We might wonder why anyone should be surprised that there are seismic effects from a seismic activity. The hydraulic fracturing process pumps fluid into the earth at up to 15,000 psi. For comparison, a crocodile's bite can be around 2,000 psi. The pressure in the Mariana Trench in the Pacific Ocean at a depth of over 30,000 feet is about 15,750 psi.
Nelson cites studies that show a marked increase in earthquakes in the Barnett Shale play in Texas and "earthquake swarms" in the Fayettville Shale Play in Arkansas. In Texas, preliminary findings indicate a "possible correlation" between injection wells and earthquakes. In Arkansas, the quakes have become so frequent that they have alarmed residents. Nelson writes,
In late October, the website for Arkansans for Gas Drilling Accountability stated: "We now have a total of over one hundred earthquakes for October and we still have days to go. Just think. Fracking and injection wells cause earthquakes...earthquakes can damage cement casings...cement casings are the front line defence to protect our water from toxic fracking fluids."Pennsylvania is a pretty seismically quiet state. But with the possibility of tens of thousands of wells being drilled and cased in coming years, is it worth possibly cracking them and the increased water toxicity that can come?
Read on here.