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.
What is 'Fracking' Fracking is a slang term for hydraulic fracturing, which is the process of creating fractures in rocks and rock formations by injecting specialized fluid into cracks to force them to open further. The larger fissures allow more oil and gas to flow out of the formations and into the wellbore, from where they can be easily extracted.