In order to better identify and understand oil and gas bearing formations, a technique called seismic imaging is used in conjunction with hydraulic fracturing. Seismic trucks generate sound waves above ground, and ultrasensitive devices called geophones record how the sound waves echo below the surface. The resulting microseismic mapping is used to not only determine the best location for the well but also to develop an optimal drilling plan.
This monitoring process produces extensive data, so seismic activity or any activity associated with hydraulic fracturing is thoroughly understood. A review of published research shows no cases of injuries or damage as a result of the very low level of seismicity related to this well-completion technique, in more than one million applications.
In one comprehensive study that monitored several thousand shale fracture treatments in various North American shale basins, the largest movement recorded had a measured magnitude of about 0.8. To put that in context, such a movement contains 2,000 times less energy than a 3.0 magnitude, (the benchmark commonly used to chart deep earthquakes that can be felt at the surface of the earth), and much less than one that could cause surface damage.