A Tertiary asthenospheric flow beneath the southern French Massif Central indicated by upper mantle seismic anisotropy and related to the west Mediterranean extension |
| |
| Authors: | Guilhem Barruol Michel Granet |
| |
| Institution: | a Laboratoire de Tectonophysique, CNRS, Université Montpellier II, 34095 Montpellier, France
b Institut de Physique du Globe, 5 rue Descartes, 67084 Strasbourg, France |
| |
| Abstract: | Upper mantle flow beneath the French Massif Central is investigated using teleseismic shear wave splitting induced by seismic anisotropy. About 25 three-component stations (short period, intermediate and broadband) were installed during the period 1998-1999 in the southern Massif Central, from the Clermont Ferrand volcanic area to the Mediterranean Sea. Teleseismic shear waves (SKS, SKKS and PKS) were used to determine the splitting parameters: the fast polarization direction and the delay time. Delay times ranging between 0.7 and 1.5 s have been observed at most of the sites. The azimuths of the fast split shear waves trend homogeneously NW-SE in the southern Massif Central suggesting a homogeneous mantle flow beneath this area. The observed NW-SE direction differs from the N100°E Pyrenean anisotropy further south. It does not appear to be correlated to Hercynian structures nor to the present-day motion of the plate but is well correlated to the Tertiary extension direction. We propose that the opening of the western Mediterranean induced by the rotation of the Corsica-Sardinia lithospheric block and the roll-back to the SE of the Tethys slab may have generated a large asthenospheric mantle flow beneath the southern Massif Central and a deflection of the up going plume centered beneath the northern Massif Central toward the SE. |
| |
| Keywords: | s-waves wave splitting anisotropy Central Massif asthenosphere Tertiary extension |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
