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 (hydraulic fracturing) is a term used to describe a natural gas drilling technique in which thousands of gallons of water, chemicals and sand are pumped into a shale formation to break apart rock and release the natural gas that is trapped below.he fluid is injected further into the formation as the rock fractures. The sand settles in the fractures, keeping them open. These new and open pathways allow the gas to flow freely into the well. Hydraulic fracturing is used mainly to stimulate production from oil and natural gas wells.