On May 11, 2011 a magnitude 5.1 earthquake hit the town of Lorca in southern Spain. It was the country's worst quake in 50 years, killing 9, injuring nearly 300 and dealing millions in damages to Spain's struggling economy. Scientists have been searching for the cause of this "unusually shallow" quake and recently published an interesting theory.
By looking at satellite images, a team of scientists from Spain, Italy and Canada found that the earthquake breached a fault near a basin that had been compromised by years of groundwater extraction. Lorca is a well-known farming community that has supplied fruits, vegetables and meat to Europe for years. But in order to keep up with demand, farmers dug very deep wells — over time, this could have shifted the stress of the surrounding rock and made it more susceptible to earthquakes.
Geologist Miguel de las Doblas Lavigne works for Spain's National Natural Science Museum and strongly supports the theory proposed by the scientists in the study. According to De las Doblas:
"This has been going on for years in the Mediterranean areas, all very famous for their agriculture and plastic greenhouses. They are just sucking all the water out of the aquifers, drying them out. From Lorca to (the regional capital of) Murcia you can find a very depleted water level. [It was] no coincidence that all the aftershocks were located on the exact position of maximum depletion. The reason is clearly related to the farming, it's like a sponge you drain the water from; the weight of the rocks makes the terrain subside and any small variation near a very active fault like the Alhama de Murcia may be the straw that breaks the camels back, which is what happened."
Jose Martinez Diez, a professor in geodynamics at Madrid's Complutense University disagrees with the findings: "There have been earthquakes of similar intensity and similar damage caused in the 17th, 18th and 19th centuries when there was no excess water extraction."
Finally, Jean-Philippe Avouac, a geologist from the California Institute of Technology says that it's unclear whether or not the earthquake would have occurred without the added element of water extraction, but that by learning more about this process, "we might dream of one day being able to tame natural faults with geo-engineering."