Paleoseismicity of the Ulubat Fault: Inferences on Seismic Behaviour of the Southern Branch of the North Anatolian Fault Zone, South Marmara

Abstract

This article presents the results of the first paleoseismological studies conducted along the Ulubat Fault and their inferences on the earthquake behavior of the south branch of the North Anatolian Fault Zone (NAFZ). The Ulubat Fault is divided into 3 segments according to its geometric characteristics and paleoseismological behavior. Along the fault segments, at least 6 paleoearthquake event have been distinguished in the last 16 thousand years with paleoseismolgic fault excavations. The dating results correlated with the historical records show that the latest surface ruptures along the Ulubat Fault occurred with the earthquakes of <161/170 AD (I=IX), 1143 AD (M=6.0) and 1855 AD (M=7.3), respectively, and migrated to the west. Although it does not provide sufficient statistical evaluation opportunity, the paleoseismological data presented in this study proves that the segments of the NAFZ south branch do not present characteristic earthquake behavior in terms of recurrence period and this irregularity may be due to the multi-fragment geometry of the fault zone in the region. © 2021 University of La Laguna. All rights reserved.