Active faults and seismologic characteristics along the Dali-Ruili railway in western Yunnan Province

The new results obtained in active fault survey show that active structure mainly consists of the Zhongdian-Dali-Ruili arcuate fault zone and active western Yunnan block around the Dali-Ruili railway in western Yunnan Province. In the active deformation area, there are ten active faults which prominently influence the crustal stability and earthquake hazard around the area along the Dali-Ruili railway. These active faults are the east piedmont fault of the Diancang Mountain, the Yunlong-Yongping fault zone, the Baoshan fault zone, the Pupiao-Shidian fault, the Taiping-Luomingba fault, the Zhen′an fault zone, the Longxin conjugated fault system, the Huanglianhe conjugated fault system, the Longchuan River fault and the Wanding fault zone from northeast to southwest. Geological and geomorphic evidence for active faulting shows that the activity of the east piedmont fault of the Diancang Mountain, the Baoshan fault zone, the Pupiao-Shidian fault, and the Wanding fault zone were evidently more stronger than other active faults during late Quaternary. Based on the historic and instrumental earthquake data and study results of active faults, the authors drew a new seismic intensity map for the area of the Dali-Ruili railway. The new earthquake intensity map shows that there are at least five high seismic intensity (intensity ≥ Ⅸ) areas along the Dali-Ruili railway. These areas include Dali-Midu, Baoshan, Pupiao-Shidian, Zhen′an-Jingzhuping and Wanding-Ruili from northeast to southwest.