The seismic structure of the lithosphere in the greater Alpine area from S-to-P converted waves

In the frame of the AlpArray project we analyse teleseismic data from permanent and temporary stations of the greater Alpine region to study seismic discontinuities in the entire lithosphere. We use broadband S-to-P converted signals from below the seismic stations. In order to avoid sidelobes, no deconvolution or filtering is applied and S arrival times are used as reference. We show a number of north-south and east-west profiles through the greater Alpine area. The Moho signals are always seen very clearly, and also negative velocity gradients below the Moho are visible in a number of profiles. The subducting European Moho is visible in the Eastern Alps west of 13.5°E (the eastern edge of the Tauern Window) and reaches there about 60km depth at 47°N. East of about 13.5°E, the image of the Moho changes completely. No south dipping European Moho is found anymore, instead the Moho is shallowing towards the Pannonian Basin. This suggests severe post-nappe emplacement modifications east of about 13.5°E, most probably associated with delamination of the mantle lithosphere within the formerly subducting European slab, i.e. mantle that separated from the crustal parts of the Alpine-West Carpathian orogen during the last ca. 20 Ma when the Pannonian basin formed and the ALCAPA block underwent its E-directed lateral extrusion.

Ratschbacher, L., Frisch, W., Linzer, H.-G. and Merle, O. (1991) Lateral extrusion in the Eastern Alps, Part 2: Structural analysis. Tectonics, vol.10, No.2, 257-271.