Deformation of Western Anatolia under the effect of the Hellenic Trench and the North Anatolian Fault

The Anatolian Plate, surrounded by the Eurasian, African and Arabian plates, represents a great laboratory for geoscientists with its all complicated tectonic settings. The region is located at a widely spread active tectonic deformation zone that has primarily been controlled by the African plate subduction beneath the Hellenic Trench and the movement of the North Anatolian Fault Zone (NAFZ). The effect of crustal thinning due to the extensional regime gave rise to the formations of horst and graben systems leading to large earthquakes (e.g. The Mw7.0 2020 Samos earthquake) with normal faulting mechanisms in western Türkiye. A precise evaluation of tectonic deformation process and the potential seismic risk in this area requires a comprehensive understanding of the quantitative impact of both the Hellenic subduction and the NAFZ to the surface movement. To distinguish these individual contributions, we examine the published regional GPS data along Greece-Türkiye region. Considering a basic elastic-viscoelastic layered earth model, our first step is to estimate the contribution of the NAFZ to the GPS velocity at each station under various average slip rare conditions. We then perform an inversion on the residual velocities obtained by subtracting the calculated velocity from the observed data. This inversion allows us to derive the subduction rate along the Hellenic Trench. Our modelling indicates an optimal slip rate of <35 mm/yr that identifies the NAF zone and an average subduction rate of about 40 mm/yr for the the Hellenic Trench. These results suggest the significance of both the Hellenic Trench slab rollback and the NAFZ movement highlighting their essential roles in the observed deformation beneath this region.