Officials with the state of Ohio ordered injection wells shut down after several minor earthquakes occurred on Dec. 24 and Dec. 25.

The Wall Street Journal reports that the injection wells are used to dispose of waste water left over from hydraulic fracturing sites, also known as fracking, which involves blasting water, sand and chemicals underground to break apart layers of rock to release trapped oil and gas for production. There is an ongoing debate that the practice can cause seismic activities as well as leak chemicals into the drinking water.

Ohio regulators previously asked the company operating the Youngstown well, D&L Energy Inc., to stop injecting wastewater after a 2.7-magnitude earthquake Dec. 24.  When a 4.0-magnitude earthquake hit within a five-mile radius of the well the following day, state officials declared a moratorium on all injections. There have reportedly been 11 small earthquakes around the well since March.

The natural gas industry denies there is a connection between hydraulic fracturing and earthquakes.

Arkansas regulators in 2011 reportedly declared a moratorium on injection wells in the vicinity of a series of earthquakes, and in 2010 researchers at Southern Methodist University reportedly found a link between injection wells in the Dallas-Fort Worth area and nearby quakes.

The decision also highlights the exportation of fracking waste water from one state to another. More than half of the fluid injected at the Youngstown well came from Pennsylvania, Andy Ware, deputy director of the Ohio Department of Natural Resources, was quoted as saying in the article.

Pennsylvania doesn't prohibit injection wells, but officials there say the state has limited geologic formations that are suitable for them. Pennsylvania has seven wells that can receive waste, while Ohio has permitted 194.

Drilling companies operating in Pennsylvania had been disposing of 95 percent of their liquid waste at treatment plants until April, when the state's governor called on them to stop over concern the facilities weren't adequately removing contaminants before discharging them into waterways, the article said. That move reportedly prompted companies to send their waste water over the state line into Ohio.

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