Partitioning Anatolian Kinematics into Tectonic Escape and Slab Rollback Dominated Domains

Abstract

Anatolia is the global archetype of tectonic escape, as witnessed by the devastating 2023 Kahramanmaraş Earthquake sequence, and the 2020 Samos Earthquake, which show different kinematics related to the framework of the escape tectonics. Global Positioning System (GPS) motions of the wedge-shaped plate differ regionally from northwestwards to southwestwards (from east to west). Anatolia was extruded westward from the Arabian-Eurasian collision along the North and East Anatolian fault systems, rotating counterclockwise into the oceanic free-faces of the Mediterranean and Aegean, with dramatic extension of western Anatolia in traditional interpretations. However, which is the dominant mechanism for this change in kinematics, extrusion related to the Arabia/Eurasia collision or rollback of the African slab beneath western Anatolia is still unclear. To assess the dominant driving mechanisms across Anatolia, we analyze recent GPS velocity datasets, 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 the 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. The 2020 and 2023 earthquake focal mechanisms 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 westwards as one plate with an additional component of 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 dominant mechanism of tectonic escape.