关键词: 祁连山北缘断裂带, 现代构造运动, 地形变

Abstract: North-frontal Qilianshan fault zone is located in the northern part of QinghaiXizang Plateau,being a large active tectonic belt in West China. A lot of data has been obtained from precise levelling and displacement measurements across the faults in this region over 20 years. Based on these data the tectonic actiyity of the fault zone is analysed.On eight levelling arrays over the region,the largest displacement gradient R_m is found to be perpendicular to the Hexi Corridor. Due to the effect of the eastern extension of Altun fault,the variation in displacement along the Hexi corridor is large (up to 0.17),with exception of Chejipu-Xingmipu section,where R ranges in general from 0.01 to 0.05,and the variation is small.In the northwestern part of Yumen area,however,R reaches up to 0.20,and the mountain body has a tendency to uplift. In Zhangye-Mile section,the southeastern part of the corridor,R is relatively small (0.06),and the mountain body has a little crossfault subsidence relative to the basin. Cross-fault trilateration has revealed a shortenning rate of 0.2—0.5mm/a. The fault is characterized by compressional shearing,accompanied by antisymmetric elevation and subsidence. In addition,local uplift and subsidence as well as faulting have occurred in the inner part of the Hexi Corricor by the effect of secondary tectonic movement.

Key words: North-frontal Qilianshan, fault zone, Recent tectonic movement, Precise levelling, Trilateration