Seismologists are tackling a troubling question with enormous implications for America’s—and the world’s—energy future: does fracking cause earthquakes? The debate is centered in Oklahoma, which has experienced a rash of earthquakes in recent years. The state has experienced more than 100 3.0+ magnitude quakes so far this year, more than five times the state’s 2009 total. Scientists suspect that fracking, which has taken off in recent years, might have something to do with it. Reuters reports:
Most earthquakes occur naturally, but the increases in frequency and magnitude are distinct new elements, researchers say. While there are already many studies linking work at injection wells to earthquakes, [Seismologist Austin Holland] and other scientists are focusing on how the quakes are triggered and on measures to mitigate seismic activity.
It’s important to delineate the mechanisms by which fracking is reportedly related to this uptick in earthquakes, because the actual process of pumping slurries into underground fissures at high pressures—hydraulic fracturing, or “fracking”—hasn’t been shown to cause earthquakes itself. Instead, scientists hypothesize two other ways in which the aftermath of fracking has released pent-up seismic stress. First, removing underground hydrocarbons leaves empty spaces behind, and as the ground settles—a process called subsidence—it can stress fault lines and potentially set off earthquakes. Second, disposing of the wastewater in underground wells, which has long been a practice in the oil and gas industry, puts new pressure on fault lines, possibly setting off quakes.
The oil and gas industry is experimenting with solutions to both of these problems. Some firms are looking at pumping carbon dioxide underground to fill up the empty spaces left behind after drilling, sequestering the greenhouse gas and preventing subsidence all in one fell swoop, but the technology isn’t yet commercially viable. The industry is much further along in addressing the wastewater disposal problem, as many are already moving towards recycling and reusing wastewater, keeping the water out of disposal wells.
Truthfully, we don’t know yet if the relationship between fracking and earthquakes in Oklahoma is correlation or causation, but given the importance of shale energy to America’s economic and energy security, this is absolutely an issue to take seriously. We’ll be watching.