The Mw 6.3 earthquake of Les Saintes (Guadeloupe) on November 21, 2004

François Beauducel, Christian Anténor-Habazac, Sara Bazin, Jean-Bernard De Chabalier, Alexandre Nercessian, Nathalie Feuillet, Eric Jacques, Didier Bertil, Georges Boudon, Anne Lefriant, Paul Tapponnier, Alfred Hirn, Jean-Claude Lépine, Pascal Bernard, Jean-Christophe Komorowski, Geoffrey C.P. King, OVSG team

Paper presented at IAVCEI European Seismological Commission Annual Workshop, Saint-Claude Guadeloupe, September 19-24, 2005.

Abstract. On November 21, 2004, a shallow Mw 6.3 earthquake occured on a normal fault South-East of Les Saintes islands (Guadeloupe), at 15.75°N, 61.54°W, 14 km depth. It was the most important tectonic event in this area since 1897, and it caused one death and important damages at Les Saintes and North Dominica, a small tsunami (2-m runup) on Les Saintes as well as the nearest shores of Guadeloupe and Dominica, and some landslides. The active but non-erupting Soufrière volcano, located about 40 km from the epicenter, has not shown developed any changes in activity (despite a reinforcement of its monitoring), excepted for superficial landslides on the edifice and it’s immediate unstable surroundings, and minor localized ground cracks. We recorded more than 2000 aftershocks in the first 24 hours and a total amount of 24,000 aftershocks after 300 days. The main aftershock ML 5.7 occured 85 days after the main shock on February 14, 2005. It’s epicenter was closer to the populated towns of Les Saintes. As of September 2005, the crisis was still going with a rate of 10 to 90 events per day. A large part of the events are localized at very shallow depths and still felt (or heard, as rumble) by the population, even small events of magnitude less than 2. We present here the evolution of aftershocks (in time, magnitude and space), and the first data and analyses of this event used to follow the crisis locally.

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