record for number of earthquakes in 2015: 857. That’s more than all the remaining states (excluding Alaska) combined. This morning people were shaken out of their beds by a 5.6 temblor, prompting state regulators to shut down 37 fracking waste injection wells.
Before 2009, Oklahoma got only a couple quakes a year. By the end of 2013 they were tallying 109, and measured 230 quakes in the first six months of 2014.
"Some parts of Oklahoma now match Northern California for the nation’s
most shake-prone," writes Doug Stanglin of USA Today, "and one Oklahoma region has a one-in-eight chance of a
damaging quake in 2016, with other parts closer to one in 20."
NBC News reports that this morning's quake was centered in north-central
Oklahoma near Pawnee, on the fringe of an area where regulators had stepped in to
limit wastewater disposal.
Oklahoma isn't the only frack-quake prone area. Ohio has experienced them, too.