Comparison of Modeling Approaches and Derived Warning Products in the Framework of the Indonesia Tsunami Early Warning System (InaTEWS)
The Indonesia Tsunami Early Warning System estimates tsunami impact by two methods: either matching scenarios from a pre-computed database or running realtime tsunami simulations. The database scenarios are based on the finite element model TsunAWI using a triangular mesh with resolution ranging from 20km in deep ocean to 300m in coastal areas and up to 50m in some highly-resolved areas. TsunAWI solves the nonlinear shallow water equations and contains an inundation scheme. The on-the-fly propagation model easyWave solves the linear shallow water equations on a regular finite-difference grid with a resolution of about 1km and utilizes several options to estimate coastal impact. This model is used for potential tsunami events in areas not covered by the database. Warning products like estimated wave height (EWH) and estimated time of arrival (ETA) along the coast are based on modeling results. Therefore comparisons of the forecasted warning levels for the two approaches are crucial. Resolutions and numerical settings of both models differ, therefore variations in the resulting outputs are to be expected; nevertheless, the extent of differences in warning levels should not be too large for identical sources. In the present study, we systematically investigate differences in warning products along forecast points facing the Sunda arc. TsunAWI determines warning products are directly in the coastal forecast points, easyWave offers several options for their approximation including projections from offshore grid points. Differences and potential reasons for variations of warning products like the role of bathymetry, resolution as well as the general approach for the assessment of EWH and ETA for different modeling frameworks are discussed.
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