Numerical simulation of submarine landslides and generated tsunamis: application to the on-going Mayotte seismo-volcanic crisis

International audience(150 mots max) Since May 2018, Mayotte Island has been experiencing seismo-volcanic activity that could trigger submarine landslides and, in turn, tsunamis. To address these hazards, we use the HYSEA numerical model to simulate granular flow dynamics and the Boussinesq FUNWAVE-TVD numerical model to simulate wave propagation and subsequent inundations. We investigate 8 landslide scenarios (volumes from 11.25´10 6 m 3 to 800´10 6 m 3). The scenario posing the greatest threat involves destabilizations on the eastern side of Mayotte's lagoon at shallow depth and can generate sea-surface deformations of up to 2 m. We show that the barrier reef surrounding Mayotte plays a prominent role in controlling water-wave propagation and in protecting the island. The tsunami travel time to the coast is very short (a few minutes) and the tsunami is not necessarily preceded by a sea withdrawal. Our simulation results provide a key to establishing hazard maps and evacuation plans and improving early-warning systems