Near- and far-field tsunami hazard from the potential flank collapse of the Cumbre Vieja volcano

As demonstrated in the pioneering (but still controversial) work by Ward and Day (2001), the potential flank collapse of the Cumbre Vieja Volcano (CVV) on La Palma (Canary Islands) could result in a large tsunami having effects throughout the North Atlantic Ocean. While recent studies have suggested that such a collapse would likely result in more moderate tsunami waves than originally thought, these would still cause devastating effects in the near-field on neighboring Canary Islands, and their far-field coastal hazard would still be significant at some locations, and hence ought to be assessed. Abadie et al. (2011) simulated landslide tsunami generation from various CVV flank collapse scenarios, using a 3D Navier-Stokes (NS) multi-fluid VOF model (THETIS) with implicit slide motion. As 3D-NS computations are both too computationally demanding and affected by numerical diffusion, they computed near-field impact in a coupled long-wave Boussinesq model (FUNWAVE-TVD). Here, for a similar series of CVV flank collapse scenarios (with 20, 40, 80, and 450 km3 volume), we further simulate and analyze the nearfield tsunami impact, and compute far-field propagation and coastal impact at distant locations (such as North America, western Europe and west Africa). A similar one-way model coupling approach is used between THETIS and a Cartesian, fully nonlinear version of FUNWAVETVD to compute near-field effects in a fine regional grid (about 15" arc mesh). Results in the latter grid are then used to initialize an ocean basin-scale grid (2' arc mesh) and compute far-field tsunami propagation, using a weakly nonlinear spherical coordinate version of FUNWAVETVD. Coastal impact is finally computed in selected locations using more finely resolved nested coastal grids (30" arc mesh). Results are analyzed in terms of wave/tsunami source characteristics, propagation features, and maximum wave elevation off distant coasts. For the most impacted coastal areas, further simulations will be performed in even finer nested grids, to compute inundation and runup. These results will be presented at the conference.