应急地震学的研究进展

Progress in Real-time Seismology

因孕震过程很难进行直接观测,人类对孕震过程及地震破裂起始过程了解尚少,地震的短临预报在短期难以取得突破。目前美、日等发达国家及地区采取的对策是,强化建筑物抗震设防、深化地震快速应急研究。应急地震学是指在地震发生后以最短的时间确定地震的位置及强度,利用现代通信的快速性,在破坏性地震波(主要是地震面波)达到之前几到几十秒的时间内采取适当的措施,避免一些人员财产损失,形成地震预警系统。应急地震学另一个重要内容则是地震灾害的快速估计,即利用国家及全球的地震波形信息,结合地震灾区的强地面震动记录,快速确定地震的起始、终止时间、地点及能量释放的具体过程,结合当地地质结构信息,从而估计各地区可能的受灾程度,为合理分配救灾资源提供第一手资料。在进一步加密我国地震台网的基础上,在东部平原大都市地区我国应可实现强震(6.5级以上)发生后20秒内快速确定震中及震级,实现地震极早期预警。同时可在几小时内确定地震能量释放过程,形成地面震动理论评估图(shakemap),按照灾情程度合理分配救灾资源,提高救灾效率。

Accurate earthquake prediction is still a far-reaching goal for modern seismology because of the complicated seismogenic process and and rupture initiation process. More reliable and rewarding measures are seismic risk assessment and enforcement of building code before earthquake. Implementation of early warning system （EWS） for strong earthquakes and rapid seismic damage mitigation are the two major components of real time seismology. EWS takes the advantage of time difference between the fast propagating weak P waves which carries definitive information of strong earthquakes, and the later arriving damaging S waves. With only a few to tens of seconds, magnitude and location of an earthquake can be estimated with the initial portion of P waves, and early warning is issued to avoid damages. Then within hours, global waveforms can be inverted to get the detailed process of seismic energy radiation, a reliable map of ground shaking can be calculated based on the inverted models with verification from strong motion records. For the dense network in Eastern China, 20 seconds early warning is realizable.