There has been an ongoing battle between researchers and the natural gas and oil industries over whether or not hydraulic fracturing (fracking) is definitively leading to an increase in earthquake activity.
Since September of 2010, nearly 1,000 earthquakes have rattled Arkansas and the area around the New Madrid Fault Line. Previous to this, Arkansas had a total of 38 quakes in 2009. Yet two cities, Greenbrier and Guy had a swarm of 30 small earthquakes in a four-day period in early 2011, which paralleled fracking activity in the same area.
Now, a study has appeared from The Geology Society of America, which investigated the largest of the quakes that rattled Oklahoma and 17 other states in November of 2011. While supporting the research of others in establishing a causal link between fracking and earthquakes, they appear to have found another even more troubling aspect to the data.
Hydraulic fracturing (fracking) pumps water and chemicals into the ground at a pressurized rate exceeding what the bedrock can withstand, resulting in a microquake that produces rock fractures. Though initiated in 1947, technological advances now allow horizontal fracturing, vastly increasing oil and gas collection. (Source)
According to the RMA, “The Rocky Mountain Arsenal deep injection well was constructed in 1961, and was drilled to a depth of 12,045 feet” and 165 million gallons of Basin F liquid waste, consisting of “very salty water that includes some metals, chlorides, wastewater and toxic organics” was injected into the well during 1962-1966.
Why was the process halted? “The Army discontinued use of the well in February 1966 because of the possibility that the fluid injection was “triggering earthquakes in the area,” according to the RMA. (Source)
They drew this conclusion even after the EPA stated that this method of deep injection was safe. Over the decades that would follow, both the U.S. Army Corps of Engineers and the U.S. Geological Survey would accumulate data that showed a link between fracking and underground instability that can trigger earthquakes.
One of the first large studies of an Oklahoma earthquake swarm which began early in 2011 was conducted by the Oklahoma Geological Survey. The results were released in August of 2011 and conclude with a probable correlation within this event, as well as citing a connection made from the historical record:
The strong correlation in time and space as well as a reasonable fit to a physical model suggest that there is a possibility these earthquakes were induced by hydraulic fracturing.
Our analysis showed that shortly after hydraulic fracturing began small earthquakes started occurring, and more than 50 were identified, of which 43 were large enough to be located. Most of these occurred within a 24 hour period after hydraulic fracturing operations had ceased. There have been previous cases where seismologists have suggested a link between hydraulic fracturing and earthquakes, but data was limited, so drawing a definitive conclusion was not possible for these cases. The first case occurred in June 1978 in Carter and Love Counties, just south of Garvin County, with 70 cases in 6.2 hours. The second case occurred in Love County with 90 earthquakes following the first and second hydraulic fracturing stages. [Nicholson and Wesson, 1990] (Source)
However, there is one more concern that is addressed in the most recent study conducted by the Geological Society of America, a non-profit organization with tens of thousands of members from nearly 100 countries. According to the abstract of this study, which looked most specifically at the largest earthquake reported, a 5.7 event that occurred in November (after the study cited above):
Significant earthquakes are increasingly occurring within the continental interior of the United States, including five of moment magnitude (Mw) ≥ 5.0 in 2011 alone. Concurrently, the volume of fluid injected into the subsurface related to the production of unconventional resources continues to rise. Here we identify the largest earthquake potentially related to injection, an Mw 5.7 earthquake in November 2011 in Oklahoma. The earthquake was felt in at least 17 states and caused damage in the epicentral region. It occurred in a sequence, with 2 earthquakes of Mw 5.0 and a prolific sequence of aftershocks.
Subsurface data indicate that fluid was injected into effectively sealed compartments, and we interpret that a net fluid volume increase after 18 yr of injection lowered effective stress on reservoir-bounding faults. Significantly, this case indicates that decades-long lags between the commencement of fluid injection and the onset of induced earthquakes are possible, and modifies our common criteria for fluid-induced events. The progressive rupture of three fault planes in this sequence suggests that stress changes from the initial rupture triggered the successive earthquakes, including one larger than the first [emphasis added]. (Source)
This is a worrisome conclusion which seems to indicate that even if fracking is halted, earthquake activity can continue as a result of previous activity, and earthquake magnitude can increase over time.
Much more studying needs to be done to confirm the above, and the full results still need to be scrutinized by the scientific community. However, in light of the worries already surrounding the historically dangerous New Madrid Fault Line, we should hope that definitive action is taken sooner rather than later to halt a process that is dubious at best, and cataclysmic at worst.
Note: beyond the risk of earthquakes, fracking has other horrendous consequences. To see what life is like for some residents within fracking zones, please do not miss the film Gasland.