Scientists Found Direct Link Between Earthquakes and Fracking

Recurring earthquakes near drilling sites in the United States has been long associated to hydraulic fracturing or fracking, but the U.S. Geological Survey kept reassuring Americans that wastewater disposal, and not the fracking operations itself, is the cause of most induced earthquakes.

Now, a new study from the University of Calgary revealed that injecting fluid deep underground could buildup enough stress to produce periodic earthquakes that can last for months after the fracking operations have stopped.

The study, published in the journal Science, showed that fracking operations in western Canada can directly influence most induced earthquakes in two ways.

"The key message is that the primary cause of injection-induced seismicity in Western Canada is different from the central United States," explained David W. Eaton, a professor of geophysics at the University of Calgary and co-author of the study, in a report from New York Times. "It's a different situation."

For the study, the researchers analyzed the seismic activity at Fox Creek, Alberta using data from four seismograph stations near six drilling sites between December 2014 and March 2015.

The researchers found two patterns to the seismic activity in the western Canada. First, most of the earthquakes in the east of fault line occurred during the fracking operations. On the other hand, few immediate quakes in the west of the fault occurred intermittently over several months after the fracking ceased.

Their analysis of the two pattern showed that the fracking process in could produce an explosion-like shock that can travel into the rock formation and disrupt the stress patterns from within. Critical changes in the stress patterns could push the fault over to the edge, creating earthquakes that can be prevented when the fracking stopped.

On the other hand, the researchers noted that the earthquakes in the west were caused by fracking fluid that remained underground in the fractured shale. These fracking fluids could lead to more persistent pressure within the fault zone, creating more earthquakes over time even the fracking operations stopped.