At the end of last month, a minor earthquake rattled southeast Ohio’s Noble County.
A few days later residents reported another. Then another.
By May 8, the Ohio Department of Natural Resources had detected 53 earthquakes in the county, prompting the agency to halt hydraulic fracturing – or fracking – at a well pad there.
“This part of the continent doesn't have a plate boundary now, but it did in the past,” said Mike Brudzinski, a professor of seismology with Miami University. “That's part of why you see fossils in this area that are from the seafloor. There's no sea here now, but there was at some point in the past.”
Fracking, he said, can disturb those long dormant faults.
How does fracking cause earthquakes?
The process of fracking involves injecting large volumes of fluid into the earth, which cracks open rocks and allows oil and gas to escape.
“The process is impressive in terms of how much more oil and gas can be harvested per well than it used to be,” Brudzinski said.
But sometimes, the injected fluids leak into deep, dormant faults.
“We do have cases where human activities can result in earthquakes that could really hurt people. Regulations in Ohio are designed to try and prevent those earthquakes from happening."Mike Brudzinski
“Those are cases where we can prop open the faults a little bit, and that can allow them to slip and cause earthquakes,” he said.
In the case of Noble County, most of the recent earthquakes were small enough not to be felt by people who live there. But a few crossed that threshold: The strongest quake on April 24 was a magnitude 3.4.
A couple weeks later, the state halted fracking operations at a well pad operated by Houston-based Encino Energy.
“This is an abundance of caution approach,” Brudzinski said. “Ohio, I think, has done a really nice job of having stringent regulations. Even at the 1.5 magnitude level, well below what we could feel, if earthquakes are recorded at that level, the operators need to start communicating with the state to talk about their plans for preventing larger size earthquakes.”
This is largely to prevent a disruption to people’s daily lives, Brudzinski said, but it’s also a way to mitigate risks.
“We do have cases where human activities can result in earthquakes that could really hurt people,” he said.
The largest earthquake associated with oil and gas activity, Brudzinski said, was a 5.8 magnitude earthquake in Oklahoma in 2016.
The past and present of fracking in Ohio
Earthquakes linked to fracking and wastewater disposal became a concern in eastern Ohio about a decade ago, Brudzinski said. That’s when the state started introducing more regulations to the process.
These days, though, the practice has become more common, especially in rural, southeast Ohio counties like Noble, Belmont, Carroll, Harrison, Jefferson, Monroe and Guernsey.
And in 2023, the state passed a law requiring the Department of Natural Resources to permit fracking on public lands.
Brudzinski says that doesn’t necessarily mean the state will experience more earthquakes.
“It has to do a lot with which rocks are being targeted in terms of whether or not there are higher or lower risks for earthquakes,” he said. “Certainly here in Ohio, there are some strategies to try and avoid areas where we have seen dormant faults get activated again by the injection.”
In fact, he said, allowing energy companies to operate on public lands could help them avoid fracking in places where earthquakes have happened in the past.
“I understand people get concerned about public land activity, and trying to preserve our natural areas is certainly something I care about,” he said.
But he’s confident in Ohio’s regulations — that they serve the state’s economic interests, while balancing environmental concerns.
“There are pretty impressive strategies for making sure that [wastewater from fracking] doesn't enter into our drinking water,” he said. “Wastewater disposal is a process that can potentially cause earthquakes, but it’s a strategy that's really trying to keep the water away from where it might harm our environment.”
