Partitioning Anatolian Kinematics into Tectonic Escape and Slab Rollback Dominated Domains

Anatolia is the global archetype of tectonic escape, as GPS (Global Positioning System) motions of the wedge-shaped plate differ regionally from northeastwards to southwestwards (from east to west). In traditional interpretations Anatolia was extruded westward from the Arabian-Eurasian collision, rotating counterclockwise into the oceanic free-faces of the Mediterranean and Aegean, with dramatic extension of western Anatolia. However, the relative contributions of extrusion related to the Arabia/Eurasia collision vs. rollback of the African slab beneath western Anatolia are unclear. To assess the dominant driving mechanisms across Anatolia, we analyze the recent GPS velocity dataset, and decomposed them into N–S and E–W components, revealing that westward motion is essentially constant across the whole plate and consistent with the slip rates of the North and East Anatolia Fault zones, while southward components increase dramatically in the transition area between central and western Anatolia, where a slab tear is suggested. This phenomenon is related to different tectonic driving mechanisms. The Arabia-Eurasia collision drives Anatolian plate uniformly westwards while western Anatolia is progressively more affected by the southward retreating African subducting slab west of the Aegean/ Cypriot slab tear, which significantly increases the southward component of the velocity field and causes the apparent curve of the whole modern velocity field. Recent earthquakes also confirm that the northward colliding Arabian plate forced Anatolia to the west, and the retreating African slab is pulling the upper plate of western Anatolian apart in extension. We propose that the Anatolian plate is moving as one plate westwards with extra extension in its west caused by the local driving mechanism, slab rollback (with the boundary above the slab tear around Isparta), rather than separate microplates or a near-pole spin of the entire Anatolian plate, and the collision-related extrusion is the main driving mechanism of tectonic escape.