The central US state of Oklahoma has gone from registering two earthquakes a year to nearly two a day and scientists point to a controversial culprit: wastewater injection wells used in fracking.
Located in the middle of the country, far from any major fault lines, Oklahoma experienced 585 earthquakes of a magnitude of 3.0 or greater in 2014. That’s more than three times as many as the 180 which hit California last year.
“It’s completely unprecedented,” said George Choy, a seismologist at the US Geological Survey.
As of last month, Oklahoma has already experienced more than 600 quakes strong enough to rattle windows and rock cars. The biggest was a 4.5-magnitude quake that hit the small town of Crescent.