HR: 1340h
AN: OS23D-1357    [Abstracts]
TI: Simulating the 1946 Aleutian far-field tsunami: The successful dislocation and the impossible landslide.
AU: HEBERT, H
EM: helene.hebert@cea.fr
AF: CEA/DASE, B.P. 12, Bruyeres-le-Chatel, 91680 France
AU: * OKAL, E A
EM: emile@earth.nwu.edu
AF: Northwestern, Univ., Evanston, IL 60208 United States
AB: We present a final set of hydrodynamic simulations of the run-up of the 1946 Aleutian tsunami at the transpacific locations obtained during the field surveys taken in 1999-2001 by Okal et al. [2002]. As a source of the tsunami, we use both (i) a dislocation model based on the updated seismological study of Lopez and Okal [2002], which features slow bilateral rupture along a 200-km long fault zone; and (ii) the asymmetric dipolar source successfully used by Okal et al. [2003] to model the near-field run-up surveyed at Unimak Island. The simulations are carried out on a series of grids featuring fine scales both in the source area, and at the receiving shores (the latter up to a final scale of 50 m), but a coarser grid on the high seas. In general, the dislocation source does fit the run-up observations in the far-field, and in particular it reproduces the strong azimuthal directivity expected in the source geometry. This extends the ressults of Titov et al. (2001), who had modeled the inundation at Hilo on the basis of a similar dislocative source, but using a different numerical method. By contrast, the dipolar source produces absolute values of run-up ranging only from a few tens of cm to 3 m on the shorelines of the Marquesas and Juan Fernandez Islands, in all cases significantly less (by a factor of 3 to 5) than observed. We conclude that the near- and far-fields cannot be both modeled by a single source. The final model of the source of the 1946 Aleutian tsunami must be a composite betweem a very large, but very slow earthquake, responsible for the far field tsunami, and a landslide generating the devastating near-field tsunami.
DE: 9355 Pacific Ocean
DE: 7215 Earthquake parameters
DE: 4564 Tsunamis and storm surges
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting