Fracking-related injection wells are likely behind the "remarkable" increase in earthquakes in Oklahoma, scientists with the U.S. Geological Survey have said.
The USGS and the Oklahoma Geological Survey on Friday issued a joint statement warning that the surging seismicity — up roughly 50 percent since October 2013 — means that central Oklahoma is at a significantly increased risk of a 5.5 or greater quake.
Since just the start of this year, 145 earthquakes of magnitude 3.0 or greater have struck the state, breaking the record 109 set last year.
Those numbers are a far cry from the two 3.0 magnitude or larger earthquakes per year that occurred between 1978 and 2008.
The USGS stated that the changes "do not seem to be due to typical, random fluctuations in natural seismicity rates."
Rather, the USGS analysis points to wastewater injection wells from the oil and gas industry as a likely culprit. Fracking operations use these Class 2 wells to inject the mystery mix of waste fluids into the earth. A 2010 EPA analysis showed that Oklahoma had over 10,000 such wells.
A recent study by the USGS also points to wastewater injection as the likely cause of the November 2011 5.0 magnitude earthquake that struck Prague, Oklahoma, and proceeded to cause a series of "thousands of aftershocks."
The USGS has previously remarked on the surge in earthquakes nationwide, with over 100 per year on average from 2010 - 2013, in contrast to the average rate of 20 earthquakes per year from 1970-2000, noting that some of the areas of increased seismicity coincide with injection wells.
The USGS states: "As the use of injection for disposal of wastewater increases, the importance of knowing the associated risks also grows. To meet these challenges, the USGS hopes to increase research efforts to understand the causes and effects of injection-induced earthquakes."