In January, more than 70 small earthquakes shook parts of Oklahoma and caused concerns that the state’s earthquake problems are worsening.

A number of citizens are blaming the oil field practice of hydraulic fracturing, which is also known as fracking, for triggering these tremors.

The Sierra Club has become involved in the debate over fracking’s possible connection to greater earthquake hazards. The environmental advocacy group recently filed a lawsuit in the U.S. District Court for the Western District of Oklahoma against Chesapeake Energy Corp., Devon Energy Production Co. and New Dominion, accusing the three companies of causing earthquakes in Oklahoma and Kansas due to their fracking activities.

According to the complaint filed by the Sierra Club, the three companies’ practice of injecting liquid oil and gas waste into deep ground wells contributed to an increase of more than 5,800 earthquakes in Oklahoma in 2015, up from an annual average high of 167 from 1977 to 2009, according to the complaint.

In the complaint, the Sierra Club is requesting that the court enter a judgment declaring the three companies’ past and present treatment, handling, storage, transportation and disposal of production wastes present an imminent and substantial endangerment to public health and to the environment in violation of the Resource Conservation and Recovery Act.

In addition, the Sierra Club is seeking to have the court order the three companies to reduce immediately the amounts of production wastes they are injecting into the ground to safe levels that do not exceed the levels that seismologists believe will not cause or contribute to increased earthquake frequency and severity. The club is also asking the court to enjoin the three companies by ordering them to reinforce vulnerable structures that current forecasts show could be impacted by large magnitude earthquakes during the interim period.

The Sierra Club is also requesting that the court order the establishment of an independent earthquake monitoring and prediction center to analyze and forecast the volume of production wastes that can be injected into a particular well or formation in a given area before seismicity is induced, and monitor how closely ongoing earthquakes conform to researchers’ predictions.

The Sierra Club is being represented in the lawsuit by several attorneys, including William Federman, a partner with Federman & Sherwood in Oklahoma City; Richard Webster, a staff attorney in the environmental enforcement project at Public Justice in Washington, D.C.; Scott Poynter, a partner, and Robin L. Greenwald, of counsel with the Poynter Law Group in Little Rock, Arkansas; and Curt D. Marshall, an associate attorney with the New York-based firm of Weitz & Luxenberg.

“The Sierra Club wants to map out the appropriate moratorium areas where injection wells cannot operate,” Poynter said.

Gordon Pennoyer, director of strategic communications with Chesapeake Energy, recently commented about the lawsuit in an emailed statement.

“We disagree with the Sierra Club’s assertions and will address them in the appropriate forum. Chesapeake respects the Oklahoma Corporation Commission’s regulatory authority and technical expertise and is complying with the Commission’s directives,” Pennoyer said.

Fred Buxton, the vice president and general counsel of New Dominion, was unavailable for comment. John Porretto, media relations director for Devon Energy, declined to comment about the case.

Currently, none of the three companies has filed a response to the Sierra Club’s lawsuit.