A study examining the causes of the 2011 earthquake in Spain's agricultural city of Lorca, shows that years of drilling and pumping water from an underground reservoir may have triggered the 5.1 magnitude event. The May 11, 2011 quake was Spain's worst in 50 years, claiming nine lives and costing the country billions of euros in damage.
The study appeared in the journal, Nature Geoscience, in September, with an online version posted Sunday.
Led by Pablo Gonzalez of the University of Western Ontario, scientists from Canada, Italy and Spain used satellite radar data to trace ground movement in the area of the quake and found that changes in the terrain correlated with a 273-yard drop in the natural groundwater level, according to the Associated Press. A drop in groundwater can cause the earth's crust to shift.
The earthquake ruptured a fault that borders a large water basin south of the city, according to the newswire.
Lorca, which exports fruit, vegetables and meat to Europe stepped up its agricultural production in the 1960s, according to the town's environment chief Melchor Morales, as told to the AP.
At the time ground water was considered private property, and farmers began digging deeper and deeper wells to irrigate their crops and provide water for livestock, Morales said. He added that the town passed laws in 1986 to limit the drilling but they are largely disregarded.
The study is prompting scientists to focus on the effects of human activity on earthquakes. "Their findings suggest that human-induced stress on faults like the one near Lorca, known as the Alhama de Murcia Fault, can not only cause an earthquake but also influence how far the fault will slip as a result," the AP reported.
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