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Elsevier, Tectonophysics, (603), p. 68-78, 2013

DOI: 10.1016/j.tecto.2011.08.006

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Seismic activity offshore Martinique and Dominica islands (Central Lesser Antilles subduction zone) from temporary onshore and offshore seismic networks

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This paper is available in a repository.

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Abstract

This work focuses on the analysis of a unique set of seismological data recorded by two temporary networks of seismometers deployed onshore and offshore in the Central Lesser Antilles Island Arc from Martinique to Guadeloupe islands. During the whole recording period, extending from January to the end of August 2007, more than 1300 local seismic events were detected in this area. A subset of 769 earthquakes was located precisely by using HypoEllipse. We also computed focal mechanisms using P-wave polarities of the best azimuthally constrained earthquakes.We detected earthquakes beneath the Caribbean forearc and in the Atlantic oceanic plate as well. At depth seismicity delineates the Wadati-Benioff Zone down to 170. km depth.The main seismic activity is concentrated in the lower crust and in the mantle wedge, close to the island arc beneath an inner forearc domain in comparison to an outer forearc domain where little seismicity is observed. We propose that the difference of the seismicity beneath the inner and the outer forearc is related to a difference of crustal structure between the inner forearc interpreted as a dense, thick and rigid crustal block and the lighter and more flexible outer forearc. Seismicity is enhanced beneath the inner forearc because it likely increases the vertical stress applied to the subducting plate. © 2011 Elsevier B.V. ; This work has been carried out with the support of the European Union “Thales Was Right” (UE-FP6-2004-NEST-C-1), the French ANR project “Subsismanti” and also partly by the OBSISMER programme for earthquake monitoring. Spanish Consolider-Ingenio 2010 Topoiberia (CSD2006-00041) now supports one of us (MR).