GNGTS 2013 - Atti del 32° Convegno Nazionale

under the Pannonian fragment corresponding to the Dinaric chain. The upper crust is here characterized by the Dinaric thrusts (upper plate) moving westwards, opposed by the Istria massive Mesozoic shelf domain, the stable part of Adria that emerge from the Adriatic Sea. Europe is in the position of lower plate beneath Adria overthrust by a Pannonian fragment with vertical offsets of the respective Moho’s, in the north; in front of the Adriatic coasts and beneath the Dinaric chain, the Moho surface seems to remain rather smooth and continuous from the foreland to the hinterland and down-bended towards the culmination of the Dinaric chain (Velebit mountains), suggesting that a major decoupling operates at or near the Moho between the Adria and Pannonian and the respective former mantle lithospheres (Šumanovac et al. , 2002). The lower crust of Adria probably plays a major role in the definition of the crust structure and evolution. The joint deep reflection seismic profiles with the WAR/R velocities could be the winning solution and give an answer to the role of the Adria indenter in a key area for crucial seismotectonic modelling. The Adria collision with the Apennines developed from late Miocene to Quaternary. Unlike in the Alps, where a major lithosphere scale fault accounts for vertical offset of the Moho between the upper and lower plate, along the Apenninic chain facing the Adriatic Sea, the Moho surface remain rather smooth and nearly continuous, gently bended, from the foreland towards the Apennine chain and up to the hinterland mantle dome. A major decoupling is operating near the Moho and only the continental lithosphere of Adria seems to be currently involved in the subduction process presently active with a nearly south-eastward directed subduction plane, as proposed by Di Stefano et al. (2009) with earthquakes tomography analysis. These authors accept the upwelling of the asthenosphere and the related thermal softening of the crust on the Tyrrhenian side. Therefore the back-arc extension and the asthenosphere upwelling, in addition to the slab pull, constitute the major driving force in the Apennine-Adria collision. The mobilized and uplifted asthenosphere, a not depleted mantle wedge, can be responsible of the lower crust lamination by magmatic intrusion. The mantle derived magmas releases heat at the base of the crust, induces anatexis in the overlying crustal rocks and produce granitoids melts, quickly migrating towards higher levels (Locardi and Nicolich, 2005). Wide-angle refraction/reflection acquisitions (Giese et al. , 1976) across the Tuscany Geothermal Province revealed a peculiar velocity structure with alternate velocity/density variations in the lower crust and a seismic waves propagation velocity not higher than 7.8 km/s, assigned to the Moho discontinuity. Crustal reflection seismic profiles give a well resolved image of the lower crust and of the brittle/ductile transition interval utilizing seismic attributes and the evaluation of strength (Accaino et al. , 2006 ). Fig. 3 – Receivers function and combined explosive and vibroseis depth migrated data line drawing along TRANSALP transect (from Lueschen et al. , 2006, modified). The presence of decoupling levels (the Sub Tauern Ramp: STR) within the subducted lithosphere poses an insight into the processes that built the geological structures of the upper crust. EU = Europe; AD = Adria; PL = Periadriatic Line. XVI GNGTS 2013 L ectio M agistralis