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Enhancing Tsunami Warning Using P Wave Coda

Lay, Thorne and Liu, Chengli and Kanamori, Hiroo (2019) Enhancing Tsunami Warning Using P Wave Coda. Journal of Geophysical Research. Solid Earth, 124 (10). pp. 10583-10609. ISSN 2169-9313. doi:10.1029/2019jb018221.

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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 P_(coda) after the direct P phases from the faulting have arrived. Event‐averaged P_(coda)/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 P_(coda) measures, but this can be suppressed by azimuthal or distance binning of the measures. Narrowband spectral ratio measures and differential magnitude measures of P_(coda) and direct P (m_B) perform comparably to broader band root‐mean‐square (RMS) measures. P_(coda)/P levels for large nonmegathrust events are also documented. Rapid measurement of P_(coda)/P metrics after a large earthquake can supplement quick moment tensor determinations to enhance tsunami warnings; observation of large P_(coda) levels indicates that shallow submarine rupture occurred and larger than typical tsunami (for given M_W) can be expected.

Item Type:Article
Related URLs:
URLURL TypeDescription
Lay, Thorne0000-0003-2360-4213
Liu, Chengli0000-0001-5643-3428
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2019 American Geophysical Union. Received 25 JUN 2019; Accepted 12 SEP 2019; Accepted article online 15 SEP 2019; Published online 31 OCT 2019. All of the broadband seismic waveforms used in this study were accessed from the Data Management Center of the Incorporated Research Institutions for Seismology ( Centroid moment tensor solutions were obtained from the website ( Maximum water height values are primarily from the National Oceanic and Atmospheric Administration, available online ( Lingling Ye provided helpful waveform plotting software. We thank Associate Editor Diego Melgar, reviewer Andrew Newman, and an anonymous reviewer for their comments on the manuscript. T. Lay's research on earthquakes is supported by the U.S. National Science Foundation Grant EAR1802364. C. Liu was supported by the National Key R & D Program on Monitoring, Early Warning and Prevention of Major Natural Disaster (2017YFC1500305) and the Visiting Scholar Program of the Chinese Science Council.
Group:Seismological Laboratory
Funding AgencyGrant Number
National Key Research and Development Program of China2017YFC1500305
Chinese Science CouncilUNSPECIFIED
Subject Keywords:tsunami warning; slip on megathrust; pwP; seismic coda; near‐trench slip; earthquake depth
Issue or Number:10
Record Number:CaltechAUTHORS:20200103-075024517
Persistent URL:
Official Citation:Lay, T., Liu, C., & Kanamori, H. (2019). Enhancing tsunami warning using P wave coda. Journal of Geophysical Research: Solid Earth, 124, 10583– 10609.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100478
Deposited By: Tony Diaz
Deposited On:05 Jan 2020 03:56
Last Modified:16 Nov 2021 17:54

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