Hugh Pickens writes writes "Oklahoma is typically seismically stable with about 50 small quakes a year but in 2009, that number jumped up to more than 1,000 and on November 5 a 5.6-magnitude tremor rattled Oklahoma — one of the strongest to ever hit the state — leading scientists to wonder if the increasingly common use of fracking, the controversial practice of blasting underground rock formations with high-pressure water, sand, and chemicals to extract natural gas, may have put stress on fault lines. Human intervention has caused earthquakes before with one "textbook case" occurring in 1967 in India, says Peter Fairley at IEEE Spectrum, when the reservoir behind the hydroelectric Koyna Dam was filled up. The added water "unleashed a magnitude 6.3 quake" by placing stress "on a previously unknown fault, killing 180 people and leaving thousands homeless." Last week’s earthquakes and aftershocks are centered in rural Lincoln County in an area about 30 miles east of Oklahoma City and there are 181 injection wells In Lincoln County. But a recent study by Austin Holland, a seismologist with the Oklahoma Geological Survey, says that it’s possible that hydraulic fracking caused a series of small earthquakes, peaking at 2.8, in an area south of Oklahoma City but doesn’t believe fracking caused the big Nov. 5, 6 and 8 earthquakes comparing a man-made earthquake to a mosquito bite. "It's really quite inconsequential," says Holland."