Three-Rivers basin, which spansthe deeply incised southeastTibetan Plateau and North Tibetan Plateau with a low relief surface, is characterized by highly varied topography and climate, strong neotectonic movement and frequent seismicity, leading to fragile geological conditions, frequent occurrence of geohazards, and resulting remarkable hazard chains. This severely threatens the safety of local residents and engineering construction, and normal operation of infrastructures. Based on landslide hazards interpreted from GoogleEarth, the characteristics of landslide hazards in Three-Rivers basin are analyzed. The GoogleEarth images were adopted to map the types and spatial distribution of landslide hazards. The results were verified with limited field reconnaissance. The SRTM digital elevation model (DEM) data with a resolution of 90 m were used to analyze the terrain parameters, including elevation, slope angle, slope aspect, and relief. The lithological groups were compiled from 1:500000-scale geological maps based on detailed lithological description. The grid layer of distance to major faults was buffered from the main faults of 1:500000-scale geological maps, compiled with the major faults obtained from 1:1500000-scale tectonic map of Tibetan Plateau and neighboring region. The tectonic units were extracted from 1:1500000-scale tectonic map of Tibetan Plateau and neighboring region. All vector layers were rasterized, and together with the raster layers, reclassified, and then overlaid with the spatial distribution of landslide hazards. Percentage of landslide area (PLA) was used to create histograms and statistically analyze significance of the factors influencing the occurrence of landslide hazards, based on geographic information system (GIS) method. A total of 60315 landslides with an area of not less than 0.001km2 for single landslide, including slides, rockfalls and deforming bodies, were mapped in the Three-River basins with an area of about 462000 km2. Landslide hazards are mostly slides in type, accounting for 97.73% of the total, and characterized by banded densely distribution along the deeply incised valleys with local differentiation, and densely distribution along some major faults, e.g. Batang fault, Weixi-Qiaohou fault, and Lawa-Wangdalong segment of Suwalong-Xiongsong fault. For terrain parameters, landslide hazards occur mostly on the slopes with angle ranging from 20 to 30°, elevation varying from 800m to 4000m, and local relief exceeding 1000 m. Of 18 lithological groups, the following 5 groups, clastic rock and slate intercalated with limestone, mudstone and shale and siltstone, ophioliticmélange, phyllite and slate, volcanic rocks, are mostly prone to slope failure. Of 25 tectonic units, the following 7 units, including Jinsha River ophioliticmélange, Zhongzalimestoneterrane, Yanyuan-Lijiang Continental margin rift basin, Naqu-Luonongforearc basin, north Lancang River ophioliticmélange, Baoshan Terrestrial sea basin, and Ganzi-Litangophioliticmélange, are more vulnerable to landslide hazards. Although slope aspect and distance to major faults might have some influence on landslide hazards, the role is not significant. Landslide hazards were densely distributed in Three-Rivers basin of southeast Tibetan Plateau. The terrain and geological parameters significantly influencing the occurrence of landslide hazards consist of slope angle, elevation, relief, lithological group, and tectonic unit. Both slope aspect and distance to major faults have little impact on landslide hazards.
