Tectonic kinematic and dynamical boundary conditions to the South of Anatolia using new geodetic constraints and numerical modeling

Abstract

The intricate plate tectonics of the Eastern Mediterranean region are driven by the interactions among three giant tectonic plates: Arabia, Africa, and Eurasia. The complexity of this region arises from the independent movements of smaller blocks or subplates, posing challenges for both kinematic and dynamic modeling. Since some pioneering works, it has been established that the northward motion of the Arabian Plate and the rollback of subduction at the Hellenic trench serve as two fundamental drivers of tectonic activity in the area, in addition to forces generated by lateral variations in crustal and upper mantle structure. However, the portion of the deformation process related to the northward motion of the Nubia Plate and its interaction with the deformation of Cyprus and South and Central Anatolia remains less comprehended. The Cyprus Arc, in particular, stands as one of the least understood segments within the broader Alpine-Himalayan tectonic belt. While historical seismicity in the region may appear limited, it may not provide a complete representation of the true long-term tectonic characteristics of the arc. The ongoing vertical uplift of Cyprus, well-documented by geomorphological studies, prompts further inquiry into the underlying mechanisms responsible for this uplift. The Cyprus Arc is bounded by the Anatolian Block to the north, the Nubian Plate and Sinai Subplate to the south, the Hellenic Arc to the west, and the Dead Sea Transform Fault and Arabian Plate to the east. Recent studies propose that subduction is still active along the Hellenic Arc, possibly continuing slowly westward from Cyprus. However, subduction likely ceased around Cyprus due to the collision and locking of microcontinental blocks, situated on the northern edge of the African Plate in the subduction zone. Eratosthenes Seamount, positioned between Cyprus and the Sinai subplate, with the passive margin of the Levant to the east, is a potential candidate for the source of these microcontinental blocks. This complex tectonic setting underscores the need for continued research to unravel the intricacies of the tectonic processes at play in the Eastern Mediterranean region. GNSS and InSAR datasets have been used to examine the present-day kinematics of the Tuz Gölü Fault with a view to documenting an 'intra-plate-like' behavior within a highly active plate boundary zone. In order to generate the strain rate field of the region, two different approaches have been employed. Both of the approaches reveal that the area has a shear-dominated deformation. Furthermore, a simple block model is constructed to understand better, especially the slip on the Tuz Gölü Fault. The results indicate that the fault behaviour can be explained by right-lateral strike-slip motion. This is in contradiction with the previous interpretations of it displaying normal fault behaviour based on geomorphological observations of limited spatial extent. On the other hand, the present-day kinematics of the fault is not in agreement with the thrust features that are observed around it. The propagation of the rupture of the North Anatolian Fault Zone may have put an end to the thrust regime along the Tuz Gölü Fault at the end of the Pliocene. It may provide guidelines for understanding the origin and behaviour of slowly deforming 'germanotype' structures within zones of rapidly deforming 'alpinotype' regions. Triple junctions involving non-subductable plates extend beyond local implications, crucial for studying the geology of convergent plate boundary zones. However, kinematic models overlook Cyprus-Anatolia motion due to limited geodetic constraints. Our study encompasses Cyprus, southern Turkey, and the Levant coast, focusing on the Kahramanmaraş triple junction where a destructive earthquake sequence occurred on February 6, 2023. We present precise positioning data merged with published velocities, constructing an up-to-date velocity field for the interseismic period. Employing two kinematic approaches, we analyze its tectonic implications. In Cyprus, we find the relative motion of Africa (Sinai Plate) and Anatolia is partitioned between convergence in the Cyprus subduction, with rate +-3.5-6.2 mm/yr, progressively decreasing from west to east and left-lateral transpressive Kyrenia fault, situated along the northern coast of Cyprus, with rate 3.2-4.2 mm/yr. The Levant Fault has a 3.5-4.7 mm/yr left-lateral slip rate, decreasing northward as part of it is transferred to offshore faults. The relative strike-slip motion between Arabia and Anatolia is partitioned between the East Anatolian Fault (slip rates 5.1-6.2 mm/yr) and some secondary faults such as Çardak and Malatya faults (slip rates 1.9-1.7 mm/yr) and causes distributed deformation for a 50-60 km wide region. The largest second invariant strain rate tensors from the continuum kinematic model also coincide with the same region which can be defined as the East Anatolian shear zone. A shear partitioning system exists around the Kahramanmaraş triple junction, from Cyprus to southeast Turkey. Strain rates appear relatively small in the Taurus range and Adana/Cilicia basin, transitioning from extensional/transtensional to compressional from east to west. The up component of GNSS velocities on the Taurus karstic plateau reaches 1.2 mm/yr, lower than Quaternary uplift rates on its southern edge. We examine Taurus uplift and Adana/Cilicia basin subsidence, considering slow convergence through earthquake distribution, seismic tomography, and modeling.