Ruiz, M., Galve, A., Monfret, T., Sapin, M., Charvis, P., Laigle, M., Evain , M., Hirn, A., Flueh, Ernst R., Gallart, J., Diaz, J., Lebrun, J. F., Bayrakci, G., Becel, A., Gailler, A., Hello, Y., Kopp, Heidrun , Krabbenhoeft, Anne, Papenberg, Cord , Planert, Lars and Weinzierl, Wolfgang and Lesser Antilles Thales Scientific Party (2013) Seismic Activity offshore Martinique and Dominica islands (Central Lesser Antilles subduction zone) from temporary onshore and offshore seismic networks. Tectonophysics, 603 . pp. 68-78. DOI 10.1016/j.tecto.2011.08.006.

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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.

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