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Abstract:
The Aegean Sea and western Anatolian peninsula are allocated 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 Mw7.0 2020 Samos earthquake, for instance, is an expression of the N-S directed extensional tectonic regime developed in response to African slab rollback movement in this region. A proper assessment of tectonic deformation process and its potential seismic hazard require a quantitative understanding of the contribution from the Hellenic subduction and the NAFZ to the surface movement. Here, we analyze the published regional GPS data along Greece-Turkey region to separate those contributions. Using a simple elastic-viscoelastic layered earth model, we first estimate the NAFZ contribution to the GPS velocity at each station with a varying slip rate. Then, we invert residual velocities obtained by subtracting the calculated velocity from the observed data, to derive subduction rate along the Hellenic trench. In the calculation, we assume the elastic thickness of 60 km based on the regional seismic tomography results. Our model results suggest 35 mm/yr of optimum slip rate of identifying the NAFZ, and ~40 mm/yr of the average subduction rate for the Hellenic Trench. The synthetic velocities can explain the observed GPS velocity within an average misfit of 2-3 mm/yr. Our results mean that the Hellenic slab rollback and the NAFZ movement are essential for the observed deformation beneath this region.
