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 or hydraulic fracturing is a method utilized by oil and gas companies to increase production of oil or gas from a well that would otherwise exhibit a low flow rate usually due to the geologic rock formation being too dense to allow for the economic recovery of hydrocarbons.