Fault modelling, seismic sequence evolution and stress transfer scenarios for the July 20, 2017 (MW 6.6) Kos–Gökova Gulf earthquake, SE Aegean

Abstract

The July 20, 2017, MW 6.6 Kos–Gokova Gulf earthquake occurred offshore, near Bodrum of Turkey and Kos of Greece. It was one of the strongest in the broader area during the last many decades causing two deaths, many injuries and extensive damages. We investigated the evolution of the seismic sequence using seismological and geological tools. The aftershock sequence was relocated mainly in order to define the geometry of the main seismic source, depicting a NNW-dipping fault plane. It also revealed significant clustering, associated with other nearby faults, and asymmetric spatio-temporal evolution. Along with morphotectonic analysis on Kos Island, and other published seismological information (e.g. focal mechanisms), we modelled the seismic source of the mainshock, as well as the one of the strongest aftershocks (August 8, MW 5.3). We applied the Coulomb failure criterion in order to investigate the effect of the mainshock on the strongest aftershock, and the rest of the sequence as well. Using the same method, we also investigated the stress changes of both strongest shocks for the prevailing E–W-trending normal faults in this area. Among other conclusions and implications, we deduce that the prevailing tectonic setting of the Gokova Gulf consists of roughly E–W-striking normal faults forming inner horsts and grabens.