Seismic Tomographic Imaging of the Eastern Mediterranean Mantle: Implications for Terminal-Stage Subduction, the Uplift of Anatolia, and the Development of the North Anatolian Fault

Abstract

The Eastern Mediterranean captures the east-west transition from active subduction of Earth's oldest oceanic lithosphere to continental collision, making it an ideal location to study terminal-stage subduction. Asthenospheric- or subduction-related processes are the main candidates for the region's ∼2 km uplift and Miocene volcanism; however, their relative importance is debated. To address these issues, we present new P and S wave relative arrival-time tomographic models that reveal fast anomalies associated with an intact Aegean slab in the west, progressing to a fragmented, partially continental, Cyprean slab below central Anatolia. We resolve a gap between the Aegean and Cyprean slabs, and a horizontal tear in the Cyprean slab below the Central Anatolian Volcanic Province. Below eastern Anatolia, the completely detached “Bitlis” slab is characterized by fast wave speeds at ∼500 km depth. Assuming slab sinking rates mirror Arabia-Anatolia convergence rates, the Bitlis slab's location indicates an Oligocene (∼26 Ma) break-off. Results further reveal a strong velocity contrast across the North Anatolian Fault likely representing a 40–60 km decrease in lithospheric thickness from the Precambrian lithosphere north of the fault to a thinned Anatolian lithosphere in the south. Slow uppermost-mantle wave speeds below active volcanoes in eastern Anatolia, and ratios of P to S wave relative traveltimes, indicate a thin lithosphere and melt contributions. Positive central and eastern Anatolian residual topography requires additional support from hot/buoyant asthenosphere to maintain the 1–2 km elevation in addition to an almost absent lithospheric mantle. Small-scale fast velocity structures in the shallow mantle above the Bitlis slab may therefore be drips of Anatolian lithospheric mantle.