I think this guy pretty much tells the story from the comment section of the article.....
In my youth, I worked on a team doing seismic test for oil. When you drill into the earth, you have no idea what the underlying structure is 50ft away from the drill hole. You have no idea of cracks or differences in soil composition and anyone who tells you otherwise is looking you right in the face and telling you a lie. So you put a hydraulic fluid in this unknown place and develop cracks and fissures to draw out the gas. You have no idea what is happening a hundred feet away from your new gas collecting space. Having someone tell you there will not be a big earthquake because statistics have shown there haven’t been any so far is like the carnival guy telling you to buy his bottle of oil that will cure your gout and grow hair on your head at the same time. They do not know what gases are put out at the wellhead. They do not know if the fluids will migrate out to water aquifers. They do not know if there will be major earthquakes. They do know it is putting money in their pockets. http://www.huffingtonpost.com/2012/06/15/fracking-earthquakes-low-risk_n_1600515.html