Structural architecture and late Cenozoic tectonic evolution of the Ulsan Fault Zone, SE Korea: New insights from integration of geological and geophysical data

Integration of geological and geophysical data is essential to elucidate the configuration geometry surface subsurface structures, as well their long-term evolution. The NNW–SSE-striking incised valley parallel mountain range in southeastern margin Korean Peninsula, extending 50 km from Gyeongju Ulsan cities, are together regarded one most prominent geographical features South Korea. This paper presents an investigation into structural architecture deformation history during late Cenozoic based on combined field observations gravity electrical resistivity surveys. Our results integrated reconciled geological, structural, follows. First, fault can be divided 1) northern part, which comprises several distributed buried or exposed strands; 2) southern a concentrated zone along eastern valley. Different between two parts controlled by lithology host rocks location neighboring major that is, Yeonil Tectonic Line (YTL) Yangsan Fault. Second, we defined Fault Zone NNW–SSE-to N–S-striking within In particular, constituent strands located have acted mainly imbricate thrust zone, characterized east-side-up with moderate low dip angles reverse-dominant kinematics shallow Quaternary. Third, reactivated Quaternary interpreted shortcut faults developed footwall Miocene subvertical predominantly YTL. addition, movements YTL were arrested NNE–SSW-striking Fault, was mature pre-existing structure. highlight spatiotemporal variation SE Korea emphasize strong control structures distribution characteristics (i.e., kinematics) subsequent under changing tectonic environments through Cenozoic.