Direct geological evidence for prior earthquakes on the 1981 Corinth Fault (central Greece)

International audienceWe present the preliminary results of geomorphic and trench investigations at the eastern end of a scarp produced by the 1981 Corinth earthquake sequence. At this site, the 1981 rupture produced average vertical displacements of 0.6–0.7 m (maximum 1.3 m) that in part occurred along a cumulative scarp which displaces the fan surface by up to 5 m. Based on this cumulative scarp displacing the Holocene fan surface, we estimate a vertical slip rate of ∼1 mm/yr that translates to 1 mm/yr N-S extension. We found evidence for two individual pre-1981 earthquakes which occurred, on the basis of preliminary radiocarbon dating on two paleosols, shortly after A.D. 590 and A.D. 1295. Each of these events produced a vertical displacement ranging between 0.5 and 1.2 m, hence comparable to the 1981 scarp height. This suggests that coseismic slip may have been characteristic at this location over the past three seismic cycles. Following this hypothesis and assuming a periodic strain release, a maximum recurrence interval of ∼700 yr is calculated. These results indicate that the 1981 surface-breaking faults accommodate only part of the regional extension deduced from the geodetic measurements