Deadly quake linked to water extraction, Fault weakened by years of pumping: Study by Frank Jordans and Jorge Sainz, The Associated Press, October 22, 2012
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 conducted by Canadian researchers suggests. The findings may add to concerns about the effects of new energy extraction and waste disposal technologies. Nine people died and nearly 300 were injured when an unusually shallow magnitude-5.1 quake hit the town of Lorca on May 11, 2011. It was the country’s worst quake in more than 50 years, causing millions of dollars in damage to a region with an already fragile economy. 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 metres as farmers bored ever deeper wells to help produce the fruit, vegetables and meat that are exported from Lorca to the rest of Europe.
Still, it isn’t the first time that earthquakes have been blamed on human activity, and scientists say the incident points to the need to investigate more closely how such quakes are triggered and how to prevent them. The biggest man-made quakes are associated with the construction of large dams, which trap massive amounts of water that put heavy pressure on surrounding rock. The 1967 Koynanagar earthquake in India, which killed more than 150 people, is one such case, said Marco Bohn-hoff, a geologist at the German Research Centre for Geosciences in Potsdam who wasn’t involved in the Lorca study.
Bohnhoff said smaller manmade quakes can also occur when liquid is pumped into the ground.
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 dollars of damage to buildings.
[Refer also to: Halcyon hot springs vanish after B.C. quake ]