Numerical modeling of the September 13, 1999 landslide and tsunami on Fatu Hiva Island (French Polynesia)

Abstract

On September 13, 1999, Omoa Bay (Fatu Hiva Island, French Polynesia) was struck by 2 to 5 m high water waves: several buildings were flooded and destroyed but no lives were lost. Observations gathered during a post‐event survey revealed the recent collapse into the sea of a 300 × 300 m2, at least 20‐m thick, cliff located 5 km southeast of Omoa. This cliff failure most certainly triggered the tsunami waves since the cliff was reported intact 45 min earlier. We simulate the tsunami generation due to a subaerial landslide, using a finite‐difference model assimilating the landslide to a flow of granular material. Numerical modeling shows that a 0.0024‐km3 landslide located in the presumed source area accounts for the tsunami waves reported in Omoa Bay. We show that the striking amplification observed in Omoa Bay is related to the trapping of waves due to the shallow submarine shelf surrounding the island.