Characteristics of Secondary Mountain Disaster Chain in Wenchuan Earthquake

Abstract

Tens of thousands of secondary mountain disasters such as landslides, debris flows were triggered after the Ms 8.0 Wenchuan earthquake on May 12, 2008. Large amounts of loose material were produced in gullies or on slopes, which will endanger resettled residents and destroy urban reconstruction. During the 5 years following the Wenchuan earthquake event, heavy rainfalls have already induced a great number of debris flows, barrier lakes and collapses in the earthquake-damaged area, resulting in serious casualties and property losses. The emergence and development of these disasters affect each other and are linked closely. Hence, it is important to understand the characteristics and shape of the disaster chains. In order to analyze the characteristics of secondary mountain disaster chain in Wenchuan earthquake, this paper carried out research using field survey and data statistical analysis. A large number of recording materials were reviewed and compiled to analyze more than 2440 debris flows, landslides, collapses and barrier lakes in different areas of Wenchuan, Beichuan, Dujiangyan and so on. The results showed that: the Wenchuan earthquake secondary mountain hazards are mainly distributed in Beichuan, Wenchuan, Dujiangyan and other regions near earthquake source, frequency decreases with the distance increasing source distance. The secondary disaster chain can be divided into 4 grades and 9 types, and a comprehensive type; each disaster chain consists of two or more disasters in earthquake. Precipitation and surface run off have great influence on secondary mountain disasters, and become important media for the formation of chain chains in secondary disasters. This study has some guidance to the judgment and prevention of the secondary disaster chain after earthquake.