The vast majority of earthquakes occur at the boundaries of tectonic plates, but did you know that some occur within the interior of a plate? The mechanism behind such intraplate earthquakes is not fully understood, but one prevailing theory is that they originate from buried ancient fault zones in weak areas of the continental crust.

A few examples of intraplate source zones include Australia, the New Madrid Seismic Zone in the central United States, and the interior of the Indian plate.

Another potential source of intraplate earthquakes is induced seismicity from the injection of wastewater from oil and gas operations and the extraction of gas by hydraulic fracturing (fracking). The increasing practice of deep fluid injection is linked to a sharp rise in the rate of small to moderate magnitude earthquakes in the central and eastern U.S. starting in 2009.