Two lawsuits were filed within days of each other in Oklahoma, claiming that energy companies engaged in hydraulic fracturing and underground disposal of produced water are causing earthquakes throughout the state. These lawsuits probably come as no surprise to the industry after the Sierra Club recently threatened to sue four oil companies for contributing to increased earthquakes in Oklahoma and southern Kansas.

A pair of Oklahoma residents, in a class-action lawsuit, have accused four energy companies of causing “a dramatic increase” in earthquakes throughout the state during the last five years. The lawsuit names Sandridge Exploration and Production, Chesapeake Operating, Devon Energy Production Company, and New Dominion as the defendants.

The plaintiffs claim that hydraulic fracturing and underground disposal of produced water are causing earthquakes across the state by increasing the pore pressure within faults making the fault more prone to slip.

The lawsuit alleges that the companies are liable to the plaintiffs and the class for nuisance, trespass, negligence, and engaging in an ultra-hazardous activity. The plaintiffs are seeking not only compensatory damages, but also punitive damages and attorneys’ fees.

The class-action suit comes at the same time another lawsuit was filed in Oklahoma against twelve energy companies for allegedly causing two earthquakes, which struck on December 29, 2015 and January 1, 2016. In this lawsuit, the plaintiffs argue that the companies “injected large volumes of drilling waste in disposal wells located near the cities of Edmond and Oklahoma City, in the vicinity of the plaintiffs’ properties, under conditions that defendants knew or should have known would result in an increased likelihood that earthquakes or other adverse environmental impacts would occur, thereby unreasonably endangering the health, safety and welfare of persons and property, including plaintiffs and others.

These lawsuits seem to be the latest in a barrage of attacks on the energy industry despite an Oklahoma Geological Survey study that concluded it was “impossible to say with a high degree of certainty whether or not these earthquakes were triggered by natural means or by the nearby hydraulic-fracturing operation.”