Groundwater extraction triggered the 11 May 2011 Lorca earthquake in southern Spain, suggests a study published online this week in Nature Geoscience. The study highlights the influence of human-induced perturbations to the Earth’s crust on seismic activity.

Last year’s magnitude 5.1 Lorca earthquake killed nine people and seriously damaged numerous buildings in the town of Lorca. Pablo Gonzalez and colleagues use satellite data to analyse the ground deformation caused by the Lorca earthquake and model the fault slip. They find that the pattern of fault slip correlates with stress changes in the Earth’s crust caused by a 250 m drop in the natural groundwater level since the 1960s as a result of groundwater extraction. The correlation implies that human-induced stress changes helped to trigger the Lorca earthquake and also influenced the extent of fault rupture, and hence the magnitude of the quake.

In an accompanying News and Views article, Jean-Philippe Avouac says that “we should remain cautious of human-induced stress perturbations […]. We know how to start earthquakes, but we are still far from being able to keep them under control.”