Co-Seismic Fault Effects of Landslides Triggered by Wenchuan Ms 8.0 Earthquake, China
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“5.12” Wenchuan Earthquake (Ms = 8.0) triggered tens of thousands of landslides throughout an area of about 100,000 km2. The distribution of landslides is definitely affected by the such factors as geomorphology, topography, lithology and human engineering activities, but the distribution of earthquake-triggered landslides are mainly controlled by the co-seismic fault, for they present zontal distribution along the co-seismic fault. Through the studies of three geo-hazard concentration areas including Dujiangyan to Wenchuan Road, Beichuan to Anxian County area, and Magong to Hongguang area, it is found that Wenchuan Earthquake-triggered landslides has the following co-seismic effects: (1) Wenchuan Earthquake is a thrust fault earthquake, the distribution of landslides show marked “hanging wall and footwall effects”, manifested by that the distribution concentration in the hanging wall of seismic fault is higher than that in the footwall and the former coverage is wider than the latter as well as that the scale of landslides is larger than that in the footwall; (2) the strong development zones of landslides are within the range of 7 km in the hanging wall of co-seismic fault. The ranges of 7–11 km in the hanging wall and 0–5 km in the footwall can be delimited as the middle development zones. A vast majority of large-scale landslides are distributed within the range of 5 km from the fault, and large-scale landslides are unlikely to occur within the range of over 10 km; (3) the transitional and staggered positions of fault are the concentration areas of landslides and large-scale landslides are likely to occur in these positions; (4) the preferred direction of landslide is NW–SE, basically vertical to the spreading direction of Yingxiu-Beichuan Fault. This may be because that Longmenshan Fault Zone has always been affected by the tectonic stress field of NW–SE extrusion area since Cenozoic Time; (5) the earthquake-triggered landslides mainly occur in the zones of seismic intensity IX and higher. The concentration of landslides in the seismic intensity zones XI is the same with that in seismic intensity zones X; the concentration in the seismic intensity zones IX equals to 1/3 of the abovementioned one; the concentration in the seismic intensity zones VIII is only 1/10 of the abovementioned one.
KeywordsWenchuan earthquake Co-seismic landsliding Earthquake fault effect Hanging wall effect Locked segment effect
The authors are grateful for the financial support from 973 National Basic Research Program (2008CB425801) and the State Key Laboratory of Geohazards Prevention and Geoenvironment Protection (SKLGP).
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