基于格网的汶川地震场地灾害监测分析

Analysis of Field Damage Distribution in Wenchuan Earthquake Based on Fishnet Technology

本文利用格网技术(Fishnet),对龙门山地区"5.12"大地震震后的多期次遥感影像数据及基础地理信息数据进行评价、整合并实现了动态管理,在此基础上得到覆盖整个龙门山构造带的、能够反映不同地物信息的影像群。汶川地震造成了大量山体崩塌、滑坡、泥石流等地震场地灾害,这些灾害体表现为成群、成带分布的特征,并且单一的小灾害体分布面积较小,但总体规模较大,难以从影像上准确无误提取所有单一的灾害体等特点。鉴于上述原因,本文提出以灾害体分布密度,将地震场地灾害分成6个密度等级,并结合格网(Fishnet),通过不同时相、不同数据源的影像之间的对比分析,解决了高起伏度地区影像中阴影区的场地灾害的提取等问题,完成了汶川地震场地灾害监测分析及野外验证,最终得到汶川地震场地灾害分布面积为972.081km2。汶川地震场地灾害的分布平行和垂直于龙门山断裂带均表现出明显的分段和分带特征。平行于龙门山断裂带,地震场地灾害的分布表现出明显的分段特征:西南部灾害体呈连片集中分布,影响范围较宽;中部表现为细脖子化,影响范围较窄;到东北部灾害体表现为以小规模的灾害体散点状分布,但是影响的区域较广。垂直龙门山断裂带方向,地震场地灾害的分布表现为分带特征:汶川地震场地灾害约80%分布在中山带;后山带,地震场地灾害主要沿着汶川-茂汶断裂及部分河流两侧分布于汶川境内;而在前山带,地震场地灾害一部分在绵竹市和安县境内的北部呈现密集分布,另一部分在江油市辖区内多呈散点状分布。

Based on Fishnet technique,by implementing data estimate,data integration and dynamic management to remote sensing images after Wenchuan Earthquake and to basic geographical information for Longmen Shan region,we got a cluster of remote sensing images which can cover the whole Longmen Shan region.Because the distribution of field damages mainly shows in group and in strap,so,slight field damages,although can not be interpreted accurately from a remote sensing image,their summation occupies a considerable area.Therefore,we divided the damages into six density classes on remote sensing images.With Fishnet technique,we resolved some troublesome problems about pick-up of filed damages from remote sensing images,by means of contrasting and analyzing among the number of different time and different data sources remote sensing images.These troublesome problems mainly were pick-up of filed damages in the deep shallows of highly relief mountain region and pick-up the field damages which takes on same characteristics or color in remote sensing image,etc.We finished the remote sensing image interpretability of field damages by artificial visual interpreting comparison and the verified partly results of interpretability in the field.Ultimately,acquired area of field damages is 972.78km2.The distribution of field damages shows apparently the characteristics in subsection parallel to Longmen Shan faults and in zoning perpendicular to Longmen Shan faults.Subsection parallel to Longmen Shan faults： in southwest zone,field damages take on sheet lumped distribution and impact on wider surface area;in the middle zone,distribution of field damages shows bottle-necked shape and range of influence is minor in surface;in the part of east north,field damages take on scattered distribution.Subsection perpendicular to Longmen Shan faults： 80% of field damages distribute in the middle mountain zone,field damages mainly distribute along Wenchuan-Maowen faults and partly river in latter mountain zone.Disasters mainly scatter in two areas,around Mianzhu and Anxian regions and Jiangyou Municipal District in the anterior mountain.