Slip rates of the Aigion and Eliki faults from uplifted marine terraces (Corinth gulf, Greece).

P. De Martini (1), D. Pantosti (1), N. Palyvos (2), F. Lemeille (3), L. McNeil (4), R. Collier (5) European Geophysical Society XXVII General Assembly - Nice, 21-26 avril 2002.

The southem side of the Gulf of Corinth is bounded by several en-echelon normal faults, which produce important coastal uplift well described by spectacular raised late Pleistocene marine platforms. These geomorphic features can provide a good approximation of long-term cumulative uplift rates, which can be translated into fault slip rates by using dislocation models. The uplifted marine terraces, preserved in the footwall of the Aigion and Eliki faults, have been mapped using 1:5000 topographic maps, air photos and field survey. No direct dating of the marine deposits blanketing the tenaces is presently available. However, to derive cumulative uplift rates over the last 200-300 ky, the individual terraces have been tentatively correlated with the eustatic sea-level curve. In the footwall block of the Aigion Fault up to seven tenaces can be distinguished; the correlation of prominent terrace sequences with major highstands at stages 5 and 7 suggests an uplift rate of 1.0-1.3 mm/yr. The Eliki Fault System is divided into two sections named herein East and West Eliki faults. The East Eliki fault ruptured during the 1861 earthquake. Up to 10 marine tenaces have been mapped in the footwall block of the two Eliki fault sections and correlated with the eustatic sea-level curve at six locations. The correlation of prominent terrace sequences with major highstands at stages 5 and 7 suggests an uplift rate of 1.0-1.5 mm/yr. This rate is consistent also with the elevation of some raised Holocene beaches. In order to obtain fault slips, and hence late Quatemary slip rates, we adopted a forward modelling procedure to fit the best observed tenace profiles for each of the faults. We compared results obtained by using codes based on a standard (elastic half-space) dislocation model with respect to those obtained by other more complicated models. Différent scenarios of regional uplift have been tested too. Considering all the uncertainties associated to, the data and assuming pure normal slip on planar 50°-dipping faults, we obtained slip rates consistently in the range of 6-11 mm/yr for thé West and East Elike fault and of 8-12 mm/yr for thé Aigion fault. For the latter this estimate appears consistent with the vertical separation of displaced correlative deposits dated at ca. 30Ka (from borehole and correlative outcrop). (1)Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy, (2)University of Athens, Geology Dept., Greece, (3)IRSN, Fontenay-aux-Roses, France, (4)School of Ocean and Earth Sciences, University of Southampton, UK, (5) School of Earth Sciences, University of Leeds, UK