Moment and Rupture Duration From Seismogeodetic Data for Local Tsunami Warnings
Session: Advances in the Science and Observation of Tsunamis [Poster]
Type: Poster
Date: 4/22/2021
Presentation Time: 03:45 PM Pacific
Description:
Because earthquakes generate most tsunamis, the first indication that a tsunami may have been generated is the earthquake itself. Therefore, tsunami warning centers provide their initial tsunami warnings to coastal populations based entirely on real-time seismic data. Prior to the 2004 Mw9.2 Sumatra earthquake, no near real-time magnitude determination method existed that would correctly estimate the size of so large an event. Since then, Kanamori and Rivera (2008) developed the W-phase source inversion method which now provides unsaturated estimates of Mw, and centroid moment tensor (CMT) solutions within 6-15 minutes of earthquake origin time. Tsunami warning centers must also rapidly identify slow “tsunami” earthquakes, for which the traditional methods using relatively short period seismic waves are not effective. Because tsunami earthquakes produce much less radiated high frequency energy than normal, even a large tsunami earthquake may not be strongly felt in the near field, making self-evacuation based upon feeling strong ground shaking problematic. Combining GNSS with strong-motion data via a Kalman filter (Bock et al., 2011) yields unclipped broadband velocity and displacement waveforms, and are sensitive to the entire spectrum of ground motions from the Nyquist frequency of the accelerometer (typically 50Hz) to the static offset of the GNSS displacement. Using this data, we test a method to estimate moment magnitude, and rupture duration within 3-5 minutes of rupture initiation. We use the velocity time series to define the appropriate co-seismic time window for the displacement record, the end of which provides a proxy for source duration. We then estimate the seismic moment from the maximum value of the integrated displacement within this window. The time that this maximum value occues provides a second proxy for rupture duration. Using seismogeodetic data for earthquakes in the Mw 7.1 to 9.1 range, we obtain accurate and reliable moment magnitudes, and rupture duration estimates within minutes of rupture initiation.
Presenting Author: Dorian Golriz
Student Presenter: Yes
Authors
Dorian Golriz Presenting Author Corresponding Author dgolriz@ucsd.edu Scripps Institution of Oceanography, University of California, San Diego |
Barry Hirshorn barryhirshorn@mac.com Seismologist |
Yehuda Bock ybock@ucsd.edu Scripps Institution of Oceanography, University of California, San Diego |
Stuart Weinstein stuart.weinstein@noaa.gov Pacific Tsunami Warning Center, NOAA |
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Moment and Rupture Duration From Seismogeodetic Data for Local Tsunami Warnings
Session
Advances in the Science and Observation of Tsunamis