Source Characteristics and Exacerbated Tsunami Hazard of the 2020 Mw 6.9 Samos Earthquake in Eastern Aegean Sea

On 30 October 2020, an Mw 6.9 normal faulting earthquake occurred off the northern coasts of Samos Island, Greece. The earthquake with moderate magnitude generated the largest tsunami in the eastern Mediterranean since the 1956 Amorgos event. Here, we investigate the earthquake source characteristics and examine the factors contributing to the exacerbated tsunami using an integrated approach, including the source inversion from InSAR and GPS data, tsunami simulation, and spectral analysis of tsunami waveforms. The results show that a set of conjugate faults, determined in this study, can explain the geodetic surface deformation equally well. Our tsunami modeling results indicate that the shallow north‐dipping fault was most likely responsible for the mainshock. With the key features of our preferred source models, we infer that the tsunami was intensified by several conditions: (a) the spatial distribution of major coseismic slips coincided with the deepest portion of the Samos Basin which served as an energy reservoir for the tsunami generation; (b) the tsunami was generated in a semi‐closed bay which trapped most of the tsunami energy; (c) the east‐west orientation of the mainshock fault and the location of the concentrated coseismic slips directed the majority of the tsunami energy toward Sığacık Bay, which formed the extremely high tsunami of 3.8 m; (d) the primary tsunami wave period, close to natural oscillation frequency of the harbor, resulted in the observed significant oscillation. We conclude that the tsunami of the 2020 Samos earthquake was exacerbated by both the source characteristics and tsunami resonance property. Plain Language Summary Tsunamis are generally generated by megathrust earthquakes in subduction zones, like the 2004 Mw 9.1 Sumatra‐Andaman earthquake. However, a normal‐faulting earthquake on 30 October 2020, in the Aegean Sea generated the largest tsunami in the eastern Mediterranean since 1956. We investigate how the Mw 6.9 normal earthquake could produce tsunami waves of up to 3 m in height and lead to such severe tsunami damage on the coasts of Izmir, Turkey and Samos Island, Greece. We explore the earthquake source characteristics and the factors exacerbating the effects of the tsunami. We evaluate six representative fault models derived from this study and others by comparing their capability of reproducing the observational data, from which we infer the most likely source features. We also analyze the period components of