You should check out how the fracking process works. They inject this slurry of heavy metals, chemicals, etc.... called "mud" into the ground at high pressure to break up layers and layers of shell to make extraction easier. If this process is done near a fault line I see the likely hood of inducing tectonic activity to be high, if pressure is already present on the apposing plates. This is not to say, however, that fracking causes earthquakes, just that it facilities them; possibly to the extent that it increases the likelihood of strong quakes.

I personally am apposed to fracking, not due to the possibility of inducing quakes, but because the environmental damage is insufferable. There is a mounting pile of evidence that shows fracking to cause various health risks to the surrounding counties where fracking has occurred. The contamination of the water table alone is reason enogh to stop this counterproductive practice.