An investigation of Anatolian - African subduction zone in southwestern Turkey : lithospheric structure beneath Isparta angle and the surroundings from rayleigh wave phase velocity inversion

Abstract

Geodynamics of Turkey is complicated by the tectonic interactions between Africa, Eurasia and Arabian plates leading to high seismic activity and internal deformation beneath this region. 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 constraints on the upper mantle structure beneath IA and the surroundings via Rayleigh wave tomography method. In this regard, we adopted a phase velocity inversion technique named as “Two-plane wave method”. With the use of this technique, we will be able to effectively map the three-dimensional velocity structure and amplitude variations 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 stations of Kandilli Observatory and Earthquake Research Institute (KOERI), Süleyman Demirel University (SDU) and IRIS/GEOFON together with temporary stations deployed with support from Missouri University and Boğaziçi University Research Fund (BAP). Following the detailed analysis of vertical component seismograms, we calculated a one-dimensional dispersion curve which served as an input for two dimensional (2-D) phase velocity inversions. Phase velocity maps were displayed in several cross sections at various periods. We also performed other series of inversions to determine the shear wave velocity distribution down to 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. These velocity anomalies provided us insights on the key elements that define the nature of subduction such as slab detachment, slab tearing, asthenospheric upwelling, and volcanism etc. The outcomes have been compared to most recent and previous studies to make reliable interpretations.