Deep-water seamounts, a potential source of tsunami generated by landslides? The Hirondelle Seamount, NE Atlantic

Abstract

Submarine mass failures represent one of the most significant marine geo-hazards. Their importance as a major contributor to tsunami generation and hazard has been recognized over the last 20–30years. This study investigates a newly mapped submarine landslide, the South Hirondelle Landslide (SHL), and its potential to generate a tsunami and to threat the surrounding coasts. The SHL is located 150km offshore South West Iberia, along the southern flank of the Hirondelle Seamount. Here, available swath bathymetry and one multichannel seismic profile show the presence of large, geometrically well constrained, deep-water landslide deposit of about 500km3 and its associated scar. The failure likely occurred in one single event and according to a detailed numerical modelling of the landslide dynamics and of the resulting water propagation the mass failure generated a mega-tsunami, with significant impact along the surrounding coastal areas of Iberia and Morocco. This result strongly supports the inclusion of tsunami induced by deep-water submarine landslides in the marine geo-hazard assessment of the North East Atlantic region.