高分辨率卫星影像提取DEM技术在活动构造定量研究中的应用--以库米什盆地南缘断裂陡坎为例

APPLICATION OF DEM GENERATION TECHNOLOGY FROM HIGH RESOLUTION SATELLITE IMAGE IN QUANTITATIVE ACTIVE TECTONICS STUDY: A CASE STUDY OF FAULT SCARPS IN THE SOUTHERN MARGIN OF KUMISHI BASIN

通过数字化地形图和野外地形测量获取数字高程模型(DEM)的传统方法存在时效性差、获取周期长、范围小等缺点,高分辨率卫星影像提取DEM技术的出现为快速获取断裂带大范围的地形地貌数据提供了全新的解决方案,极大地提高了野外地形地貌数据获取的效率,该方法与激光雷达扫描技术(Li DAR,Light Detection and Ranging)相比成本低,与Sf M(Structure from Motion)摄影测量方法相比覆盖范围大。然而,国内外目前尚缺乏针对用该方法获取的DEM精度是否满足活动构造定量研究要求的报道。文中以LPS(Leica Photogrammetry Suit)为软件平台,以Worldview-2全色波段立体像对为数据源,选择植被覆盖稀疏的东天山库米什盆地南缘最新发现的地表破裂带作为研究区,提取了0. 5m分辨率DEM,基于该DEM数据测量了不同期次洪积扇上的断层陡坎高度,并与后差分GPS(DGPS,differential GPS)野外实测的地形剖面进行了对比分析与精度评价。研究结果表明:由该方法获取的DEM高程与野外DGPS实测高程相差约-2. 82～4. 87m,经高程校正后与DGPS测线的吻合度很高,形态差异为0. 30m,能够精细刻画陡坎形态;对断层陡坎高度的测量精度可以达到0. 22m,能够满足活动构造定量研究中高精度地形地貌数据获取的需要,为快速获取断裂精细几何结构、断层剖面形态以及断层垂直位错带来了极大的便利,为后续野外工作中选择探槽开挖点、典型断错地貌点以及年代样品采集点提供了重要参考,在活动构造研究中具有广阔的应用前景。

Traditional method to generate Digital Elevation Model(DEM)through topographic map and topographic measurement has weak points such as low efficiency,long operating time and small range.The emergence of DEM-generation technology from high resolution satellite image provides a new method for rapid acquisition of large terrain and geomorphic data,which greatly improves the efficiency of data acquisition.This method costs lower compared with LiDAR(Light Detection and Ranging),has large coverage compared with SfM(Structure from Motion).However,there is still lack of report on whether the accuracy of DEM generated from stereo-imagery satisfies the quantitative research of active tectonics.This research is based on LPS(Leica Photogrammetry Suit)software platform,using Worldview￣2 panchromatic stereo-imagery as data source,selecting Kumishi Basin in eastern Tianshan Mountains with little vegetation as study area.We generated 0.5m resolution DEM of 5￣km swath along the newly discovered rupture zone at the south of Kumishi Basin,measured the height of fault scarps on different levels of alluvial fans based on the DEM,then compared with the scarp height measured by differential GPS survey in the field to analyze the accuracy of the extracted DEM.The results show that the elevation difference between the topographic profiles derived from the extracted DEM and surveyed by differential GPS ranges from-2.82 to 4.87m.The shape of the fault scarp can be finely depicted and the deviation is 0.30m after elevation correction.The accuracy of measuring the height of fault scarps can reach 0.22m,which meets the need of high￣precision quantitative research of active tectonics.It provides great convenience for rapidly obtaining fine geometry,profiles morphology,vertical dislocations of fault and important reference for sites selection for trench excavation,slip rate,and samples.This method has broad prospects in the study of active tectonics.