Imaging structure and geometry of slabs in the greater Alpine area – a P-wave travel-time tomography using AlpArray Seismic Network data

Abstract. We perform a teleseismic P-wave travel-time tomography to examine the geometry and structure of subducted lithosphere in upper mantle beneath Alpine orogen. The is based on waveforms recorded at over 600 temporary permanent broadband stations dense AlpArray Seismic Network deployed by 24 different European institutions greater region, reaching from Massif Central Pannonian Basin Po Plain river Main. Teleseismic travel times residuals direct P waves 331 events magnitude 5.5 higher between 2015 2019 are extracted using combination automatic picking, beamforming cross-correlation. resulting database contains 162 000 highly accurate absolute residuals. For tomographic inversion, we define model domain encompassing entire region down depth km. Predictions computed hybrid way applying fast TauP method outside continuing wave fronts into marching method. iteratively invert demeaned for velocities regular discretization with an average lateral spacing about 25 km vertical 15 inversion regularized towards initial constructed 3D priori crust uppermost 1D standard earth beneath. provides detailed image slab configuration Apenninic orogens. Major features partly overturned Adriatic Apennines 400 still attached its northern part but exhibiting detachment southeast. A anomaly western Alps indicates short whose easternmost end located 100 Penninic front. Further east following arcuate shape Periadriatic Fault System, deep-reaching coherent complex internal generally dipping SE suggests origin limited Giudicarie fault 200 extending beyond this depths. In eastern it detached overlying lithosphere. east, well-separated central merging below, another deep-reaching, nearly vertically high-velocity existence presumably same which completely orogenic root. Our does not require polarity switch because dip full Fast anomalies Dinarides weak concentrated northernmost shallow Low-velocity regions surrounding west northwest follow trend as ones, indicating kinematically thick subducting region. Alternatively, these may signify presence seismic anisotropy horizontal axis parallel belt due asthenospheric flow around slabs. contrast, low-velocity suggest upwelling driven retreat Carpathian extrusion while low south evidence hydration their position above slab.