Lorca 5.1 earthquake: Blame Spain's farmers and their deep wells?
Spain's worst earthquake in 50 years may have been triggered by farmers drilling deep wells to water their crops, says a new study. With the rise in 'fracking,' man-made earthquakes are a focus of seismic study.
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"There have been earthquakes of similar intensity and similar damage caused in the 17th, 18th and 19th centuries when there was no excess water extraction," said Jose Martinez Diez, a professor in geodynamics at Madrid's Complutense University who has also published a paper on the quake.Skip to next paragraph
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Still, it isn't the first time that earthquakes have been blamed on human activity, and scientists say the incident points to the need to investigate more closely how such quakes are triggered and how to prevent them.
The biggest man-made quakes are associated with the construction of large dams, which trap massive amounts of water that put heavy pressure on surrounding rock.
The 1967 Koynanagar earthquake in India, which killed more than 150 people, is one such case, said Marco Bohnhoff, a geologist at the German Research Centre for Geosciences in Potsdam who wasn't involved in the Lorca study.
Bohnhoff said smaller man-made quakes can also occur when liquid is pumped into the ground.
A pioneering geothermal power project in the Swiss city of Basel was abandoned in 2009 after it caused a series of earthquakes. Nobody was injured, but the tremors caused by injecting cold water into hot rocks to produce steam resulted in millions of Swiss francs (dollars) damage to buildings.
Earlier this year, a report by the National Research Council in the United States found the controversial practice of hydraulic fracturing to extract natural gas was not a huge source of man-made earthquakes. However, the related practice of shooting large amounts of wastewater from "fracking" or other drilling activities into deep underground storage wells has been linked with some small earthquakes.
In an editorial accompanying the Lorca study, geologist Jean-Philippe Avouac of the California Institute of Technology said it was unclear whether human activity merely induces quakes that would have happened anyway at a later date. He noted that the strength of the quake appeared to have been greater than the stress caused by removing the groundwater.
"The earthquake therefore cannot have been caused entirely by water extraction," wrote Avouac. "Instead, it must have built up over several centuries."
Still, pumping out the water may have affected how the stress was released, and similar processes such as fracking or injecting carbon dioxide into the ground — an idea that has been suggested to reduce the greenhouse effect — could theoretically do the same, he said.
Once the process is fully understood, "we might dream of one day being able to tame natural faults with geo-engineering," Avouac said.
Copyright 2012 The Associated Press.