Abstract:

In the 21st century, the global seismicity is in a relatively active period, which has occurred in several large destructive earthquake. Most destructive earthquakes are associated with the occurrence of secondary disasters. On April 20, 2013 an earthquake of magnitude 70 occurred in Lushan county in Sichuan province (103°E, 30°18′N) . The focal depth was 13 km. The Epicenter was about 100 kilometers away from Chengdu. Large energy was released by the earthquake. Local people suffered great harm and important buildings and facilities were severely damaged. We selected Lushan earthquakestricken area including 21 counties (cities, districts) as the study area. We applied field survey and the high resolution remote sensing visual interpretation as the method. Combining the relevant statistical data of local land, water conservancy, construction and other departments, a systematic analysis on the main characteristics of secondary mountain hazards in Lushan earthquakestricken area was performed in this study. There were 782 secondary mountain hazards which had been record their detailed information. With the support of GIS technology, we made further investigation about environmental background, distribution and cause of secondary mountain hazards in Lushan earthquakestricken area, and finally the results showed that the secondary mountain hazards were mainly distributed in the areas with seismic intensity of ⅧⅨ, low mountain elevation, slope gradient of 0°-40°, slope aspect of east and west, tertiary period mudstone gravel, intense river erosion activity and annual rainfall ＞1 200 mm. The formation of secondary mountain hazards are mainly associated with landform, geological structure, climate, hydrology and human activities. Topography on the formation of secondary mountain hazards demonstrates the impact of nonseismic conditions of the new features. Reconstruction of the surface morphology under seismic effect and development provide a lot of loose solid materials for secondary mountain hazards. Precipitation and surface runoff changes affecting slope stability provide power for the secondary mountain hazards. Excessive human socioeconomic activity accelerates the formation of secondary mountain hazards. According to the “4.20” Lushan earthquake, this paper carried out the analysis and research of  the distribution characteristics and causes  of secondary mountain hazards in Lushan Earthquakestricken Area, and this research provided reference and guidance for restoration and reconstruction, settlement relocation and readjustment of population distribution