Distribution Regularity and Disaster Mode of Secondary Mountain Hazards Induced by the Ludian Earthquake in Longquan River Basin

Taking Longtoushan-Tianshengqiao of Longquan river basin in Ludian as study area, using image interpretation and field investigation data, this paper discusses the distribution regularity and disaster mode of secondary mountain hazards reduced by Ludian earthquake. The results show that:(1) The secondary mountain hazards are mainly caused by the secondary faults at the Longquan river right bank and the extension of Baogunao-Xiaohe fault(Xiashuigou strike-slip faults).The distance between Longquan river and the faults is smaller than two kilometers, which result in the 4.125/km maximum density of mountain hazards; (2) The mountain hazards mainly took place on the bulge slope, account for 46.3%, and furthermore, the hazards are more likely to take place on slopes of the back of faults; (3) 60% of the collapses and landslides develop in the surface residual layer, and 40% of rocky landslide collapses are hard limestone, dolomite and breccias; (4) The secondary mountain hazards mode are as follows:damaging roads, interrupting traffic, forming barrier lakes which inundate upstream bed, damaging downstream bed and facility and buildings along the river.