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Study links large overseas earthquakes to tremors at US fracking sites

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A team of U.S. researchers has claimed that powerful earthquakes taking place thousands of miles away can have an impact in areas where oil and gas is extracted from wells in the Unites States. A new report, published in the journal Science, said that the findings can help explain an increased rate of earthquakes in the central Unites States, where fracking is being used as a primary means to extract natural gas, Reuters reported.

Large earthquakes around the world have been linked to tremors at U.S. sites where wastewater from gas drilling operations is injected into the ground, the study found. For example, the massive 9.0 magnitude earthquake in Japan in 2011 started a series of earthquakes in the town of Snyder, Texas, near the Cogdell oil field. These led to a 4.5 magnitude quake there about six months later, researchers noted. Similarly, smaller quakes were observed near injection wells in Prague, Okla., shortly after the 8.8 magnitude quake in Chile in 2010. Unusual seismic activity shook the region 16 hours after the Chile quake, when a 4.1 magnitude tremor was detected. Quakes continued until a 5.7 magnitude quake in November 2011, explained researchers at Columbia University's Lamont-Doherty Earth Observatory, who conducted the study.

Meanwhile, the big earthquake in Chile also led to increased seismic activity in Trinidad, Colo. There was a 5.3 magnitude quake in August 2011, in an area where methane is extracted from the coal bed and where wastewater is injected underground.

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Results from the study were announced at the same time as the U.S. Environmental Protection Agency (EPA) is carrying out research on the impact of fracking on the environment, looking at wastewater disposal in particular. The EPA started the research after a series of studies found evidence that seismic activity was repeatedly detected around fracking sites which have not been active in the past.

Nicholas van der Elst of Columbia University, leader of the study, commented that researchers had not been confident in the link between wastewater injection and earthquakes but they have found evidence that the fluids that are injected in wells contribute to underground faults reaching their tipping point and triggering small to medium strength tremors. If you look at earthquakes in isolation, they certainly look like a coincidence but a systematic analysis reveals the presence of a physical relationship, he said.

A separate study published in Science stated that there were 300 earthquakes in the central United States from 2010 to 2012 with a magnitude of 3.0 or more, compared to an average of 21 such quakes per year between 1967 and 2000. The change coincides with the natural gas revolution in the country over the past few years. The technique used, known as fracking, relies on using large amounts of fluids to crack open rocks and access natural gas.

The U.S. oil and gas industry has reacted cautiously to the report. Kathryn Klaber, chief executive of the Marcellus Shale Coalition, told Reuters that more fact-based research will be needed to further reduce the already low rates of occurrence of seismic activity and to promote safer and more responsible natural gas development.

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