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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />

(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />

Interior<br />

JSS002 Oral Presentation 1775<br />

Tsunami moment magnitudes (Mwt) of the 1 April 1946 Unimak and the 28<br />

March 1964 Alaska tsunamis<br />

Dr. Liujuan Tang<br />

NOAA Center for Tsunami Research Research Scientist<br />

Vasily V. Titov, Christopher Chamberlin, Yong Wei, Michael Spillane<br />

Previous studies of seismic, geodetic and water-level data have provided the possible sources for some<br />

destructive tsunamis in Pacific (Kanamori and Ciper, 1974, Johnson et al, 1994, 1996, Johnson and<br />

Satake, 1999). Derived based on low-resolution tsunami propagation models, most of these source<br />

estimates are subject to debate and adjustment. NOAA Center for Tsunami Research (NCTR) is<br />

developing the next generation tsunami forecast system and implementing it at NOAAs Tsunami<br />

Warning Centers (TWCs). It includes DART detection, inversion to a pre-computed propagation<br />

database, and site-specific inundation forecasts by Stand-by Inundation Models (SIMs). The propagation<br />

database contains of 836 synthetic unit tsunami scenarios at the major subduction zones in Pacific<br />

Ocean, using the Method of Splitting Tsunami (MOST) numerical model. With resolution of 60-90 meter<br />

in nearshore area, SIM is optimized for speed and accuracy to provide 4-hour event inundation forecast<br />

less than 10 minutes. In addition, a Reference Inundation Model (RIM) with higher resolution of 10-30<br />

meter was also developed to provide numerical references for each SIM, as well as a useful tool for<br />

tsunami hazard mapping projects.The components of the forecast system provide a unique chance to<br />

re-investigate the historical destructive tsunamis by inversion of the coastal water level data with the<br />

high-resolution quality inundation and propagation models. Application of this approach gives tsunami<br />

moment magnitudes of Mwt = 8.5, for 1 April 1946 Unimak tsunami and Mwt = 9.0 for the 28 March<br />

1964 Alaska tsunami. Excellent model-observation comparisons, including first arrivals, wave periods<br />

and amplitudes for first waves of over 2 hours, are achieved at coastal tide stations in Hawaii, Alaska<br />

and U.S. West Coast respectively. Modeled inundation limit at Hilo for the 1946 tsunami agrees well with<br />

the observations.<br />

Keywords: tsunami moment magnitude

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