Geodetic and seismological investigation in the Ionian area

Geodetic and seismic evidence of crustal deformations in the Ionian area are shown in this paper. The Ionian GPS network, composed of nine sites crossing the Ionian Sea from Calabria, Southern Italy, to Northwestern Greece, was established and surveyed in 1991, 1994, 1995 within the framework of the TYRGEONET project (Anzidei et al., 1996). In 1996 a return campaign was carried out after the occurrence of seismic activity in 1995. The displacement pattern obtained for the Greek side of the network agrees well with those previously displayed, both in magnitude and direction, confirming a mean displacement rate of about 1-2 cm1/yr. The same agreement is not found for the Italian side of the network, where no significant deformations were detected between 1994 and 1996. Seismic deformation was also studied for the same area, starting from the moment tensors of events which occurred in the last 20 years with magnitude greater than 5.0; evident similarity with the displacement field exhibited by the Greek side of the Ionian Sea by geodetic surveys was inferred. On the contrary, the motion detected for the Italian area cannot be simply related to seismic activity.