Monitoring the Gediz Graben supra-detachment fault by GNSS technique

Along the Gediz Graben, which shapes a corridor extending from the Aegean Sea to the interior of Western Anatolia in the E-W direction, many destructive earthquakes occurred in the instrumental period and some of these earthquakes formed surface fractures. In addition, the southwestern edge of the graben was reactivated by 6.9 magnitude earthquake on March 28, 1969. There are many studies in the literature to investigate the faulting structures in the Gediz graben. In this study, 47-sites GNSS network was established to investigate the kinematic structure of the low-angle supra-detachment fault located in the south of the Gediz Graben. Unlike the literature, this study covers the entire Gediz Graben. For this reason, previous GNSS data of the sites used in these studies were obtained. Two more campaign GNSS measurements were carried out in 2021 and 2022 at the sites in the network and all data were processed with GAMIT/GLOBK software. Eurasian plate fixed velocity field and strain rates were computed. When the velocity field is analyzed, it is determined that the region moves in the west-southwest direction with an annual velocity of 14-25 mm. When the time series were analyzed, it was calculated that there was a vertical deformation of 103 mm/yr at TRAZ station. When the strain fields were analyzed, the largest extensions in the Gediz Graben was observed in the NE-SW direction. Using the current velocity field, both the block model in the literature for the graben was tested and a new block model study was carried out. The error of the suggested block model is ±0.8 mm for both components. At the boundary between the northern block of the graben and the intra-graben block, 1 mm/yr the error of the suggested block model left lateral movement and 2.3 mm/yr extensional regime were obtained.