introduction

the 1964 Alaska tsunami

three phases of tsunami evolution:
• generation
• propagation
• runup

the model and grids

references

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We calculate the extent of inundation caused by tsunami waves using numerical modeling of tsunami wave runup. The model is based on the vertically integrated nonlinear shallow water equations of motion and continuity with friction and Coriolis force (Murty, 1984). We apply a space-staggered grid, which requires either sea level or velocity as a boundary condition. The first order scheme is applied in time and the second order scheme is applied in space. Integration is performed along the north–south and west–east directions separately as described by Kowalik and Murty (1993).
In order to propagate the wave from a source to various coastal locations we use embedded grids, placing a coarse grid in deep water and coupling it with finer grids in shallow water areas. We use an interactive grid splicing, therefore the equations are solved on all grids at each time step, and the values along the grid boundaries are interpolated at the end of every time step (Troshina, 1996). The radiation condition is applied at the open (ocean) boundaries (Reid and Bodine, 1968). At the water–land boundary, the moving boundary condition is used in those grids that cover areas selected for inundation mapping (Kowalik and Murty, 1993). In all other grids, the velocity component normal to the coastline is assumed to be zero.

The region shown in the above figure has a number of embedded grids. The first grid of 24-second resolution covers the lower part of Cook Inlet and waters around Kodiak Island. The two 8-second grids cover Kachemak Bay and waters adjacent to Resurrection Bay. There are several 3-second resolution grids covering communities of Homer, Seldovia and Seward. Finally, there are 1-second resolution grids where runup calculations are performed. In these grids, the combined bathymetric and topographic data allow for application of the moving boundary condition as well as calculating the runup heights and extent of the inundation.