THE STRAIN FIELD IN NORTHWESTERN GREECE AND THE IONIAN-ISLANDS - RESULTS INFERRED FROM GPS MEASUREMENTS

Recent crustal movements detected by the analysis of repeated satellit e geodetic measurements reflect the ongoing geodynamic processes in th e Alpine-Mediterranean area. Superimposed on the large-scale countercl ockwise rotation of the African plate, complex dynamic processes are a ffecting the lithospheric fragments between the African and Eurasian p lates. Key features to better understand the driving forces and associ ated seismic activity in the Africa/Eurasia collision zone are the Cal abrian and Hellenic arcs. In this paper geodynamic investigations alon g the West Hellenic are are discussed. They are based on two epochs (1 989 and 1993) of satellite geodetic measurements carried out using the US Global Positioning System (GPS). The results are presented in term s of relative displacements and strain rates. Within the time span of 4 years southwestern Greece has moved to the southwest relative to sou theastern Italy by an average of 120 mm, increasing from 80 mm at Lefk ada, in the center of the Ionian Islands, to 160 mm at the Peloponnesu s. The maximum strain rate is 0.18 mu strain/a located in the vicinity of Lefkada, where anomalously high earthquake activity is observed. T he data provide strong evidence for dextral strike-slip motion on the order of 25 mm/a along the Kephalonia Fault Zone (KFZ). The deformatio n field of the KFZ is interpreted as a transition zone between the kin ematics of the Apulian platform and the West Hellenic fold and thrust belts.