Deadly Spain Earthquake Triggered By Groundwater Removal

By Becky Oskin, OurAmazingPlanet Staff Writer | LiveScience.com

In this May 12, 2011 file photo, a police officer inspects damage caused by an earthquake the previous day in Lorca, Spain, Thursday, May 12, 2011. Farmers drilling ever deeper wells over decades to water their crops likely contributed to a deadly earthquake in southern Spain last year, a new study suggests. The findings may add to concerns about the effects of new energy extraction and waste disposal technologies. (AP Photo/Alberto Saiz, File)

Groundwater removal triggered the unusually shallow and deadly earthquake that hit Lorca, Spain, in 2011, according to a new study.

Scientists have known for decades that pumping water into the Earth can set off small earthquakes. But this is the first time that removing water has been identified as an earthquake trigger, researchers said. Both the size and the location of the quake were influenced by groundwater pumping, the study found.

"The fact that the very tiny stress changes due to normal processes, such as the extraction of groundwater, could have an effect on very large systems such as faults, that's very surprising," said Pablo González, lead study author and a postdoctoral scholar at the University of Western Ontario in Canada.

The researchers were also able to precisely calculate the physical changes that generated the quake. The results will help seismologists better understand the physics that control when an earthquake starts and stops — an important step in predicting when and where a quake will occur, and its size.

"We need observations of this sort to calibrate physical models" of faults, said Jean-Philippe Avouac, a geologist at Caltech in Pasadena, Calif., who was not involved in the study. "The initiation and arrest of [fault] ruptures are something we are trying to constrain," he told Our Amazing Planet.

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