四川汶川Ms 8 级地震引发的滑坡与地层岩性、坡度的相关性

    Contribution of strata lithology and slope gradient to landslides triggered by Wenchuan Ms 8 earthquake, Sichuan, China

    • 摘要: 震后遥感影像解译与调查结果表明,在大约48678km2的区域内,汶川Ms 8.0级地震诱发了不低于48000处滑坡灾害。基于GIS的空间分析方法,使用滑坡面积百分比(LAR)与滑坡密度(LC)2个参数,对地震滑坡的空间分布与地层岩性、坡度之间的关系进行统计分析。在整个研究区范围内,滑坡面积百分比约为1.4622%,滑坡密度约为0.9862个/km2。结果表明,滑坡多发生在坡度25~50°的区域内,滑坡易发性随着坡度的增加而升高。寒武纪地层中滑坡易发性最大,LAR约10%,LC约6.5个/km2,震旦系、奥陶系和侵入岩次之,这些地层和岩石对地震滑坡的发生均是敏感的。综合分析坡度、地层岩性与滑坡空间分布的关系,结果表明,在以较破碎岩石为主的地层中,滑坡多发生在坡度小于30°的部位;在以较坚硬岩石为主的地层中,滑坡多发生在坡度大于40°的部位。

       

      Abstract: It′s indicated by remote sensing images interpretation and field investigations that within an area of 48678km2, there are more than 48000 landslides geo-hazards triggered by Wenchuan earthquake. The purpose of this study was to detect correlation between landslide occurrences and strata lithology and slope gradient based on Geographic Information System (GIS) by using two parameters: namely landslide-area ration (LAR) and landslide concentration (LC). Within the study area, LAR was defined at 1.4622% and LC was defined at 0.9862 landslides/km2. The result of statistical analyses shows that LAR and LC have a positive correlation with slope gradient and most of the slides occur with slope between 25° and 50°. The Cambrian Formation has the most concentrated landslide activity with highest LAR value of 10%, LC of 6.5 ls/km2, secondly Sinian Formation, Ordovician Formation and intrusive rocks, all of these strata have high susceptibility in terms of earthquake triggered landslide. It is also indicated by comprehensive research of slope, lithology and landslide spatial distribution that in strongly fractured rocks most landslides occur at where the slope angle is less than 30°, in weakly fractured rocks, most landslides occur at where the slope angle is more than 40°.

       

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