许冲, 徐锡伟, 吴熙彦, 戴福初, 姚鑫, 姚琪. 2013: 2008年汶川地震滑坡详细编目及其空间分布规律分析. 工程地质学报, 21(1): 25-44.
    引用本文: 许冲, 徐锡伟, 吴熙彦, 戴福初, 姚鑫, 姚琪. 2013: 2008年汶川地震滑坡详细编目及其空间分布规律分析. 工程地质学报, 21(1): 25-44.
    XU Chong, XU Xiwei, WU Xiyan, DAI Fuchu, YAO Xin, YAO Qi. 2013: DETAILED CATALOG OF LANDSLIDES TRIGGERED BY THE 2008 WENCHUAN EARTHQUAKE AND STATISTICAL ANALYSES OF THEIR SPATIAL DISTRIBUTION. JOURNAL OF ENGINEERING GEOLOGY, 21(1): 25-44.
    Citation: XU Chong, XU Xiwei, WU Xiyan, DAI Fuchu, YAO Xin, YAO Qi. 2013: DETAILED CATALOG OF LANDSLIDES TRIGGERED BY THE 2008 WENCHUAN EARTHQUAKE AND STATISTICAL ANALYSES OF THEIR SPATIAL DISTRIBUTION. JOURNAL OF ENGINEERING GEOLOGY, 21(1): 25-44.

    2008年汶川地震滑坡详细编目及其空间分布规律分析

    DETAILED CATALOG OF LANDSLIDES TRIGGERED BY THE 2008 WENCHUAN EARTHQUAKE AND STATISTICAL ANALYSES OF THEIR SPATIAL DISTRIBUTION

    • 摘要: 最新研究成果表明, 2008年5月12日汶川MS 8.0级地震触发了超过197000处滑坡。首先,基于GIS与遥感技术构建了汶川地震滑坡的3类编目图,分别为单体滑坡面分布数据、滑坡中心点位置和滑坡后壁点位置。构建方法为基于地震前后高分辨率遥感影像的目视解译方法,区分单体滑坡并圈定其边界,对滑坡后壁进行识别与定点,并开展了部分滑坡的野外验证工作。这些滑坡分布在一个面积大约为110000km2的区域内,滑坡总面积约为1160km2。选择一个面积约为44031km2的区域作为研究区,区内滑坡数量为196007个,滑坡面积为1150.622km2,这是最详细完整的汶川地震滑坡编录成果,也是单次地震事件触发滑坡最多的记录。其次,开展研究区内的地震滑坡空间分布规律的研究。基于滑坡面与滑坡中心点分别构建滑坡空间分布面积密度图与点密度图,结果表明:滑坡多沿着映秀北川断裂分布,多发生在断裂的上盘。滑坡的高密度区位于映秀北川同震地表破裂的南西段(映秀镇与北川县之间)的上盘区域,这一区域恰对应着逆冲分量为主的断裂上盘,表明逆冲断裂对上盘区域发生滑坡的极强烈的控制作用,而该区域正是形变最大的区域,因此说明是地震滑坡发生的强烈控制作用。基于滑坡面密度(LAP)、滑坡中心点密度(LCND)与滑坡后壁点密度(LTND)这3个衡量指标,使用统计分析方法,评价了汶川地震滑坡与地震参数、地质参数、地形参数的关系。结果表明:LAP、LCND与LTND这3个衡量指标与坡度、地震烈度与PGA存在明显的正相关关系; 与距离震中、距离映秀北川同震地表破裂存在负相关关系; 斜坡曲率越接近0,滑坡越不易发生; LAP、LCND与LTND的高值高程区间为1200~3000m; 滑坡发生的优势坡向为E、SE、S方向; 滑坡发育的易发岩性为砂岩与粉砂岩(Z)、花岗岩; 滑坡与坡位的相关关系不太明显。统计结果还表明LCND与LTND两个衡量指标的差异对地震与地质因子不敏感,而对地形因子较敏感。最后将本文的统计结果与以往的汶川地震滑坡空间分布规律统计成果进行了一些对比,对比结果表明,对于某些因子,如高程、岩性、距离震中、距离映秀北川断裂的统计分析结果,采用不完整的滑坡分布数据或点数据,与采用较完整的滑坡分布面数据会有一定的差异,这种差异并未出现在针对坡度与坡向等因子的统计对比结果中。总之,作者认为一个完备、详细的地震滑坡分布面要素编目图是地震滑坡空间分布规律定量分析、危险性定量分析与滑坡控制的地震区地貌演化研究的重要基础,否则,与实际情况相比,得到统计结果会有一定的偏差,本文的研究成果与以往成果的对比结果证明了这一点。

