Implementation of tsunami early warning using earthquake rupture duration

1. Implementation of tsunami early warning using earthquake rupture duration Michelini A.1 and Lomax, A.2 1.Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy, alberto.michelini@ingv.it 2.ALomax Scientific, Mouans-Sartoux, France. anthony@alomax.net

2. Talk Structure • Problem and earlier work • Duration-Exceedance Alarm design and implementation • Data • Examples movie of tsunami (and non-tsunami) alerts • Summary 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

3. Problem and earlier work • Rapid tsunami assessmentare critical for rapid alerts and intervention. • P-waves can provide very first information on earthquake size and tsunami potential • Tsunami Warning centers, depending whether local or regional, rely on earthquake location and magnitude and on pre-determined tsunami scenarios for early warning • Effective regional warning requires assessment in < 15’ • Mwp (Tsuboi et al., 1995) is the quickest methodology at teleseismic distances to determine earthquake size but • Accurate up to Mw~7.5 • Underestimates Mw>7.5 and tsunami earthquakes because it does not account for long duration ruptures (i.e., later pulses on the waveforms indicative of source duration) 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

4. Problem and earlier work (2) • Duration Magnitudes (e.g., MED, Mwpd, mBc, Mhara) take into account the source duration explicitly, are calibrated against MWCMT and do not saturate • Theta (i.e., energy to moment ratio) proposed as indicator of tsunami earthquakes (Newman and Okal, 1998) • P-wave duration, To, alone appears to be a reliable indicator of tsunami genesis (Lomax and Michelini, 2009a,b; Bormann and Saul, 2009) 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

5. Duration-amplitude processing steps: 12 September 2007, M8.4 Sumatra raw, velocity seismogram Duration Duration 1.5 Hz, Gaussian-filtered seismogram T0 T0 estimate: smoothed, velocity-squared envelope ground-displacement seismogram Amplitude M0 estimate: integral of displacement over duration T0 (Mwpd=8.5) 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

6. Tsunamigenic earthquakes: rupture duration To > 50s(To versus Mw discriminant) 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

7. Tsunami Early Warningusing Duration - Exceedance 2006, Mw7.7, T0=180s, It=18 Indonesia tsunami earthquake 2009, Mw7.6, T0=39 s, It=1 Tonga Islands (from Lomax & Michelini, 2009b; http://s3.rm.ingv.it/D-E.php 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

8. Discrimination of tsunamigenic earthquakes 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

9. IMS auxiliary seismic network 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

10. IMS primary seismic network 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

11. IRIS SeedLink-realtime station subset 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

12. D-E for September 29, 2009 Mw=8.2 Samoa 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

13. D-E for September 30, 2009 Mw=7.7 Sumatra 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

14. Summary • Tsunami warning should rely on different tools in order to issue alerts • Real time data at global scale such as those provided through the SeedLink protocol implemented at IRIS can be used for dedicated tsunami warning procedures • Duration-Exceedance, D-E, can be used as fast and reliable discriminant of tsunami occurrence • D-E is visualized in real-time on the INGV seismic center video-wall and the procedure is available at http://s3.rm.ingv.it/D-E.php 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

15. Acknowledgements • This work has been funded by the Italian Civil Protection (project INGV-DPC 2007-2009 S3 contract) • The data have been obtained from IRIS accessing the realtime DMC SeedLink server • The plots are made with GMT (http://gmt.soest.hawaii.edu). 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

17. Problem and earlier work (3) Earliest tsunami warnings: • Primarily Magnitude (Mwp) at US tsunami centers (PTWC and WCATWC; T ~ 5-10’) • JMA/Japan warnings based on Magnitude and predetermined scenarios (T ≤ 3’) • GITEWS/German-Indonesian based on magnitudes (e.g., mB, mBc) alone ( T≤ 5’) • Australian Tsunami Warning System based on magnitude (T ≤ 15’) 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

18. To versus Mw discriminant 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

19. The duration-amplitude procedure produces rapidly an earthquake moment magnitude Mwpd from P-wave recordings at teleseismic distances (30-90º) • Mwpd available within < 20 minutes after OT. • For large earthquakes Mwpd (with moment scaling) matches MwCMT typically within ±0.2 magnitude units. • Mwpd does not exhibit saturation for the largest events. • Mwpd equals or is better than other procedures for rapid moment magnitude determination. • Duration, T0, seems to be a robust indicator for tsunamigenic earthquakes (i.e., T0 ≥ 50 s) • The Duration-Exceedance proxy to T0, produces rapid estimates (5-10 minutes) for tsunamigenic earthquakes • From Lomax and Michelini, 2009a 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

20. IMS auxiliary seismic network 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II

21. Tsunami importance, It, and Duration, T0, for identification of tsunami earthquakes It- Tsunami importance based on water height, h, and 0-4 descriptive indices, i, of tsunami effects (deaths, injuries, damage, houses destroyed) (NOAA/WDC Historical Tsunami Database (NGDC, 2008) From Lomax and Michelini, GJI, 2009a 2009 AGU Fall Meeting S33D. Research and Development in Nuclear Explosion Monitoring II