区域地震滑坡体积计算模型研究及应用——以2008年汶川地震滑坡为例

It is indicated that more than 197,000 landslides triggered by the May 12, 2008 Wenchuan earthquake (Ms 8.0) in China base on our latest research result. There is important scientific significance and practical value to build a new regional seismic landslide volume calculation model and calculate regional landslides deposit volume distribution related with the earthquake. First of all, a detailed inventory of landslides triggered by the earthquake and the landslide property database, containing three dimensional geometric factors and controlling parameters of all landslides, were established using remote sensing and Geographical Information Systems (GIS) technologies combined with selected field measurements. The second, hundreds of landslide, selected as samples for subsequent landslide volume model training, were obtained according to the topographic differences before and after landslide occurrence. And then, landslide volume calculation mathematical model was constructed based on the relationship between landslide volume and three-dimensional geometric factors and controlling parameters, and constants of the model were calculated using the above landslide volume samples and statistical method. The method can be applied in similar study of other regional seismic landslide events. Finally, the model was used in all landslides triggered by the earthquake for landslides volume calculation, and landslide accumulation volume contours were constructed eventually. The result is of great significance on rivers and geomorphic evolution, seismic geomorphologic changes and earthquake hazard analyses relate with seismogenic faults in different geometric characteristics and movement habits.

最新的汶川地震滑坡解译与调查结果表明，2008年汶川地震触发了超过197,000处滑坡。构建一种全新的区域地震滑坡体积计算模型与求取滑坡体积分布具有重要的科学意义与实用价值。本项目在进行详细完善的汶川地震滑坡编录的基础上，结合测量、GIS与遥感技术，获取滑坡的三维几何参数与环境控制变量，建立滑坡属性数据库；选取一定数量的滑坡样本，根据滑坡发生前后地形差别计算其体积，进行滑坡体积数学模型的训练；根据滑坡体积与滑坡三维几何参数、环境控制变量之间的关系，构建一种滑坡体积计算数学模型，对其它区域地震滑坡事件具有指导意义；应用滑坡样本与统计分析方法确定滑坡体积模型的参数；将这一模型应用于汶川地震滑坡数据库，从而得到每个滑坡的体积，进而构建整个震区堆积物体积分布等值线图，为开展后续汶川地震区河流与地貌演化、不同几何特征与运动习性断裂控制下的地表破坏特征与范围、地貌改变量研究等奠定基础。

求取滑坡体积当前是一个难题，由于其是一个三维分量，并且部分滑面往往在地下。本研究提出了3个区域地震滑坡体积优化模型来计算2008年汶川地震触发滑坡的体积。我们基于GIS与遥感技术构建了汶川地震滑坡的三类编目图，分别为单体滑坡面分布数据，滑坡中心点位置，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110000 km2的区域内，滑坡总面积约为1160 km2。选择一个面积约为44031 km2的区域作为研究区，区内滑坡数量为196007个，滑坡面积为1150.622 km2，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。基于汶川地震前后SPOT 5影像提取到的DEM数据，结合少数滑坡的剖面图，获得了1415处汶川地震滑坡堆积区体积，作为地震滑坡体积模型训练样本。在常规区域滑坡“体积—面积”模型基础上，提出3个优化模型。分别利用数据对数化线性拟合与直接非线性拟合方法对那1个常规模型与3个优化模型进行拟合。结果表明了采用接非线性拟合方法并考虑了滑坡长、宽、高、岩性、坡度、PGA、坡向的优化模型标准误差最小，回归得到的滑坡总体积与滑坡样本总体积也非常接近。将这一模型应用于所有汶川地震滑坡，分别得到每个滑坡的体积。最终结果表明汶川地震滑坡相对密集分布区内的196007处滑坡的堆积物体积约1.2 × 1010m3，源区体积约为1 × 1010m3。根据前人“地震震级—滑坡总体积”经验公式得到的结果仅仅是本文结果的7.5~9%，这提醒我们有必要基于更多的单次地震触发滑坡总体体积数据对“地震震级—滑坡总体积”的关系进行更新。同时，文中的优化模型对同类研究也有显著的参考价值。