Modeling Tsunami Sources and Their Propagation in the Atlantic Ocean for Coastal Tsunami Hazard Assessments and Inundation Mapping along the U.S. East Coast

摘要

Numerical simulations are performed to develop tsunami inundation maps for the U.S. East Coast (USEC), as envelopes of surface elevations caused by the probable maximum tsunamis (PMTs) in the Atlantic Ocean basin. These PMTs are triggered by various sources, identified from historical records or hypothetical, including : (i) near-field submarine mass failures (SMF) on or near the continental shelf break; (ii) an extreme hypothetical M9 seismic event occurring in the Puerto Rico Trench; (iii) a repeat of the historical 1755 M9 (Lisbon) earthquake occurring in the Madeira Tore Rise; and (iv) large scale volcanic flank collapses (80 and 450 km3) of the Cumbre Vieja volcano (CVV) on La Palma, in the Canary Archipelago. Tsunamis caused by: (1) earthquakes, are obtained from the estimated coseismic seafloor deformation; (2) SMF sources, modeled as rigid slumps, are generated using the 3D non-hydrostatic model NHWAVE; and (iii) the CVV sources are modeled as subaerial flows of a heavy fluid, using a 3D Navier-Stokes model. For each source, tsunami propagation to the USEC is then modeled in a series of nested grids of increasingly fine resolution, by one-way coupling, using FUNWAVE-TVD, a nonlinear and dispersive (2D) Boussinesq model. High-resolution inundation maps have been developed based on these results, so far for about a third of the USEC. A comparison of coastal inundation from each tsunami source shows similar alongshore patterns of higher and lower inundation, whatever the initial source direction; this is due to wave focusing and defocusing effects induced by the shelf bathymetry. Once developed for the entire USEC, inundation maps will fully quantify coastal hazard from the selected PMTs and allow developing site-specific mitigation measures and evacuation plans. Besides maximum inundation, other "products" available at high-resolution are maximum momentum flux, currents, and vorticity, although these are not systematically developed as maps in this phase of work.