"And what others may consider concern, we consider potential. As two plates of Earth's crust naturally shift along their fault line, they can sometimes get hung up on rocky "hooks" called asperities. As the plates keep trying to move, stress builds and builds. The huge earthquakes we all fear occur when the stored energy has built enough to break through the asperity: the gradual slide becomes a destructive jerk.
Small tremors, on the other hand, reduce the pressure one bit at a time. Whenever there is a major earthquake or a discussion of when California or Vancouver or Japan will get hit with the next Big One, someone often laments, "If only we had a way to release the pressure beforehand!""
Find additional research here: http://turnkeyoil.com/2012/02/02/tell-the-fracking-truth/