The State of Oklahoma sits on the "stable craton" of North America, far from active tectonic regions. Nevertheless, prior to 2011, it had a history of occasional earthquakes, likely induced by pressure shifts along old suture lines in the deep, Precambrian basement rock (see Unsettled Basement).
Over the past five years, however, the incidence of earthquakes has exploded across Oklahoma. Following a magnitude 5.6 earthquake near Prague, in November of 2011 (the strongest recorded in the State's history), the number of quakes has been climbing dramatically from year to year. Before 2008, Oklahoma experienced an average of 1-2 magnitude 3.0 or greater earthquakes per year; more than 900 occurred in 2015 and a magnitude 5.1 quake occurred near Fairview this past weekend.
State officials have reluctantly come to conclude that this seismic shift is directly related to the use of deep disposal wells in the fracking process. As one might expect, the oil and gas industry has attempted to minimize this association and has fought efforts to be held financially responsible for damage caused by the earthquakes. They might want to consult the tobacco industry, which has managed to evade public responsibility for many decades now.