Tectonic implications of the Mw 6.8, 30 October 2020 Kuşadası Gulf earthquake in the frame of active faults of Western Turkey

Abstract

A Mw 6.8 earthquake struck Western Turkey and Eastern Greece that occurred on October 30, 2020 in Kuşadası Gulf. The earthquake epicentre is located north of Samos Island and the focal mechanism solution shows that a normal fault was reactivated. The main shock and aftershock analysis imply that the large earthquake occurred on a north dipping normal fault which might be the western continuation of the Efes Fault in Western Turkey. We propose that the western continuation of the Efes Fault steps over right somewhere in northeast of Samos Island and continues further west along the northwest margin of the island, in the form of a transfer fault between two segments. The aftershock distribution shows that both the western segment and the transfer fault were reactivated during the 30 October 2020 earthquake. This fault geometry can be compared with the E-W trending Gediz Graben where the southern boundary fault steps over right around Turgutlu and continues further west in Manisa. The historical records show that the source region and its vicinity is susceptible to frequent large earthquakes taking place on normal and strike-slip faults. The stress tensor inversion of the focal mechanisms of 55 aftershocks covering the source area shows dominant normal faulting mechanism which suggests NNE-SSW extensional stress regime in the region.