Tsunami warnings: predicting arrivals

In the context of earthquake warning, predictions are made, among others, on the possible attacks of tsunami. Decision makers encounter two major issues. The first issue is the possible impacts of tsunami due to its hydrodynamics such as overtopping force. Another issue is the arrival time which is related to the physical nature of wave propagation. To address the second issue, this chapter firstly presents the understanding of tsunami generation and then discusses the applications of water wave theories in the post-earthquake period. Large seismic disturbances on the sea floor can create tsunami waves that spread ocean-wide with profound effects on coastal landscapes. Tsunami waves, originating in or near the area of the earthquakes that create it, propagate outwards in all directions at a speed that depends upon the ocean depth. In these circumstances, the need for rapid estimation of tsunami arrivals becomes obvious if warnings are to be issued in sufficient time for local evacuation. The research on water wave has entered into a phase where much emphasis has been put on the complicated tsunami simulation models. The theory of linear water waves provides decision makers with a capability of estimating the arrival time of tsunami with a reasonable accuracy and then allocating resources according to the contingent plan. To verify the validity of the linear water wave theory, we test several historical data of tsunami arrivals. The results suggest that the linear water wave theory can be readily applied to estimate the time left for emergency evacuation. The tsunami arrival estimation in earthquake warning is the key action of reducing damage due to the earthquake that may generate series of tsunamis