A new report, published online in the Bulletin of the Seismological Society of America, shows that the controversial practice of hydraulic fracturing, or simply “fracking”, triggered a series of minor earthquakes in Poland Township, Ohio last year. One of these small earthquakes was strong enough to be felt by the inhabitants of the area, which prompted officials to shut down the well responsible for the disruption.
Fracking is a process whereby sand, water and different types of chemicals are injected into shale rock to break it up and release trapped oil and natural gas. This technology has been widely adopted in the US, but remains a contentious issue in Europe.
Robert Skoumal, lead author of the study and a graduate student in seismology at Miami University, Ohio, teamed up with his colleagues and correlated the earthquakes to fracking operations. Then they compared the location of active wells in relation to the quakes. This helped them determine that the earthquakes were caused by a small part of the fracking operation in the North Eastern quadrant.
“These earthquakes near Poland Township occurred in the Precambrian basement, a very old layer of rock where there are likely to be many pre-existing faults,” said Skoumal. “This activity did not create a new fault, rather it activated one that we didn’t know about prior to the seismic activity.”
The drilling in Ohio was undertaken by Hilcorp Energy, which shut down its activities on 10 March after the 3.0 magnitude earthquake. Prior to the operation, no seismic events were registered in this region of Ohio. According to Skoumal and his team, 77 earthquakes ranging from 1 to 3 in magnitude occurred between March 4 and 12. “The company happened to be unlucky because they were hydraulic fracturing near an unknown fault”, he explained.
Most fracking operations have been demonstrated to be relatively safe and the minor earthquakes they trigger are too weak to be felt by people living in the surrounding area. All of that notwithstanding, anti-fracking activists often cite the risk of dangerous seismic events as one of the reasons why this method should not be engaged. Last year, the state of Oklahoma saw a fivefold increase in earthquakes – 564 of them being above the magnitude of 3.0. This makes Oklahoma the most seismically active state in mainland US.
Skoumal and his team claims that identifying faults before fracking is extremely difficult and expensive, yet people should not be alarmed: “People in areas with ongoing hydraulic fracturing should not panic about induced earthquakes. The chances that hydraulic fracturing operation will induce felt seismicity is rare.”
On top of that, increased communication between responsible parties should make the process even safer than it is right now. “It makes sense to have close cooperation among government, industry and the scientific community as hydraulic fracturing operations expand in areas where there’s the potential for unknown pre-existing faults.”