LANDSLIDE HAZARDS TRIGGERED BY THE 2008 WENCHUAN EARTHQUAKE, SICHUAN, CHINA YUEPING YIN. FAWU WANG. PING SUN LANDSLIDES (2009) 6:139–151 指導老師 : 董家鈞 老師 學生 : 李玟璇 報告日期 :2011/01/06

Introduction 2  Wenchuan earthquake  the distribution of the landslides; analyze the properties of landslides and landslide lakes 地工技術，第 116 期 P.102

Distribution of landslides triggered by the earthquake 3  Geohazards have frequently occurred in the zone along the Longmenshan active fault system. landslidesrockfallsdebris flows unstable slopes total Before After

Table 1 Potential geohazards in the counties that experienced extremely severe effects caused by earthquake 4

Fig. 1 Comparative histograms of geohazards in the counties affected by the Wenchuan earthquake before and after the earthquake 個 2782 個 617% ↑ 123% ↑ 152% ↑ Total 237% ↑ 480% ↑

Fig. 2 Map of earthquake-triggered landslides in Beichuan 斷層帶

Beichuan

Fig. 4 Cross section of the Xinbei Middle School landslide in Beichuan 8 length 560m width 200m average thickness 20m

Fig. 6 Cross section of the Tangjiashan landslide 9 landslide-length 610m ， width 800m landslide dam height m

Distribution of landslides triggered by the earthquake 10  Besides these large volume landslides and rockfalls, many small-scale landslides and rockfalls occurred along the road and caused severe damage.(ex. national highway from Chengdu City to Jiuzhaigou Resort)

Fig. 5 Distribution of landslide-dammed lakes 11

Landslide-dammed lakes and their risk assessment 12  three factors: (1)Landslide dam height. (2)The capacity of the landslide-dammed lake. (3)The structure of the dam material. Risk Factor Extremely high risk High riskMedium riskLow risk Landslide dam height (m) >10050–10025–50<25 Capacity (×10 4 m 3 ) – –10 3 <10 2 Material of the landslide dam Mainly debrisDebris with boulders Boulders with debris Mainly boulders

Fig. 7 Three types of sliding surfaces of landslides triggered by the earthquake 13

Fig. 8 Stages of formation of stair, or terrace-shaped landslide 14

Example-the Chengxi landslide in Beichuan County Town 15 Fig. 11 Cross section of the Chengxi landslide in Beichuan

Example-the Chengxi landslide in Beichuan County Town 16 Oblique aerial view (a) and vertical air photo (b) of the Chengxi landslide in Beichuan

Example-the Donghekou landslide- debris flow in Qingchuan County 17 Oblique aerial view of the Donghekou landslide in Qingchuan County

Example-the Donghekou landslide- debris flow in Qingchuan County 18 Fig. 14 Cross section of the Donghekou landslide/debris flow, Qingchuan County

Conclusions 19  There are more than 10,000 potential geohazard sites induced by the Wenchuan earthquake, mainly by rockfalls, which reflect the effects of the earthquake on high, steep slopes in mountain areas, including topographic amplification effects on mountain summits and ridges.

Conclusions 20  The landslides can be classified into the following three types, i.e., convex, concave, and terraced, according to the shape of their sliding surface.

21 Thanks for your attention ！