Tsunami runup model and forecast.

摘要

This study addresses the dynamics of tsunami generation, propagation, and runup as well as the relationship between tsunami signals near the source and the runup at distant locations. This is motivated by the need to provide timely waveform and runup forecasts using real-time water-level data near the tsunami source. The work includes the development of a long-wave runup model, an inverse algorithm for tsunami forecast, and a methodology for real-time prediction of tsunami runup.; The finite-volume model calculates long-wave propagation and run-up in the two-dimensional horizontal plane. The formulation uses a conservative form of the nonlinear shallow-water equations with source terms and an explicit Godunov-type scheme along with the exact Riemann solver for the flux and moving waterline. The surface-gradient method leads to a well-balanced formulation of the flux and source terms. This provides accurate descriptions of the conserved variables and small water surface perturbations during runup. The computed surface elevation and flow velocity are verified by analytical solutions and the runup is validated by laboratory data.; An inverse algorithm assesses the severity of a tsunami in progress based on real-time water-level data near the source. This study focuses on the Alaska-Aleutian source region and its potential threat to Hawaii. The source region is divided into a number of potential sub-faults for generation of a precomputed database of synthetic mareorams at water-level stations near the source and warning points in the Pacific. Regression of recorded tsunami signals provides the slip distribution at the source and the expected waveforms around the Pacific. A jackknife re-sampling scheme provides the confidence interval bounds of the predictions. The algorithm along with the database is verified and validated using both numerical and observed water-level data of past tsunami events.; The inverse algorithm can synthesize tsunami generation at the source and propagation across the Pacific through superposition of pre-computed mareograms. This approach defines the boundary conditions for the finite volume model, which in turn provides runup forecasts at predefined areas during a tsunami event. The results are validated for Haleiwa of Oahu using 1946 Alaska-Aleutian tsunami. Sensitivity studies show the feasibility and reliability of the forecast methodology for implementation.