GNGTS 2015 - Atti del 34° Convegno Nazionale

may plausibly explain the spatio- temporal distribution of major Neogenic deformations observed in the study area, whereas other authors (e.g., Malinverno and Ryan, 1986 ; Faccenna et al. , 2007) argue that such driving mechanism cannot account for the generation of back arc basins and invoke the contribution of slab roll-back. The spreading of opinions about the geodynamic setting in the Mediterranean region is also due to the fact that the kinematics of the main confining plates (Africa and Eurasia) is not uniquely recognized yet. Uncertainty mainly concerns the trend of the Nubia (sensu De Mets et al. , 2010)-Eurasia convergence and the configuration and kinematics of the Adriatic plate. Global kinematic models based on the analysis of long- term evidence [late Pliocene- Quaternary, DeMets et al. (2010)] suggest that at Mediterranean latitudes Nubia moves roughly NW to NNW ward with respect to Eurasia. Global models inferred from short-term space geodesy data (Argus et al. , 2010) provide a Nubia-Eurasia relative motion with an even larger westward component. However, as argued by Mantovani et al. (2007), the motion trends mentioned above can hardly be reconciled with several major features of the Plio-Quaternary tectonic setting in the whole Mediterranean region, which rather suggests a NNE ward orientation of such plate convergence. In this work, we make an attempt at gaining insights into the above problem by considering the possible tectonic implications of the present velocity field in the Italian area derived by the analysis of geodetic observations carried out by a fairly dense network of continuous GPS stations (Fig. 1). Details about the network and the acquisition and analysis of GPS data are given by Cenni et al. (2012, 2013). Southern Adria kinematics and Nubia-Eurasia relative motion. The geodetic velocity field shown in Fig. 1 clearly indicates that the Apulia zone (south-eastern Italy), certainly belonging to the southern Adriatic domain (e.g., Fantoni and Franciosi, 2010), is moving roughly NE ward, with a rate of about 4-5 mm/year. This evidence is fairly robust since it is coherently indicated by a relatively high number (more than 20) of GPS velocity vectors. Since no clear active tectonic discontinuity is actually recognized between southern Adria and Nubia (e.g., Babbucci et al. , 2004), one can reasonably expect a coherent kinematics of these two domains. However, this condition is not fulfilled if the Nubia-Eurasia relative motion is taken from the global kinematic models (Argus et al. , 2010, De Mets et al. , 2010), which provide a roughly NW to NNWward motion of the Nubian domain in the Mediterranean area (Mantovani et al. , 2007). To tentatively overcome this major problem, a number of authors have hypothesized the presence of an active tectonic decoupling between Adria and Nubia [see Babbucci et al. (2004), Fig. 1 – Horizontal velocity vectors of the GPS sites considered in this work, with respect to a fixed Eurasian frame [Euler pole at 54.23 N, 98.83 W, ω 0.257 /Myr; Altamimi et al. (2012)]. GNGTS 2015 S essione 1.2 121