Enhancing Tsunami Warning Using P Wave Coda
Enhancing Tsunami Warning Using P Wave Coda
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DOI：
10.1029/2019jb018221
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
T. Lay;Chengli Liu;H. Kanamori
中科院分区：
文献类型：
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作者：
T. Lay;Chengli Liu;H. Kanamori
大多数大海啸是由近海板块边界巨型逆冲断层上的地震引起的。影响海啸激发的主要因素是地震矩、断层几何形状和断层深度。提供快速海啸警报的努力强调了地震和大地测量方法，以快速确定事件规模和断层几何形状。地震破裂的上倾程度对海啸的激发有重要影响，但目前尚难以确定。Telese-P波可以限制这个问题;深水下的滑动产生强烈的Telese-P水混响，在断层的直接P相到达后，这些混响作为振铃Pcoda持续存在。在大震中距离（> 80 °）处的事件平均Pcoda/P振幅测量值，调整到深水Pcoda P的主导周期（~12 - 15 s），与滑动是否延伸到海沟附近的独立模型相关性良好。在较近的范围（30 °至80 °）的数据减少所需的时间滞后推断破裂的上倾程度<15分钟。PP和PPP阶段的到来污染近距离Pcoda措施，但这可以抑制方位角或距离装箱的措施。Pcoda和直接P（mB）的窄带频谱比测量和差分幅度测量执行更宽频带均方根（RMS）测量。Pcoda/P水平的大型nonmegathrust事件也有记录。大地震后快速测量Pcoda/P指标可以补充快速矩张量测定，以增强海啸预警;大Pcoda水平的观测表明，发生了浅层海底破裂，并且可以预期会发生比典型海啸（对于给定MW）更大的海啸。
Most large tsunamis are generated by earthquakes on offshore plate boundary megathrusts. The primary factors influencing tsunami excitation are the seismic moment, faulting geometry, and depth of the faulting. Efforts to provide rapid tsunami warning have emphasized seismic and geodetic methods for quickly determining the event size and faulting geometry. It remains difficult to evaluate the updip extent of rupture, which has significant impact on tsunami excitation. Teleseismic P waves can constrain this issue; slip under deep water generates strong pwP water reverberations that persist as ringing Pcoda after the direct P phases from the faulting have arrived. Event‐averaged Pcoda/P amplitude measures at large epicentral distances (>80°), tuned to the dominant periods of deep water pwP (~12–15 s), correlate well with independent models of whether slip extends to near the trench or not. Data at closer ranges (30° to 80°) reduce the time lag needed for inferring the updip extent of rupture to <15 min. Arrival of PP and PPP phases contaminates closer distance Pcoda measures, but this can be suppressed by azimuthal or distance binning of the measures. Narrowband spectral ratio measures and differential magnitude measures of Pcoda and direct P (mB) perform comparably to broader band root‐mean‐square (RMS) measures. Pcoda/P levels for large nonmegathrust events are also documented. Rapid measurement of Pcoda/P metrics after a large earthquake can supplement quick moment tensor determinations to enhance tsunami warnings; observation of large Pcoda levels indicates that shallow submarine rupture occurred and larger than typical tsunami (for given MW) can be expected.