Identifying Main Lithospheric Structures in the Eastern Alpine Domain by Joint Inversion of Receiver Function and Surface Wave Measurements for Seismic Anisotropy

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Mountain building in the Alps started in the Neogene when crustal units derived from Eurasia, inter-vening oceanic basins and microcontinents got strongly deformed and folded by the approaching Adriatic intender. The eastern Alps are ideally suited to study the full complexity of mountain building including crustal delamination and deformation, nappe stacking and lateral escape. The underlying processes and in particular the driving forces remain enigmatic, however, because the crustal and deep lithospheric structure in the eastern Alpine domain are still poorly resolved. A pre-requisite for the understanding of mountain building processes since the Neogene in the eastern Alps is the identification of the shape of the intender and of the decoupling horizon for the lateral escape north of the suture as well as the clarification of the deep lithospheric structure. It re-mains an open question if Adria or Eurasia are the upper plate or if mountain building is the result of bivergent subduction. Also, properties of the mantle lithosphere need to be resolved as they are key for the quantification of tectonic forces causing collision and mountain building. AlpArray – the densest regional seismic array ever deployed contemporaneously - provides a unique opportunity to study the deep lithospheric structure of the orogen in detail. The complete data set for the eastern Alps will be available in 2021. Building on surface-wave and receiver-function measure-ments carried out in separate projects in the first phase of the SPP, we will perform a joint inver-sion of the data that will result in a high-resolution, shear-wave velocity model of the lithosphere to resolve both the absolute shear-wave velocity and major crust and mantle discontinuities. We will extend stochastic inversion schemes to obtain isotropic and anisotropic models and their uncertain-ties. The resulting high-resolution model will yield a seismic model for the eastern Alpine litho-sphere. Relating it to the geological record at the surface, the tectonic affinity of the main deep structures will be identified. Based on seismological observations, we will develop together with co-operation partners focusing on the research theme “Reorganizations of the lithosphere during moun-tain building” a 4D comprehensive model of the tectonic evolution of the lithosphere in the eastern Alps since the beginning of the Neogene. It will provide the basis for numerical geodynamic modelling of mountain building.