基于GIS的汶川地震滑坡灾害影响因子确定性系数分析

 2008年5月12日14时28分，四川省汶川发生了8.0级大地震，地震诱发了数以万计的滑坡灾害。在大约48 678 km2的区域内，采用震后航空像片与多源卫星影像解译并结合野外调查验证的方法，共圈定出48 007个地震滑坡灾害。在此基础上，选取地层、岩性、断裂、地震烈度、宏观震中、地表破裂调查点、地形坡度、坡向、顺坡向曲率、高程、水系与公路共12个影响因子作为汶川地震诱发滑坡影响因子，利用GIS强大的空间分析能力与确定性系数方法，对这12个影响因子进行敏感性研究。研究结果表明：(1) 寒武与震旦系是地震滑坡易发地层，侵入岩组、灰岩为主的岩组是地震滑坡发育的高敏感性岩组；(2) 地震滑坡受中央断裂影响最大，同时还受控于前山断裂，受后山断裂的影响较小；(3) 地震滑坡易发性分别随着地震烈度、与震中的距离、与地表破裂点距离的增加而减少；(4) 坡度大于40°是地震滑坡的易发坡度，E，ES方向为地震滑坡的易发坡向，高程范围为1 000～2 000 m，尤其是高程1 000～1 500 m范围为地震滑坡易发区；(5) 400 m水系缓冲区和2 000 m公路缓冲区范围内滑坡易发性较高。确定研究区内各地震滑坡影响因子最利于滑坡发生的数值区间，为进一步地震滑坡区域评价及预测奠定基础。

GIS BASED CERTAINTY FACTOR ANALYSIS OF LANDSLIDE TRIGGERING FACTORS IN WENCHUAN EARTHQUAKE

On May 12，2008 at 14：28(local time)，a catastrophic earthquake with surface wave magnitude of 8.0 struck the Sichuan Province of China. Tens of thousands of landslides were triggered by this earthquake over a broad area. 48 007 landslides were interpreted from aerial photographs and multi-source remote sensing imageries，and they are verified by field investigation. Based on the interpretation results，landslide triggering factors with certainty analysis is carried out by means of GIS spatial analysis. The 12 impact factors contributing to the Wenchuan earthquake-induced landslide occurrences include stratigraphic，lithology，main faults，seismic intensity，macroscopic epicenter，surface rupture points，slope gradient，aspect，profile curvature，elevation，drainages，and roads. The certainty factor analysis result shows that five categories of high landslide susceptibility value are as follows：(1) stratigraphic of Cambrian，Ordovician，Permian and Carboniferous，lithology of intrusive rock group and limestone rock group；(2) Wenchuan earthquake-induced landslides are most affected by the main central fault，and also controlled by the Qianshan fault，the little impact for Houshan fault；(3) there are correlations between landslide susceptibility and seismic intensity，distance from the epicenter and surface rupture zone；(4) slope gradient of more than 40°，aspects of east and southeast directions，elevations between 1 000 m and 2 000 m，especial between 1 000 m and 1 500 m were susceptible for landslide occurrence；and (5) distance to drainages is less than 400 m and less than 2 000 m away from roads. The results show that the numerical intervals of each factor are inclined to landslides. This work is the basement for further study of earthquake- induced landslides hazard evaluation and prediction.