The Corinth Rift, central Greece, enables analysis of early rift development as it is young (<5 Ma) and highly active and its full history is recorded at high resolution by sedimentary systems. A complete compilation of marine geophysical data, complemented by onshore data, is used to develop a high-resolution chronostratigraphy and detailed fault history for the offshore Corinth Rift, integrating interpretations and reconciling previous discrepancies. Rift migration and localization of deformation have been significant within the rift since inception. Over the last circa 2 Myr the rift transitioned from a spatially complex rift to a uniform asymmetric rift, but this transition did not occur synchronously along strike. Isochore maps at circa 100 kyr intervals illustrate a change in fault polarity within the short interval circa 620-340 ka, characterized by progressive transfer of activity from major south dipping faults to north dipping faults and southward migration of discrete depocenters at~30 m/kyr. Since circa 340 ka there has been localization and linkage of the dominant north dipping border fault system along the southern rift margin, demonstrated by lateral growth of discrete depocenters at~40 m/kyr. A single central depocenter formed by circa 130 ka, indicating full fault linkage. These results indicate that rift localization is progressive (not instantaneous) and can be synchronous once a rift border fault system is established. This study illustrates that development processes within young rifts occur at 100 kyr timescales, including rapid changes in rift symmetry and growth and linkage of major rift faults.

High resolution seismic reflection surveys over one of the most active and rapidly extending regions in the world, the Gulf of Corinth, have revealed that the gulf is a complex asymmetric graben whose geometry varies significantly along its length. A detailed map of the offshore faults in the gulf shows that a major fault system of nine distinct faults limits the basin to the south. The northern Gulf appears to be undergoing regional subsidence and is affected by an antithetic major fault system consisting of eight faults. All these major faults have been active during the Quaternary. Uplifted coastlines along their footwalls, growth fault patterns and thickening of sediment strata toward the fault planes indicate that some of these offshore faults on both sides of the graben are active up to present. Our data ground‐truth recent models and provides actual observations of the distribution of variable deformation rates in the Gulf of Corinth. Furthermore they suggest that the offshore faults should be taken into consideration in explaining the high extension rates and the uplift scenarios of the northern Peloponnesos coast. The observed coastal uplift appears to be the result of the cumulative effect of deformation accommodated by more than one fault and therefore, average uplift rates deduced from raised fossil shorelines, should be treated with caution when used to infer individual fault slip rates. Seismic reflection profiling is a vital tool in assessing seismic hazard and basin‐formation in areas of active extension.

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Discrimination between different lithospheric extension models focusing on the roles of low-angle vs. high-angle faulting, and how strain is distributed, requires high-fidelity imaging of brittle deformation. High-resolution seismic reflection and multibeam bathymetric data in the western Gulf of Corinth continental rift were collected to establish the contribution of offshore faults to extension. Onshore fault slip here is significantly less than expected from geodetic strain rates. The rift at this location is a half-graben tilted to the north by S-dipping faults within the uppermost crust. A basement horst on the northern margin is uplifted by the North and South Eratini faults, and the axial channel is fault controlled. Subsided lowstand shorelines in the hanging wall of the North Eratini and the well-studied Aigion fault suggest that the faults have similar displacements. Summed extension from the four major faults across this part of the rift (Eliki, Subchannel, South Eratini, North Eratini) is ϳ8-16 mm/yr, thereby reconciling geologic and geodetic data sets. Distributed deformation across isolated multiple faults can model this part of the rift without recourse to, and potentially incompatible with, an underlying low-angle detachment. Figure 1. Aegean tectonic setting and Gulf of Corinth map indicating known onshore faults. Sparker seismic tracklines (3A, 3B-see Fig. 3) and study area are shown. Plates: EU-Eurasian; AN-Anatolian; AF-African.

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