       

      Abstract: The latest research results indicate that the 2008 Wenchuan Earthquake(MS 8.0)triggered more than 197000 landslides. Base on Geographic Information Systems(GIS) and remote sensing technologies, three(nearly) complete landslide catalogs are constructed firstly. The three catalogs are corresponds to respective landslide polygons, landside centroid points, and landslide top points respectively. These catalogs indicate that there were 197481 landslides triggered by the Wenchuan earthquake throughout an area of about 110000km2.These landslides are delineated as respective individual solid polygons, landslide central dots, and landslide top dots using visual interpretation of high resolution aerial photographs and satellite images taken pre-and post-earthquake, verified by selected field checking. These landslides cover a total area of about 1160km2.An area covers about 44031km2 is selected as study area. There are 196007 landslides. They have a total area of 1150.6km2 occurred in the study area. This landslide catalog is the most detailed and complete landslide inventory related with the 2008 Wenchuan earthquake. It is also the largest landslide inventory record related to a single earthquake event. Subsequently, spatial distribution statistical analysis of landslides triggered by the 2008 Wenchuan earthquake are carried out in the study area. Base on the inventories of landslide polygons and landslide centroid points, two density maps, named landslide area density map and landslide point density map were constructed, respectively. Both the two landslide density maps show that landslide activities primarily concentrate along the Yingxiu-Beichuan co-seismic surface fault-rupture, and most of the landslides occurred on the hanging wall. The highest landslide density areas appear in the northwest direction areas, on the hanging wall, of a section of the Yingxiu-Beichuan fault(from the Yingxiu Town to the Beichuan County).Those high intensive landslide areas correspond to high deformation areas during the earthquake. So, it can be concluded that the earthquake triggered landslides is very strongly affected by co-seismic deformation. Furthermore, correlations of landslide occurrence with seismic parameters, geologic and topographic conditions are analyzed using the three landslide catalogs. Statistical analysis of these landslides spatial distribution using (a) landslide area percentage(LAP),defined as the percentage of the area affected by the landslides,(b) landslide centroid number density(LCND),defined as the number of landslide centroid per square kilometer, and (c) landslide top number density(LTND),defined as the number of landslide top point per square kilometer, is carried out to determine how the occurrence of landslides correlates with elevation, slope angle, slope aspect, slope position, slope curvature, lithology, distance from epicenter, seismic intensity, distance from the Yingxiu-Beichuan surface fault-rupture, peak ground acceleration(PGA).It is observed that the LAP,LCND, and LTND values have positive correlations with slope angle, PGA, and seismic intensity, and have negative correlations with distance from epicenter, and distance from the Yingxiu-Beichuan surface fault-rupture. More slope curvature close to zero, more difficult to landslide occurrence. The highest values of one LAP and two LND appear at range from 1200m to 3000m in elevation. The landslides have preferred orientations, dominated by the eastern, southeastern, and southern directions. The sandstone, siltstone(Z) and granitic rocks have more concentrated landslides. No apparent correlations were found between LAP,two LND values and slope position. Statistical results also show that differences between LCND and LTND is very small for earthquake and geologic parameters, rather more difference relate with topographic parameters. Some qualitative comparisons between the results in this paper and others published papers are carried out finally. There would be obvious differences of statistical results related to correlations of landsides and elevation, lithology, distance from the epicenter, distance from the Yingxiu-Beichuan fault from the present results and in other publications. In addition to those parameters, the statistical result from other factors including slope angle and slope aspect show similar tendency. So, it can be concluded that a complete, detailed and accurate landslide catalog is an essential part for seismic landslide hazard analyses and spatial distribution statistical analyses. Otherwise, parts of results obtained from analyzing uncompleted landslide distribution data would be controversial. It is rather necessary and important to construct complete landslide catalogs for seismic landslide spatial distribution statistical quantitative analyses, hazard assessment, and landscape evolution controlled by earthquake triggered landslides in earthquake struck area, et al.

       

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