Spatial distribution of large-scale landslides induced by the 5.12 Wenchuan Earthquake |
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Authors: | Qiang Xu Shuai Zhang Weile Li |
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Institution: | 1. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, 610059, China
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Abstract: | The 5.12 Wenchuan Earthquake in 2008 induced hundreds of large-scale landslides. This paper systematically analyzes 112 large-scale
landslides (surface area > 50000 m2), which were identified by interpretation of remote sensing imagery and field investigations. The analysis suggests that
the distribution of large-scale landslides is affected by the following four factors: (a) distance effect: 80% of studied
large-scale landslides are located within a distance of 5 km from the seismic faults. The farther the distance to the faults,
the lower the number of large-scale landslides; (b) locked segment effect: the large-scale landslides are mainly located in
five concentration zones closely related with the crossing, staggering and transfer sections between one seismic fault section
and the next one, as well as the end of the NE fault section. The zone with the highest concentration was the Hongbai-Chaping
segment, where a great number of large-scale landslides including the two largest landslides were located. The second highest
concentration of large-scale landslides was observed in the Nanba-Donghekou segment at the end of NE fault, where the Donghekou
landslide and the Woqian landslide occurred; (c) Hanging wall effect: about 70% of the large-scale landslides occurred on
the hanging wall of the seismic faults; and (d) direction effect: in valleys perpendicular to the seismic faults, the density
of large-scale landslides on the slopes facing the seismic wave is obviously higher than that on the slopes dipping in the
same direction as the direction of propagation of the seismic wave. Meanwhile, it is found that the sliding and moving directions
of large-scale landslides are related to the staggering direction of the faults in each section. In Qingchuan County where
the main fault activity was horizontal twisting and staggering, a considerable number of landslides showed the feature of
sliding and moving in NE direction which coincides with the staggering direction of the seismic faults. |
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