GNGTS 2013 - Atti del 32° Convegno Nazionale

in Palano et al. (2012). To improve the overall configuration of the network and to tie the regional observations to an external global reference frame, data coming from 10 continuously operating IGS (International GNSS Service) stations were introduced in the processing. By using the GLOBK module, the regional observations are then combined, on a daily basis, with global solutions of the Scripps Orbital and Permanent Array Center (SOPAC) at University of California, San Diego (Bock et al. , 1997) and aligned to the ITRF2008 reference frame through a seven-parameter Helmert transformation (3 translations, 3 rotations and a scale factor). We then combined the corrected daily position estimates and their full covariance matrices to estimate a long-term average site velocity in the ITRF2008 reference frame. Our GPS network shares some stations with the ones processed by Walpersdorf et al. (2006), Masson et al. (2007), Tavakoli et al. (2008), Djamour et al. (2011) allowing a rigorous integration by applying a Helmert transformation of the five estimated velocity fields. To adequately show the crustal deformation pattern over the investigated area, we rotate the final ITRF2008 GPS velocity solution into an Arabian fixed reference frame (Fig. 3a; Palano et al. , 2013). In addition, we compute the 2D strain-rate tensor over the studied area. In particular, as a first step, by taking into account the observed horizontal velocity field and associated Fig. 3 – a) GPS velocities and 95% confidence ellipses in a fixed Arabian plate (see Palano et al. , 2013 for more details). b) geodetic strain-rate field: arrows represent the greatest extensional (red) and contractional (blue) horizontal strain-rates. 79 GNGTS 2013 S essione 1.1