Monday, September 29, 2014

USGS study links fracking wastewater injection with surge in Raton Basin earthquakes

A surge in earthquakes in southern Colorado and New Mexico has almost certainly been caused by the injection of fracking wastewater deep into the ground, U.S. Geological Survey scientists reported last week. The study details several lines of evidence directly linking the injection wells to the seismicity. The timing and location of the quakes is clearly linked with the the documented pattern of injected wastewater. Detailed investigations of two seismic sequences (2001 and 2011) places them in proximity to high-volume, high-injection-rate wells, and both sequences occurred after a nearby increase in the rate of injection. A comparison between seismicity and wastewater injection in Colorado and New Mexico reveals similar patterns, suggesting seismicity is initiated shortly after an increase in injection rates. For example, two injection wells near the epicenter of a 2011 5.3 earthquake had about 5 million cubic meters of wastewater injected just before the quake — more than seven times the amount injected at the Rocky Mountain Arsenal well that caused damaging earthquakes near Denver, Colorado, in the 1960s. The August 2011 M 5.3 event is the second-largest earthquake to date for which there is clear evidence that the earthquake sequence was induced by fluid injection. The study looked at the Raton Basin, which stretches from southern Colorado into northern New Mexico. The basin was seismically quiet until shortly after major fluid injection began in 1999. Since 2001, there have been 16 quakes magnitude 3.8 or greater (including M 5.0 and 5.3), compared to only one (M 4.0) the previous 30 years. The increase in earthquakes is limited to the area of industrial activity and within 5 kilometers of wastewater injection wells...more

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