Active fault segmentation of the Çivril Graben System and surface rupture of the 1 October 1995 Dinar earthquake (Mw 6.2), Southwestern Anatolia, Turkey

Abstract The Civril Graben System (CGS) is one of the important tectonic structures developed within the Western Anatolia extensional tectonic regime. The CGS has an arcuate geometry looking south, and comprises two main geometric sections of the NW-striking Dinar Graben and the NE-striking Baklan Graben, with a total length of 100 km. The main faults limit the north edge of the CGS, while the south edge is bounded by their antithetic structures. The northern boundary structures of the graben comprise two main fault segments of Dinar and Civril. Graben fill is Plio-Quaternary lacustrine-fluvial sediments with Late Pleistocene-Holocene flood plain, lacustrine-marsh and alluvial fan sediments. Historical records and destructive earthquakes occurred in the last century indicate the region is one of the significant seismogenic zones. The last destructive earthquake in the graben was the 1995 Dinar Earthquake (Mw 6.2) which caused approximately 10 km-long surface rupture on the Kizilli segment of the Dinar Fault. Field-based geological mapping and structural geology in this study and available seismic and paleoseismological data reveal that the other sub-segments of the Dinar and Civril faults which have not ruptured in the last 150 years have the potential to produce earthquakes with Mw 6.0 and larger. The paleoseismic rate is assessed to be 1 mm/year for the Kizilli segment, while the geologically long term slip rate range is calculated to be 0.27 ± 0.05 mm/year.