Numerical modelling of historical landslide-generated tsunamis in the French Lesser Antilles

Abstract

Abstract. Two historical landslide-induced tsunamis that reached the coasts of the French Lesser Antilles are studied. First, the Martinique coast was hit by a tsunami down the western flank of Montagne Pelée at the beginning of the big eruption of May 1902. More recently, the northeastern coast of Guadeloupe was affected by a tsunami that had been generated around Montserrat by pyroclastic flows entering the sea, during the July 2003 eruption of the Soufrière Hills volcano. We use a modified version of the GEOWAVE model to compute numerical simulations of both events. Two source hypotheses are considered for each tsunami. The comparison of the simulation results with reported tsunami height data helps to discriminate between the tested source decriptions. In the Martinique case, we obtain a better fit to data when considering three successive lahars entering the sea, as a simplified single source leads to an overstimation of the tsunami wave heights at the coast. In the Montserrat case, the best model uses a unique source which volume corresponds to published data concerning the peak volume flow. These findings emphasize the importance of an accurate description of the relevant volume as well as the timing sequence of the source event in landslide-generated tsunami modelling. They also show that considering far-field effects in addition to near-field effects may significantly improve tsunami modelling.

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

“…They then identified the scenarios that would be the most impactful for Mayotte. As a first attempt to assess tsunami hazards in Mayotte for national and local authorities in charge of risk mitigation, the deformation of the sea surface generated by each of the potential submarine landslides was calculated with the TOPICS software [Tsunami Open and Progressive Initial Condition System; Watts et al, 2003], based on simple empirical relations for the landslide description [Le Roy et al, 2015, Poisson and Pedreros, 2010and Di Risio et al, 2011 for a review of such empirical relations]. These relations represented the landslide motion as a rigid block moving along a constant slope.…”

A Methodology for a Comprehensive Probabilistic Tsunami Hazard Assessment: Multiple Sources and Short-Term Interactions

“…The values of the other parameters in Equation (25) are: K = 0.011, c = 0.00004, Π = 1.16, α = 1.3, G = 1.1 and q = 1.5 according to [85]. As stated in Equation (13), the T otP T HA short−term is performed again through Equation (6) where the source phase probability in Equation (7) is assessed accounting for SI through Equation (10)…”

“…where the first term is assessed by Equation (22) and λ ET AS through Equation (25). We consider an exposure time window ∆t of 7 days.…”

“…However, it has been demonstrated that in many areas, major causes of tsunami are the non-seismic sources, such as mass failures (whether or not triggered by seismic events) ( [17,18]), volcanic activity ( [19][20][21][22][23][24][25]). In particular, volcanic flows ( [26,27]), landslides and rock slides on coastal areas ( [28][29][30][31][32]) and submarine mass failures ( [33][34][35][36]) may lead to the catastrophic tsunamis, but very few analyses treated such non-seismic tsunamigenic sources in a probabilistic frame ( [13,37]).…”