Spain Earthquake, Drilling Wells Linked In New Study Of Lorca Tragedy
Reference: huffingtonpost.com/2012/10/2 … 97629.html
Farmers drilling ever deeper wells over decades to water their crops likely contributed to a deadly earthquake in southern Spain last year, a new study suggests. The findings may add to concerns about the effects of new energy extraction and waste disposal technologies.
Using satellite images, scientists from Canada, Italy and Spain found the quake ruptured a fault running near a basin that had been weakened by 50 years of groundwater extraction in the area.
During this period, the water table dropped by 250 meters (274 yards) as farmers bored ever deeper wells to help produce the fruit, vegetables and meat that are exported from Lorca to the rest of Europe. In other words, the industry that propped up the local economy in southern Spain may have undermined the very ground on which Lorca is built.
The researchers noted that even without the strain caused by water extraction, a quake would likely have occurred at some point.
But the extra stress of pumping vast amounts of water from a nearby aquifer may have been enough to trigger a quake at that particular time and place, said lead researcher Pablo J. Gonzalez of the University of Western Ontario, Canada.
“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,” he told The Associated Press in a telephone interview. “From Lorca to (the regional capital of) Murcia you can find a very depleted water level.”
De las Doblas said 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 camel*s back, which is what happened,” he said.
He said excess water extraction was common in Spain.
A pioneering geothermal power project in the Swiss city of Basel was abandoned in 2009 after it caused a series of earthquakes. Nobody was injured, but the tremors caused by injecting cold water into hot rocks to produce steam resulted in millions of Swiss francs (dollars) damage to buildings.
In an editorial accompanying the Lorca study, geologist Jean-Philippe Avouac of the California Institute of Technology said it was unclear whether human activity merely induces quakes that would have happened anyway at a later date. He noted that the strength of the quake appeared to have been greater than the stress caused by removing the groundwater.“The earthquake therefore cannot have been caused entirely by water extraction,” wrote Avouac. “Instead, it must have built up over several centuries.”