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Title: Enhancing Tsunami Warning Using P Wave Coda

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. TeleseismicPwaves can constrain this issue; slip under deep water generates strongpwPwater reverberations that persist as ringingPcodaafter the directPphases from the faulting have arrived. Event‐averagedPcoda/Pamplitude measures at large epicentral distances (>80°), tuned to the dominant periods of deep waterpwP(~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 ofPPandPPPphases contaminates closer distancePcodameasures, but this can be suppressed by azimuthal or distance binning of the measures. Narrowband spectral ratio measures and differential magnitude measures ofPcodaand directP(mB) perform comparably to broader band root‐mean‐square (RMS) measures.Pcoda/Plevels for large nonmegathrust events are also documented. Rapid measurement ofPcoda/Pmetrics after a large earthquake can supplement quick moment tensor determinations to enhance more » tsunami warnings; observation of largePcodalevels indicates that shallow submarine rupture occurred and larger than typical tsunami (for givenMW) can be expected.

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Award ID(s):
Publication Date:
Journal Name:
Journal of Geophysical Research: Solid Earth
Page Range or eLocation-ID:
p. 10583-10609
DOI PREFIX: 10.1029
Sponsoring Org:
National Science Foundation
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