【作者】 戴娅琼；

【导师】 任金卫； 申旭辉； 张景发；

【作者基本信息】 中国地震局地震预测研究所 ， 构造地质学， 2008， 硕士

【摘要】 西藏高原位于我国西南部,平均海拔高度在4500m以上,高原四周为巨大山系所环绕,地势雄伟,屹立于塔里木盆地和印度河—恒河平原之间,形成一个规模巨大的高原,故有“世界屋脊”之称。西藏高原又是地球上最年轻的构造活动区之一,具有独特的地质构造和复杂的地质结构。西藏高原是现代构造强烈活动的地区。在其周缘和内部都存在许多活断层和地震地表破裂。但是,青藏高原周围和内部活动断层的性质、规模,活动幅度、深部构造以及形成演化历史等方面均有明显的差别,有待于我们加深对其的探索和认识。西藏高原与全球气候、生态环境以及人类社会未来发展等一系列重大问题密切相关。对西藏地区的探索并不能完全离开亲临高原,但如果只凭人类的足迹去一点一滴地揭开它的奥秘是不科学的。空间对地观测技术为人类探测青藏高原,发现其资源,认知其机理打开了新的局面,为人类更深刻地认识青藏高原提供了更广阔的途径。合成孔径雷达干涉测量作为一种极具潜力的空间对地观测技术,在近10多年得到迅速发展,也成为国际上的研究热点。其优势在于全天候、全天时工作,不受云雾干扰,并能一次大面积成像。一方面对人类难以到达的区域进行大规模、大面积的地形测量;更重要的是差分干涉测量能得到同震形变图,永久散射体差分干涉测量能监测厘米甚至毫米级的形变,为监测西藏活动断层的变化提供了方法,甚至可以为整个青藏高原的动态变化和研究青藏高原与全球的关系提供线索。本文研究目的主要是为我国西藏地区研究提供技术支持,探索新途径。我国目前有许多地区由于自然条件恶劣,缺少高精度的地形数据。本文一方面对InSAR技术本身不断探索,另一方面探讨将此技术更好地应用到西藏地区研究中。本文主要研究内容包括:(1)利用InSAR生成西藏当雄—羊八井地区数字高程模型利用ERS-1/2 tandem星载SAR数据,在综合分析SRTM和1:50000DEM的前提下,成功获取当雄—羊八井地区的数字高程模型。在基于和1:50000DEM的比较分析,论证了InSAR-DEM具有较高的准确性,证明了InSAR用于西藏地区制图的可行性。(2)分析了InSAR技术测高的影响因素特别是基于所用的生成DEM的SAR数据对,深入分析了短基线在用于生成DEM中的不利因素,抗误差能力差,说明了在选择数据时遵循最优基线原则的重要性,空间基线不仅影响空间相关性而且影响高程对干涉相位差的灵敏度,揭示了地面坡度对干涉相位的影响不可忽视,如果高程变化太快,干涉条纹产生重叠,会导致严重的失相关,从而无法对高程进行准确推算。(3)外部DEM在干涉测量中的应用详细分析了外部DEM在干涉测量中的实质,与在差分干涉测量应用中的异同,并论证了外部DEM在利用干涉测量生成DEM过程中的作用,其主要贡献在于提供参考坐标和降低解缠难度,特别是对于陡坡地段有明显的效果,使地形剖面线走势改善至和真实地形一致。(4)PS-InSAR技术的初步应用研究通过对处理后PS点进行分析,可以发现,盆地南部所有点随时间呈负向运动,北侧呈正向运动,这也意味着盆地南侧仍处于不断的沉降阶段,北部处于隆升阶段。最大年平均沉降速率为6mm/y,上升速率为7mm/y。(5)专题图制作利用ETM+光学影像、InSAR-DEM和大范围的SRTM,制作阴影图、坡度图、坡向图和三维立体图,提取研究区的构造地貌信息。更多还原

【Abstract】 Tibetan Plateau, with an average elevation of over 4500 meters, is located in the southwest of China. The plateau is surrounded by mountains, with Tarim Basin in north and Indo-Gangetic Plain in south, so it is also called the Ridge of the World. Tibeten Plateau is one of the youngest tectonic activitive areas in the world, of particular geological structures. It is also a strong tectonic activitive area, with a lot of active faults and surface ruptures. The different characters, dimensions, active ranges, deep-seated structures, and formational and evolutional histories, are worth our exploration and acqierement.Tibetan Plateau is in very close relationship with the global climate, ecology environment and the future of the human being. It is impossible to explore the Tibetan Plateau without any field measurement. However, it is unscientific to reveal its mysteries foot by foot. The technologies of the earth observation from space provide us more approaches to understand the Tibetan Plateau profoundly, and open a new situation for us to detect its mechanism.Synthetic aperture radar interferometry (InSAR) has been proposed as a potential earth observation technique, and it is an international research hotspot now. It has the advantages of all time and all weather operation, and cost-effective data acquisition for large areas. So it can be utilized for digital elevation model (DEM) generation, topographic mapping in large areas, especially those areas that are inaccessible. Moreover, D-lnSAR can get the co-seismic fields, and PS-lnSAR can detect the surface changes in cm even mm level, and can be adopted to monitor the changes and movements of active faults, to obtain the dynamic changes of the whole Plateau, which provide the information and clue for the relationship of the plateau area and the globe.The main research motive is to support the Tibetan research expedition, to provide new technology and explore new ways. Traditional mapping methods are no longer the most efficient means of obtaining topographical maps or DEM in large areas especially in inaccessible or difficult environments. Therefore, InSAR technology should be studied carefully, and on the other hand, it should be applied to the Tibetan Plateau research more and more perfectly.The main contents of the thesis are:(1) Digital Elevation Model generation of Damxung-Yangbajain, Tibet with InSAR On the premise of comprehensive analysis of SRTM and 1:50000 DEM, the Digital Elevation Model (DEM) of Damxung-Yangbajain, Tibet is obtained successfully with ERS-1/2 tandem data. Based on the comparison of InSAR DEM and the 1:50000 DEM, it is demonstrated that the InSAR DEM is in high accuracy and confirmed that InSAR can be utilized in Tibet topographic mapping.(2) Influential factor analysis of height measurement by InSAREspecially based on the SAR image pairs in the study, the small baseline in InSAR DEM generation is analyzed that it is very sensitive to errors. Therefore, it is very important to follow the optimum baseline principle. Meanwhile, the results reveal that the influence of ground gradient to interferometric phase can’t be neglected. If the height changes quickly, it results in interferogram overlap and severe decorelation, and the height can’t be calculated correctly.(3) Using external DEM in InSAR DEM generationThe essential of using external DEM in InSAR DEM generation, as well as the similarities and differences of using external DEM in differential InSAR is analyzed in detail. Meanwhile, the benefit of external DEM in InSAR DEM generation is demonstrated, which provides the referenced coordinate and makes the phase unwrapping much easier especially for the steep slope, and the profiles that deviate from the ground truth are corrected to be consistent with the truth.(4) Primary applied study of PS-lnSARBased on the analysis of the permanent scatter points, the result can be achieved, that points in the south of the basin subside, while points in the north rise. The maximal sedimentation rate is 6mm per year, while the maximal ascending rate is 7mm per year.(5) Execution of special mapsSlope, aspect, shade and 3D maps are made by ETM+ images, InSAR-DEM and SRTM. Tectonic physiognomy of the study area is identified.更多还原