LANDSLIDE HAZARDS TRIGGERED BY THE 2008
WENCHUANEARTHQUAKE, 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
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Introduction
Wenchuan earthquake-2008.5.12. the distribution of the landslides; analyze
the properties of landslides and landslide lakes
地工技術,第 116 期 P.102
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Distribution of landslides triggered by the earthquake
Geohazards have frequently occurred in the zone along the Longmenshan active fault system.
landslides
rockfalls
debris flows
unstable slopes
total
Before
3572 600 737 521 5430
After 1701 1844 304 1093 4970
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Table 1 Potential geohazards in the counties that experienced extremely severe effects caused by earthquake
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Fig. 1 Comparative histograms of geohazards in the counties affected by theWenchuan earthquake before and after the earthquake
1169 個 2782 個
617% ↑
123% ↑
152% ↑
Total 237% ↑
480% ↑
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Fig. 2 Map of earthquake-triggered landslides in Beichuan
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3 2
斷層帶
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Beichuan
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http://www.iseis.cuhk.edu.hk/gb/special/sichuan_rs.htm
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Fig. 4 Cross section of the Xinbei Middle School landslide in Beichuan
length 560mwidth 200maverage thickness 20m
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Fig. 6 Cross section of the Tangjiashan landslide
landslide-length 610m , width 800mlandslide dam height 80-120m
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Distribution of landslides triggered by the earthquake
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)
http://www.iseis.cuhk.edu.hk/gb/special/sichuan_rs.htm
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Fig. 5 Distribution of landslide-dammed lakes
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Landslide-dammed lakes and their risk assessment
three factors:(1)Landslide dam height.(2)The capacity of the landslide-dammed
lake. (3)The structure of the dam material.RiskFactor
Extremely high risk
High risk Medium risk
Low risk
Landslide dam height (m)
>100 50–100 25–50 <25
Capacity (×104 m3)
104 103 –104 102 –103 <102
Material of the landslide dam
Mainly debris
Debris with boulders
Boulders with debris
Mainly boulders
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Fig. 7 Three types of sliding surfaces of landslides triggered by the earthquake
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Fig. 8 Stages of formation of stair, or terrace-shaped landslide
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Example-the Chengxi landslide in Beichuan County Town
Fig. 11 Cross section of the Chengxi landslide in Beichuan
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Example-the Chengxi landslide in Beichuan County Town
Oblique aerial view (a) and vertical air photo (b) of the Chengxi landslide in Beichuan
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Example-the Donghekou landslide-debris flow in Qingchuan County
Oblique aerial view of the Donghekou landslide in Qingchuan County
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Example-the Donghekou landslide-debris flow in Qingchuan County
Fig. 14 Cross section of the Donghekou landslide/debris flow, Qingchuan County
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Conclusions
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.
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Conclusions
The landslides can be classified into the following three types, i.e., convex, concave, and terraced, according to the shape of their sliding surface.
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Thanks for your attention !