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.

Using finite-frequency teleseismic P-wave tomography, we developed a new three-dimensional (3-D) velocity model of the mantle beneath Anatolia down to 900 km depth that reveals the structure and behavior of the subducting African lithosphere beneath three convergent domains of Anatolia: the Aegean, Cyprean, and Bitlis-Zagros domains. The Aegean slab has a relatively simple structure and extends into the lower mantle; the Cyprean slab has a more complex structure, with a western section that extends to the lower mantle with a consistent dip and an eastern section that is broken up into several pieces; and the Bitlis slab appears severely deformed, with only fragments visible in the mantle transition zone and uppermost lower mantle. In addition to the subducting slabs, high-amplitude slow velocity anomalies are imaged in the shallow mantle beneath recently active volcanic centers, and a prominent fast velocity anomaly dominates the shallow mantle beneath northern Anatolia and the southern Black Sea. As a whole, our model confirms the presence of well-established slow and fast velocity anomalies in the upper mantle beneath Anatolia and motivates two major findings about Eastern Mediterranean subduction: (1) Each of the slabs penetrates into the lower mantle, making the Eastern Mediterranean unique within the Mediterranean system, and (2) the distinct character of each slab segment represents different stages of subduction termination through progressive slab deformation. Our findings on the destructive processes of subduction termination and slab detachment have significant implications for understanding of the post detachment behavior of subducted lithosphere.

[1] Receiver functions obtained at INDEPTH III stations located near the Bangong-Nujiang suture in central Tibet display a weak Moho signal and strong P to S conversions within the first 5 s that vary systematically with backazimuth. A single station with representative azimuthal variations located at the sharp onset of strong SKS splitting, is modeled for both dipping layers and seismic anisotropy by using a global minimization technique. Inversion results indicate strong anisotropy (>10%) near the surface and in the middle crust separated by a south-dipping ($25°) layer, possibly related to the earlier phase of crustal shortening. Near-surface anisotropy has a fabric dipping steeply southward and trending WNW-ESE that correlates with the suture and younger strike-slip faults. In contrast, midcrustal anisotropy occurs in a low-velocity zone and has a fabric dipping gently ($18°) northward that might be related to a well-developed near-horizontal rock fabric induced by crustal flow.

Subduction beneath central Anatolia represents the transition between continuous subduction along the Aegean trench in the west and slab break-off and/or subduction termination at the Arabian-Eurasian collision zone in the east. Using recently collected seismic data from the Continental Dynamics-Central Anatolian Tectonics project alongside a newly developed approach to the creation of a 3D shear-velocity model from the joint inversion of receiver functions and surface-wave dispersion data, we can gain important insights into the character of the downgoing, segmenting African lithosphere and its relationship with the overriding Central Anatolian plate. These results reveal that the mantle lithosphere of central Anatolia is thin and variable (<50-80 km) due to the decoupling of the crust of accreted lithospheric blocks from their associated lithospheric mantle, which continued to subduct and was subsequently removed by slab delamination during early-mid Miocene times. The resulting lithospheric thickness variations appear to control deformation as well as the distribution of vol canism throughout the region. In the Central Anatolian Volcanic Province, the upper most mantle is characterized by very slow shear velocities (<4.2 km/s) consistent with the presence of melt in the uppermost mantle. The fastest shear velocities observed in this study (>4.5 km/s) underlie the Central Taurus Mountains, which have experienced ~2 km of uplift in the past ~8 m.y. These velocities are consistent with lithospheric mantle, and we interpret that the recent uplift of these mountains is due to a rebound of the subducting slab after slab break-off and/or fragmentation rather than asthenospheric influx.