Earthquake 'triggered by groundwater extraction'

Spanish earthquake in Lorca 'triggered by groundwater extraction'

A major earthquake in Spain that killed nine people and destroyed hundreds of homes was triggered by groundwater extraction, a scientific study has found.

The Telegraph,

22 October, 2012

The magnitude 5.1 tremor struck the historic town of Lorca in Spain's southeastern region of Murcia 17 months ago, toppling buildings and left nine dead and more than 100 injured.

Scientists have found evidence that the disaster was man-made – the result of water being sucked out of the ground to feed domestic supplies.

Loss of the water caused stress changes in the earth's crust along a major fault line and was enough to trigger a rupture in the rock, leading to the earthquake, scientists said.

The findings, published in the journal Nature Geoscience, highlight the extent to which human activity can influence seismic shocks.

A scientific team led by Dr Pablo Gonzalez, from the University of Western Ontario in Canada, used satellite data to map the ground deformation caused by the Lorca earthquake.

They then carried out computer simulations of the fault slip. The results showed a pattern that correlated with stress changes due to loss of groundwater.

Since the 1960s, natural groundwater levels in the region had dropped by 250 metres, they said.

The researchers wrote: "We conclude that the presented data and modelling results are consistent with a groundwater crustal unloading process, providing a reasonable explanation for the observed fault slip pattern."

The findings implied that "anthropogenic activities could influence how and when earthquakes occur".

In an accompanying commentary article, Professor Jean-Philippe Avouac, from the California Institute of Technology in Pasadena, US, wrote: "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."

More than a year after the quake shook the historic town, many residents have yet to return to their homes. More than 250 buildings were demolished and a further 160 properties have been condemned as uninhabitable.

An estimated 10,000 of the town's 90,000 residents have been forced to move away in the aftermath of the earthquake.