Between 1978 and 2008, Oklahoma experienced an average of just two quakes of 3.0 magnitude of greater. In 2014, as of Thursday, there have been about 207 such quakes recorded in the state, according to the U.S. Geological Survey.
The upward trend started in 2009, with 20 quakes of 3.0 magnitude or greater, then 43 the following year, and jumping every year with the exception of 2012.
California has seen 140 3.0-plus quakes this year to Oklahoma's 207. Why the sudden increase? Scientists from the U.S. Geological Survey believe that the blame may lie with wells that discard wastewater from oil and gas drilling operations by pumping it deep underground:
A report issued last year by the U.S. Geological Survey found that most of these new earthquakes have taken place near active injection wells. Geophysicist William Ellsworth, the lead author of the report, wrote that it is completely plausible that the high water pressure often used in wastewater injections could nudge previously dormant faults out of their “locked” positions. The quakes, he wrote, are “almost certainly manmade.”
The practice is similar to "fracking," though the goal of fracking is to release new oil and gas, not discard drilling byproducts. It doesn't appear that anyone has been killed or seriously injured in any of the state's recent quakes.