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我们研制出一种在大地震发生之前数秒钟能够对地震发生做出早期警报的系统。我们假定宽带P波波形的垂直位移是地震的远场震源时间函数。基于地震矩与震源持续时间的关系,当初始P波震相持续时间超过3 s时,我们就可以发布发生了一次震级大于6级地震的早期警报。我们已把这种算法应用于日本宽带观测台站记录到日本近期发生的大地震的宽带地震图。我们发现,真的可能在P波到达后3 s内判断震级超过6级的地震的发生。
We have developed a system that can give early warning of an earthquake just seconds before a major earthquake occurs. We assume that the vertical displacement of the broadband P-wave waveform is a function of the far-field focal time of the earthquake. Based on the relationship between seismic moment and source duration, when the duration of the initial P wave phase exceeds 3 s, we can release an early warning that a magnitude 6 earthquake occurred. We have applied this algorithm to the broadband seismograms recorded by Japan’s broadband observatory stations to the recent earthquakes in Japan. We found that it is indeed possible to determine the occurrence of an earthquake of magnitude 6 or greater within 3 s after arrival of the P wave.