Tsunami symposium held


  • Harold G. Loomis


A tsunami symposium was held December 6–7,1979, at the Australian Academy of Sciences, as part of the IUGG meeting in Canberra. Twenty-one papers were given in three sessions which covered the full range of tsunami research.

The first session, chaired by Rogert Braddock (Australia), was about tsunami generation and propagation. The paper by Voyt, Lebeder, and Sebekin (USSR) reported a continuation of Soviet efforts to solve the generation problem, treating the complete earth-ocean system together. The coupled dynamic equations are written, and by means of Laplace transforms in time and Fourier transforms in space an integral expression is found for the disturbance at the ocean surface. The rest of the papers in this session were primarily numerical. The paper by Shaw and Neu (U.S.) treated laterally uniform geometries where time-harmonic standing-wave forms are possible. Loomis (U.S.) and Murty (Canada) discussed an interpretation of tsunami forerunners as a portion of the tsunami in the deep ocean that is diffracted onto a shelf or island ridge. The paper by Hebenstreit, Bernard, and Vastano (U.S.) treated the time-dependent wave problem for the Hawaiian Island chain. A guassian wave form was timestepped into the chain, and the energy as a function of frequency and shoreline location was stored. This was intended to show the frequencies that were trapped by various islands and the effect of direction of arrival on trapping. The paper by Farrar (U.S.) included turbulent mixing as a damping factor in the response of harbors to tsunamis. The paper by Melville (U.S.) was about the mach-stem effect in which waves traveling obliquely to a coast have an additional amplification. The effect is essentially nonlinear, and the Boussinesq formulation is used. Tank experiments do not measure the effect as predicted, and it is suggested that the problem lies in an inconsistency in the formulation of the mathematical model.