EXTENSIONAL TECTONICS OF THE CORINTH GULF (CENTRAL GREECE) AND THE GEOMETRY OF THE DELPHI-ORACLE FAULT

The Gulf of Corinth is a rapidly expanding E-W intra-continental extensional rift, across the Alpine formations of the Greek orogene. The initiation of the rift is estimated as Late Pliocene and is currently involving extension along segmented and individual normal faults of W-E to WNW – ESE. Recent published data evidence the active extension deformation of the Corinth Rift, such as historical and instrumental earthquakes, intense microseismic activity, morphotectonic criteria of active faults, as well as geodetic measurements (GPS). The scope of this study is to fill a gap of onshore poorly mapped faults in the northwestern part of the rift, further understand the structure of Corinth rift and document the transitional zone between the Gulf of Corinth and the northern active extensional structures.

New results for the recent tectonic activity in the northern part of Corinth rift are presented. Geological mapping and morphotectonic study re-populate the area of study with numerous active and possible active faults. The area is dominated by individual and segmented normal faults along with major structures like the Delphi fault. The results are in accordance with recent studies that reveal a more complex and wider structure of Corinth Rift.

The Delphi fault zone is a large active extensional structure that defines the southern slope of Parnassos Mountain. The fault consists of two normal fault segments dipping south, with a length of about 10 km each. The most recent activation occurred the 31 July/1 August 1870 earthquakes (main event estimated magnitude is Ms=6.7), one of the strongest historical earthquakes in central Greece. A complex array of normal and strike-slip faults with a W-E/WNW-ESE strike was mapped displacing Quaternary sediments as well. The link of this fault complex with the Delphi Fault Zone is unknown.

The area of the northern Gulf of Corinth Rift is comprised of individual and en-echelon normal faults with a low slip-rate (0.1-0.2 mm/yr) and evident of a lesser extensional activity. The fault structure seems to deviate from the previous understanding of a general uniform subsidence and inactivity of the area.