http://oilprice.com/Energy/Energy-Ge...rthquakes.html
Oklahoma is a leading U.S. energy producer with an economy increasingly concentrated on the oil and gas industry. Economist and Dean of the University of Central Oklahoma’s College of Business Administration, Dr. Mickey Hepner, notes that roughly 25 percent of all employment in Oklahoma is either directly or indirectly connected to the energy industry.
The good news is that much of Oklahoma’s output increasingly comes from releasing subterranean hydrocarbons via hydraulic fracturing, or “fracking,” a controversial technique that involves injecting liquids containing a variety of substances deep underground to break up geological formations to release trapped deposits of natural gas.
The bad news in Tulsa is that since fracking began, the state has experienced a rise in seismic events. In a report entitled “Earthquake Swarm Continues in Central Oklahoma,” released on 22 October in partnership with the Oklahoma Geological Survey, the U.S. Geological Survey noted, “
Since January 2009, more than 200 magnitude 3.0 or greater earthquakes have rattled Central Oklahoma, marking a significant rise in the frequency of these seismic events… Studies show one to three magnitude 3.0 earthquakes or larger occurred yearly from 1975 to 2008, while the average grew to around 40 earthquakes per year from 2009 to mid-2013. ‘We've statistically analyzed the recent earthquake rate changes and found that they do not seem to be due to typical, random fluctuations in natural seismicity rates. Bill Leith, USGS seismologist noted, ‘These results suggest that significant changes in both the background rate of events and earthquake triggering properties needed to have occurred in order to explain the increases in seismicity. This is in contrast to what is typically observed when modeling natural earthquake swarms.’"