Earthquake alert system set to shake up
US Los Angeles - Scientists working in Southern California have proposed a
way of interpreting feeble tremors that herald a large earthquake - a step
that could help in providing advance warning.
Richard Allen of the University of Wisconsin-Madison and Hiroo Kanamori of the California Institute of Technology developed a way to determine the location, origin, time and - most importantly - magnitude of an earthquake from as little as four seconds of measurements of the P wave. The system would rely on seismic instruments already deployed across the greater Los Angeles region. "If we can detect this P wave and use the information contained in it to estimate the hazard associated with an earthquake, then there is the potential to issue a warning before any significant ground motion reaches the surface," Allen said. The amount of forewarning would depend on the distance of the sensors from an earthquake's epicentre. If directly above the epicentre, there would be no time for a warning, since the S wave would arrive almost immediately after the P wave. At 60km from the epicentre, the system could give a magnitude estimate 16 seconds before the arrival of the S wave and the strong ground motion that accompanies it, Allen said. Allen and Kanamori are now testing their system on the regular earthquakes in the Los Angeles region to determine if it can provide accurate magnitude estimates in real time. There are no immediate plans to develop an actual warning system. The study may settle the question of whether earthquakes of different magnitudes begin in different ways, said Lucy Jones, scientist in charge of the US Geological Survey office in Pasadena, California. The study suggests they do. - Sapa-AP |
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