Fault models for the Bodrum–Kos tsunamigenic earthquake (Mw6.6) of 20 July 2017 in the east Aegean Sea

Abstract

We investigate a fault model for the shallow, strong (Mw6.6) tsunamigenic earthquake of 20 July 2017 with source area in the east Aegean Sea between Bodrum peninsula (Turkey) and Kos Isl. (Greece). Fault plane solutions are consistent with the regional active tectonics indicating normal faulting striking about E–W. A relocated hypocenter of the main shock was obtained and the rupture time-space history for two alternative fault solutions dipping either to the south or to north was approached by inverting P-waves recorded at teleseismic (30°–90°) distances. In both fault solutions the seismic moment calculated corresponds to magnitude Mw=6.6 while the earthquake had total rupture duration of less than 10 s. The maximum co-seismic slip was close to the hypocenter ∼1.6m and ∼2.2m for the south and north dipping faults, respectively. Close to the surface coseismic slip of ∼0.3m was calculated. Our analysis of Sentinel satellite InSAR images showed ground deformation fringes indicating ∼13 cm vertical displacement change between the North and South coasts of the Karaada islet. This result is in line with our preference of the south dipping fault, supported primarily by GPS displacements, regional tectonics, aftershock activity and tsunami observations, although results of InSAR inversion fit equally well both solutions.