In 2011, a 5.1 magnitude earthquake struck the Spanish city of Lorca, resulting in the loss of 9 lives and the injury of over 100 people. Now, researchers studying the case believe groundwater extraction played a crucial role in triggering this earthquake.

A couple hugs in the aftermath of the 2011 Lorca earthquake.

A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Much like earthquakes take place at the boundary of tectonic plates, similar, smaller scale earthquakes are caused by faults; such earthquakes are greatly influenced by fault frictional properties and preseismic stress.

The study’s lead author, Pablo Gonzalez of the University of Western Ontario, said he and his colleagues had a hunch groundwater extraction had something to do with the earthquake, and they set out to verify their intuition – especially considering how measurements of human caused near-field, surface ground deformation are a rare sight.

They used satellite data to analyze how the terrain moved as a result of the earthquake, and then correlated these results with stress changes caused by groundwater extraction in a nearby basin aquifer. The results fitted in perfectly, and thus, the results are pretty clear: the Lorca earthquake was triggered, and probably amplified by human activity – specifically groundwater extraction. However, we have to keep in mind that Lorca is a seismically active region, and it is quite possible that the earthquake would have happened on itself sometime in the future.

“We cannot set up a rule just by studying a single particular case, but the evidence that we have collected in this study could be necessary to expand research in other future events that occur near … dams, aquifers and melting glaciers, where you have tectonic faults close to these sources,” Gonzalez said.

Still, this draws a big question mark regarding many geoengineering projects. It’s obvious we still don’t have a grasp on how human activity can cause or amplify earthquakes.

“For now, we should remain cautious … We know how to start earthquakes, but we are still far from being able to keep them under control,” Jean-Philippe Avouac of the California Institute of Technology wrote.

The full study was published in Nature