"A dramatic jump in the number of earthquakes in Oklahoma to a rate never seen there by scientists before, appears to be caused by a small number of wells where wastewater associated with oil and gas production is injected into the ground, a study released on Thursday said.

Just a few of these so-called disposal wells, operating at very high volumes, "create substantial anthropogenic seismic hazard," according to findings from Cornell University researchers published in the journal Science.

Earthquake activity in Oklahoma has skyrocketed in recent years, and the U.S. Geological Survey recently warned that the state faces increasing risk of more potentially damaging earth-shaking activity.

Through the end of June, the number of potentially damaging earthquakes - magnitude 3.0 or larger - was up more than 120 percent compared to all of last year, according to state officials."

Carey Gillam reports for Reuters July 4, 2014. [2]