Linking surface kinematics to deep structure of the Adriatic indenter near a potential subduction-polarity switch, the Giudicarie Belt (Southern Alps)

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This seismotectonic study of a transverse zone (Giudicarie Belt, GB) will test the idea that Miocene kinematics at the leading edge of the Adriatic indenter is related to a suspected switch in subduction polarity beneath the Eastern Alps. It challenges conventional notions of uniform-sense subduction of European lithosphere beneath the Alps by attempting to link slab anomalies at the junction of the Central and Eastern Alps with deformation patterns in the crust and at the surface.The object is to trace both active and defunct faults down to lithological, structural and seismological discontinuities in the crust and upper mantle. Prime targets include (1) a potential lithospheric tear (offset) in the vicinity of the GB, (2) a purported crustal wedge in the Tauern Window area, and (3) thrusts extending from the GB and the eastern Southern Alps into the Veneto-Friuli foreland basin. To map the 3D geometry of faults, we will use data from SWATHs C and D, and the AlpArray station network to pinpoint low-magnitude events and to delineate offsets of rock-physical domains (Vp, Vp/Vs, Qp, Qs) by using local earthquake tomography. This will be complimented by state-of-the-art structural and kinematic (fault-slip) analyses of thrust-and-fold zones along 5 lithospheric profiles crossing key parts of the GB and adjacent units of the Southern and Eastern Alps. The results will be integrated with data along the TRANSALP section as well as with with existing thermo-chronological data at the surface to develop a fully 4D model of late Alpine collision and Adriatic indentation.Preliminary work shows that the magnitude and rate of seismicity in the Giudicarie-Veneto-Friuli target area will allow the use of local earthquake tomography, double-difference localization and receiver functions to image the Moho, as well as km-scale shear zones in the crust and upper mantle. The aforementioned lithospheric profiles will be tectonically balanced and the resulting shortening patterns and rates compared with Adria-Europe convergence to see whether the kinematics have remained the same through time, or have changed in response to rotation, and possibly N-directed subduction, of the Adriatic plate.This proposal addresses SPP research themes 1, 3 and 4, and is part of activity fields 1, 3, 4, and 5. Besides its dependence on the densified station swaths and the AlpArray network, it is closely linked to studies in the Eastern Alps and Tauern Window (Pleuger et al., Wolff et al.), and at the transition from Alps to Dinarides (Grützner et al.). Collaboration is national and international, with a co-applicant in Zürich (ETH) and cooperation partners in Austria, Italy, Slovenia and Switzerland.