Pennsylvania environmental officials attributed a series of small earthquakes in 2016 in Lawrence County to fracking.
It was the first instance of fracking-related earthquakes in the state. Hilcorp Energy Company was fracking wells in the Utica Shale formation near New Castle when seismic monitors recorded five quakes with magnitudes between 1.8 and 2.3. As a result, the Pennsylvania Department of Environmental Protection issued more stringent requirements for gas development in the area.
Though fracking — the process of injecting water, chemicals and sand at high pressures into a well to perforate rock — can lead to earthquakes, it causes far fewer tremors than wastewater disposal, another aspect of shale oil and gas development.
In places like Oklahoma and Ohio where wastewater is injected underground, earthquakes are more common. Wastewater, also known as produced water or brine, is a salty liquid that comes to the earth’s surface alongside natural gas and oil at well sites. It’s often injected back underground into different wells.
Pennsylvania has authorized 11 of these underground injection wells, but much of the wastewater produced in the state is trucked to Ohio and disposed there, where more wells exist.