HR: 11:20h
AN: OS21D-05    [PDF]
TI: Hydrodynamic modeling of the 1946 Aleutian tsunami in the far field using a dislocation source
AU: * Hebert, H
EM: helene.hebert@cea.fr
AF: DASE - CEA, B.P. 12, Bruyeres-le-Chatel, 91680 France
AU: Okal, E A
EM: emile@earth.nwu.edu
AF: Northwestern University, Locy Hall, Evanston, IL 60208 United States
AB: We present the results of simulations of the amplitude of 1946 Aleutian tsunami at about 25 transpacific locations, principally in Polynesia, and compare them to the database obtained during the field surveys taken in 1999-2001 by Okal et al. The source used is an elastic dislocation with a seismic moment of 9*10**28 dyn-cm as suggested by the recent analyses of Lopez and Okal [2002]. The simulation is carried out on a series of grids of increasingly fine scale, up to a final 50 m. We consider only overland locations, and do not model run-up in narrow river beds. Absolute values are found to vary from 2.5 m to 7 m on the shorelines of the Marquesas and Juan Fernandez Islands. A dataset of 22 comparisons with values surveyed in the field shows an average ratio (computed/observed) of 0.84 (-0.07 decimal logarithmic units) with a standard deviation of 0.17 d.l.u. (*/ by a factor of 1.48). In particular, the values computed overland in the principal bays of the Marquesas are generally well reproduced. Most importantly, we compute a small amplitude at Juan Fernandez Island (2.5 m; measured: 2.7 m). We are thus able to reproduce the sharp directivity of the wave in the far field, a consequence of the longitudinal extent of the source region along the trench. When combined with previous successful modeling of run-up in Hilo from a dislocation source by Titov [2001], we conclude that the far field of the 1946 tsunami can be adequately modeled by an acceptable seismic dislocation, rather than by a landslide source. The latter, which is necessary to model the near field [Okal et al., 2003] most probably took place, but did not contribute substantially to the far field.
DE: 4255 Numerical modeling
DE: 4564 Tsunamis and storm surges
DE: 9355 Pacific Ocean
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting