20 July 2017 Bodrum-Kos Earthquake (Mw:6.6) in southwestern Anatolia, Turkey

Semir Över,Süha Özden,Zeynep Coşkun,Ali Pınar,Esra Kalkan Ertan,Fatih Turhan

doi:10.15446/esrj.v25n3.87080

Abstract

In the Aegean Sea, the western part of Gökova Gulf, Kos and Bodrum were struck by a 6.6 (Mw) earthquake on July 20, 2017. The fault plane solution for the main shock shows an E-W striking normal type fault with approximately N-S (N4°E) tensional axis (T-axis). Fault plane solutions of 33 aftershocks show two groups of normal type fault with E-W and NE-SW to ENE-WSW orientations. The inversion of the focal mechanisms of the aftershocks yields two different normal faulting stress regimes: one is characterized by an approximately N-S (N5°E) σ3 axis (minimum horizontal stress axis). This extension is obtained from 13 focal mechanisms of aftershocks with approximately E-W direction. The other is characterized by approximately NW-SE (N330°E) σ3 axis. The latter is calculated from 21 seismic faults of aftershocks with approximately NE-SW direction. These aftershocks occurred on relatively small-scale faults that were directed from NE-SW to ENE-WSW, and possibly contributed to expansion of the basin in the west. The 24 focal mechanisms of earthquakes which occurred since 1933 in and around Gökova Basin are introduced into the inversion analysis to obtain the stress state effective in a wider region. The inversion yields an extensional stress regime characterized by an approximately N-S (N355°E) σ3 axis. The E-W directional metric faults, measured in the central part of Gökova Fault Zone bordering the Gökova Gulf in the north, also indicate N-S extension. The NE-SW extension obtained from NE-SW aftershocks appears to be more local and is responsible for the expansion of the western part of the asymmetric Gökova Basin. This N-S extension which appears to act on a regional-scale may be attributed to the geodynamic effects related to the combined forces of the southwestward extrusion of Anatolia and the roll-back process of African subduction beneath Anatolia.

Highlights

Plate boundary forces caused by relative movements between Africa, Arabia, and Eurasia resulted in complex tectonic structures in the western Anatolia-Aegean region (Fig. 1)
We introduced the focal mechanisms of both the main shock and its aftershocks into the inversion algorithm
The current results indicate that the fault that ruptured during the 20 July 2017 earthquake is not the same as the Gökova Fault or its western continuation in the gulf

Summary

Introduction

Plate boundary forces caused by relative movements between Africa, Arabia, and Eurasia resulted in complex tectonic structures in the western Anatolia-Aegean region (Fig. 1). The northern segment extends to the east of Kos (Karasözen et al, 2018), while the southern segment is listric (Kurt et al, 1999) Analyzing both bathymetric and seismic reflection data, İşcan et al (2013) revealed the existence of active strike-slip faults with various directions in the Gulf of Gökova. The interpretation of new multichannel seismic profiles by Ocakoğlu et al (2018) shows the existence of active strike-slip and normal faults in different directions in the Gulf of Gökova. They pointed out southern-dipping et al, 2018)

Methods

Findings

Discussion

Conclusion