After a series of earthquakes hit Southern California recently, some residents and city officials turned their attention to hydraulic fracturing— or fracking — and possible links between the controversial practice and seismic activity.
But what is the evidence behind this claim?
“There are some earthquakes in the U.S. that have been linked to fracking,” said Justin Rubinstein, a geophysicist with the U.S. Geological Survey, on Take Two. “But these are earthquakes on the order of about magnitude 3.”
Most notably, there’s been an increase of sesimic activity in Oklahoma: the state averaged just one magnitude 3 earthquake per year in the 40 years up to 2009. That’s risen to 40 per year since 2011, said Rubinstein.
But the geophysicist cautioned against making the link to recent seismic activity in Los Angeles.
“Right now, I don’t believe there’s any evidence that indicates these earthquakes are related to waste water injection or fracking within the Los Angeles area,” said Rubinstein.
The greater concern is over waste-water injection, said Rubinstein, a practice in which salt water and the waste from drilling is thrust deep into the earth and can have the potential to disrupt already-existing fault lines.
These injection wells can take place in a gas field whether or not fracking is taking place.
A January study from the USGS found an increase in seismic activity across Western states where oil and grass drilling is taking place, but noted that fracking is only “very rarely” the direct cause of the quakes.
It also notes that “induced earthquakes,” or quakes caused by man-made activites, have been documented for decades and can be caused by a variety of factors, including “impoundment of water in reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations.”
Science is a careful, complex process that can be at odds with how the public views a current topic, said Dr. Jay Malone, executive director of the History of Science Society at Notre Dame University.
“We like to think of science as having these Eureka moments where scientists can tell us definitely this thing happened for this reason,” said Malone. “And it just usually doesn’t happen this way.”
Environmentalists, such as those with the Center for Biological Diversity, warn that a fracking boom poses the risk of increased seismic activity, while the industry maintains that the warnings are overblown.
In the meantime, Rubinstein and scientists at the USGS say more research needs to run its course before the link is established in quake-prone Southern California.