Modeling the La Palma landslide tsunami

The tsunami expected from a lateral collapse of the Cumbre Vieja Volcano on La Palma in the Canary Islands was modeled. The flank collapse for a ‘worst case ” landslide was modeled as a 650 meter high, 20 kilometer radius water wave after 30 kilometers of travel as predicted by physical modeling studies of Fritz at ETH in Zurich, Switzerland. The modeling was performed using the SWAN code which solves the nonlinear long waver equations. The tsunami generation and propagation was modeled using a 10 minute Mercator grid of 600 by 640 cells. The small wavelength and period of the tsunami expected from the landslide source results in an intermediate wave rather than a shallow water tsunami wave. The use of a shallow water model only describes the geometric spreasing of the wave and not the significant dispersion such a short period wave would exhibit. Dispersion would reduce the wave amplitudes to less than one-third of the shallow water amplitudes. The upper limit shallow water modeling indicates that the east coast of the U.S.A. and the Caribbean would receive tsunami waves less than 3 meters high. The European and African coasts would have waves less than 10 meters high. Full Navier-Stokes modeling including dispersion and geometric spreading for the Fritz initial wave profile predicts that the maximim wave amplitude off the U.S. east coast would be about a meter. Even with shoaling the wave would not present a significant hazard