Insights into present-day crustal motion in the central Mediterranean area from 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 are obtained by the analysis of more than 30 observing sites at which at least three different GPS campaigns were carried out in the time span 1991-1999. The results are presented both in the ITRF96 reference frame and with respect to a Eurasian fixed reference frame. The sites located along the northern African margin, in Sicily and southern Italy show prevalent northeastward movements: with a mean velocity of roughly 0.7 cm yr(-1). The relatively dense network available in the southern Apennines led us to try a tentative 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 Ionian Greece the two sites located south of the Kephallinia discontinuity (Lefkas and Kastro Ilias) consistently indicate a south to southwestward motion at an average rate of roughly 15 mm yr(-1).