Fracking, or hydraulic fracturing, caused a rare earthquake felt by residents in Ohio back in March, adding to the accumulating evidence that this kind of drilling leads to more frequent man-made earthquakes, according to a new study.
During the commonly known process as fracking, gas and oil is extracted from shale rock by injecting a high-pressure water mixture into the ground. Not only does this supposedly contaminate groundwater as well as have an impact on animals, but it also results in micro-earthquakes normally too insignificant for humans to notice. However, in March 2014 fracking in Poland Township, Ohio activated a previously unknown fault, triggering a series of five recorded earthquakes, ranging from magnitude 2.1 to 3.0. State officials shut down the well, located just within one kilometer (0.6 miles) away, two days after the earthquake hit.
"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," study co-author Robert Skoumal of Miami University in Ohio said in a statement. "This activity did not create a new fault, rather it activated one that we didn't know about prior to the seismic activity."
"We just don't know where all the faults are located," he added. "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."
There is no doubt that hydraulic fracturing operations across the country have increased in the past decade. And as its popularity rises, so does the number of earthquakes - felt or unfelt. The intense drilling involved in such practices can lead to tremors, which sparks earthquakes that are caused by a shift in Earth's tectonic plates at what is called the fault line. Some believe this evidence supports the idea of including fracking in earthquake hazard assessments.
According to a report by Environment America, as of 2013 fracking is ongoing in 17 states, with more than 80,000 wells drilled or permitted since 2005. And such activity is only expected to expand, with oil and gas industry looking to build fracking sites in states like New York, California and North Carolina, for example. (Scroll to read on...)
The average number of earthquakes per year with a magnitude of 3.0 or higher - the same magnitude as the one felt in Poland Township - increased from only 20 several decades ago to more than 100 within the past four years.
As for the Ohio earthquakes, Skoumal and his colleagues found via a technique called template matching that "fingerprints" tiny quakes that typically go unnoticed on people's radar.
"It can identify signals that, to our eyes, would be just noise," Skoumal told Live Science.
Comparing the Poland Township case with seismic data from past earthquakes of similar magnitude, the researchers found a clear correlation in time and space with hydraulic fracturing.
The Ohio Department of Natural Resources (ODNR) now requires that companies install seismometers when drilling within 3 miles (5 kilometers) of known faults or near an area that has recently experienced earthquakes.
What's more astonishing, the well held responsible for this event may have been close by, but according to prior findings, disposal wells can be as far away as 30 kilometers (19 miles) and still be blamed for man-made quakes.
Scientists still have yet to fully understand the mechanisms that cause rumbling earthquakes such as the 3.0-magnitude one felt in Ohio, let alone how fracking plays a role, but there's no doubt that the evidence is mounting.
The latest findings were published online by the Bulletin of the Seismological Society of America (BSSA).
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