Development, testing, and applications of site‐specific tsunami inundation models for real‐time forecasting

Abstract

[1] The study describes the development, testing and applications of site-specific tsunami inundation models (forecast models) for use in NOAA's tsunami forecast and warning system. The model development process includes sensitivity studies of tsunami wave characteristics in the nearshore and inundation, for a range of model grid setups, resolutions and parameters. To demonstrate the process, four forecast models in Hawaii, at Hilo, Kahului, Honolulu, and Nawiliwili are described. The models were validated with fourteen historical tsunamis and compared with numerical results from reference inundation models of higher resolution. The accuracy of the modeled maximum wave height is greater than 80% when the observation is greater than 0.5 m; when the observation is below 0.5 m the error is less than 0.3 m. The error of the modeled arrival time of the first peak is within 3% of the travel time. The developed forecast models were further applied to hazard assessment from simulated magnitude 7.5, 8.2, 8.7 and 9.3 tsunamis based on subduction zone earthquakes in the Pacific. The tsunami hazard assessment study indicates that use of a seismic magnitude alone for a tsunami source assessment is inadequate to achieve such accuracy for tsunami amplitude forecasts. The forecast models apply local bathymetric and topographic information, and utilize dynamic boundary conditions from the tsunami source function database, to provide site-and event-specific coastal predictions. Only by combining a Deep-ocean Assessment and Reporting of Tsunami-constrained tsunami magnitude with site-specific high-resolution models can the forecasts completely cover the evolution of earthquake-generated tsunami waves: generation, deep ocean propagation, and coastal inundation. Wavelet analysis of the tsunami waves suggests the coastal tsunami frequency responses at different sites are dominated by the local bathymetry, yet they can be partially related to the locations of the tsunami sources. The study also demonstrates the nonlinearity between offshore and nearshore maximum wave amplitudes.Citation: Tang, L., V. V. Titov, and C. D. Chamberlin (2009), Development, testing, and applications of site-specific tsunami inundation models for real-time forecasting,

Tsunamis: bridging science, engineering and society

“…Then, given the offshore scenario based on this estimate, high-resolution MOST with three nested telescoping grids takes over to produce inundation predictions at a specific coastal site. The methodology and examples are presented in Tang et al [18,67] and Wei et al [68].…”

“…Since 2004, NOAA has been developing real-time tsunami flooding forecast capabilities for the US coastlines and its territories [18,67,68] in support of TWCs in Hawaii and Alaska operated by NOAA's National Weather Service [65] in addition to long-term forecasting capabilities and hazard assessment products for the US National Tsunami Hazard Mitigation Program. As Synolakis & Kânoglu [29] describe, during an event, the NCTR methodology integrates real-time deep-ocean observations of evolving tsunamis from several tsunameters with a pre-computed basin-wide propagation database of wave amplitudes and flow velocities through an inversion algorithm to refine the tsunami source as combinations of tsunamigenic unit sources.…”

Dynamic tsunami generation due to sea-bottom deformation: Analytical representation based on linear potential theory

“…Ocean-bottom pressure gauges are often used for recording tsunamis (e.g., Tang et al, 2009). The pressure in the ocean is given by the sum of the hydrostatic pressure and an excess pressure due to the tsunami, i.e., −ρ 0 g 0 z + p e , where the excess pressure is given by the velocity potential as p e = −ρ 0 ∂ϕ/∂t.…”

A nested-grid Boussinesq-type approach to modelling dispersive propagation and runup of landslide-generated tsunamis

“…This algorithm depends on the real-time measurements of DART sensors, and constrains the tsunami source by fitting these measurements to a linear combination of precomputed tsunami source functions (Tang et al, 2009). A tsunami source function is defined as the time series of water surface displacements and water velocities in an ocean basin caused by a unit earthquake source, which has a dimension of 100 × 50 km 2 , and a slip value of 1 m, equivalent to a moment magnitude of 7.5 (Gica et al, 2008).…”