Charvis, Philippe

Evain, Mikael

Flueh, Ernst R.

Galve, Audrey

Laigle, Mireille

Weinzierl, Wolfgang

English

OceanRep

Geophysical Research AbstractsVol. 12, EGU2010-PREVIEW, 2010EGU General Assembly 2010© Author(s) 2010A 3D seismic tomography of the Lesser Antilles Subduction Zone offshoreDominica and Martinique islandsMikaël Evain (1), Audrey Galve (1), Philippe Charvis (1), Mireille Laigle (2), Ernst Flueh (3), and WolfgangWeinzierl (3)(1) Géoazur, Université de Nice Sophia-Antipolis, Observatoire de la Côte d’Azur, INSU-CNRS, IRD, Villefranche-sur-Mer,France, (2) Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, (3) IFM-GEOMAR, Leibniz Institute for MarineScience, Kiel, GermanyAlong the eastern border of the Caribbean plate the Lesser Antilles islands form an active volcanic arc above theAtlantic subducting lithosphere. The crustal structure of this convergent margin is presented here from first arrivaltomographic inversion of a 3D wide-angle seismic dataset acquired offshore Dominica and Martinique islands bya network of 27 Ocean Bottom Seismometers (OBS).The resulting 3D velocity model shows good resolution from 7-8 km down to ∼15 km depth in a 150 km x 150km area.Though our study area is located at the northern termination of one of the world’s largest accretionary prisms westill observe about 5 to 7 km of sediment (v< 4 km/s) in the southeastern corner of our model.Our network is centered on a remarkable bathymetric feature: the Arawak Basin, a 6 km deep basin trendingNW-SE, filled with 3 km of sediment on average. The western side of the Arawak Basin is bordered at depth by abasement high, highlighted by the rise of the 6.0-6.5 km/s velocity contours up to 2 km below seafloor.To the east of the Arawak Basin, below the accretionary prism, SW-NE cross-sections show two successive risesof velocity contours from 4.0 to 6.0 km/s. The first one, also clearly seen on the MCS data, is coincident withthe eastern border of the Arawak Basin, while the second one seems located ∼30 km to the East, below the thickaccretionary prism. We interpret these highs as basement uplifts associated with the subduction of the Tiburonridge.We do not sample the interplate contact mainly due to high seismic attenuation in the accretionary wedge.More insight into the geometry of this contact may arise from the processing of a ∼285 km long wide-anglerefraction/reflection profile parallel to the convergence that cross our 3D velocity model in its middle andcontinues across the entire subduction complex. Preliminary tomographic results from this dataset recorded by 45densely spaced OBS confirm the observations described above. This new 2D line reveals also two high velocityzones interpreted as plutonic formations below the active and eastern remnant arcs that diverge northward fromthe Martinique Island. Further work using for instance direct modeling of later arrivals may give us considerableinformation on the interplate contact and on the depth of the Caribbean Moho below the Lesser Antilles volcanicarc.

A 3D seismic tomography of the Lesser Antilles Subduction Zone offshore Dominica and Martinique islands

Abstract

Similar works

Full text

Available Versions

OceanRep