Palaeoseismological assessment for a seismic gap located very close to the epicentre of the 30 October 2020 Samos Earthquake (M6.9), western Anatolia, Turkey

Abstract

The Tuzla Fault (TF), considered one of the most important seismic sources in İzmir province, is defined as a strike–slip fault with N10E–N60E striking between Gaziemir and Doğanbey districts. A 50-km-long fault consists of three segments which are, from north to south Çatalca, Orhanlı, and Doğanbey segments. Recent studies claim that the part of the TF extending to Kuşadası Bay is also in a kinematic relationship with the Samos Fault that caused an earthquake on 30 October 2020 (Mw = 6.9). In this study, in order to analyse the historical behaviour of the fault, three trench-based palaeoseismology studies across the fault scarp were conducted on three geometric segments of the TF. Palaeoseismology findings show that seven historic/prehistoric earthquakes were generated by TF. According to Oxcal distribution using the Bayesian methods, the time of the events lie between 46.2 ± 6.1 and 1.6 ± 0.3 ka. When the events are compared with the historical earthquakes, the last event is correlated with the earthquakes of 47 AD and/or 177/178 AD on the Doğanbey segment. Moreover, the other events can be attributed to the late Pleistocene–Holocene earthquakes that are prehistorical periods. Our results provide a recurrence interval of an earthquake along the TF to between 0.7 and 4.3 ka for the Holocene period. The elapsed time since the most recent surface faulting earthquake on the TF is 1844 years. It is suggested that it is predicted that TF has the potential to produce destructive earthquakes in the near future, especially in Orhanlı and Çatalca segments which may be considered as a seismic gap.