Résumé
We investigate the seismic anisotropy signature of the continental rifting process. Severa! sources of anisotropy are considered: the lithospheric deformation, the asthenospheric flow, and the occurrence of oriented melt pockets in the asthenospheric mande. Our results show that contrasted anisotropy patterns should be associated with the various conceptual models of rifting. Thus seismic anisotropy measurements may allow one to discriminate between these models. Anisotropy measurements in the Rio Grande, East-African and Rhine rifts suggest that these rifts formed by a transtensional deformation of the lithospheric mande rather than by homogeneous extension of the lithosphere. Alignment of melt-lenses in the asthenospheric wedge may also account for a significant part of the seismic anisotropy recorded in the internai domains of these rifts.