Spain: A new study has revealed that groundwater removal triggered the unusually shallow and deadly earthquake that hit Lorca, Spain, in 2011. Both the size and the location of the quake were influenced by groundwater pumping, the study found.
“The fact that the very tiny stress changes due to normal processes, such as the extraction of groundwater, could have an effect on very large systems such as faults, that”s very surprising,” said Pablo González, lead study author and a postdoctoral scholar at the University of Western Ontario in Canada.
Using data from satellite imagery and GPS stations, González and his colleagues first confirmed the quake occurred on the Alhama de Murcia fault. Then, they calculated how the crust responded to removing the weight of the water. Releasing the load increased the stress on the Alhama de Murcia fault by a few tens of kilopascals — less than atmospheric pressure — the study found.
During the quake, the fault broke only in areas where removing groundwater increased stress on the fault. From this correlation, González inferred that the groundwater removal not only helped trigger the quake, but also controlled the size of the fault rupture and the earthquake”s magnitude.
However, the amount of energy released by the quake far exceeded that built up by groundwater extraction. Thus, the earthquake released both stress caused by groundwater extraction and several centuries of regional deformation, the study concludes. Southeastern Spain is near the plate boundary region that separates the Eurasia and Africa tectonic plates.
Source: Live Science