Normal Fault System of the Western Corinth Rift (Greece): 3D Geometry, Kinematics and Evolution

We use an integrated approach from field analyses (stratigraphy, structural geology, seismicity) to 3D geomodelling of the Corinth rift to characterize the initiation and early stages of continental rifting. The Gulf of Corinth is a rapidly opening rift superimposed on the external Hellenides orogenic belt and lying above an active subduction zone. The early Corinth rift is today uplifted and spectacularly exposed along the southern margin of the Gulf. The Plio-Pleistocene syn-rift stratigraphy and normal fault system have been mapped across an area of 600 km2. Major normal faults are planar and have a low level of connectivity. Rare listric intra-basinal faults are observed. Fault strikes vary from N070° to N120° with an average strike of N110°. Fault dips, predominantly toward the north, vary from 45° to 65°. Extension directions vary from N355° to N020°. Total extension across the whole rift (offshore and onshore) is estimated to be 10km (b=1.2). Fault activity and depocentres migrated north with time as the rift narrowed. Syn-rift stratigraphy records three phases of rifting. Extension accelerated significantly at around 1.4 Ma and around 800-600 ka. Uplift of the south flank started sometime 800-600 ka. Field data alone are not sufficient to constrain a valid 3D model of geometry and displacement distribution on the normal fault network, in particular because of their irregular and often sparse distribution. 3D model construction therefore requires the integration of theoretical assumptions, in particular, (1) a coherent distribution of displacement across the fault network, (2) an acceptable ratio of displacement to fault length, (3) a consistent level of connectivity. In the initial onland model, faults surfaces are extended to a depth of 2 km. In contrast, the surface trace of active fault surfaces can be linked with earthquake nodal planes located at depths of 5-8 km depth. These models suggest that the north dipping zone of micro-seismicity in the western Gulf may not represent a extensional decollement zone.