An anonymous reader writes: Oklahoma has already experienced about 240 minor earthquakes this year, roughly double the rate at which California has had them. A recent study (abstract) has now tied those earthquakes to fracking. From the article: "Fracking itself doesn't seem to be causing many earthquakes at all. However, after the well is fracked, all that wastewater needs to be pumped back out and disposed of somewhere. Since it's often laced with chemicals and difficult to treat, companies will often pump the wastewater back underground into separate disposal wells. Wastewater injection comes with a catch, however: The process both pushes the crust in the region downward and increases pressure in cracks along the faults. That makes the faults more prone to slippages and earthquakes.
... More specifically, the researchers concluded that 89 wells were likely responsible for most of the seismic activity. And just four wells located southeast of Oklahoma City were likely responsible for about one-fifth of seismic activity in the state between 2008 and 2013."