藏南仲巴裂谷带地貌和断裂活动特征研究

Study on the Tectonic Geomorphology and Fault Activity Characteristics of the Zhongba Rift, Southern Tibet

仲巴裂谷位于藏南裂谷系的西侧,其断层发育、断错地貌清晰.但目前,该断裂活动性研究尚属空白,制约了对整个藏南裂谷系变形机制的探索.基于GIS空间分析技术,利用数字高程模型数据系统提取该区的河流地貌参数,包括地形坡度、地形起伏度、河流陡峭指数和裂点等.对该裂谷两侧36个流域盆地的地形参数结果进行统计和分析后发现:地形坡度与k_(sn)之间具有一致性,仲巴裂谷西侧北、中段坡度陡峭,k_(sn)值较高,南段支流中间部分陡峭,两端较缓,对应k_(sn)值中间高两端低;东侧坡度和k_(sn)分布呈现中段陡峭,两端变缓的特征.河流纵剖面上表现出裂点上下陡峭系数的差异,东西两侧河流均在出水口处河段有最高河道陡峭系数,向上游段减小,总体上西侧河道陡峭系数大于东侧.综合地形坡度、河流纵剖面及裂点分析结果,认为仲巴裂谷西侧断裂的构造活动性可能强于东侧.

The Zhongba rift zone located on the west side of the southern Tibet rift system has well-developed faults and clear faulted landforms. However, the study on the activity of the fault is still lacking, which hinders our understanding of the deformation mechanism of the entire southern Tibet rift system. Based on GIS spatial analysis technology, we used the Digital Elevation Model data system to extract geomorphic parameters in this area, including topographic slope, topographic relief,channel steepness index, and knickpoints. We analyzed 36 basins on both sides of the Zhongba rift. The results show that the topographic slope is consistent with k_(sn). On the west side of the Zhongba rift, tributaries located on the north and middle sections have steeper slopes and higher k_(sn);tributaries in the south have steeper middle section with higher k_(sn)value. On the east side, the slope and k_(sn)are steep at the middle part and gentle at both ends. The river profiles display that the channel steepness are different on both sides of the knickpoints. The rivers of the east and west sides have the highest channel steepness near the outlets, and decrease towards the upstream. Generally, the river channels on the west sides are steeper than ones on the east side. Based on the analysis results of the topographical slope, river profiles, and knickpoints, we suspect that the tectonic activity of the faults on the west side of the Zhongba rift may be stronger than that on the east side.