Simulation of the 2004 tsunami of Les Saintes in Guadeloupe (Lesser Antilles)

摘要

Subduction zones are areas with significant tectonic activity, complex fault systems, volcanic edifices and growth of islands. Earthquakes in this context are associated with sudden subsidence or uplift of the sea floor with the potential to trigger landslides and tsunamis. A tsunami initiated by a megathrust earthquake can generate strong currents, and is able to carry massive quantities of sediments. The inhabited islands and coasts near subduction areas are threatened by those destructive earthquakes and tsunamis. The arc of the Lesser Antilles which formed due to the plunge of the Atlantic oceanic plate under the Caribean plate, is one of them. The tsunamigenic earthquakes in this region are rare, poorly documented and the only available data are qualitative (observations of coseismic displacement, intensity of the damages). Quantitative data is lacking as no seismograms or tide-gauge were set up before 1968. This lack of data increases the uncertainty on the existent fault models and the shortness of the catalog of seismicity does not enable a good analysis of the recurence cycle of the megathrust earthquakes. The most recent tsunamigenic earthquake occured in 2004 in the area of Les Saintes normal fault system. This Mw6.3 earthquake generated small waves with 2m of run-up in several bays of Les Saintes, a group of island in the South of Guadeloupe. A recent survey done on the fault scarp revealed important coseismic displacement at the surface which had not been predicted in the seismic source models resulting from the joint inversion of teleseismic and GPS data. Tsunami simulations of those different models of fault enable the calculation of the associated time arrivals and water heights of the waves. Compared to the reported observation, those results give complementary informations and additional constrains on the source parameters.