Abstract:The Sanweishan fault extends along the northwest margin of Sanweishan, with a total length of 175 km. On the basis of its geometric characteristics, the fault can be divided into three segments, namely, the western segment (Xishuigou-Shugouzi), the middle segment (Shugouzi-Shigongkouzi), and the eastern segment (Shigongkouzi-Shuangta). The tectonic activity intensity and geomorphological development degree of each segment are obviously different. On the basis of fault scarp measurement and regional chronological comparison, the vertical slip rate of the western segment of the Sanweishan fault is approximately 0.1 mm/a and that of the middle and eastern segments is relatively low. To further quantify the influence of the Sanweishan fault on the topography and geomorphology of the study area, we use the geomorphic factors (i.e., elevation, slope, channel steepness index, and stream gradient index) to quantitatively analyze the geomorphic features of each segment. Results show that the value of the western segment is larger than that of the middle and eastern segments, indicating that the uplift rate of the western segment is higher than that of the two other segments. This finding further indicates that the topography has a good response to tectonic activity. From the comparison between lithology, rainfall, and tectonic activity, we propose that the segmentation of the Sanweishan fault is the main reason for the differential uplift of each segment. Moreover, new activities of the Mingshashan fault accelerated the differential uplift of the west segment of the Sanweishan fault.
