Youngstown, Ohio, had a rockin’ New Year’s Eve, but not the kind it hoped for—a 4.0 magnitude earthquake shook the city just one week after a 2.7 magnitude earthquake hit. Fortunately, there was no significant damage or injuries; the focus has primarily been on the cause of the earthquake. Although no definitive connection has been made, seismologists are pointing to oil and gas activity as a likely culprit; consequently, Ohio state officials indefinitely closed five wells used to store wastewater from natural gas drilling. D&L Energy, the owners of the five wells, are commissioning a geologic study ^[1] to determine the cause of the seismic activity, although some seismologists are confident that the injection wells are the culprit.

Here’s what we know so far:

• Hydraulic fracturing is a successful process safely used for 60 years. Producers inject a fluid composed of 99 percent water and 1 percent sand into wells to free oil and gas trapped in rock formations. This process did not cause the earthquakes. Injection wells, an efficient and cost-effective way to dispose of briny wastewater, are more likely a contributing factor, according to some seismologists. Art McGarr with the U.S. Geological Survey said ^[2], “The location of the earthquakes is quite close to the wells. Secondly, the timing of the waste water injection also coincides with the earthquakes.” While there have been instances in other states of seismic activity near wastewater wells, there has not been conclusive evidence that directly links the wastewater injection to the Ohio earthquakes.

• Seismic activity as a result of underground activity is not limited to wastewater well injection, nor is it a new phenomenon. The Department of Energy has been observing induced seismic activity from energy-related activities since the 1930s. The agency concludes that ^[3] “oil and gas induced seismicity has been dealt with successfully and is well understood. In that last several years induced seismicity is receiving more attention not because it is a hazard (although some recent cases in Texas have drawn attention to it), but as in the case of geothermal it can be used to trace the success of inducing permeability.” But induced seismicity does not occur only from oil and gas activities. Carbon sequestration ^[4]—removing carbon from power plants and storing it underground—and geothermal activities ^[5], utilizing thermal energy naturally stored in the earth, have also caused relatively small earthquakes.

• Although induced seismic activity is not a new phenomenon, it is a rare one ^[6]. Ohio has 177 Class II injection wells—those in which the injected fluid is mostly saltwater—that have operated without incident for decades. In total, more than 144,000 of these Class II wells ^[7] are in operation across the United States. While there have been other instances of induced seismic activity, they have been few and far between.

Governor John Kasich and the Ohio Department of Natural Resources have taken a prudent approach by treating the earthquake as an isolated incident and indefinitely suspending injection well activity near the earthquake (within five miles of the epicenter) but allowing the other disposal wells to operate. Studies have shown that minor seismic activity has coincided ^[8] with wastewater injection wells, but not all wells induced seismic activity. It’s important to understand that this has not been a consistently reoccurring problem, but just as important to understand what caused the earthquake and what can be done to prevent future ones.

Governor Kasich’s spokesman affirmed ^[9] that they would ensure safety while allowing the state to realize the economic potential of increased energy production: “Natural gas could generate tens of thousands, if not hundreds of thousands, of jobs in Ohio. For those out there who are willing to drive a stake through the heart of what could be an economic boon, we’re not going to let that happen.”