Tsunami inundation modelling using RiCOM

The New Zealand coastline faces the risk of tsunami from a variety of sources, including remote and local earthquakes, submarine landslides, and volcanoes. Palaeotsunami studies indicate New Zealand has undergone periods of catastrophic tsunami activity, such as in the 1500s. It is important to be able to quantify the hazard posed by tsunamis. In this paper we detail the process of modelling tsunami propagation and inundation from source to destination using RiCOM, a finite element coastal hydrodynamic model on an unstructured grid. We give examples of model outputs, such as maps of tsunami inundation depth, maximum speeds, wave arrival times and time spent inundated, which can be used to quantify the hazard. We also perform sensitivity analysis of the response of the tsunami to the average slip on, and length and width of, the fault surface while keeping the moment magnitude and all other parameters constant. Larger average slip is shown to produce larger tsunamis. The width/aspect ratio of the slip has a more variable effect on the size of the tsunami, which depends upon the local coastal geometry. This information can be used to identify risk areas, plan escape routes, protect people and infrastructure and, more generally, to inform the public as to the tsunami risk in their region.