Ohio officials say they've ruled out oil and gas waste injection as a cause of a series of earthquakes near Youngstown but have ordered activities to stop at a Utica Shale production site near the epicenters.
"We were able to rule out injection," said Mark Bruce, spokesman for the Ohio Department of Natural Resources. "We can't say for sure if it's natural causes, production or something else. We're looking for the cause."
Five earthquakes have rattled the area near the Pennsylvania border 8 miles southeast of Youngstown since Monday morning, according to U.S. Geological Survey data. The epicenters are grouped in a rural area near Poland, Ohio.
The closest injection well is 14 miles away, Bruce said.
The area has little history of natural earthquakes, but the seismic ruptures have shaken loose memories of a series of quakes starting in 2011 that were linked to an injection well in Youngstown. That led to new rules for injection wells in the state.
There are 13 seismic instruments deployed in Mahoning County (which includes Youngstown) and Trumbull County to the north, some by ODNR, some by companies, some from USGS and one by a university.
Hilcorp Energy Co. has seven wells on two well pads in the area, only one of which was producing as of Tuesday, according to a statement from the company. The wells are on the site of a landfill. Completion activities began on the second pad last month and have not concluded.
The department ordered the company to shut down production, and the company complied without need for further official action, Bruce said.
"We would like to remind the community that a number of Utica wells have been drilled in Ohio in recent years without incident," the company said in its statement. "Nevertheless, we do acknowledge that public safety is of paramount importance to our company. Hilcorp always strives to be a good neighbor and responsible corporate citizen in the communities that we operate in."
Geologists have known for decades that deep underground injection can, on rare occasions, lubricate faults and unleash earthquakes. The largest linked to injection was a magnitude-5.7 quake east of Oklahoma City in November 2011.
The potential for hydraulic fracturing and other production activities to cause earthquakes is less clear. Fracturing has been linked to earthquakes, but nothing as large.
Seismologist Austin Holland of the Oklahoma Geological Survey found that hydraulic fracturing may have triggered a swarm of small earthquakes in 2011 near Elmore City, Okla. They peaked at magnitude 2.8 and caused no injuries or property damage (E&ENews PM, Nov. 2, 2011).
Cuadrilla Resources, a British shale gas developer, has found that it was "highly probable" its fracturing operations caused minor quakes of magnitude 2.3 and 1.5 in Lancashire, England.
The largest earthquakes linked to fracking reportedly occurred in British Columbia's shale-rich Horn River Basin. The province's Oil and Gas Commission said the basin was shaken from 2009 to 2011 by earthquakes ranging from magnitude 2.2 to 3.8. That's still unlikely to cause damage, especially in such a sparsely populated area (EnergyWire, Sept. 7, 2012).
That has some researchers scratching their heads. John Armbruster, a seismologist with Columbia University's Lamont-Doherty Earth Observatory, has been looking into potentially man-made earthquakes in northeast Ohio since 1987.
"The facts as they play out now don't make sense," Armbruster said in an interview yesterday. "There's so many thousands of fracking wells in Pennsylvania and Ohio. Could this really be the first example of them causing earthquakes? That would be surprising."