Paleoseismology and earthquake potential of Gülbahçe fault zone, İzmir, West Anatolia

In this study, it was aimed to carry out trench-based paleoseismological studies on the Gülbahçe Fault Zone, which is one of the southwestern segments of the İzmir Balıkesir Transfer Zone, and to determine the Pleistocene and Holocene activity of the fault. For this purpose, trenches were dug on the Gülbahçe Fault Zone, which is 24 km long on land and has the character of a dextral strike-slip fault. Radiocarbon (14C) and Optically Stimulated Luminescence (OSL) methods were applied to age the sediments belonging to surface rupturing earthquakes. . According to the structural geology, stratigraphic analysis of the trench walls and age data of the collected samples, four events were identified on the Gülbahçe Fault Zone in the late Pleistocene-Holocene. According to the 14C and OSL analysis data obtained, it is definedthat the Gülbahçe Fault Zone is the source of the historical period earthquakes in the region. According to the calibration of the aging results of the samples taken from the trenches with OxCAL, it was determined that the Gülbahçe Fault Zone last produced an earthquake on March 20, 1389. In addition, it has been determined that the earthquake recurrence period varies between 1400 years and 6200 years for the Holocene and that the zone may produce an earthquake with a magnitude of M=7.20 in the future. It has been determined by geomorphological studies as well as paleoseismological data that the Gülbahçe Fault Zone produced earthquakes in the Holocene. Morphometric analyzes of geomorphological indices were performed to evaluate the active tectonic behavior of the Gulbahçe Fault Zone. Thirty sub-basins identified using ArcGIS 10.5 (ESRI) were determined by fore-mountain sine index (Smf), valley width valley height ratio (Vf), basin asymmetry factor (Af), basin shape index (Bs), drainage density (Dd), and hypsometric integral. (Hi ) values The results obtained indicate that the Gülbahçe Fault Zone is in the range of very high tectonic activity and moderately active tectonic.