Preliminary Study On Active Fault Systems And Assessment Of Post-earthquake Hazards Of Central North China Block

North China Craton is the oldest craton of China.Since the Mesoic，the NorthChina Craton has been active.A large number of thrust and folds developed in theEarly Yanshannian and a widespread of rifting developed in the Late Yanshannian. Inthe Cenozoic，there is under blocking with different activity.The Taihang mountainsstrongly uplifted;the Bohai Bay Basin and the Fenwei Graben developed.Until now，North China Block is still a major area of earthquakes.Besides，the earthquakes ofM>6in this area struck the part that the intersection of the NNE-NE and NW trendingfaults，infleting the relationship between the active fault and eatthqukes.Therefore，itis very significant to study the active tectonics geomorphology in the center of theNorth China Craton.Combined with previous studies, field investigations, DEM, earthquakedistribution, ground fracture， trench, isotopic dating and deposition rate of the basinand the features of tectonics cycle, the activity and intersection and evolution of faultswith different strikes since late Holocene, for understanding the active tectonism asfollows. North China Block can be divided into two active fault systems, NNE dextralstrike-slip fault system and NNW Left-lateral slip fault systems. the former includeTaihang mountains Fault Zone、Cang Dong Fault Zone, Tanlu Fault Zone and thelatter include Zhangjiakou-peilai Fault Zone, Hengshui Fault Zone,Jiexiu-Xinxiang-Liyang Fault Zone.They cut north china block into6rhombicblocks.these subblocks’ boundary and junction are the palce that earthquake activenowadays.The central of North China Block has planation surface of3-grade left. Riverterraces of4-grade and are formly developed and8periods of magama stronglyactivity. Analysising characteristics of distribution of quaternary strata, depositionrate，biuld order of magmatic rock, planation surface, river terrace, the study area hasgone through6geomorphic cycle periods：K3-E3, N12-N23, Q1-Q23, Q3, Q41, Q43tillnow.Besides, from the Holocene, the activity of tectonics in North China area hasbecome stronger.Since Neogene, North China has gone through2strong deposition stages whichare redpond to the Tibet Plateau rapidly uplifted of5Ma and Holocene, illustratingthat the India Plate affects the tectonics of the North China area. In the Holocene, therate of the deposition in Ji-Zhong depression and Weihe-Yuncheng basin is thehighest， which is related to the order of the depression formed, stating that thecentral of the North China are in the same tectonics background.According to the activity and distribution of faults, earthquake and groundfracture in the North China area， the central of the North China block is under thestress field of NEE-SWW trending extrusion and NNW-NNE trending tension. In thiscondition， NNE right-lateral slip fualts and NWW left-lateral slip faults formedShanxi graben system，earthquake active belt and NE trending normal dip-slip faults.