Upper-mantle deformation beneath the Pyrenean domain inferred from SKS splitting in northern Spain and southern France

Mickaël Bonnin (1) , Sébastien Chevrot (2) , Ianis Gaudot (1) , Méric Haugmard (1)

1 LPG - Laboratoire de Planétologie et Géodynamique [UMR 6112]
2 GET - Géosciences Environnement Toulouse

We performed shear wave splitting analysis on 203 permanent (French RLPB, CEA and Cat-alonian networks) and temporary (PYROPE and IberArray experiments) broad-band stations around the Pyrenees. These measurements considerably enhance the spatial resolution and coverage of seismic anisotropy in that region. In particular, we characterize with different shear wave splitting analysis methods the small-scale variations of splitting parameters φ and δt along three dense transects crossing the western and central Pyrenees with an interstation spacing of about 7 km. While we find a relatively coherent seismic anisotropy pattern in the Pyrenean domain, we observe abrupt changes of splitting parameters in the Aquitaine Basin and delay times along the Pyrenees. We moreover observe coherent fast directions despite complex lithospheric structures in Iberia and the Massif Central. This suggests that two main sources of anisotropy are required to interpret seismic anisotropy in this region: (i) lithospheric fabrics in the Aquitaine Basin (probably frozen-in Hercynian anisotropy) and in the Pyrenees (early and late Pyrenean dynamics); (ii) asthenospheric mantle flow beneath the entire region (imprint of the western Mediterranean dynamics since the Oligocene).

Mots clés: Mantle processes; Europe; Body waves; Broad-band seismometers; Seismic anisotropy; Dynamics of lithosphere and mantle

Domaines: Géophysique [physics.geo-ph]

Mickaël Bonnin, Sébastien Chevrot, Ianis Gaudot, Méric Haugmard. Upper-mantle deformation beneath the Pyrenean domain inferred from SKS splitting in northern Spain and southern France. Geophysical Journal International, 2017, 210 (2), pp.898-910. ⟨10.1093/gji/ggx193⟩. ⟨hal-02304709⟩