A preliminary 5.6 magnitude earthquake rattled Oklahoma and several other states on Saturday morning.
The center was believed to be northwest of Pawnee, Oklahoma, about 55 miles from Tulsa. People as far north as Fargo, North Dakota, and as far south as San Antonio, Texas, said they felt it.
In March, the U.S. Geological Survey released a map showing its forecast of damage from earthquakes. It was the first time the maps included human-induced earthquakes — from processes like fracking and wastewater disposal — instead of just naturally occurring ones. The three states with the potential highest hazards were Oklahoma, Kansas and Texas — three of the states most widely affected by Saturday's quake.
According to the USGS, the number of earthquakes per year with a magnitude of 3 or higher in the central and eastern parts of the country have more than quadrupled in recent years. It reports the central and eastern U.S. saw an average rate of 21 earthquakes per year with a magnitude of 3 or higher between 1973 and 2008. That number jumped to 99 per year between 2009 and 2013. In 2014 alone? There were 659.
Immediately after Saturday's quake, people on Twitter were blaming fracking.
The U.S. has seen a significant increase in the number of fracking wells over the past 15 years or so.
But even according to USGS, fracking causes small earthquakes that are "almost always too small to be a safety concern." And it says fracking isn't the main cause of human-induced earthquakes in the central part of the country. Instead, it says wastewater disposal from fracking and other drilling operations are to blame. But it's quick to point out that a number of factors go into the earthquakes that are caused by wastewater disposal.
Even so, Oklahoma has experienced a lot more earthquakes over the past few years. According to the state, there were 109 magnitude 3 or greater earthquakes in 2013. In 2015, 907 were reported.