Ohio Earthquake Likely Caused by Fracking Wastewater

Residents of Youngstown, Ohio, received an extra surprise on Christmas Eve and again on New Year's Eve—earthquakes, measuring 2.7 and 4.0 on the Richter scale, respectively. No one was injured and only a few cases of minor damage were reported after the Dec. 31 event.

Scientists have quickly determined that the likely cause was fracking—although not from drilling into deep shale or cracking it with pressured water and chemicals to retrieve natural gas. Rather, they suspect the disposal of wastewater from those operations, done by pumping it back down into equally deep sandstone.

Fracking is part of a nationwide boom in the production of natural gas, which is a ready replacement for home heating oil and could lessen dependence on foreign fossil fuels if vast underground shales could be hydraulically fractured. Opposition to fracking has arisen mostly out of fear that the technique could potentially contaminate drinking water supplies.

Nine small earthquakes had already occurred between March and November 2011 within an eight-kilometer radius of a wastewater injection well run by Northstar Disposal Services. Because quakes are otherwise rare in the Youngstown area, the Ohio Department of Natural Resources in November asked Columbia University's Lamont–Doherty Earth Observatory (LDEO) to place mobile seismographs in the vicinity to better determine what was going on. John Armbruster from LDEO installed four seismographs on November 30.

By triangulating the arrival time of shock waves at the four stations, Armbruster and his colleagues needed only a day or two to determine with 95 percent certainty that the epicenters of the two holiday quakes were within 100 meters of each other, and within 0.8 kilometer of the injection well. The team also determined that the quakes were caused by slippage along a fault at about the same depth as the injection site, almost three kilometers down.  More  Scientific American >>