(NaturalNews) Yet another study has linked fracking and similar oil and gas mining practices to earthquakes, this time in Texas.
The new study was conducted by researchers from China University of Geosciences and the University of Texas at Austin and published in the Proceedings of the National Academy of Sciences. The researchers analyzed 93 separate earthquakes that took place in Texas between March 2009 and December 2010. They found that many of the earthquakes occurred shortly after oil and gas companies had injected carbon dioxide into their wells.
"The timing of gas injection suggests it may have contributed to triggering the recent seismic activity," the researchers wrote. "If so, this represents an instance where gas injection has triggered earthquakes having magnitudes 3 and larger."
Carbon dioxide is injected into aging oil and gas wells as a way of extending their output. As easy-to-obtain oil and gas runs out around the world, such extreme drilling practices are becoming more common. For example, Occidental Petroleum says that nearly 60 percent of its West Texas and southeast New Mexico oil production uses carbon dioxide flooding techniques.
Carbon dioxide flooding is similar to the more well-known technique of hydraulic fracturing, or fracking, in which water is used to crack open subterranean rocks to facilitate the extraction of oil and gas. This produces huge quantities of toxic and radioactive wastewater. One of the favored techniques for disposing of fracking wastewater is to simply inject it into the ground again, usually in a different location.
Fracking wastewater injection has been strongly linked to earthquakes, most recently in a study conducted by researchers from Columbia University and published in the journal Geology. In that study, the researchers showed that this practice was most likely responsible for the 5.7 magnitude earthquake that struck Prague, Oklahoma, in November 2011. That earthquake, felt in Milwaukee more than 800 miles away, destroyed 14 homes and damaged a federal highway.
The study was possible because the 5.7 quake had actually been preceded by a 5.0 quake, which caused a University of Oklahoma seismologist to set up several seismographs as a way of recording aftershocks. This enabled scientists to discover that the 5.7 quake came from a fault rupture no more than 650 feet from active wastewater injection wells, and in the same level of rock. Further research showed that 13 years of wastewater injection had caused the injection pressure to rise more than 10 fold.
"When you overpressure the fault, you reduce the stress that's pinning the fault into place and that's when earthquakes happen," study coauthor Heather Savage said.
The researchers noted that the 5.7 earthquake was actually the result of a series of several smaller quakes, which in turn seem to have been caused by wastewater injection. This suggests that earthquakes can be caused even by relatively small injection sites.
"There's something important about getting unexpectedly large earthquakes out of small systems that we have discovered here," coauthor Geoffrey Abers said.
Scientists have known since at least the 1960s that underground fluid injection can lead to earthquakes. Water injection into oil wells was also linked to Texas earthquakes that occurred between 1975 and 1982. More recently, researchers have linked underground injection to earthquakes in Arkansas and Colorado and blamed it for an 11 fold jump in the rate of earthquakes in the central U.S. over the past three decades. The National Academy of Sciences has called for further research to help understand and respond to this growing threat.
Other human activities have also been shown to cause earthquakes, including geothermal drilling, water impoundment by large dams, enhanced oil recovery, rock quarrying and solution salt mining.