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.
However, faults also exist in South Texas, an area currently experiencing a fracking boom with thousands of wastewater wells, yet is reporting little to no seismic activity, Frohlich said. Also, the Bakken Shale in North Dakota is in the midst of an oil boom thanks to hydraulic fracturing â yet no earthquakes.