reported per year in Oklahoma, but the state experienced nearly 50 in 2009 and more than 1,000 in 2010.

The Scientific American quoted Art McGarr, a seismologist with the U.S. Geological Survey, who said the earthquakes might be caused by "lubricating an already stressed fault zone and thus making it easier for the land to shift."

If they can't stop the earthquakes, the drillers might be getting a better idea of how to control them. McGarr, cited in Nature, said scientists can now give a rough predication of if an earthquake will be triggered by fracking or well injections done by the industry, and how big it will be.

So far, there haven't been any reports of earthquakes caused by drilling activity in Pennsylvania. That could be due to Pennsylvania's geology, or the fact that it only has seven active injection wells, versus hundreds in other states experiencing drilling.

But with dozens more injection wells and thousands of additional horizontal wells planned for the state, the role that the industry might play in causing earthquakes will likely take a more prominent place in the environmental concerns listed by anti-drilling advocates in their arguments for slowing down the industry's work in the state.

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