Post-seismic deformation associated with the 2020 M_W7.0 Samos (Aegean Sea) earthquake constrained by InSAR and GNSS observations

This study investigates the post-seismic deformation following the October 30, 2020 M_W7.0 Samos earthquake using Copernicus Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) time series and continuous Global Navigation Satellite System (GNSS) observations spanning more than four years after the main shock. Prior to the post-seismic analysis, a reference co-seismic slip model was derived from co-seismic GNSS offsets within a seismologically constrained finite-fault geometry. Post-seismic deformation is largely confined to Samos Island, with no resolvable signal detected on adjacent islands or along the Turkish coast, indicating a near-field-dominated response. The post-seismic deformation within Samos Island is spatially asymmetric, characterized by sharp displacement gradients in the western and central parts of the island and smoother deformation towards the east. The joint inversion of GNSS and InSAR data indicates that post-seismic deformation is dominated by shallow afterslip concentrated primarily up-dip and laterally adjacent to the co-seismic rupture. Peak cumulative afterslip reaches ~0.6 m, releasing a post-seismic moment equivalent to approximately 20% of the co-seismic one. The spatial relationship between the co-seismic slip, afterslip, and aftershocks suggests efficient stress release during the main rupture, followed by aseismic afterslip on shallow parts of the fault plane. Localized deviations from the afterslip model, particularly in coastal areas, imply that poroelastic rebound may have contributed secondarily to the post-seismic deformation.