GNGTS 2015 - Atti del 34° Convegno Nazionale

several compressional and traspressional active faults have been identified (e.g., Lacan and Ortuno, 2012). In our opinion, the fact that both the boundary zones between Iberia and Eurasia are affected by significant seismicity cannot easily be reconciled with a null relative motion between such plates. As concerns the Morocco microplate, Argus et al. (2010) point out a discrepancy between the predictions of the Morocco-Nubia pole provided by Mantovani et al. (2007) and the geodetic velocities at Maspalomas (Canary Islands). However, it must be considered that such site lies along an active tectonic boundary zone (as recognized by Argus et al. , 2010) and that consequently the real meaning of such observation cannot easily be recognized. Argus et al. (2010) also suggest discrepancies between the predictions of the Mantovani et al. (2007) Morocco-Eurasia pole and the geodetic velocities in the Ponta Delgada (Azores) and Rabat sites (lying inside the presumed Morocco microplate). However, the entities of such discrepancies are compatible with the possible uncertainty of geodetic data. Adria plate? The GPS velocity field shown in Fig. 1 provides very significant information on the present kinematics of two zones certainly belonging to the Adria continental domain (Fig. 3), one is the Apulia, as discussed in the previous point, and the other is the Venetian plain and Istria, i.e. the northernmost sector of the Adria foreland which underthrusts the eastern southern Alps (e.g., Fantoni and Franciosi, 2010). This evidence is very significant since it is coherently indicated by a relativel high number (more than 20 for both zones) of subparallel velocity vectors. If Adria were assumed as a rigid independent plate, the two geodetic constraints mentioned above would imply an Adria-Eurasia rotation pole roughly located in the western Alps. This result, also supported by the analysis of earthquake slip vectors in peri-Adriatic zones (e.g., Anderson and Jackson, 1987; Weber et al. , 2010) would mean that Adria does not move in close connection with Nubia, whatever Nubia-Eurasia pole is considered among the ones so far proposed. However, such conclusion can hardly be reconciled with the lack of a clear active tectonic decoupling zone between the present Adria domain and Nubia (Babbucci et al. , 2004; Argnani, 2006; Mantovani et al. , 2006). Thus, we rather suppose that the present velocity field in the Adria domain results from a transient non rigid behaviour of the Adria domain. This effect may be due to the peculiar distribution of seismic decouplings and related post seismic relaxation effects that have occurred in the periAdriatic boundary zones during the last tens of years. For the choice of such time interval we have taken into account the Fig. 3 – Tectonic setting and long term kinematics in the central Mediterranean area, compatible with the post-early Pleistocene deformation pattern (Viti et al. , 2006, 2011; Mantovani et al. , 2007a, 2009): 1-2) African and Adriatic continental domains, 3) oceanic Ionian domain, 4) outer sector of the Apennine belt carried by Adriatic plate (Adria). Green arrows indicate the long-term kinematic pattern (middle Pleistocene to Present) with respect to Eurasia. AP Apulia, CAL Calabrian wedge, Ce Cephalonia fault system, ESA eastern Southern Alps, Gi Giudicarie, HYB Hyblean wedge, Is Istria, LA Ligurian Alps, NA, CA, SA northern, central and southern Apennines, Pa Palinuro fault system, SV Schio-Vicenza fault system, Sy Siracusa fault system, VP Venetian Plain, Vu Vulcano fault system. GNGTS 2015 S essione 1.2 123