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 has been documented in 10 California counties â Colusa, Glenn, Kern, Los Angeles, Monterey, Sacramento, Santa Barbara, Sutter, Kings and Ventura. Oil companies have also fracked offshore wells hundreds of times in the ocean near Californiaâs coast, from Seal Beach to the Santa Barbara Channel.