A New Approach to Active Tectonics SW of Altınova (Yalova) with Paleoseismological Data, NW Türkiye

This study aims to provide a new perspective on the active tectonics south of the Hersek Delta in the Sea of Marmara based on paleoseismological trenches in the southern part of the North Anatolian Fault Zone. Within this scope, one natural trench was examined at Çavuşçiftliği, immediately southwest of Altınova (Yalova), and a total of five trenches were excavated in Geyikdere and Havuzdere villages. Radiocarbon (¹⁴C) dating methods indicate at least five paleo-earthquake events occurred in the region. They may have occurred between AD 66 ± 43 and AD 873 ± 57, AD 873 ± 57 and AD 972 ± 40 in the Geyikdere trenches; AD 1202 ± 32 and AD 1350 ± 30, AD 1350 ± 30 and AD 1359 ± 33, and AD 1359 ± 33 and AD 1875 ± 30 in the Havuzdere trenches. These events may have been related with large earthquakes that likely affected İzmit and surroundings on the northern branch of the North Anatolian Fault Zone. Although a NW–SE directed compressional regime constitutes the main tectonic regime in NW Anatolia currently, ENE–WSW, WNW–ESE and E–W trending normal faults detected in the study area are related to a local NNE-SSW extensional tectonic regime.