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 is the use of sand, water, and chemicals injected at high pressures to blast open shale rock and release the trapped gas inside. Horizontal drilling is just like it sounds: after the well drill reaches a certain vertical depth in the ground, the well is then drilled horizontally.