3-DIMENSIONAL MODELING OF TSUNAMI GENERATION DUE TO A SUBMARINE MUDSLIDE

Submarine landslides are a common cause of tsunamis in coastal and est uarine areas. To study this phenomenon, a numerical model is developed to simulate tsunami generation due to a viscous mudslide on a gentle uniform slope. A formulation of the dynamics of the problem is present ed, where the mudslide is treated as an incompressible three-dimension al viscous flow. Seawater is treated as an inviscid fluid, and the wat er motion is assumed irrotational. The long-wave approximation is adop ted for both water waves and the mudslide. The resulting differential equations are solved by a finite-difference method. The focus of this paper is to examine the effects of the longitudinal spreading as well as the transversal spreading of the slide upon surface wave generation , and the spreading of water waves sideways. Three-dimensional picture s are presented for successive profiles of the mud surface, the horizo ntal velocities of the mudslide, the evolution of the surface elevatio ns, and the velocities of the water motion. Comparisons of the present three-dimensional calculations with previously published two-dimensio nal results indicate small differences for large length/width ratios f or a small time after the initiation of the slide. Generally, however, the water surface profiles deviate significantly from the two-dimensi onal results. Adequate simulations thus require accurate representatio n of the aspect ratio of the sliding mass.