The process of fracking can be natural and man made. Either way it is done, the result is the same. This is when a liquid is pressed up against a rock bed which causes it to break or fracture. The most common use for this process is in the oil and natural gas exploration field, but it can also be used to stimulate a groundwater well.
The first use of fracking rock was in North Carolina around 1903. At the Mount Airy quarry, fracking was and still is, used to separate the granite rock from the surrounding rock bed. This process was modified in 1947 to fracture the rock bed deep in the earth through the borehole of a well. It was so successful that it became common practice by 1949. Today, this practice is still used around the world to help extract additional trapped energy reservoirs.
Once the rock bed was cracked or fractured, a means was need to keep these newly developed openings from closing. This is the purpose of adding sand to the water. This slurry has worked very efficiently because the sand is porous enough to allow the water, oil, and natural gas to be released but has enough integrity to keep the rock from closing again once the pressure is released.
Microseismic monitoring is the way those causing the fracking to locate and identify where the fractures occurred in the borehole and surrounding rock bed. With the information from the monitors, a map can then be produced and used by the engineers of the well.
The injection rate of the slurry mixture of water and sand can be as high as 100 barrels a minute or 265 liters per second. The actual pressure that builds up, which causes the fracking of the rock bed, can be as great as 15000 psi.