An investigation of anatolian-african subduction zone in southwestern Turkey: Lithospheric structure beneath Isparta angle (IA) and the surroundings from rayleigh wave phase velocity inversion

Geodynamics of Turkey is complicated by the tectonic interactions between Africa, Eurasia and Arabian plates. These processes lead to high seismic activity and internal deformation beneath this region and its vicinity. Subduction of African Plate beneath Western Anatolia along Hellenic and Cyprus Arcs even more complicates the overall picture. In this sense, Isparta Angle (IA) plays a key role in understanding the neotectonic development of the Eastern Mediterranean. In this research, our goal is to put consistent constraints on the upper mantle structure beneath IA and the surroundings via Rayleigh wave tomography method. Depending on their frequency content, surface waves help us image the velocity variations at various depth ranges. In this regard, we adopted a phase velocity inversion technique named as "Two-plane wave method". With the use of this method, we will be able to effectively map the three-dimensional (3-D) velocity structure and amplitude variations beneath southwestern Turkey to a certain extent. In August 2006 - September 2009 time frame, we recorded teleseismic earthquakes (30 <  < 120) with magnitudes greater than 5.5 using the permanent seismic networks of Kandilli Observatory and Earthquake Research Institute (KOERI), Süleyman Demirel University (SDU) and IRIS/GEOFON together with temporary stations (a total of 48 sensors) deployed with support from Missouri University and Boğaziçi Research Fund (BAP). Following the detailed analysis of vertical component seismograms, we calculated a one-dimensional (1-D) dispersion curve which served as an input for two dimensional (2-D) phase velocity inversions. Phase velocity maps were generated and displayed in several horizontal cross sections at various periods. Since surface waves bring integrated information from certain depth ranges, we also performed other series of inversions to determine the absolute shear wave velocity distribution beneath Southwestern Turkey down to a depth of nearly 250 km. Furthermore, construction of a 3-D shear velocity model enabled us to address the significant issues regarding the complex slab geometry of Anatolian-African subduction mechanism. The locations of pronounced fast and slow velocity anomalies provided us useful insights about the important elements that mostly define the nature of subduction such as slab detachment, slab tearing, asthenospheric upwelling, and volcanism etc. The outcomes of this study have been compared to most recent and previous studies to make reliable interpretations.