A North Texas geologist says wastewater injection wells are the likely culprit for the recent minor earthquakes in Johnson County.
Johnson County, home to more than 200 injection wells, has had four earthquakes in four days -- and 10 earthquakes in the past 30 days.
"Some frequency of these events is beginning to look like we maybe need to take a look at some of the activities in the area and, in this case in Johnson County around Cleburne, we certainly have to look at disposal wells," said Ken Morgan, director of Texas Christian University's Energy Institute.
Energy companies inject wastewater from drilling back deep into the ground. Morgan said he believes earthquakes would be less frequent if the energy companies back off a bit.
"What you have to do is not pump so much fluids into the disposal well," he said.
Morgan suggested that local leaders talk to the energy companies about reducing the wastewater injection.
Johnson County Judge Roger Harmon and Cleburne Mayor Scott Cain said they had not done so.
"Because we haven't had any evidence of damage or injuries within the city limits, there's really not anything we need to do until the experts tell us otherwise," Cain said.
Harmon said the quakes make some people uneasy and said it may be time to look at ways to prevent them.
The recent quakes have all been between 2 and 3.2 magnitude. But North Texans should not be worried about drilling causing major earthquakes.
"They really can't be any bigger," Morgan said. "The pressures they're using are really quite mild and minor, so there's really no chance of it (an earthquake) getting larger."
"In other states where regulators have required operators to stop wastewater injection, the earthquakes spatially associated with the injection locations stopped almost immediately," Jim Coleman, a research geologist with the US Geological Survey, told a concerned North Texan in a letter.