Despite a relatively quiet history of seismicity, the region east of the central Andes Mountains could see earthquakes of far greater magnitude than previously expected, according to researchers in the University of Hawaiʻi at Mānoa’s Hawaiʻi Institute of Geophysics and Planetology.
Using GPS data to map movement of the Earth’s surface in the Subandean margin along the eastern flank of the Andes Mountains, Benjamin Brooks, James Foster and colleagues documented a sharp decrease in surface velocity from west to east.
The scientists ran millions of simulations on a model that relates the surface movement to subsurface faults. They concluded that the shallow section in the east of the region is locked in place over a length of about 100 kilometers. This allows stress to build as the tectonic plates move against each other. A rupture of the entire locked section by one earthquake could generate an earthquake of magnitude 8.7 to 8.9, they report in the June 2011 issue of Nature Geoscience.
“No one suspected the previous estimates of magnitude 7.5 were too low,” says Brooks, who studies how mountains grow and deform. The information could help public officials gauge geological hazards in Bolivia.
Meanwhile, the international team of scientists is performing paleoseismologic research to determine dates and sizes of past earthquakes and monitoring the earthquake zone to see if some of the accumulated strain can be released aseismically, possibly postponing a major earthquake.
The research was funded by the National Science Foundation.