*I'm gonna cross-post this to 'Muddog's - 4.2 mag quake in Kansas' thread as well.
Article from 12/14/13


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The State of Oklahoma has never been known as a particularly earthquake prone area with approximately 50 minor quakes on an annual basis. Residents have experienced nearly 2,600 over the past year. This huge increase in seismic activity has sparked the interest of scientists. These researchers have hypothesized that the increase in earthquakes may be directly linked to the increase of hydraulic fracturing or fracking by area gas and oil companies

[link to commonground.edrnet.com]