Submarine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey

Abstract

The North Anatolian fault (NAF) in the Marmara Sea is a significant hazard for the city of Istanbul. The use of paleoseismological data to provide an accurate seismic risk assessment for the area is constrained by the fact that the NAF system is submarine; thus a history of paleoearthquakes can be inferred only by using marine sediment cores. Here, a record of turbidites was obtained in two cores and used to reconstruct the earthquake history along the Cinarcik segment, a main branch of the NAF. Klg04 was collected from a berm north of the fault, and Klg03 was positioned in the Cinarcik basin, south of the fault. The cores were correlated using long-term geo-chemical variations in the sediment, and turbidites deposited simultaneously at both sites were then identified. Radionuclide measurements suggest the most recent turbi-dite was triggered by the 1894 C.E. M w 7.3 earthquake. We conclude that the turbidites identified at both sites are earthquake generated, based on their particular sedimento-logical and geochemical signatures; the correlation of turbidites at berm and basin sites; and the match of the most recent turbidite with a nineteenth century historical earthquake. To date older turbidites, we used carbon-14 and paleomagnetic data to build an OxCal model with a local reservoir correction of 400 50 yr. The Cinarcik segment is found to have ruptured in 1509 C.E., sometime in the fourteenth century, in 989 C.E., and in 740 C.E., with a mean recurrence interval in the range of 256–321 years. Finally, we used the earthquake record obtained to review the rupture history of the adjacent segments over the past 1500 years.