The 5.7 magnitude earthquake that jolted Oklahoma in 2011 has been linked to human-caused activity—oil wastewater injection.
Scientists describe the connection in a study published Tuesday in the journal Geology.
“There appears to be a strong correlation between the wells that are injecting wastewater in Lincoln County and the earthquakes in 2011,” Katie Keranen, study co-author and University of Oklahoma seismologist, told The Oklahoman.
The study also found that the seismic activity could last years after the original wastewater injection.
“After decades instead of months of pumping, we think there's strong geological evidence to support that this is a different type of induced earthquake,” Keranen added. “The pressure built up over time rather than rapidly.”
Reporting on the study, BBC adds:
[...] the authors of the new study focus on the significantly larger and delayed events in Prague [Oklahoma], which they wrote "necessitate reconsideration of the maximum possible size of injection-induced earthquakes, and of the time scale considered diagnostic of induced seismicity".
Study co-author Geoffrey Abers of Columbia University said that "there's something important about getting unexpectedly large earthquakes out of small systems that we have discovered here," adding that "the risk of humans inducing large earthquakes from even small injection activities is probably higher" than had been believed.
Some media reports on the new study include reaction from the Oklahoma Geological Survey, who said the 2011 quake was due to natural causes, but The Oklahoman's Adam Wilmoth notes this:
The journal Geology is published by the Geological Society of America, which has called for public policy changes aimed at reducing greenhouse gasses that many scientists believe contribute to climate change. The Oklahoma Geological Survey, on its website, said its most important objective is “to maximize the ultimate recovery of the energy resources that Nature so generously has bestowed upon us.”
The new study's finding follows similar conclusions from a study last year by the U.S. Geological Survey that found the spike in earthquakes since 2001 near oil and gas extraction operations is “almost certainly man-made.”
Local news station KJRH has video: