Groundwater Extraction Triggered Earthquake in Spain

Deeper wells drilled to remove groundwater might have caused the powerful earthquake that struck Lorca, Spain, in 2011, finds a new study.

At least nine people were killed and more than 100 injured when an earthquake of magnitude 5.2 hit the southern Spanish town of Lorca last year. A team of international researchers from Canada, Italy and Spain have found that the earthquake could have been triggered by excessive removal of groundwater from a nearby aquifer in the area.

Using satellite images, researchers found the earthquake ruptured the Alhama de Murcia fault that runs near a basin weakened by removal of groundwater for the last 50 years, reported the Associated Press.

The study suggests that the increased stress caused by extraction of groundwater likely triggered the earthquake. Since 1960, the groundwater table in Lorca region has dropped by 820 feet (250 meters), said the researchers.

"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," geologist Miguel de las Doblas Lavigne, from the Spain's National Natural Science Museum and who was not involved in the study, told The Associated Press in a telephone interview.

"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 camel's back, which is what happened," he said.

Although earlier studies have suggested human activity (like pumping groundwater into Earth) can cause small earthquakes to occur, this is the first time researchers have recognized that removing groundwater can also trigger earthquakes, a report in OurAmazingPlanet said.

However, researchers suggest that the earthquake was not triggered only due to groundwater extraction. The total amount of energy released by the quake was far greater than the stress caused by removal of groundwater.

The study concludes that the earthquake was triggered by groundwater removal and also by ground deformation over several centuries.

Experts suggest that the process needs to be fully understood to keep the natural faults under control with geo-engineering.

The findings of the study are published in the journal Nature Geoscience.