New insight into a series of fracking-related earthquakes in Eastern Ohio shows that deeper drilling is tied to stronger seismic activity.
The study from Miami University also found that smaller earthquakes can occur at a shallower drilling level than previously thought.
The Ohio quakes took place about 70 miles west of Pittsburgh between 2013 and 2015. They were minor, causing virtually no damage.
Drilling has taken place in the natural gas-rich Utica Shale for years, which lies about 6,000 feet underneath much of Ohio and Pennsylvania. But this research is the first time drilling in the shallower sedimentary layer of the shale, rather than the deep basement layer, has been tied to seismic activity, according to Penn State Geosciences Professor Andy Nyblade.
"Now that they're showing the induced seismicity can also occur in faults inside the sedimentary section itself, it raises a new level of concern," Nyblade said.
There are thousands of fracking sites in Eastern Ohio and Western Pennsylvania, and earthquakes triggered by fracking are very rare. The only confirmed fracking-related earthquakes in Pennsylvania took place in Lawrence County in 2016.
But Nyblade said the research suggests that Western Pennsylvania drillers should be aware of the possibility of seismic activity in the sedimentary layer, in part because the geology is very similar to Eastern Ohio.
"The fact that these events have been happening in Ohio indicates that they certainly could happen in Pennsylvania as well," he said.
The research did not make recommendations on where drilling should or should not take place.