Hydraulic fracturing (fracking) is back in the news since the Ohio Department of Natural Resources indicated that it was likely that disposal of those fluids after the actual fracturing operation was likely the cause of seismic activity in the Youngstown area, the largest of which was a magnitude 4.0 on 20111231. It turns out that it us usually not the fracturing activity itself that caused the seismic, but rather deep well injection for disposal of the spent fluids after use.
This not the only potential problem with this procedure, however. I have written about the process before, but am returning to give a more in depth treatment of it. I was first drawn to the subject when earthquakes occurred in Guy, Arkansas last year. The Guy area is not known for seismic activity, but sure enough after deep well injection of the spent fluids began so did the earthquakes.
Before we look at the potential problems with this process, we should look into why it is done and some historical background. It turns out that the process is over a century old.