Résumé
Our aim is to understand better the rifting process by imaging the Moho depth variation beneath Corinth and Evvia. We present here the results of a gravity inversion analysis in the region of the Corinth and Evvia rift system, and compare them to those obtained independently from teleseismic tomography and receiver function analyses. The results of these different studies appear to be consistent and show (1) a 10km crustal thickening in the western part of the area beneath the Hellenides mountains, (2) NW-SE-trending periodic crustal thinning, and (3) a maximum crustal thinning north of the Gulf of Corinth. This 4km thinning is unlikely to be the result of the rifting alone, which seems to have been reactivated since only 1Ma. We propose here a geodynamical scenario in two major steps to explain the evolution of Corinth area. Aegean Miocene extension involving boudinage resulted in periodic crustal thinning, consistent with observations. These lithospheric instabilities could have favoured rupture initiation in particular areas, especially near the city of Corinth. Then, the reactivation of the Corinth Rift extension, 1Myr ago, led to westward rift propagation. The offset observed between the maximum crustal thinning and the Gulf of Corinth could be accommodated by a low-angle normal fault at about 10-15km depth. The Corinth Rift is thus asymmetrical and was initiated in places of crustal weakness due to Miocene lithospheric instabilities.