LANDSLIDE HAZARDS TRIGGERED BY THE 2008 WENCHUAN EARTHQUAKE, SICHUAN, CHINA YUEPING YIN. FAWU WANG....

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 ！