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Survey to chart Himalaya quake risk.

Survey to chart Himalaya quake risk

Mount Everest grows about 1 centimeter taller each year, driven by forces created in the ongoing collision between the Indian and Asian landmasses. Those same forces are straining the entire Himalayan region, making the area especially prone to large earthquakes. For a clearer picture of which faults pose the most pressing seismic risks, U.S. scientists will begin a long-term project next spring using space-age technology to survey tectonic changes along the Himalaya.

Roger Bilham and his colleagues at the University of Colorado in Boulder will measure distances between horizontal points with the satellite-based Global Positioning System (GPS), and vertical elevations with an xtremely accurate gravity meter. By comparing sets of measurements collected several years apart in the same locations, the researchers hope to gauge how quickly the land surface warps under tectonic stresses as India and Asia collide at a rate of about 5 centimeters a year.

The project represents the first Himalayan application of GPS technology, which can distinguish changes as small as the width of a pencil over distances of almost 500 kilometers. The researchers say they have had some difficulty getting nations in the region to agree to the survey, since GPS relies on radio waves emitted by U.S. military satellites. However, Nepalese officials formally granted permission for the project earlier this month.

Nepal has suffered many disastrous earthquakes, including a 1934 quake that killed 11,000 people along its border with India. Bilham thinks the nation's swelling population--which doubles every 20 to 25 years--is compounding the earthquake threat. Population growth not only fills the quake-prone region with more residents but also forces the government to build new housing quickly -- often paying too little attention to the seismic threat, he says. "Nepal's earthquake hazard is increasing by leaps and bounds," says Bilham, who hopes the new survey will help focus attention on the specific areas facing the greatest danger.
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Publication:Science News
Date:Aug 25, 1990
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