Wednesday, October 15, 2014
A new study suggests that fracking triggered hundreds of too-small-to-be-felt earthquakes in eastern Ohio late last year, months before the state first linked seismic activity to the oil-and-gas extraction technique in Poland Township.
The report, which appears in the November issue of the journal Seismological Research Letters, identified nearly 400 tremors on a previously unmapped fault in Harrison County between Oct. 1 and Dec. 13, 2013.
That included 10 quakes of magnitudes of 1.7 to 2.2. That’s intense enough to have temporarily halted activity under Ohio’s new drilling-permit rules had they been in place at the time, but is still considered minor.
The quakes fell along a fault lying directly under three hydraulic-fracturing operations and tended to coincide with nearby activity, researchers found.
About 190 quakes were detected in a single three-day period last October, beginning within hours of the start of fracking. None of the quakes was reported felt by people.
Fracking involves the high-pressure injection of water, sand and chemicals into shale to break up the rock and release trapped oil and gas.
Bethany McCorkle, a spokeswoman for the Ohio Department of Natural Resources, said the state has installed seismic monitoring equipment throughout eastern Ohio over the past year and is keeping close watch for earthquakes strong enough to be felt.
Rowena Lohman, an assistant professor of geophysics at Cornell University who was not involved in the study, said some faults cannot be discovered until underground activity is attempted. She said the latest findings can be used to try to prevent worse quakes.
“We’ve known for a really long time, going back to the ’70s, that when you do any subsurface manipulation you cause small earthquakes,” she said. “The big question is: Are we doing something now that increases the probability that it will induce larger quakes?”
Study co-author Paul Friberg, a seismologist at New York-based Instrumental Software Technologies Inc., said fracturing rock results in micro-earthquakes but that some of the Harrison County tremors were significantly larger than expected.
Earthquakes have been linked to fracking operations in the Mahoning Valley since 2011, according to Vindicator files.
A 4.0-magnitude earthquake struck shortly after 3 p.m. on New Year’s Eve in 2011 under the D&L Energy Inc. brine-injection well in Youngstown. That well injects brine, a byproduct of fracking, about 9,300 feet into the ground.
That quake followed months of Vindicator reporting about the links between that well and a spate of earthquakes.
Earlier this year, on March 10, an earthquake with a magnitude of 3.0 shook Poland Township. That and subsequent quakes were linked to a fracking operation by Hilcorp Energy Co. at the Carbon Limestone Landfill.
In a March 23 Vindicator story, geologists outside of an ODNR investigation considered the linkage between that fracking operation and the earthquake, something that mining officials previously insisted was not possible.
In April, the ODNR confirmed that fracking was a “probable” trigger of the earthquakes and indicated that fracking aggravated a small, previously undetected fault.
The ODNR imposed a moratorium on drilling at the site but allowed Hilcorp Energy Co. to recover oil and gas from five previously drilled wells, with seismic monitoring at the location.