Research highlight

Unexpectedly high earthquake risk east of the Andes

Nature Geoscience

May 9, 2011

More than two million people living in the southern Subandean mountain ranges are exposed to significantly higher seismic risk than previously thought, suggests a study online this week in Nature Geoscience. Contrary to a recent hazard assessment ? estimating a maximum expected earthquake magnitude of 7.5 ? the paper suggests a quake of magnitude 8.7 to 8.9 is possible in the region.Benjamin Brooks and colleagues used GPS data to map movement of the Earth’s surface in the Subandean margin, along the eastern flank of the Andes Mountains. They report a sharp decrease in surface velocity from west to east. From these data, the researchers conclude that the shallow section in the east of the region is currently locked in place over a length of about 100 km, allowing stress to build up as the tectonic plates in the region slowly move against each other. Rupture of the entire locked section by one earthquake could result in shaking of magnitudes up to 8.9, they estimate.

doi: 10.1038/ngeo1143

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