Insights into present-day crustal motion in the central Mediterranean areafrom GPS surveys

In this paper we present observations of crustal motion related to a large GPS network located in the central-western Mediterranean area. Velocities a re obtained by the analysis of more than 30 observing sites at which at lea st three different GPS campaigns were carried out in the time span 1991-199 9. The results are presented both in the ITRF96 reference frame and with re spect to a Eurasian fixed reference frame. The sites located along the nort hern African margin, in Sicily and southern Italy show prevalent northeastw ard movements: with a mean velocity of roughly 0.7 cm yr(-1). The relativel y dense network available in the southern Apennines led us to try a tentati ve estimate of the average strain rate in this zone, resulting in a maximum extension of 0.021 +/- 0.006 x 10(-6) yr(-1) normal to the chain. In Ionia n Greece the two sites located south of the Kephallinia discontinuity (Lefk as and Kastro Ilias) consistently indicate a south to southwestward motion at an average rate of roughly 15 mm yr(-1).