基于AHP和GIS的陕西省地震次生地质灾害危险性评价

采用层次分析法，选取了地层岩性、地质构造、地形地貌、河流、植被、降雨量和人类活动7个一级指标，以及工程地质岩组、地震密度、地震动峰值加速度、坡度、坡向、河流、植被覆盖度、年降水量和公路9个二级指标，通过构建层次结构、构造判断矩阵、层次单排序和一致性检验，确定各评价指标权重。并利用GIS空间分析功能，对各个评价因子进行综合评价，得到陕西省地震次生地质灾害危险性等级区划图。最后，对评价结果进行了验证。研究结果表明：1）陕西省地震次生地质灾害危险性等级可以划分为不危险区、低危险区、中危险区和高危险区4个等级，其中不危险区面积39766.99km2，低危险区面积74284.39km2，中危险区面积63636.89km2，高危险区面积27652.87km2，所占比例分别为19.37%，36.18%，30.99% 和13.47%； 2）危险性等级自北而南逐渐增加，陕北黄土高原地震次生地质灾害以中低危险为主，关中渭河平原整体危险性较小，陕南秦巴山地高危区面积最大，高危险区主要分布在陕南秦巴山地和陕北黄土高原地区，尤其是秦巴山地，需要重点防控； 3）危险区空间分布具有相对集中性和局地差异性的特点； 4）所选取灾害点样本的分布与危险性等级区划具有一致性，86.62% 的灾害点落在危险区内，具有一定的可信度，达到了预期的区划效果。

DANGER ASSESSMENT OF EARTHQUAKE-INDUCED GEOLOGICAL DISASTERS IN SHAANXI PROVINCE BASED ON AHP AND GIS

There are marked differences of geological structure between south and north of Shaanxi Province, which is situated in the middle of China. From north to south, the topography of Shaanxi can be divided into three parts: the Loess Plateau, Weihe Plain and Qinba Mountains. Owing to the special geographical location and the complicated tectonic environment, Shaanxi and its surrounding areas frequently suffer from earthquakes, as well as earthquake-induced secondary geological disasters. It is no exaggeration to say that Shaanxi suffers from the most serious secondary geological disasters in China. According to statistics, from 1972 to 2012, more than 641 earthquakes with magnitudes above ML3.0 rocked Shaanxi and its neighborhoods. The collapse, landslide, ground crack, ground subsidence, ground collapse and debris flow are the most common types of geological disasters. In 2008, ten days after the Wenchuan earthquake, 157 disasters were found in Shaanxi Province which caused incalculable loss to the people's lives and property. Hence, it is very urgent and necessary to carry out the risk evaluation of earthquakes-induced secondary geological disasters and delimit the risk areas of earthquakes, which has very important practical significance to territory planning, risk management of geological, disaster reduction and prevention and government decision making. In this paper, 7 first-grade indexes including lithology, geological structure, topography, rivers, vegetation, rainfall and human activity and 9 second-grade indexes including engineering geological petrofabric, density of the earthquake, earthquake acceleration, gradient, aspect, rivers, vegetation fraction, rainfall and roads were chosen, and the weights of which were determined by building a hierarchy, structuring judgment matrix, hierarchical single arrangement and consistency check through using Analytical Hierarchy Process(AHP). The risk grade region division chart of earthquake-induced secondary geological disasters of Shaanxi will be got from the synthetic evaluations to every index by using GIS spatial analysis function and verified by the survey datas of the earthquake-induced secondary geological disasters sites. The results showed that:(1)the risk levels of earthquake-induced secondary geological disaster in Shaanxi Province can be divided into 4 grades: no dangerous region, low dangerous region, moderate dangerous region and high dangerous region, whose area are 39766.99km2, 74284.39km2, 63636.89km2, 27652.87km2, respectively, in the percentage of 19.37%, 36.18%, 30.99% and 13.47%. (2)The risk grade has a increasing trend from north to south, which means Loess Plateau is low and moderate dangerous region, overall risk of Weihe Plain is lesser, and Qinba Mountains was absolute the high-risk area. More attention should be paid to Qinba Mountains because its high dangerous of geological disasters. (3)On the spatial distribution, the dangerous area distribution has the characteristics of relatively centralized and local differences. (4)Verification results show that the spatial distribution of the disaster sites is consistent with risk grade region division of earthquake-induced geological disasters. 86.62% of the disaster sites fell into the risk grade region division chart of earthquake-induced geological disasters, which demonstrated the credibility of this research.