Earthquake Caused By Groundwater Extraction: Did Watering Plants Cause The Deadly Lorca Quake?
The deadly earthquake that killed 10 and left 403 injured in Lorca, Space in 2011 was caused by groundwater extraction, a new study, published in the journal Nature Geoscience. Researchers used satellite to study what parts of the ground moves during the earthquake, and found that the places that moved are strongly correlated to locations where groundwater had been drained, showing that human activity can have a profound effect on nature.
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Researchers used satellite data to trace the ground movement of the magnitude 5.1 Lorca earthquake, which struck in 2011. They traced the movements back to their origin and found that the earthquake resulted from the slippage of a very shallow fault near a water basin in southern Lorca.
The earthquake occurred only 1.8 miles deep - very shallow for an earthquake, which explains why there was so much damage for a relatively small earthquake.
The team wanted to learn what caused the fault to slip, and found that the water table near the fault dropped 820 feet over the last 50 years as people used it up, mostly for irrigation purposes, such as watering plants. Their calculations showed that this groundwater extraction put extreme stress on the fault, triggering the earthquake.
In an article accompanying the study, Jean-Philippe Avouac, a researcher with the California Institute of Technology, said that the researcher's findings make sense, as it doesn't take a lot to trigger an earthquake.
"It does not take much to trigger an earthquake - even strong rainfall can do the job," he said. "Numerous examples of seismicity triggered by the impoundment of reservoir lakes, hydrocarbon extraction, quarrying and deep well injections have been documented over the years."
But while the evidence that the Lorca earthquake was caused groundwater extraction is strong, researchers said water use for irrigation won't always cause an earthquake.
"We cannot set up a rule just by studying a single particular case," Pablo Gonzalez, study author and researcher with the University of Western Ontario, told BBC News. "But the evidence that we have collected in this study could be necessary to expand research in other future events that occur near... dams, aquifers and melting glaciers, where you have tectonic faults close to these sources."
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