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The earthquake capital of the United States is not California, as many may think, but Oklahoma, according to an analysis posted here last year. Quakes are triggered by the disposal of wastewater, a waste product from fracking, into deep injection wells. Ohio and Texas are also affected.
Ironically, the injection wells were "once considered the most environmentally responsible way for oil companies to deal with their wastewater," writes David Baker, who covers energy and clean tech for the San Francisco Chronicle.
Baker reports on a new research that reveals these man-made quakes are likely affecting Kern County, the center of California's oil production. The Golden State is the third highest oil producer in the United States, after Texas and North Dakota, which aren't as seismologically active as California.
Researchers on Thursday [Feb. 4] tied a September 2005 swarm of moderate earthquakes in Kern County to three wastewater disposal wells... The research paper, published by the American Geophysical Union, could not prove with absolute certainty that the wastewater injections caused the quakes, (B)ut the authors calculated only a 3 percent chance that the Kern County swarm was mere coincidence.
The study also does not offer any indication of how common such human-induced quakes may be in California. “However, considering the numerous active faults in California, the seismogenic consequences of even a few induced cases can be devastating,” the authors note.
How injection wells cause earthquakes
In addition to chemical-laced water used in fracking, naturally occurring ground water mixed with petroleum surfaces when drilling which "can either be treated for reuse, dumped into evaporation ponds or pumped back underground for disposal," writes Baker.
Scientists had previously tied quakes to underground injections of water into California’s geothermal energy fields, but not to injections of oil-field waste water.
The wastewater and groundwater that is not reused or sent to evaporation ponds is pumped into deep injection wells, "often into different rock formations than it came from — they can change the pressure within the rocks, making faults more likely to slip," writes Baker.
The quakes included in the new study, which struck near the Central Valley’s southern edge, weren’t large, with the most powerful registering magnitude 4.7. But injection wells have been linked elsewhere to quakes as large as magnitude 5.6, said the research paper’s lead author, Thomas Goebel, with UC Santa Cruz.
California’s oil field regulating agency — the Division of Oil, Gas and Geothermal Resources [DOGGR] — is trying to get a sense of how prevalent the problem may be, a spokesman said Thursday. The agency has commissioned Lawrence Berkeley National Laboratory to study the issue
In addition to being associated with earthquakes, DOGGR and non-profits like the Center for Biological Diversity have been researching how the disposal of wastewater from fracking could be poisoning groundwater and drinking water aquifers.
Hat tip to MTC-ABAG Library