Earthquake history of the Gokova fault zone by paleoseismologic trenching, SW Turkey

Abstract

The Gulf of Gokova is a half-graben that is located on the southernmost part of the Aegean Extensional Region. The gulf is bounded on its north by the Gokova Fault Zone, which is an active fault zone that is composed of normal fault segments. We performed paleoseismological trenching throughout the fault zone at two sites, Keramos and Gereme sites. We have recognized two paleoearthquake horizons in Gereme trench and one paleoearthquake horizon in Keramos trench. Dating of samples by OSL and radiocarbon dating methods, and outcomes of Bayesian calculation in Oxcal, bracket the age of the older paleoevent as BCE 1099-161 and the younger event as CE 961-1574. Depending on the age bracket and written accounts in historical catalogues we compare the older paleoevent to the BCE 412-411 historical earthquake and the younger event to the CE 1493 historical earthquake. In conclusion, from this study, we have evidence for at least two surface faulting earthquakes during the Holocene, the most recent one representing the latest onshore surface rupturing event on the Gokova Fault Zone. Furthermore, depending on moment magnitude and rupture length relationships we suggest that the younger paleoearthquake event was about M = 7 according to a possible similar to 60-km-long surface rupture in at least between Kos island and Oren village.