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.
Highlights
Mass wasting events affecting volcanoes are known to be potentially tsunamigenic (Latter, 1981; Lockridge, 1990)
Two historical landslide-induced tsunamis that reached the coasts of the French Lesser Antilles are studied
The Martinique coast was hit by a tsunami down the western flank of Montagne Pelee at the beginning of the big eruption of May 1902
Summary
The Lesser Antilles arc extends over 800 km from north to south between the Atlantic Ocean and the Caribbean Sea (Fig. 1). Two volcanic events involving ocean-entering debris flows are known to have generated tsunamis on the coasts of the French Antilles. Big volumes of pyroclastic material entered the sea at several times during successive phases of eruption They likely generated several tsunamis, among which only one is described in historical documents (New York Times, 1902; Berte, 1902; Chretien and Brousse, 1988; Scarth, 2002, Table 1). We first try to use model parameters taken from a published modelling study of the same event (Mattioli et al, 2007) As these parameters give poor results on the Guadeloupe shore, we modify them with the help of other published data in order to better match the observations. The different parameters are discussed through the comparison between simulation results and historical observations
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