Combination of permanent and non-permanent GPS networks for the evaluation of the strain-rate field in the central Mediterranean area

The deformation pattern of the Mediterranean is characterized by a complex space-time distribution of compressional and tensional events, in part related to the collision between the African and Eurasian plates. The present day appearance of this complex evolution consists of a high number of crustal wedges, interacting with one another. In the central Mediterranean, and in particular in the Adriatic/Tyrrhenian and Ionian domains, the present number of permanent GPS stations, and the relatively short observation time span of most of them, do not allow a detailed description of the kinematics of this complex tectonic framework. For this reason, non-permanent GPS networks play an important role for improving the determination of the deformation pattern of this area, if rigorously combined with information provided by permanent GPS stations. We combined non-permanent GPS observations, collected during more than ten years, surveying regional and sub-regional geodetic networks in the central Mediterranean, and the ITRF2000 velocity solution of the European Permanent GPS Network. We used the final velocities of 32 IGS stations to constrain a stable Europe reference frame. The residual velocity field with respect to this reference frame shows remarkable features for the relatively higher rate deforming zones, such as the Italian peninsula and the Aegean area, and suggests that the Aegean area, Calabrian arc and Central-Southern Apennines are subject to strain rates higher than that of longer wavelength in the rest of the Mediterranean area.