Seismic Cycle Observations of the Lesser Antilles Megathrust Based on Coral Microatolls

Thursday, 18 December 2014
Belle Philibosian1, Nathalie Feuillet1, Eric Jacques1, Jennifer Weil Accardo1, Anne-Sophie B Meriaux2, Abel Guihou3 and André Anglade4, (1)Institut de Physique du Globe de Paris, Paris, France, (2)Newcastle University, Newcastle Upon Tyne, NE1, United Kingdom, (3)CEREGE Europole de l Arbois, Aix en Provence, France, (4)Observatoire Volcanologique et Sismologique de la Guadeloupe, Gourbeyre, Guadeloupe
The recent occurrence of giant earthquakes in areas where such events were previously thought to be impossible has inspired the geoscience community to re-evaluate the seismic potential of other “low-hazard” subduction zones. One such example is the Lesser Antilles megathrust, which has not produced any large earthquakes in modern times and has been consequently considered largely aseismic. Recent GPS observations also suggest low coupling, but the scarcity of observations in the forearc leaves much of the strain accumulation poorly constrained. Additionally, recent studies elsewhere have revealed that geodetic rates measured over the short instrumental period are not necessarily representative of long-term deformation rates. Historical records of great earthquakes, which were almost certainly megathrust ruptures, demonstrate that the subduction is not entirely aseismic. Using the method of coral microatoll paleogeodesy developed in Sumatra, we examine century-timescale vertical deformation on the forearc islands of the Lesser Antilles and infer the underlying strain accumulation on the megathrust.