GNGTS 2014 - Atti del 33° Convegno Nazionale

56 GNGTS 2014 S essione 1.1 km all along the morphological front of the Alps, along a relatively narrow belt that follow the arcuate shape of the mountain front (Fig. 2). This pattern suggests that the current seismicity maps the zone of brittle creep and interseismic straining in the velocity-strenghtening portion of the fault zone between the fully ductile shear zone at depth (beneath the seismicity cut-off at 15-18 km depth) and the base of the locked fault zone where seismic events nucleate (Perfettini and Avouac, 2004). GPS data. We analyzed GPS data from continuous sites established by various agencies (ASI, EUREF, IGS, FReDNet, FVG, OLG, SOPAC, Rete GPS Regione Veneto, Leica ITALPOS and RING networks) in NE Italy and surrounding area. Code and phase data have been analyzed using the GIPSY-OASIS II software package. Carrier phase ambiguities have been resolved using the Ambizap strategy (Blewitt, 2008). Satellite orbit and clock and coordinate transformation parameters into ITRF2005 were provided by JPL. Noise properties, linear velocities, periodic signals and antenna jumps of the temporal series were computed using the CATS software (Williams, 2005). In order to interpret the crustal motion across the southern front of the Alps, we rotate the GPS velocity field in a reference frame defined by the minimization of the residual velocities of 15 stations located on the Venetian-Friulian plane, lying far from the active Apennines and southern Alps front. In this reference frame the motion of stations in the Alps shows a direction consistent with shortening along the southern front. The internal part of the Alps has a negligible deformation and a distinct kinematics relative to Eurasia, suggesting that a fraction Fig. 2 – Estimated interseismic coupling distribution on the modelled thrust fault and background seismicity (a). The boxes enclose the seismicity projected onto three directions (b, c, and d) perpendicular to the strike of the fault. The cross sections show epicenter solutions (circles) superimposed to the modelled fault plane and coupling distribution at depth, and expected temperature at a depth of 15 km (dashed line). The grey histograms represent the normalized seismicity rate.