Active faulting in Samos Basin, Eastern Aegean Sea, Greece and paleogeographic implications

The geological analysis of the Samos Island region, particularly the Samos Basin, based on seismic profiling, has revealed a complex tectonic history marked by significant deformation and seismic activity. The Mw 7.0 earthquake in October 2020 is linked to the activation of the E-W marginal fault, resulting in the formation of a south-tilted half-graben. This was followed by aftershocks ranging from Mw 3.2 to 4.5, which correspond to the activation of smaller normal faults, mainly within the Vathy Hills. No significant deformation extends into the eastern margin of the Ikaria Basin, likely due to the different orientations and dips between the Samos Basin faults (E-W, dipping 40° N) and those in the Eastern Ikaria Basin (NE-SW, dipping 65° NW). The eastern Ikaria segment represents the primary seismic hazard for the Samos area, with a potential magnitude of 6.5. Low-angle normal faults of Tortonian age have been identified primarily in the eastern Vathy Hills and along the western segment of the E-W marginal fault of Samos, separating the basement from the overlying sediments. The basement is found beneath the Eastern Samos Basin and Vathy Hills but deepens to over 1600 m to the west. The overall deformation shows a significant westward increase, with displacements 4–5 times greater (700 m vs. 3300 m) over 50 km from Eastern Samos to Eastern Ikaria. Stratigraphic analysis indicates an eastward sea transgression during the Middle-Late Pleistocene over Messinian-Pliocene continental deposits. Canyons and landslides are observed along the southern margin of Samos. The paleogeographic evolution includes the uplift of the metamorphic basement during the Early Miocene, followed by the formation of continental sedimentary basins in the Middle-Late Miocene, marked by N-S marginal faults and volcanic activity. The Samos Island horst emerged due to E-W faulting, with the subsidence of the Samos Basin occurring during the Early-Middle Pleistocene.