As the practice of hydraulic fracturing to produce natural gas continues to spread not only in the U.S. but worldwide, the scientific community has increasingly focused on the environmental consequences of the technique. The most worrisome side effect of "fracking" is the rise of earthquakes in areas where the practice is extensive.
The latest evidence comes in the form of an article in the March 26 issue of Geology, a publication of the Geological Society of America.
Entitled "Potentially induced earthquakes in Oklahoma, USA: Links between wastewater injection and the 2011 Mw 5.7 earthquake sequence," the study was coauthored by University of Oklahoma Geophysics Professor Katie Keranen, U.S. Geological Survey geophysicist Dr. Elizabeth Cochran and Columbia University's Lamont-Doherty Earth Observatory's seismologist Dr. Heather Savage and Dr. Geoffrey Abers.
The study focused its research on seismic activity in Oklahoma over the past two years and concluded that a 4.8-magnitude earthquake centered near Prague on Nov. 5, 2011, was "induced" by the injection wells. Two subsequent earthquakes, including a 5.7-magnitude "event" the following day, was the biggest in contemporary state history, were caused by the first earthquake and existing tectonic stresses in the earth.
Oklahoma's Nov. 6, 2011 earthquake was the state's largest recorded with modern instrumentation. Two people were injured in the quake, which destroyed 14 homes, buckled pavement and was felt in 17 states, as far north as Wisconsin.
Professor Keranen said during an interview that there is excellent seismic data to back up the paper's conclusions, stating, "The evidence that we collected supports this interpretation. We can say several things with certainty: That the earthquakes begin within hundreds of meters of the injection wells in the units they inject into, so spatially we don't have much doubt, there is a direct spatial link."
The credentials of Keranen's coauthors are impressive. Dr. Abers is Associate Director of Seismology, Geology and Tectonophysics of the Lamont-Doherty Earth Observatory and Dr. Savage Lamont, Assistant Research Director, while in October 2011, President Barack Obama named Dr. Cochran a recipient of a Presidential Early Career Award for Scientists and Engineers for her contributions to the understanding of earthquake physics and earthquake triggering, the physical properties and geometry of earthquake fault zones and their evolution after earthquakes, and to the development of a new method of earthquake monitoring using low-cost earthquake sensors, the "Quake-Catcher Network (QCN)."
The pair's methodology was thorough. The paper reported that within 24 hours of the first earthquake Dr. Keranen and Oklahoma Geological Survey research seismologist Austin Holland set up seismic recorders in the area. The Geology study reports that 1,183 aftershocks were recorded by the seismic network and subsequently examined, of which 798 were studied closely.
Oklahoma's official seismologist, the Geological Survey's Austin Holland is skeptical of the link between injection wells and earthquakes, stating that more research is needed, with the OGS stating, "The interpretation that best fits current data is that the Prague Earthquake Sequence was the result of natural causes." Holland's view is, not surprisingly, shared by the Corporation Commission and the Oklahoma Independent Petroleum Association, a trade group that lobbies for the interests of oil and gas producers.
Farther afield, seismologists suspect that oil and gas activity may have triggered earthquakes in Texas, Arkansas, Colorado and Ohio. States have adopted differing approaches to the issue, but there is now no doubt that the seismic issue is beginning to impact state legislatures considering fracking activities. Regulators in Arkansas voted to ban injection wells from one particular region after a series of earthquakes rattled the state two years ago. Oil and gas regulators in Colorado now require a review by a state seismologist before injection well permits are issued, and Illinois has passed legislation requiring injection wells to stop operating if related earthquakes cause a public safety risk. But as of yet, earthquake risk has not impacted state fracking regulations in California, Texas, New York or Oklahoma.
In any case, it would appear that Holland and his fellow skeptics will not have long to wait to comment yet again on local earthquakes, as on March 4, the U.S. Geological Survey reported that a 3.5-magnitude earthquake struck southern Oklahoma, also centered around Prague.
In the last four years, the number of quakes in the middle of the United States surged 11-fold from the three decades prior.
Something to ponder when you read the hydrocarbon industry rubbishes the latest scientific research on fracking as "fuzzy science."
Cross-posted with Oilprice.com
John C.K Daly is the chief analyst at the energy news site Oilprice.com. Dr. Daly received his Ph.D. in 1986 from the School of Slavonic and East European Studies, University of London.
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