Merzifon–Esençay splay fault within the North Anatolian Fault system: segmentation and timing of the last two surface faulting events on Esençay segment

Abstract

North Anatolian Fault (NAF) as a seismically active intracontinental plate boundary is characterized by splay faults in a half fishbone geometry, reaching into the Anatolian plate. Recent crustal deformations within Central Anatolia Tectonic Province are accommodated by dextral and sinistral strike-slip splay fault systems. Sinistral splays extend conjugate to the NAF and subparallel to the East Anatolian Fault (EAF), while the dextral splays are subparallel to the NAF. Sungurlu–Ezinepazar (SEF) and Merzifon–Esencay (MEF) faults are two major dextral splays bifurcating from Niksar pull-apart basin, which distinguish eastern and central NAF. Geodetic and geological data suggest a total of 3 mm/year slip rate along these splays in a setting of slip partitioning with the main strand of the NAF. These two splays undertake 12–13% of the lateral motion within a broad deformation zone of the NAF where the MEF accommodates 1/3 of this amount. 227 km-long MEF is divided into six fault segments, which are separated from each other’s by releasing and restraining jogs. Cumulative offsets up to 3.0 km on Kizilirmak River valley and tributaries of Yesilirmak River since latest Pliocene-Early Pleistocene (~ 3 Ma) suggest an approximately 1 mm/year long-term geological slip rate on the MEF. Paleoseismological findings from Esencay segment reveal two discrete surface faulting events within the last 7 ka with a return period of maximum 2200 and minimum 1320 years. The lapse time since the last event is about 3700 years. This implies ~ 3.7 m of strain accumulation on the Esencay segment for present. The segments have the potential to produce induvial earthquakes with magnitudes varying between Mw 6.8 and Mw 7.2. Existing information imply that major fault splays have the potential to produce multi-segment large earthquakes within the NAF zone in addition to well-known Yedisu and Central Marmara seismic gaps.