Kinematics of contemporary subduction, extension, and shear localization across the Aegean Sea and Anatolia

Abstract:

The Hellenic subduction zone and the Anatolian plate constitute a cohesive tectonic system comprising the westward extrusion of Anatolia, latitudinal extension of the Aegean lithosphere, and rapid Hellenic slab rollback and trench retreat. Despite the heavily studied nature of this natural tectonic laboratory, the kinematics and driving forces of the deformation are still debated. Here, we exploit an extensive set of geodetic observations to build a consistent kinematic model of subduction, extension, and shear localization across the Aegean Sea and Anatolia. Creep along the Aegean section of the Hellenic slab occurs at a median rate of 49.8 mm/yr with no noticeable signs of slip deficit accumulation although the creep velocity tapers to 13.4 mm/yr in the Cyprian section. The North Anatolian Fault is a trans-lithospheric fault that bounds the westward extrusion of Anatolia and extends beyond the Karliova triple junction to the Turkish-Iranian Plateau, where the indentation of the Arabian plate also results in eastward extrusion and a diffuse zone of conjugate strike-slip faults in the brittle crust above the mantle shear zone. In contrast, the East Anatolian Fault does not extend to mantle depths, presumably because of its relatively young age and smaller long-term slip rate. Rapid extension in the Aegean Sea is accommodated in the lower crust by a diffuse extension of the North Anatolian Fault from the Sea of Marmara to the Gulf of Corinth, and by cooperative shear zones in the Hellenic mantle wedge involving the dextral Keffalonia transform fault to the west and the sinistral Pliny and Strabo trenches to the east. This deep-seated deformation is manifest in the brittle crust by slip-partitioning among grabens concentrated at the termination of strike-slip faults. From mainland Greece to eastern Turkey, the source mechanisms of normal and strike-slip earthquakes correspond closely to the direction of maximum extension and maximum shear, respectively, of plastic strain accumulation at lower-crustal and mantle depths. The kinematic model illustrates the present-day role the North Anatolian Fault plays in accommodating tectonic indentation and slab rollback in the diffuse collision zone between the Arabian, African, and Eurasian plates.