For the first time, Ohio regulators said recent earthquakes in the state were probably caused by fracking operations.

In early March, five small earthquakes up to 3.0 in magnitude shook Mahoning County, which is close to the Pennsylvania-Ohio border. Youngstown, Ohio, experienced a separate series of earthquakes in 2011 and 2012, but those were linked to nearby deep underground injection wells used to store fracking wastewater. PublicSource wrote about the political aftermath of those earthquakes last year.

The recent earthquakes are the first documented cases in Ohio that show the likelihood that hydraulic fracturing can cause earthquakes.

From the Youngstown Vindicator:

[Ohio Department of Natural Resources] geologists believe the sand and water injected into the well during the hydraulic fracturing process may have increased pressure on an unknown microfault in the area,” the agency responsible for regulating the state’s oil and gas industry said in a statement.

On March 23, The Vindicator reported that geologists outside of an Ohio Department of Natural Resources investigation were considering the theory that fluid from a fracking well at the Carbon Limestone Landfill could have seeped into an unknown fault extending upward from the Precambrian basement, causing the ground to shake March 10.

ODNR’s investigation turned up no link to the Precambrian formation, but it did indicate that fracking aggravated a small, previously undetected fault in the overlying Paleozoic rock.

As a result, Ohio state officials have issued new permit conditions in certain areas, thought to be some of the strictest in the nation, according to a recent Associated Press article.

More from the AP:

Under the new permit conditions, all new drilling sites in Ohio within 3 miles of a known fault or seismic activity of 2.0 magnitude or higher will be conditioned on the installation of sensitive seismic-monitoring equipment.

Results will be directly available to regulators, Simmers said, so the state isn’t reliant on drilling operators providing the data voluntarily.

If seismic activity of 1.0 magnitude or greater is felt, drilling will be paused for evaluation. If a link is found, the operation will be halted.

Ohio officials ordered an indefinite moratorium on drilling at the Hilcorp Energy Co. site, where the March earthquakes occurred. However, oil and gas extraction still continues at five existing wells at the site.

It’s the Utica Shale getting tapped at this site, not the better-known Marcellus Shale. The Utica Shale lies below the Marcellus and companies have only recently started drilling it.

Reach Natasha Khan at or 412-315-0261.

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Natasha is PublicSource's creative director. She runs the organizations visuals team, edits and produces interactive graphics, data visualizations and web packages for PublicSource. She manages the website...