A series of five small earthquakes within the span of 24 hours in Lawrence County in western Pennsylvania has led to the shutdown of nearby fracking operations. The earthquakes range in magnitude from 1.69 to 1.91 on the Richter scale, placing them in a category of small earthquakes that are typically not felt on the surface.
The quakes occurred just after midnight on Monday in the vicinity of Mahoning Township, with the last one registering at 10:10 PM the same day, according to the U.S. Geological Survey (USGS). Department of Environmental Protection spokesman Neil Shader says Hilcorp Energy shut down its operation on Tuesday, and the DEP is investigating whether the string of small quakes was caused by fracking.
Penn State professor Andrew Nyblade says there is a correlation in space and time between the quakes and the fracking operation. But a causal link has not yet been established.
“These are the first seismic events that have been correlated to fracking [in Pennsylvania],” Nyblade says. “That’s not to say this hasn’t happened before.”
One of Nyblade’s graduate students, Kyle Homman, recently wrote his thesis on seismicity in the state and did not find evidence linking earthquakes to oil and gas activity. The study spanned 23 months, from February 2013 to December 2014. Nyblade says the research identified more than 1,500 seismic events and linked them to blasting activities at coal mines and quarries. He says there were about 10 earthquakes not linked to mining activity.
Earthquakes caused by fracking are rare. It’s more common to see earthquakes result from the disposal of oil and gas waste water through deep injection wells, such as the recent spate of earthquake activity in Oklahoma. Last month, the USGS published a forecast of natural and human-induced earthquakes across the nation. Pennsylvania showed no threat of any significant quakes. The USGS also said fracking is not the major cause of human-induced earthquakes.