Dynamics of the Niumiangou Creek rock avalanche triggered by 2008 Ms 8.0 Wenchuan earthquake, Sichuan, China |
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Authors: | Ming Zhang Yueping Yin Shuren Wu Yongshuang Zhang Jinliang Han |
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Institution: | (1) Institute of Geomechanics, Chinese Academy of Geological Sciences, 11#, Min Zu Da Xue Nan Lu, Haidian District, Beijing, 100081, People’s Republic of China;(2) China Geological Survey, 45#, Fu Wai Da Jie, Beijing, 100037, People’s Republic of China |
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Abstract: | The Niumiangou Creek rock avalanche was triggered by an Ms 8.0 earthquake that happened on 12 May 2008 in the Sichuan Province, China. The rock avalanche traveled a horizontal distance
of 3.0 km over a vertical elevation difference of 0.89 km, equivalent to a coefficient of friction of only 0.29. The travel
path of the rock avalanche can be divided into three segments: (1) failing and disintegrating, (2) flying, (3) flowing. In
the failing and disintegrating segment, the rock slope failed because of the coupled action of horizontal and vertical force
of the earthquake, then smashed into the opposite mountain and disintegrated. In the flying segment, the disintegrating rock
mass changed direction and flew into the Lianhuaxin Creek, which was different from the previous research results that concluded
rock debris flowed in Lianhuaxin Creek. A great amount of air trapped and compressed under the rock debris acted as air cushion
and supported the rock debris to fly a further distance. In the flowing segment, the rock debris flowed on the ground surface
in Niumiangou Creek. The flowing velocity has been estimated from the maximum elevation and runup according to the damaged
trimlines of the debris. The saturated fine material in Niumiangou Creek entrained by the failed debris mass is thought to
have contributed to the long runout of the debris. The Niumiangou Creek rock avalanche is one of the three longest rock avalanches
triggered by Wenchuan earthquake. The conclusions of the paper have implications for hazard assessment of potential rock avalanches
in the earthquake area and the other similar mountainous area in west China. |
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