Several recently-released studies have examined whether any link exists between hydraulic fracturing activities and recent seismological events. Rather than shaking up common industry understandings, these studies create confusing rumblings from media outlets reporting on the studies. These incomplete media reports create needless confusion as to the tenuous link between hydraulic fracturing operations and seismic activity. In short, no study has directly linked hydraulic fracturing activities to any increase in seismic events.
The closest study of which we are aware comes from the U.K. In response to two low-level earthquakes near Blackpool, England in April and May of 2011, an area well operator commissioned a number of studies regarding any link between the earthquakes and their operations. Britain’s Department of Energy and Climate Change released earlier this month a report indicating that the operator’s activities likely induced the two small earthquakes, but that additional controls and monitoring could be implemented to prevent future seismic events from occurring. Specifically, the report noted that “direct fluid injection into an adjacent fault zone” helped to trigger the seismic events, and it recommended that “seismic hazards should be assessed prior to proceeding with [fracturing] operations”. An earlier version of this report noted that it took a rare confluence of several factors (primarily geologic ones) to produce this event.
At best, these studies have linked individual seismological events to limited instances of wastewater disposal into injection wells sited near fault lines or other seismologically sensitive areas. Various media reports claiming a connection between hydraulic fracturing and earthquakes have rushed to conflate the disposal of wastewater from oil & gas activities (among many other industrial activities) with “fracking” as a cause of earthquakes. For example, the U.S. Geological Survey recently published an abstract of a study it presented at a conference earlier this month; in the study the USGS examined earthquake data in the midcontinental U.S. since 1970, particularly the recent uptick in earthquakes in that region. The abstract never mentions hydraulic fracturing. Instead, it only states that recent changes in seismicity rates are “almost certainly man-made” and that some recent seismic events in Arkansas are likely linked to “deep waste water injection wells.”
Nonetheless, numerous media outlets jumped at the abstract as a possible indicator that the federal government had found the smoking gun many environmental groups insist must be present. The level of misinformation became so pernicious that the Deputy Secretary of the U.S. Department of the Interior released a statement several days later clarifying that “there is no evidence to suggest that hydraulic fracturing itself is the cause of the increased rate of earthquakes.” Here is a larger excerpt from the Deputy Secretary’s April 11 statement:
USGS’s studies do not suggest that hydraulic fracturing, commonly known as “fracking,” causes the increased rate of earthquakes. USGS’s scientists have found, however, that at some locations the increase in seismicity coincides with the injection of wastewater in deep disposal wells.
Wastewater is a byproduct of oil and natural gas production from tight shale formations and coal beds. Generally, wastewater produced from many oil and gas production wells within a field may be injected through a single or just a few disposal wells.
In preliminary findings, our scientists cite a series of examples for which an uptick in seismic activity is observed in areas where the disposal of wastewater through deep-well injection increased significantly. These areas tend to be in the middle of the country – mostly in Colorado, Texas, Arkansas, Oklahoma and Ohio.
A similar reaction played out with respect to the Dec. 31, 2011 Youngstown, OH earthquakes that we previously discussed, even though Ohio DNR clearly noted in its March 2011 preliminary report that a “number of coincidental circumstances appear to make a compelling argument for the recent Youngstown-area seismic events to have been induced [by operation of the injection well].” And none of the operations analyzed in the studies discussed above conducted any pre-drilling seismological information that might have warned the operators or regulators of future seismic activity. Ohio, among other states, is proposing regulations and increased agency staffing to address this problem going forward.
Takeaways: Be skeptical of what you read regarding any linkage between fracking and earthquakes. Correlation does not equal causation. And instances exhibiting a correlation between hydraulic fracturing activities, including injection well disposal, and seismic activity are rare and site-specific — especially as to site geological conditions.