After a week-long investigation, state regulators on Friday said that two underground injection wells are the likely cause of a 2.1-magnitude earthquake recorded by the U.S. Geological Survey (USGS) in northeast Ohio on Aug. 31, and ordered them to shut down ahead of a full investigation.

Those wells, located about 12 miles northwest of Youngstown and operated by Ohio-based Avalon Holdings subsidiary American Water Management Services, were at the epicenter of the earthquake, USGS said (see Shale Daily, Sept. 2).

“Due to the seismic array proactively placed in the area, the Ohio Department of Natural Resources (ODNR) was able to determine that possible evidence exists linking the American Water Management Services’ injection well operation to a recent 2.1 seismic event,” spokeswoman Bethany McCorkle said in a statement. “This is a relatively minor event, but out of an abundance of caution, ODNR issued chief’s orders to the company to suspend injection operations while a full investigation takes place.”

After a 4.0 magnitude earthquake on New Year’s Eve 2011 that was linked to another injection well operated by a different company in Youngstown (see Shale Daily, Jan. 4, 2012), ODNR set forth a plan to begin installing seismic monitoring devices throughout eastern Ohio, which was recently completed (see Shale Daily, May 22).

After the latest incident, the agency had been reviewing data from nine of those devices in the area, along with others operated by the company. It said shortly after the earthquake that it was trying to determine if the injection wells had caused the event, with a spokesman telling NGI’s Shale Daily that regulatory action could follow.

In interviews with local news media last week, Avalon CEO Ron Klingle reportedly called the earthquake a “non-event” and said it was no different than those that go unnoticed throughout the region and the country nearly every day. According to the USGS, a 2.1-magnitude earthquake is not strong enough for those living nearby to feel. No damage was reported after the incident.

ODNR said Friday that the company has cooperated with its request, and the two injection wells were closed. McCorkle said “we will continue to evaluate all the data to determine what exactly happened and will share more information as it is available.”

Shortly after the earthquake, a local activist group, FrackFree Mahoning Valley, stepped up its calls against the area’s oil and gas waste disposal business and asked local and state officials to shut down both the injection wells.

ODNR’s latest order comes just months after it shut down operations in March at a Hilcorp Energy Co. site near Youngstown (see Shale Daily, March 11; March 12), where it determined that well stimulation operations likely triggered a 3.0-magnitude earthquake (see Shale Daily, April 11).