DIRECT GEOLOGICAL EVIDENCE FOR PRIOR EARTHQUAKES ON THE 1981 CORINTH FAULT (CENTRAL GREECE)

We present the preliminary results of geomorphic and trench investigat ions at the eastern end of a scarp produced by the 1981 Corinth earthq uake sequence. At this site, the 1981 rupture produced average vertica l displacements of 0.6-0.7 m (maximum 1.3 m) that in part occurred alo ng a cumulative scarp which displaces the fan surface by up to 5 m. Ba sed on this cumulative scarp displacing the Holocene fan surface, we e stimate a vertical slip rate of similar to 1mm/yr that translates to 1 mm/yr N-S extension. We found evidence for two individual pre-1981 ea rthquakes which occurred, on the basis of preliminary radiocarbon dati ng on two paleosols, shortly after A.D. 590 and A.D. 1295. Each of the se events produced a vertical displacement ranging between 0.5 and 1.2 m, hence comparable to the 1981 scarp height. This suggests that cose ismic slip may have been characteristic at this location over the past three seismic cycles. Following this hypothesis and assuming a period ic strain release, a maximum recurrence interval of similar to 700 yr is calculated. These results indicate that the 1981 surface-breaking f aults accommodate only part of the regional extension deduced from the geodetic measurements.