Basin progress: active deformation analysis by tectonostratigraphic elements and geophysical methods on North Anatolian Fault System (Eastern Marmara Region, Turkey)

Abstract

The Northern Branch of the North Anatolian Fault System controls and deforms the Izmit Basin and the Sapanca Lake Basin in the study area. Unlike the Sapanca Lake Basin, the oblique normal faults with WNW-ESE trending with maximum length of 5 km in the south of the basin have contributed to the deformation process in the formation of Izmit Basin. The fault sets mainly incline to the north. The N-S width of the dextral strike-slip active deformation was determined as 9 km at Izmit basin and 3.8 km at Sapanca Lake basin. Further, the minimum principal stress axes (σ3) vary in the trending ranges of N11°-74° E, which are caused by the transtensional stresses associated with strikeslip faulting in the Izmit Basin by a different tectonic source than the Sapanca Lake Basin. Besides, the crust depth of main strand of NAFS-NB was determined up to 1112 m by magnetic method. The secondary faults were determined by both magnetic and resistivity methods up to a depth of 110 m. The depression area between Izmit bay and Sapanca Lake on the northern Anatolian fault is an integrated basin with two dextral strike-slip tectonic origins. Thus, the Izmit Basin, along with the main strike-slip faulting, has been developed in the asymmetric negative ower structure, where only the southern boundary has become a fault. The Sapanca Lake Basin is a lazy-Z-shaped pull-apart system formed by the E-W trending fault as a releasing bend. A simple shear deformation ellipsoid with a long axis of approximately 35 km on the Northern Branch of the North Anatolian Fault System is de ned for the Izmit -Sapanca integrated basin. Therefore, intra-basin deposits have different depths estimated from the gravity data in the Izmit -Sapanca integrated basin, and the maximum sediment thickness estimated is 2200 m in the middle of the Izmit Basin. Ogawa et al. 2001; Ogawa and Honkura 2004). Ateş et al. (2003) have identi ed the faults in the deep section of the crust along the NAFS-NB based on the high-speed zones and the regions where coincident with gravity and magnetic highs. Bohnhoff et al. (2016b), suggested that a coseismically introduced lateral and vertical slip de cit is systematically compensated postseismically in both the brittle and ductile portions of the crust in east Marmara region.This study explains the development of an integrated basin-like ISIB consisting of Izmit basin and Sapanca Lake basin with different basin morphology, located on a right-lateral strike-slip fault (NAFS). In this sense, the deformation geometry of the active structural elements, which are associated with lithofacies features, the sedimentary processes of the basin-lling formations, and which are different from each other in each basin, are formed from the surface to a certain depth of the upper crust. The tectonostratigraphic observations made on the surface were correlated with the geophysical data collected by the resistivity, magnetic, gravity, and joint inversion methods, identi ed the traces of active deformation in the upper depths of the ISIB. Thus, the charac...