多轨PSInSAR监测华北平原地表垂直形变场

针对PSInSAR技术监测大空间尺度地表垂直形变场的不足,提出通过基准转换与数据拼接、融合不同轨道多个独立片区(Frame)获取大空间尺度地表垂直形变场方法.由于不同轨道主影像选取的参考基准不一致、不同轨道垂直基线不同、不同片区相位解缠的参考PS不同等因素影响,使得PSInSAR获得的不同轨道地表垂直形变场的空间基准存在差异,提取的地表形变信息不具有可比性.利用两个相邻片区重叠区域的PS点集,根据迭代最近点算法提取两片区公共区域内同名点,并兼顾同名点距离的权,精确计算两片区的配准参数,实现两片区的"无缝"连接,最后使各独立片区拼接成一个连续的大空间尺度地表垂直形变场.本文推导了多轨PSInSAR技术获得的不同片区形变场基准转换与数据拼接的数学模型,并以华北平原(115.32°E—118.79°E, 36.81°N—40.58°N)为实验区,解析了3个不同轨道共12个片区PS目标,获取了研究区2006—2010年地表垂直形变速度场.分析表明:(1)研究区大范围处于下沉状态,形成以北京、廊坊、天津、沧州、泊头—德州等城市为中心向外扩展的地表沉降发展态势,几个沉降中心的平均沉降速率分别达到-34.7 mm/a、-26.3 mm/a、-64.2 mm/a、-34.6 mm/a和-37.7 mm/a;(2)地表沉降的空间分布特征表明,城市工业生产和生活抽取地下水是地表沉降的主要诱因,农业灌溉和油气开采是导致华北平原大范围地表沉降的另一个重要因素;(3)研究区最大沉降带沿北北东向展布,与区内断裂分布一致,表明沉降的空间分布受到断裂带控制;(4)利用地表同期一等水准测量成果检验了本研究结果,精度达到4.72 mm,表明本文提出的数据处理策略能够满足大时空尺度地表形变监测的需求.

Monitoring vertical ground deformation in the North China Plain using the multitrack PSInSAR technique

In this paper, we present a method to reveal vertical deformation characteristics through reference transformation, data splicing and data fusion in multiple regions, which can overcome the shortage of traditional single-track PSInSAR techniques. In order to solve the problem that the ground deformation is not comparable, which is derived from various methods with reference difference in multi-tracks, vertical baseline difference in multi-tracks and reference PS difference in phase unwrapping, we calculate accurate transformation parameters and realize seamless connection of adjacent two frames through corresponding PS point analysis of the overlapped region and same point identification using the shortest distance algorithm based on proper weight. On the basis of algorithm research, we deduce the model to extract deformation information through data connection and reference transformation in multi-track PSInSAR technology, and then process the data collected in the North China Plain(115.32°E—118.79°E, 36.81°N—40.58°N) which include 3 different orbits and 12 frames, and obtain the vertical deformation of the study area for the period 2006—2010. The results indicate that the research area is in a sinking status, forming several subsidence centers including Beijing, Langfang, Tianjin, Cangzhou and Botou-Dezhou with average subsidence rates up to -34.7 mm/a, -26.3 mm/a,-64.2 mm/a, -34.6 mm/a and -37.7 mm/a, respectively. The spatial distribution of subsidence shows that groundwater extraction of industry and daily life are the main reasons, meanwhile agricultural irrigation and gas exploitation are the other primary causes. The major subsidence zones, trending NNE, coincide with the orientations of the fault zones, implying the subsidence distribution is controlled by the faults. These research results are verified by leveling measurements with errors about 4.72 mm, which shows that the data processing method in this paper can meet the requirement of large spatial scale deformation monitoring.