The 2017 July 20 M-w 6.6 Bodrum-Kos earthquake illuminates active faulting in the Gulf of Gokova, SW Turkey

Date

2018-07-01

Author

Karasozen, Ezgi
Nissen, Edwin
Buyukakpinar, Pinar
CAMBAZ, MUSAVVER DİDEM
Kahraman, Metin
Ertan, Esra Kalkan
Abgarmi, Bizhan
Bergman, Eric
Ghods, Abdolreza
Özacar, Atilla Arda

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The 2017 July 20 Bodrum-Kos earthquake (Mw 6.6) is the largest instrumentally recorded earthquake in the Gokova graben, one of the primary physiographic features of SW Turkey. Using seismology and satellite geodesy, we investigate its source characteristics, aftershock distribution, relationship with earlier instrumental seismicity, and association with known surface faulting. We show that the earthquake ruptured a planar (non-listric) normal fault that dips gently (similar to 37.) northwards beneath the northern Gulf of Gokova coastline, initiating at a depth of similar to 11 km and rupturing upwards and bilaterally. Aftershocks concentrate around (but not necessarily on) the western, eastern and downdip edges of the similar to 25 km-long rupture plane, and have maximum focal depths of similar to 15 km. The main shock surface trace bounds a bathymetric ridge east of Kos island, and may be one of the several faults imaged previously in this area using seismic profiling and multibeam sonar. The fault thus lies within the hangingwall of the lower-angle (similar to 20. N-dipping) South Datc a fault, which it presumably cross-cuts at depth. Through calibrated relocations, we confirmthat sequences of moderate (Mw 5-5.5) earthquakes in 1989, 2004 and 2005 occurred in the eastern and central Gulf of Gokova, many of them likely within the hangingwall of the S-dipping Gokova fault. Overall, our results indicate a switch from dominant S-dipping normal faulting in the eastern graben to dominant N-dipping faulting in the west, but we find no support for a proposed NE-SW-trending left-lateral fault in the central Gulf; most colocated focal mechanisms involve similar to E-W normal faulting. Finally, the Bodrum-Kos main shock adds to growing set of examples from across the Aegean region of large normal faulting earthquakes that cut the seismogenic layer as simple planar structures.

Subject Keywords

Satellite geodesy, Earthquake source observations, Seismicity and tectonics

URI

https://hdl.handle.net/11511/47511

Collections

Department of Geological Engineering, Article