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Earthquake warning: racing the waves.

When the San Andreas fault finally unleashes the "Big One" on southern California, a sophisticated warning system could provide 60 seconds of advance notice before damaging vibrations start rattling Los Angeles buildings. Although no such system exists in the United States at present, a panel of experts says little stands in the way of its development.

Seismologists and engineers assembled by the National Research Council recommended last week that U.S. officials move now to install a prototype system that can quickly sense seismic waves from a strong quake and send warning signals to outlying areas.

"Technology is not a barrier. It could be implemented now," says panel member Nafi Toksoz. a seismologist at the Massachusetts Institute of Technology.

The system would rely on a network of advanced sensors that detect seismic waves before they spread from the epicenter of a quake. A central computer would use data transmitted by the sensors to determine the size and location of the quake, and within seconds would send out information to areas in the path of the damaging vibrations. While such systems would not benefit regions closest to the epicenter, they could provide seconds to tens of seconds of advance warning to more distant areas.

The early notice could activate automated systems that would save lives and property, the panel maintains. Utilities could shut off gas lines, reducing the risk of damaging fires. Computers could retract disk file heads to protect stored information. Broadcasts could alert people to seek safety under a strong desk or table.

The proposed system could also provide information immediately after the quake to help emergency officials locate the sites hardest hit by the shaking. At present, accurate postquake information takes hours or days to obtain because tremors disrupt power and telephone lines.

For two decades, Japan has used a warning system that automatically stops high-speed trains in a quake. In October 1989, during the days that followed the Loma Prieta quake in the San Francisco Bay area, the U.S. Geological Survey (USGS) installed a simple warning system that detected aftershocks in the epicentral region and radioed a warning to Oakland, providing 12 to 20 seconds of warning for people working on the collapsed 1-880 highway overpass.

The panel recommends upgrading an existing seismic network, probably in California, to create a sophisticated prototype sytem. Since the seismometers used in most such networks were designed to measure small earthquakes, the prototype would require newer devices that can gauge strong vibrations as well.

The panel provided little information about th price of a full-scale prototype. Panel member Thomas H. Heaton, a USGS seismologist in Pasadena, Calif., told SCIENCE NEWS that he estimates a cost of about $5 million per year for developing and operating the prototype system.

The idea has yet to win widespread endorsement from companies and government agencies that would use such a system. According to a 1989 poll, most potential users in California fear that false alarms could prove excessively costly. The panel contends, however, that these groups have difficulty envisioning the benefits of an early warning system. Says Heaton, "It's like asking people 30 years ago: What would you do with a computer in your home?"
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Title Annotation:warning system proposed for southern California
Author:Monastersky, Richard
Publication:Science News
Date:Sep 7, 1991
Words:531
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