Some two million people in Bolivia face the risk of a magnitude 8.9 megaquake, 125 times stronger than the previously calculated potential maximum, according a study published Sunday. The findings, reported in Nature Geoscience, came as a surprise, the researchers said.
"No one suspected that the previous estimates were too low," said Benjamin Brooks, a geophysicist at the University of Hawaii Manoa and lead author of the study.
Earlier calculations had set the most powerful expected earthquake for the region east of the central Andes mountains at magnitude 7.5, based in part on a relatively quiet seismic history.
But a careful analysis of Global Positioning System (GPS) data from the eastern flank of the mountain chain showed a build-up of stress consistent with a maximum magnitude of 8.7 to 8.9, Brooks said.