On September 10, the Texas Railroad Commission absolved a second oil and gas company of causing a series of earthquakes in northern Texas finding that the seismic activity was due to “natural tectonic processes.” The Commission issued two preliminary reports in the past two weeks addressing whether two oil and gas companies—XTO Energy and EnerVest— caused earthquakes by injecting wastewater into the ground produced by the drilling industry. The Commission, which oversees Texas’s oil and gas industry, found the connection between the two companies’ wastewater injection practices and the recent increase in earthquakes to be too small to imply causation.

In October 2014, the Commission adopted amendments to rules concerning wastewater disposal wells in areas that have experienced or are likely to experience seismic activity. Under the rule amendments, the Commission was granted authority to modify, suspend, or terminate a disposal well permit if it is determined that a disposal well is likely to be or determined to be contributing to seismic activity. The XTO and EnerVest hearings were the first conducted by the Commission under that newly granted authority. The hearing was also prompted by a study published by Southern Methodist University in Nature Communications finding that the injection wells most likely caused a number of recent earthquakes.

As part of the announcement of the show cause hearings for XTO and EnerVest, Commissioner David Porter said, “Due to the fact that the wells were permitted prior to the Commission’s rule amendments addressing disposal well activity and seismic activity, and in light of the new research contained in SMU’s report, it’s appropriate and necessary for the Commission to consider the operation of these wells in a fully informed and determine the appropriate course of action.”

At the June hearings, representatives of the two oil and gas companies testified at length concerning the holes in the study—no SMU representatives appeared. The Commission ruled in favor of upholding the gas companies’ disposal well permits, explaining that the SMU study only presented data indicating “a weak temporal correlation between injection and seismic activities.”

The peer reviewed SMU study analyzed data from the U.S. Geological Survey’s National Earthquake Information Center, concluding, “while some uncertainties remain, it is unlikely that natural increases to tectonic stresses led to these events.”

Oklahoma regulators have formally acknowledged a connection between wastewater injection and earthquakes, and in response issued new restrictions on injection wells in an area that experienced an increase in minor earthquakes. The regulations required operators to decrease their waste injections by 38%. Kansas has issued similar wastewater injection restrictions.