Geological identification of historical tsunamis in the Gulf of Corinth, Central Greece

Abstract. Geological identification of tsunami deposits is important for tsunami hazard studies, especially in areas where the historical data set is limited or absent. Evidence left by historical tsunamis in the coastal sedimentary record of the Gulf of Corinth was investigated by trenching and coring in Kirra on the north coast and Aliki on the south coast. The Gulf of Corinth has a documented tsunami history dating back to the 4th century BC. Comparison of the historical records and the results of stratigraphical, sedimentological and foraminiferal analyses show that extreme coastal flooding events are detectable in the coastal sequences. The geological record from Kirra shows four sand layers deposited by high-energy marine flooding events. The deposits identified show many similarities with tsunami deposits described elsewhere. The lower sand deposit (layer 4) was radiocarbon dated to 3020–2820 BC. Assuming an average sedimentation rate of 2.6 cm (100 yr)⁻¹, the ages of the other three sand layers were estimated by extrapolation to the time windows 1200–1000 BC, AD 500–600 and AD 1400–1500. There are no historical tsunamis which correlate with layers 2 and 3. However, layer 1 may represent the major AD 1402 tsunami. Sand dykes penetrating from layer 1 into the overlying silts suggest soil liquefaction during an earthquake event, possibly the 1 August 1870 one. At Aliki, no clear stratigraphical evidence of tsunami flooding was found, but results from foraminiferal and dating analyses show that a sand layer was deposited about 180 years ago from a marine flooding event. This layer may be associated with the historical tsunami of 23 August 1817, which caused widespread destruction in the Aegion area. The work presented here supports the idea that geological methods can be used to extend tsunami history far beyond the historical record. Although the tsunami database obtained will be incomplete and biased towards larger events, it will still be useful for extreme event statistical approaches.