Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
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.
ISSN: 0040-1951

hal-01052679
https://hal.archives-ouvertes.fr/hal-01052679
DOI : 10.1016/j.tecto.2011.08.006

Éditeur(s) : [S.l.] : Prault
Résumé : 14e volume d'une encyclopédie, consacré aux Amériques
Siècle(s) traité(s) : 18
Droits : Domaine public
Provenance : Philippe Batrosse - Libraire à Cayenne
Permalien : http://www.manioc.org/patrimon/HASH01001fa66eeaf87b39563da1
HASH01001fa66eeaf87b39563da1

Éditeur(s) : Amer Geophysical Union
Résumé : After the January 12, 2010, Haiti earthquake, we deployed a mainly offshore temporary network of seismologic stations around the damaged area. The distribution of the recorded aftershocks, together with morphotectonic observations and mainshock analysis, allow us to constrain a complex fault pattern in the area. Almost all of the aftershocks have a N-S compressive mechanism, and not the expected left-lateral strike-slip mechanism. A first-order slip model of the mainshock shows a N264 degrees E north-dipping plane, with a major left-lateral component and a strong reverse component. As the aftershock distribution is sub-parallel and close to the Enriquillo fault, we assume that although the cause of the catastrophe was not a rupture along the Enriquillo fault, this fault had an important role as a mechanical boundary. The azimuth of the focal planes of the aftershocks are parallel to the north-dipping faults of the Transhaitian Belt, which suggests a triggering of failure on these discontinuities. In the western part, the aftershock distribution reflects the triggering of slip on similar faults, and/or, alternatively, of the south-dipping faults, such the Trois-Baies submarine fault. These observations are in agreement with a model of an oblique collision of an indenter of the oceanic crust of the Southern Peninsula and the sedimentary wedge of the Transhaitian Belt: the rupture occurred on a wrench fault at the rheologic boundary on top of the under-thrusting rigid oceanic block, whereas the aftershocks were the result of the relaxation on the hanging wall along pre-existing discontinuities in the frontal part of the Transhaitian Belt. Citation: Mercier de Lepinay, B., et al. (2011), The 2010 Haiti earthquake: A complex fault pattern constrained by seismologic and tectonic observations, Geophys. Res. Lett., 38, L22305, doi:10.1029/2011GL049799.
Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2011-11 , Vol. 38 , N. L22305 , P. 7 p.

Droits : 2011 by the American Geophysical Union
http://archimer.ifremer.fr/doc/00054/16557/14071.pdf
DOI:10.1029/2011GL049799
http://archimer.ifremer.fr/doc/00054/16557/

Éditeur(s) : Wiley / Blackwell
Résumé : For the first time, a deep seismic data set acquired in the frame of the Algerian-French SPIRAL program provides new insights regarding the origin of the westernmost Algerian margin and basin. We performed a tomographic inversion of traveltimes along a 100-km-long wide-angle seismic profile shot over 40 ocean bottom seismometers offshore Mostaganem (Northwestern Algeria). The resulting velocity model and multichannel seismic reflection profiles show a thin (3-4 km thick) oceanic crust. The narrow ocean-continent transition (less than 10 km wide) is bounded by vertical faults and surmounted by a narrow almost continuous basin filled with Miocene to Quaternary sediments. This fault system, as well as the faults organized in a negative-flower structure on the continent side, marks a major strike-slip fault system. The extremely sharp variation of the Moho depth (up to 45 +/- 3 degrees) beneath the continental border underscores the absence of continental extension in this area. All these features support the hypothesis that this part of the margin from Oran to Tenes, trending N65-N70 degrees E, is a fossil subduction-transform edge propagator fault, vestige of the propagation of the edge of the Gibraltar subduction zone during the westward migration of the Alboran domain.
Geophysical Journal International (0956-540X) (Wiley / Blackwell), 2015-02 , Vol. 200 , N. 2 , P. 1027-1043

Droits : The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society
http://archimer.ifremer.fr/doc/00255/36670/35278.pdf
http://archimer.ifremer.fr/doc/00255/36670/35279.pdf
DOI:10.1093/gji/ggu454
http://archimer.ifremer.fr/doc/00255/36670/

Éditeur(s) : Paris : L. Larose
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie
Permalien : http://www.manioc.org/patrimon/FRA11114
FRA11114