The range of 60-70 decibels sound pressure level is about as loud as normal conversation in 1 meter distance. The distance from the ears to the sound source is very important to the value of the SPL. Scroll down to related links and look at Table of Sound Pressure Levels.
1 Primarily, during the fracking process:  [Earthquakes] were caused by fluid injection during hydraulic fracturing in proximity to pre-existing faults.. 2  Secondarily, via the disposal of fracking wastewater via underground injection.
Fracking likely causes earthquakes, but only low magnitude ones that humans don't notice. There is no evidence that it causes high magnitude earthquakes. They've been fracking heavily in Nebraska and there hasn't been an earthquake in decades (an earthquake noticeable by humans that is).