基于ALOS-PALSAR DEM的山体阴影图识别断裂线性——以西秦岭地区为例

IDENTIFYING FAULT LINEAMENT BASED ON ALOS-PALSAR DEM:A CASE STUDY FROM THE WEST QINLING MOUNTAINS

在传统的断裂解译工作中,人们更重视高分辨率的光学影像和DEM,而对中分辨率DEM的重视程度较低。文中基于分辨率为12.5m的ALOS-PALSAR DEM和断裂线性解译标志,对断裂几何学研究薄弱的西秦岭“V”形断裂系进行了目视解译。所得结果包括:1)新发现了多条断裂线性带,例如位于礼县-罗家堡断裂和两当-江洛断裂之间的以NE向为主的断裂线性带;2)完善了已知活动断裂的几何展布图像;3)西秦岭的断裂线性呈“V”形,NW、NE 2组断裂的构造转换方式主要包括相互截切和弧形过渡。研究结果表明,ALOS-PALSAR DEM具有突出的断裂线性显示能力,是高分辨率光学遥感图像的有效补充。研究结果对于完善西秦岭“V”形断裂系的几何图像具有重要意义,也是进一步深入开展断裂几何学、运动学研究的基础。

The most significant feature of active faults on remote sensing images is fault lineament.How to identify and extract fault lineament is an important content of active fault research.The rapid development of remote sensing technology has provided people with extremely rich remote sensing data,and has also created the problem of how to choose suitable data for fault interpretation.In the traditional fault interpretation,people pay more attention to high-resolution optical images and high-resolution DEM,but optical remote sensing images are greatly affected by factors such as weather condition,vegetation and human impacts,and the time and economic costs for obtaining high-resolution DEM are relatively high.Due to the low resolution,the medium-resolution DEM(such as Aster GDEM,SRTM1,SRTM3,etc.)is generally used to automatically extract structural lineament,and then analyze the overall regional structural features,but it is rarely used to visually interpret active faults.ALOS-PALSAR DEM is generated from SAR images acquired by the phased array L-band synthetic aperture radar mission sensor of the Japanese ALOS satellite.It is currently a free DEM with the highest resolution(resolution of 12.5m)and the widest coverage.Based on ALOS-PALSAR DEM and ArcGIS 10.4 software,this paper generates a hillshade map and visually interprets the fault lineaments in the West Qinling Mountains.When generating a hillshade map,we set the light azimuths to be oblique or orthogonal to the overall trend of the linear structures,the light azimuths to be consistent with the slope direction of the hillslope,and the light dips to be a medium incident angle.Based on the hillshade map generated from ALOS-PALSAR DEM,this paper summarizes the typical performance and interpretation markers of fault lineaments on the hillshade map(generated by DEM),and visually interprets the V-shaped fault system in West Qinling Mountains where the research on fault geometry is limited based on the interpretation markers.The results of the research are as follows:First,this study discovers a number of fault lineament zones,including the fault lineament located between the Lintan-Dangchang Fault and the Guanggaishan-Dieshan Fault,the NE-directed fault lineament zone between the Lixian-Luojiapu Fault and the Liangdang-Jiangluo Fault,and the arc-shaped dense fault lineament zones distributed south of the Hanan-Daoqizi Fault and the Wudu-Kangxian Fault;Second,this study completes the geometric distribution images of the known active faults,such as the western and eastern sections of the Lintan-Dangchang Fault,the western and eastern sections of the Liangdang-Jiangluo Fault;Third,fault lineaments in the West Qinling Mountains exhibit a“V”shape,with two groups of fault lineaments trending NW and NE,whose tectonic transformation mainly consists of two kinds:mutual cutting and arc transition.The Lintan-Dangchang Fault cuts the Lixian-Luojiapu Fault,the Lintan-Dangchang Fault and the Guanggaishan-Dieshan Fault are connected with the Liangdang-Jiangluo Fault in arc shape,and the Tazang Fault is connected with the Hanan-Daoqizi Fault in arc shape.The research results show that ALOS-PALSAR DEM has an outstanding capability to display fault lineaments due to its topographic attributes and strong surface penetration.In circumstances when the surface is artificially modified strongly,the spectrum of ground objects is complex and the vegetation is dense,the ALOS-PALSAR DEM can display fault lineament that cannot be displayed on optical remote sensing images,indicating that the medium-resolution DEM is an effective supplement to high-resolution optical remote sensing images in the fault lineament interpretation.The research results are of great significance for improving the geometric image of the V-shaped fault system in the West Qinling Mountains.It is also the basis for further research on fault geometry,kinematics,regional geodynamics and seismic hazard.