FAULT ACTIVITIES IN THE AREA OF THE LOWER REACH OF TEKES RIVER, XINJIANG

The Qiabuqihai and Shankou Hydropower Stations,which are planned to be constructed on the Tekes River, Xinjiang Uygur Autonomous Region,are located in Tianshan area, where fault structures with intense Rrecent activities are widely developed.Field investigation shows that 5 major faults within the engineering sites were active during the Quaternary.Various techniques,including microstructural analysis of deformed rocks,analysis of surface textures of quartz grain,and TL dating,were used in the study of the samples collected from the Tekes fault and F1 fault within the engineering sites.The results show that ductile deformation at lower strain rate occurred along the faults during early stage,followed by a brittle fracturing process in the later stage.The main period of fault activity was by the end of Pliocene to Early Pleistocene.The differential stress during the faulting process in this period is 130 MPa.The faults are characterized principally by compressional movement.The faults have been activated since the pleistocene, although the intensity of fault activities has become weaked.The lower time limit of the last strong faulting event was by the end of late Pleistocene or the beginning of the Holocene.In order to ensure the safety of constrctions,it is suggested that the engineering sites should keep away from the active faults,and some safety measures should be considered in the design.