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Another rare case of fracking-caused earthquakes has jolted Ohio. A new study connects some 400 micro-earthquakes near the town of Canton, in Harrison County, to hydraulic fracturing wells. The three wells operated from September through October 2013 in the Utica Shale. Ten of the quakes registered between magnitude 1.7 and magnitude 2.2, but the tremors were too deep to cause damage or to be easily felt by people, according to the study, published Tuesday in the journal Seismological Research Letters.
The new study is the second report this year of fracking-linked earthquakes from drilling in the Utica Shale. In March, scientists with Ohio's Department of Natural Resources shut down drilling at seven Utica Shale gas wells in Poland Township after fracking triggered two small earthquakes.
The Harrison case is one of the few scientifically documented incidents of hydraulic fracturing causing earthquakes on a fault, said lead study author Paul Friberg, a seismologist and owner of Instrumental Software Technologies Inc. The other locations include Oklahoma; the United Kingdom; British Columbia, Canada; and Ohio's Poland Township.
Fracking involves pumping large volumes of water, sand and chemicals into underground shale or other rocks, such as coal. The pressure forces open the rocks, allowing trapped oil and gas to escape. Within the oil and gas industry, hydraulic fracturing is known to cause earthquakes, but the tremors are usually so small that seismometers barely wiggle in response.
The Harrison County quakes struck less than 1 mile (1.4 kilometers) below the horizontal wells. Shaking started just 26 hours after fracking began on Sept. 29, 2013. Nearly 190 earthquakes hit during a 39-hour period on Oct. 1 and 2. The quakes tapered off after the fracking was completed on the wells, the study reports.