The fluid pumped underground can change alter pressure in faults, spurring quakes.
Oklahoma had some seismic activity prior to 2008, with one or two earthquakes (magnitude 3 or higher) a year. But that jumped in 2009, going from two in 2008 to 20 in 2009. In 2015, Oklahoma experienced 887 magnitude 3 or higher earthquakes, according to the U.S. Geological Survey.
Between June 2008 and July 2017, Oklahoma saw more than 2,600 magnitude 3 or higher earthquakes. The USGS now says that Oklahoma has more earthquakes on a regular basis than California. And Casey, a postdoctoral researcher at University of California Berkeley, found that more earthquakes means more Google searches for anxiety, according to a recently published study in the journal of Environmental Epidemiology.