Ohio officials are still investigating whether oil and gas activity caused a New Year's Day earthquake near Youngstown, but scientists have known for years that injecting oil and waste underground causes such earthquakes.
"Oil and gas induced seismicity has been dealt with successfully and is well understood," the Department of Energy states on its website.
But a growing number of critics have a less sanguine view of production methods that trigger temblors. The magnitude-4.0 quake near a deep injection well has widened unease in Ohio and Pennsylvania about oil and gas production from shale, which some have labeled "fracking," for the process of hydraulic fracturing.
Similar "underground injection" of brine from shale is believed to have caused earthquakes in Arkansas earlier this year. Oil and gas production itself has caused earthquakes, most famously in Wilmington, Calif., where oil extraction caused earthquakes that stretched from 1947 to 1961.
But it's not just oil and gas activity that makes the ground shake. More "earth-friendly" production methods, such as geothermal and carbon sequestration, are also known to have set the earth rumbling.
A National Academy of Sciences panel is already studying how oil and gas production and other types of energy production can lead to man-made earthquakes.
Sen. Jeff Bingaman (D-N.M.) requested the study of "induced seismicity" a year and a half ago, troubled that the kind of fears triggered by the Ohio quake could shake public confidence in the country's growing energy industry.
"Much of public opposition to the deployment of advanced energy technologies in the United States stems from a lack of clear, trusted information regarding the safety of those new energy facilities for the local communities that are their neighbors," Bingaman wrote in a June 2010 letter to Energy Secretary Steven Chu, asking for interagency cooperation on such a study.
The NAS study committee has met seven times since the study began in September 2010: twice in California, once in Texas and four times at NAS headquarters in Washington, D.C. It is expected to issue a report in early summer.
In Youngstown, earthquakes have shaken support for oil and gas production, which Gov. John Kasich (R) has promoted as a "gold rush" (ClimateWire, Sept. 20, 2011). The eastern part of the state sits atop the gas-rich Marcellus Shale and the Utica Shale, which is emerging as a new potential source of gas liquids and oil.
Suspicion in the Youngstown-area earthquakes centers around not drilling itself, or the fracturing process, but underground injection of brine.
Fracturing shale requires the use of millions of gallons of water, and subsequently creates millions of gallons of salty, "briny" waste more toxic than what was fired down the hole. Drillers must figure out how to dispose of it. Some reuse some of it in the next "frack job," but often it gets injected back underground in a deep disposal well.
Nationally, EPA records show there are 150,851 "Class II" injection wells associated with oil and gas, and 177 of them are in Ohio. Underground injection is also used to dispose of radioactive waste, hazardous waste, mining fluids and carbon dioxide. There are about 500,000 other types of injection wells that dispose of non-hazardous waste.
In Pennsylvania, just across the border from Youngstown, state regulators under pressure from U.S. EPA have been pushing drillers not to send water to treatment plants that discharge into rivers. That means companies either reuse the water or ship it off for injection, and there are relatively few injection wells in Pennsylvania.
State officials Tuesday announced an agreement with the owner of the well at the center of the controversy, a small, independent oil and gas operator called D&L Energy Inc., to halt operations. It has halted operations at four other injection sites within 5 miles. A series of smaller earthquakes preceded the New Year's Day quake.
"While our research doesn't point to a clear and direct correlation to drilling at this site and seismic activity, we will never gamble when safety is a factor," said Ohio Department of Natural Resources Director James Zehringer.
D&L has a history of at least 120 violations at 32 injection and extraction wells in Ohio and Pennsylvania during the past decade, according to the Youngstown Vindicator newspaper. Ohio officials have never fined the company, though regulators documented a lack of corrective action by the company.
EPA, which oversees the injection program in Ohio, does not require states to look at earthquake potential when permitting underground injection wells for oil and gas waste.
Quakes in other areas
At the time Bingaman requested the federal action, scientists in Texas and at DOE's Lawrence Livermore National Laboratory had documented connections between earthquakes and gas production and other energy production. Bingaman noted that all of the quakes had been small.
One of the most famous instances of man-made earthquakes, or "induced seismicity," occurred in the late 1960s at the Rocky Mountain Arsenal near Denver, where the Army manufactured chemical weapons.
The NAS team has heard about geothermal plants in Northern California that local residents accuse of causing earthquakes that have damaged their home.
They've also heard about hydraulic fracturing from drilling companies such as Halliburton subsidiary Pinnacle and Apache Corp., which have stressed that while fracturing is seismic activity, it doesn't spur earthquakes that can be felt at the surface.
But in November, British Shale gas developer Cuadrilla Resources reported it was "highly probable" that its fracturing operations caused minor quakes of magnitude 2.3 and 1.5 in Lancashire, England. And the Oklahoma Geological Survey has found that hydraulic fracturing may have triggered a swarm of small earthquakes earlier this year in Oklahoma. The quakes, which struck on Jan. 18 in a rural area near Elmore City, peaked at magnitude 2.8 and caused no deaths or property damage (E&ENews PM, Nov. 2, 2011).