Groundwater extraction from agriculture and industry that lowered a nearby aquifer helped spark a quake in Spain last year that killed nine people, according to a study published today in Nature Geoscience.
The May 2011 earthquake in Lorca, which measured 5.1 on the Richter scale, was Spain’s deadliest since 1956. It was triggered following a 250-meter (820-foot) drop in groundwater from pumping since the 1960s ruptured the Earth’s crust along the Alhama de Murcia faultline, according to the study led by Pablo J. Gonzalez of the University of Western Ontario.
The shallow-depth quake at 2-4 kilometers (1.2 to 2.5 miles) in one of the highest seismic risk areas in Spain was “human-induced” by groundwater changes, the study said. The results imply that anthropogenic or manmade activities “could influence how and when earthquakes occur.”
Fracking, or hydraulic fracturing, blasts water mixed with sand and chemicals underground to free trapped hydrocarbons from shale formations. The disposal of saltwater and used fracking fluids in deep injection wells sometimes impacts fault lines and has caused small quakes in such places as Ohio though no deaths.
The Nature Geoscience study suggests “that the stress change induced by water extraction in the Guadalentin basin may have done more than advance the time of an earthquake that would have happened anyway,” Jean-Philippe Avouac from the California Institute of Technology in Pasadena said in an e-mail.
The Lorca quake has a “tectonic origin due to the slow relative motion of Africa and Eurasia plates in this part of the western Mediterranean area of southeast Spain,” Gonzalez said in an e-mail. “It means that even without the human-induced additional stress of that fault, the earthquake would certainly have happened.”