09 May 2011 Last updated at 08:47 GMT
According to a recent study, a region in Bolivia faces the risk of a magnitude 8.9 earthquake. This magnitude of earthquake is 125 times more powerful than what had been previously calculated as its maximum strength. The findings of the study surprised most of the scientists that had been working closely on the project. A projected 2 million people are at risk from the massive earthquake.
Benjamin Brooks, a geophysicist from the University of Hawaii Manoa and the lead author of the study stated that no one in their group had expected the initial estimates to be too low. The previous calculations had set the most powerful of the earthquakes to be just a magnitude 7.5 based on the quiet seismic history of the region. The region is located just east of the central Andes Mountains in Bolivia. .
But after careful analysis from GPS (Global Positioning System) data of the eastern side of the mountain chain, Brooks said that it showed a buildup of stress formations that would be more consistent with a magnitude 8.7 to 8.9 earthquake. Monitoring small changes in the place of GPS stations enables scientists to determine surface velocity to as small as a small fraction of a millimeter per year.
The data gathered by the satellite showed that the area to the west of the Mandeyapecua thrust fault, which runs north to south in Bolivia, has moved farther than the area east of the thrust fault. This accumulation of pressure poses as a dangerous precursor to a high magnitude earthquake. The fault is among the biggest in the world and occupies a large area of Bolivia.
Researchers have found that a shallow section of the thrust fault is locked in place over a length of over 100 kilometers or 62 miles. The study had showed that a rupture of the entire locked section by just one earthquake could lead to aftershocks as powerful as a magnitude 8.9. Brooks added that there is no way for scientists to predict when such an event will happen of if it will ever happen in the future.
To follow up with the study, Brooks will be investigating the ancient seismic history of the region to determine the dates and locations of past earthquakes, and to find out if there has ever been an earthquake of that magnitude in the area. Several earthquakes in recent years, such as the 9.0 off the coast of Japan, and an 8.8 magnitude in Chile, has forced scientists to reevaluate and reassess previous forecasts around the world. .