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Prepare to Shake!

14 August 2002 (All day)
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Reduced to rubble. But a new system could turn off gas lines in time to prevent fires like the one that destroyed these San Francisco homes after a 1989 quake.

A new seismic monitoring system developed in Taiwan can give up to 25 seconds warning of a large earthquake. It may not seem like much, but experts say it's enough time to shut off gas pipelines, stop trains, save computer databases and alert doctors performing surgery.

When an earthquake strikes, seismic waves speed away from the epicenter like ripples in a pond. For large temblors, the destructive waves can spread as far as 160 km and travel for 40 seconds. Taking advantage of the fact that electronic information can travel much faster than seismic waves, Yih-Min Wu of the Taiwan Central Weather Bureau and Ta-liang Teng of the University of Southern California in Los Angeles devised a system that can pinpoint the location and magnitude of an earthquake in seconds and send a warning to areas farther than 75 km from the epicenter.

Taiwan is home to one of the most sophisticated and complete networks of seismic recording stations in the world. But with so many stations producing so much data, it can take well over a minute after an earthquake begins to calculate the location and magnitude. So Teng and Wu created a system that uses the first bits of data to choose between six and 12 stations near the epicenter. After receiving 10 seconds of data from these stations, the system needs only 5 more seconds to calculate the exact location and size of the quake and alert cities that are about to be shaken. When the researchers tested their method between December 2000 and June 2001, it pinpointed 54 small earthquakes with 100% accuracy. They report their findings in the current issue of the Bulletin of the Seismological Society of America.

While the technology behind the early warning system is well-known among seismologists, Teng and Wu are the first to demonstrate how to successfully implement it. "This is the promise we've all been hoping to see," says Mary Lou Zoback of the U.S. Geological Survey in Menlo Park, California. The system is already online in Taiwan, connected to emergency systems that would, among other things, automatically shut off gas lines and slow bullet trains in the event of an earthquake rating 6.5 or higher on the Richter scale. Unfortunately, most earthquake-prone areas around the world aren't equipped with the modern stations needed to run the early warning system. And even in the Los Angeles area, which does have updated stations, work on an early warning system stalled after funding dried up.

Related sites
Ta-Liang Teng's Web page
Southern California Earthquake Center at the University of Southern California
Taiwan Central Weather Bureau
USGS Earthquake Hazards Program

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