Source characteristics of long runout rock avalanches triggered by the 2008 Wenchuan earthquake,China |
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Authors: | Shengwen Qi Qiang Xu Bing Zhang Yuande Zhou Hengxing Lan Lihui Li |
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Institution: | 1. CERI, Centre for Research on Prevention, Prediction and Control of Geological Risks, Sapienza Università di Roma, Piazza U. Pilozzi 9,00038, Valmontone (RM), Italy;2. Dept. of Earth Sciences, Sapienza Università di Roma. P.le Aldo Moro 5, 00185 Roma, Italy;3. ENEA, Centro Ricerche Casaccia, Unità Tecnica Antartide, Via Anguillarese, 301,00123 Santa Maria di Galeria (RM), Italy;1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;2. Key Laboratory of Neotectonic Movement and Geohazard, MLR, Beijing 100081, China;3. Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, USA;4. China Railway Eryuan Engineering Group Ltd., Chengdu 610031, China |
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Abstract: | The May 12, 2008 Wenchuan, China Earthquake which measured Mw = 8.3 according to Chinese Earthquake Administration – CEA (Mw = 7.9 according to the USGS) directly triggered many landslides, which caused about 20,000 deaths, a quarter of the total. Rock avalanches were among the most destructive landslides triggered by this seismic event, and have killed more people than any other type of landslide in this earthquake. The Donghekou rock avalanche, one example of a catastrophic avalanche triggered by the Wenchuan earthquake, occurred in Qingchuan and buried one primary school and 184 houses, resulting in more than 780 deaths, and in addition, caused the formation of two landslide dams, which formed barrier lakes.Combining aerial images (resolution of 0.5 m) with field investigations, this paper lists some parameters of 66 cases in one table, and details source characteristics of six typical cases. It has been found that most of the long runout rock avalanches have source areas with high relief and steep inclination, causing the debris in the travel courses to accelerate. There was also a large amount of saturated Holocene-age loose deposits formed by a river or gully that existed in the travel courses. Comparison studies indicate that saturated Holocene loose deposits in the travel courses could be the most important factor for the causes of the long runout characteristic of the rock avalanches especially when they traveled over gentle or even flat ground surfaces.Furthermore, the relationships among the relief slope gradient, runout and covered area are investigated, and a threshold line for predicting the maximum horizontal runout distance under certain change in elevation is presented. |
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