The Wenchuan earthquake was measured 8.0 Ms (surface wave magnitude scale). It occurred on May 12, 2008, in the Sichuan province of China. It is the most damaging and influential of all earthquakes that have occurred in China since 1949. Tremors were also felt in Vietnam, Thailand, Mongolia, Bangladesh, Nepal, India, Pakistan, and Russia. Ten counties that were worst hit were Wenchuan, Beichuan, Dujiangyan, Pengzhou, Shifang, Mao, An Xian, Pingwu, Qingchuan, and Mianzhu.19 A sketch of this epicenter and region is showed in Fig. 1. Mean altitude is 2034 m and landform is complex, with many hills in this region. According to the vegetation classification, there are about 18 kinds of plants.20 SI varied from SI7 to SI11, with the higher values occurring mainly in the east and south of this region. About 9.8%, 11.23%, and 23.38% of this region experienced SI11, SI10, and SI9, respectively.