Numerical Simulation of Tsunami Generation, Propagation, and Runup

A numerical model is applied to calculate runup and inundation along the east coast of New Zealand arising from tsunami generated locally along the New Zealand coastal margin. In general, tsunami can be generated by a sudden movement of the ocean bed or by objects such as subaerial landslides and bolides falling into the ocean; however, this study is restricted to fault ruptures and submarine landslides. The model is based on the Reynolds-averaged Navier-Stokes (RANS) equation and uses a finite element spatial approximation, implicit time integration, a semi-Lagrangian advection approximation, and several different methods for treating pressure variations. These methods include the hydrostatic approximation, a simplified pressure interpolation scheme, and a full solution with pressure Poisson equation. The different methods of approximation are being evaluated against test problems for wave runup and submarine avalanches. Although these results are preliminary, the results with a simplified pressure model are encouraging in that they provide a realistic approximation to non-hydrostatic effects while remaining competitive with the efficiency of depth-averaged models.