The crustal structure of Southwestern Turkey using local seismic data
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The primary objective of this study is to image the crustal seismic structure of southwestern Turkey by employing the double-difference travel time seismic tomography. In addition, this study accurately located seismicity based on the double-difference method. Southwestern Turkey is characterized by a complex tectonic regime and is the most seismically active region in Turkey. The Cyprean and Aegean subduction zones, particularly the Aegean slab retreat, play a major role in the tectonic activity of the region that is dominated by extension in western Anatolia. In this study, earthquake data from the three catalogs from 2000 to 2022 were integrated into a single catalog dataset, allowing for the application of strict filters before relocating the earthquakes. The relocation of the earthquakes was performed using the HypoDD algorithm, which employs the double-difference method. The results show that the Cyprean slab subducts almost vertically to approximately 140 km, while the Aegean slab subducts at an angle of approximately 60 degrees to the west and extends to 157 km. The Gediz, Buyuk Menderes, and Gokova grabens are among the major geological structures in southwestern Turkey. The relocated earthquakes in the region are concentrated in the Gokova Graben and the Denizli Basin. The earthquakes in the vicinity of the Gokova graben indicate the presence of a fault that intersects with the Fethite-Burdur Fault Zone to the east of the graben. The Gediz and Buyuk Menderes grabens exhibit relatively high seismic activity at their eastern and western ends while showing low seismic activity in their central parts. Specifically, the seismicity in the central part of the Buyuk Menderes graben is represented by only a few earthquakes. The seismogenic depth in the region appears to be between 15 and 20 deep. The TomoFDD algorithm, which is based on the double-difference method, was used in this study to apply travel time seismic tomography to investigate the crustal seismic structure of the region. The tomographic results show the presence of low P and S wave velocities in the Gokova Graben and Denizli Basin. Additionally, high S wave velocities were found in the areas where the Menderes Massif is located, particularly in the Central and Northern Menderes Massif. In the vicinity of the Isparta Angle, low P and high S wave velocities were observed. It appears that the dominant factor affecting seismic velocities in this region is rock deformation and composition rather than temperature.
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M.S.