GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 Upper Mantle structure below the Western Alps from P and S receiver functions S. Monna (1) , C. Montuori (1) , F. Frugoni (1) , C. Piromallo (1) , L. Vinnik (2 ) and AlpArray Working Group (1) Isttuto Nazionale di Geofsica e Vulcanologia, Rome. Italy (2) Insttute of Physics of the Earth, Moscow. Russia In spite of numerous actve and passive seismological investgatons on the Alpine orogen, many of the published observatons focus on the Moho or the deeper part of the mantle, while reliable informaton on the LAB below the Alps is scarce. We investgated the Moho and Lithosphere-Asthenosphere Boundary (LAB) for a broad region encompassing the Western Alps and including the Ivrea Geophysical Body (IGB), a fragment of mantle emplaced in the lower contnental crust. Afer calculatng a set of Receiver Functon (RF) measurements from data recorded by the dense, broadband AlpArray Seismic Network, we produced seismic velocity profles of the crust-uppermost mantle below each of the 50 analyzed statons down to about 250 km depth, through the joint inversion of P and S RFs. Lateral variatons of the Moho and LAB topographies across the colliding plates, are constrained together with errors related to our measurements. We considerably expand the published data of the Moho depth and add a unique set of new measurements of the LAB (Monna et al., 2022) and provide a contributon to the debate on the existence of contnuous or interrupted contnental subducton below the Western Alps. In fact, we fnd a comparable thickness (on average 90–100 km) of the Eurasia and Adria lithosphere, which are colliding below the IGB. Summarizing, Eurasia is not presently subductng below Adria with vertcal contnuity and there is a gap between the superfcial (contnental) European lithosphere and the deep (oceanic) lithosphere. These observatons agree with the discontnuous structure of the Eurasia lithosphere imaged by some seismic tomography models (Fig. 1). Corresponding authors: stephen.monna@ingv.it, caterina.montuori@ingv.it ;