Landslide‐generated tsunamis at Réunion Island

Abstract

[1] Landslides that occur on oceanic volcanoes can reach the sea and trigger catastrophic tsunamis. Réunion Island has been the location of numerous huge landslides involving tens to hundreds of cubic kilometers of material. We use a new two-fluid (seawater and landslide) numerical model to estimate the wave amplitudes and the propagation of tsunamis associated with landslide events on Réunion Island. A 10 km 3 landslide from the eastern flank of Piton de la Fournaise volcano would lift the water surface by about 150 m where it entered the sea. The wave thus generated would reach Saint-Denis, the capital of Réunion Island (population of about 150,000 people), in only 12 min, with an amplitude of more than 10 m, and would reach Mauritius Island in 18 min. Although Mauritius is located about 175 km from the impact, waves reaching its coast would be greater than those for Réunion Island. This is due to the initial shape of the wave, and its propagation normal to the coast at Mauritius but generally coast-parallel at Réunion Island. A submarine landslide of the coastal shelf of 2 km 3 , would trigger a ∼40 m high wave that would severely affect the proximal coast in the western part of Réunion Island. For a landslide of the shelf of only 0.5 km 3 , waves of about 2 m in amplitude would affect the proximal coast.

Rheological considerations for the modelling of submarine sliding at Rockall Bank, NE Atlantic Ocean

“…In numerical modelling of submerged motion, such an approach has been used for many cases. 20,26,42 Here, we consider a fixed density of ρ = 1, 200 kg m 3 .…”

“…It has been efficiently used to study many cases of subaerial and submarine sliding. 19,25,26 A frictional model, based on the Mohr-Coulomb failure criterion, was used to study the flow motion. A simplified Bingham rheology is also implemented.…”

Source mechanisms of volcanic tsunamis

“…[63,64]). Their rheology is also poorly constrained, but it has a minor effect on the characteristics of the tsunami, compared with uncertainties on failure mechanisms (figure 1; [63,65,66]). Marine conglomerates found at unusually high elevations in Hawaii, Cape Verde, Mauritius (figure 2), and the Canary Islands were interpreted as being the result of tsunami waves generated by massive flank failures [65,[67][68][69][70].…”

Numerical simulations of tsunamis generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

“…Similar behaviour is also observed in mass flow generated tsunamis (e.g. Tinti et al, 1999;Lynett and Liu, 2002;Liu et al, 2005;Kelfoun et al, 2010;Giachetti et al, 2011) contrary to caldera collapse triggered tsunamis (e.g. Maeno et al, 2006;Maeno and Imamura, 2011;Novikova et al, 2011).…”