Segmented African lithosphere beneath the Anatolian region inferred from teleseismic P-wave tomography

Abstract

SUMMARY Lithospheric deformation throughout Anatolia, a part of the Alpine–Himalayan orogenic belt, is controlled mainly by collision-related tectonic escape of the Anatolian Plate and subduction roll-back along the Aegean Subduction Zone. We study the deeper lithosphere and mantle structure of Anatolia using teleseismic, finite-frequency, P-wave traveltime tomography. We use data from several temporary and permanent seismic networks deployed in the region. Approximately 34 000 P-wave relative traveltime residuals, measured in multiple frequency bands, are inverted using approximate finite-frequency sensitivity kernels. Our tomograms reveal segmented fast seismic anomalies beneath Anatolia that corresponds to the subducted portion of the African lithosphere along the Cyprean and the Aegean trenches. We identify these anomalies as the subducted Aegean and the Cyprus slabs that are separated from each other by a gap as wide as 300 km beneath Western Anatolia. This gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere. The eastern termination of the subducting African lithosphere is located near the transition from central Anatolia to the Eastern Anatolian Plateau or Arabian–Eurasian collision front that is underlain by large volumes of hot, underplating asthenosphere marked by slow velocity perturbations. Our tomograms also show fast velocity perturbations at shallow depths beneath northwestern Anatolia that sharply terminates towards the south at the North Anatolian Fault Zone (NAFZ). The associated velocity contrast across the NAFZ persists down to a depth of 100–150 km. Hence, our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary. Overall, the resolved upper-mantle structure of Anatolia is directly related with the geology and tectonic features observed at the surface of the Anatolian Plate and suggest that the segmented nature of the subducted African lithosphere plays an important role in the evolution of Anatolia and distribution of its tectonic provinces.