Tsunami Inundation Modeling

Tsunami inundation modeling simulates the entire life of a tsunami — its generation by seafloor displacement, its propagation across the ocean, and its runup and flooding of the coast — by numerically solving the equations of shallow-water hydrodynamics. The shallow-water approximation holds because a tsunami's wavelength vastly exceeds the ocean depth, so the wave behaves as a long wave whose speed depends on water depth, refracting and shoaling as it approaches shore. Titov and Synolakis's 1998 work on numerical modeling of long-wave runup established the Method of Splitting Tsunami (MOST), a finite-difference solver that became the operational standard for tsunami forecasting and inundation mapping. Because such models drive emergency planning, Synolakis and colleagues' 2008 paper set out the analytical, laboratory, and field benchmarks every tsunami model must pass to be trusted. The defining technical challenge is the moving shoreline — the wetting and drying of land as the wave advances and retreats. The output is a map of maximum inundation depth, extent, and runup elevation along the coast.