HR: 08:15h
AN: OS21E-02    [Abstracts]
TI: Propagation of Short, Dispersive Tsunami Waves in Ocean Basins
AU: * Kirby, J T
EM: kirby@udel.edu
AF: Center for Applied Coastal Research, University of Delaware, Newark, DE 19716 United States
AU: Shi, F
EM: fyshi@coastal.udel.edu
AF: Center for Applied Coastal Research, University of Delaware, Newark, DE 19716 United States
AU: Watts, P
EM: phil.watts@appliedfluids.com
AF: Applied Fluids Engineering, Inc., PMB\#237 5710 E 7th Street, Long Beach, CA 90803 United States
AU: Grilli, S T
EM: grilli@oce.uri.edu
AF: Separtment of Ocean Engineering, University of Rhode Island, Narragansett, RI 02882 United States
AB: Tsunami waves generated by mass failure events oscillate with relatively higher frequencies than waves generated in response to seismic faulting. As a result, these waves can be significantly modified by frequency dispersion effects while propagating over distances typically found in coastal seas or open ocean basins. Recent investigations have indicated that large scale underwater slide events are capable of generating significant transoceanic tsunami waves, as (for example) is hypothesized in the case of the 1946 Ugamak slide in the Aleutian Islands. In order to provide a comprehensive framework for modeling weakly dispersive waves from source to eventual landfall, we have developed a Boussinesq-type model for water surface waves in an ocean-scale basin. The basic model is formulated in spherical polar coordinates. Scaling analysis is utilized to simplify the model and to distinguish between the regime of long waves (with horizontal length scales approaching the basin dimensions) and shorter waves with horizontal scales commensurate with the short wave packet dimensions. The second scaling produces a model in which the usual weakly-dispersive Boussinesq model corrections are retained. The model retains a fully nonlinear formulation in its treatment of surface boundary conditions, allowing for accurate modeling of runup and propagation in the nearfield of shorelines. The model also retains the specification of an arbitrary (but for now externally prescribed) bottom motion, allowing for direct simulation of the response at the source. Finally, we are presently developing a formulation in curvilinear coordinates to allow for mapping computational grids to the ocean basin geometry. The model is used to examine tsunamis generated by several idealized sources in idealized ocean basins, in order to characterize farfield response to hypothetical slide properties. We hope to examine the 1946 Aleutian Islands event in detail by the time of the presentation.
DE: 4560 Surface waves and tides (1255)
DE: 4564 Tsunamis and storm surges
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting