Quick worker

Promising earthquake warning system tested

Published: Sunday 15 September 2002

a computer system tested in Taiwan can give people as much as 25 seconds warning of an impending earthquake. This may not seem very long, but it is enough time for automated emergency systems to stop trains, shut down gas lines or tell surgeons to stop their work. "This could be the perfect 911 emergency call for earthquakes across the world," says Ta-Liang Teng of the us-based Southern California Earthquake Centre at the University of Southern California, who has developed the system.

When an earthquake strikes, waves radiate out from the epicentre at about four to six kilometres per second. Most tremors are not strongly felt more than 160 kilometres away from the epicentre. Many earthquake-prone areas, like California and Japan, already have systems in place to relay information from seismometres near the epicentre of a quake out to surrounding areas. But these systems react slowly because they do not have enough detectors. They usually pick up the fast-moving pressure waves of a quake, but do not have time to analyse the slower waves.

The latter can help pin down how destructive the quake will be, which is critical to deciding what action to take. Keeping this in mind, Teng and colleague Yih-Min Wu devised a computer programme that automatically picks a dozen key seismograph stations from within 60 kilometres of a quake's epicentre. By analysing that data alone, the detection and processing time is considerably reduced -- less than 40 seconds. In a trial run, they analysed at least 54 quakes between December 2000 and June 2001, and managed to send out information about them within 14 to 41 seconds.

However, the system still has a central 'blind spot' -- since the earthquake travels faster than the warning system in areas within 50 kilometres of the epicentre, it is difficult to send fast warning signals there.

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