September 8, 2016
A magnitude 5.6 earthquake shook Oklahoma on Saturday, tied for the strongest quake ever recorded in the state. Odds are it was triggered by fracking operations, specifically the subsurface injection of fracking wastewater.
There is a direct connection between fracking and earthquakes in the central and eastern United States (Figure 1). But the earthquakes are not a result of fracking itself. They mostly result from the injection of fracking wastewater at depths well-below the fracking horizon. The larger the volumes of wastewater injected into the subsurface, the larger the earthquakes can be.
