Earthquake Early Warnings Show Promise

A clever 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. 

When an earthquake strikes, waves radiate out from the epicentre at about 4 to 6 kilometres per second. Most tremors will not be strongly felt more than 160 kilometres away from the epicentre, giving a 40 second window to warn people on the outskirts of the quake zone of a coming shock.

Many earthquake-prone areas, like California and Japan, already have systems in place to relay information from seismometers near the epicentre of a quake out to surrounding areas. But these systems react slowly because they do not have enough detectors.

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Taiwan, however, has one of the densest networks of seismographs on Earth. There, the problem was on overload of information to analyse within the 40 second window. So scientists have devised a computer program 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 reduced to under the 40 second limit.

In a trial run, they analysed 54 quakes between December 2000 and June 2001, and managed to send out information about them within 14 to 41 seconds.

Category: Science & Technology
Source: adapted from New Scientist, 13 August 2002
Word count: 241 words

早期地震警报展示希望

    一种在台湾经过测试的智能电脑系统，可以对即将来临的地震向人们发出长达25秒的警告。这看起来不是很长，但是对于用自动紧急系统将火车停住、将气体管线关闭或告诉外科手术医生停止他们的工作，这已经是足够的时间了。

当地震袭来的时候，震波从震中以每秒约4至6公里的速度向外传播。绝大多数震动在离距震中多于160公里远的对方将不会被强烈地感觉到，这样就有一个40秒的间隔可以向处在震区外缘的人们就即将来临的震动发出警告。

很多地震多发地区，如加利福尼亚和日本，已经装有系统将靠近震中的各个地震检波器获得的信息传递到周围地区。但是这些系统反应迟缓，因为它们没有足够的探测器。

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但是台湾拥有地球上最稠密的地震仪网络之一。那里的问题是要在40秒的间隔内分析过量的信息。因此，科学家们编制了一个电脑程序用以自动选取十二个主要的、距震中60公里内的地震仪站。由于只需分析这些数据，探测和处理时间就缩短到了40秒的限制之内。

在试运行中，科学家们分析了发生在2000年12月至2001年6月中的54次地震，并且成功的将有关这些地震的信息在14至41秒内发送出去。