New Interpretations of the Deep Structure of the Alps based on 3D Anisotropy

In a recent study, a large amount of splitting intensity measurements of the seismic anisotropy for the Central Mediterranean region has been made available, to retrieve an anisotropy tomography (see Baccheschi et al. and Confal et al. posters of session GD7.1). Here we focus on the images obtained for the Alpine region, that strongly benefit of AlpArray and Cifalps1 and 2 data. 
The 3-D distribution of seismic anisotropy, from 70 to 300 km of depth, has been compared with previous SKS shear wave splitting measurements and has been interpreted taking into account remnant and active pieces of slabs. Most of previously defined mantle flows are confirmed, as the asthenospheric toroidal flow around the tip of the slab beneath the Western Alps. Shallower anisotropy pattern show strong relation with main tectonic structures, from the Rhine Graben to the Western Alps arc and so on. However, the no uniqueness of available seismic velocity anomalies mapping keep some part of the interpretation open, as for instance the detectability of proper slab anisotropy. Out of the directional patterns, this splitting intensity tomography gives a map of anisotropy intensity and its variations with depth, with some strong heterogeneities corresponding to regions where previous seismic anisotropy studies described the presence of complex structure, as for the upper mantle beneath the Eastern Alps. All these new information, if integrated with the most recent studies for the Alpine region, may be a relevant support to innovative hypotheses on crust-to-mantle Alpine transition and structure.