East to West Acceleration of the Slip Rates Along the North Anatolian Fault and Its Implıcations Regarding Plate Tectonics and Earthquake Cycle

Abstract

Using GPS measurements, historical earthquake records, and instrumental earthquake data, we investigated GPS slip rates along the rupture zone of the 1668 Great Anatolian Earthquake (M8.1). We found three complete and one incomplete earthquake cycles since 1254 compiling all available historical and paleo-earthquake records in the literature. These records verified that a ~750-kilometer section of the North Anatolian Fault Zone was ruptured in 1668.  To simultaneously estimate segment-based slip rates and locking depths, we combined all available GPS measurements and modeled them using an arctangent approach. Slip rates are used to estimate preliminary inter-seismic slip storages assuming fault segments are fully locked after a mainshock. Large residuals between preliminary slip estimates and co-seismic slips indicate that the fault segments do not store slip for some time after a major earthquake. The creeping and locked stages vary in time and space, as our investigation revealed. Our results show that the slip rates along the NAFZ systematically increase from east to west suggesting that the Aegean extensional regime is the main driving force for the westward movement of the Anatolian Plate. Additionally, the locking depths show an east-to-west decreasing pattern verifying east-to-west thinning of crustal thickness along the Anatolian Plate. The earthquakes over the past three complete cycles and the current incomplete cycle indicate that the failure of the NAFZ begins in the east and moves westward reflecting a decelerating pattern. The failure is typically completed within a time period of 239±3 years.