利用InSAR技术研究青藏高原冻土形变特征

doi:10.12196/j.issn.1000-3274.2020.03.014

摘要/Abstract

摘要： 由于自然环境的限制, 青藏高原的大地测量网络十分稀疏, 不能满足区域地壳运动监测的需求。干涉合成孔径雷达(InSAR)是非接触监测地壳运动的一种重要方式, 但在高原上受到冻土的影响。本文基于2014~2018年的Sentinel-1卫星C波段雷达数据, 采用InSAR时序技术分析了冻土形变的时空特征。针对InSAR位移时间序列, 采用空间滤波去除了大气延迟、地形效应等局部公共误差, 提高了时间序列的信噪比。结果显示, 青藏高原的冻土运动可分为差异较大的两类: 在大部分冻土区域, 与周边高山(基岩)区域相比, 冻土地区显示类似的季节波动或一定的长期沉降; 在部分冻土地区存在异常快速下沉区域, 例如在西藏中部布若错湖西南侧的沉积盆地内, 存在一个直径约2 km的漏斗型沉降区, LOS向沉降速率可达约10±2.1 mm/a。构造运动造就了高原上大量沿断裂线分布的河流、湖泊, 河床和沉积盆地等广泛分布着冻土, 给准确分析构造形变带来很大挑战, 本文所得的结果可作为区分冻土运动与构造变形的一种有效判据, 也有益于研究高原冻土的物理特性及变形机理。

关键词: InSAR, 冻土, 沉降, 构造形变, 青藏高原

Abstract: The geodetic observation network in the Tibetan Plateau (TP) is sparse due to the limitation of natural environment, which is insufficient for motoring regional crustal movement. Interferometric Synthetic Aperture Radar (InSAR) technique is an important method for monitoring crustal movement in a non-contact mode; however, it is affected by permafrost in the plateau. Based upon the C-band radar data collected by Sentinel-1 satellites during 2014~2018, this paper analyze the spatiotemporal characteristics of permafrost deformation using the InSAR technique. The spatial filtering is used to remove the localized common errors (e.g., the atmospheric delay and topographic effect) in InSAR displacement time series, and improve the signal-to-noise ratio of the data. The results show that there are two distinct categories of permafrost movements in the Tibetan Plateau: similar seasonal fluctuation and certain long-term subsidence in most permafrost areas, compared to nearby mountain (bedrock) region; and abnormal rapid subsidence in a few permafrost areas, e.g., the sedimentary basin to the southwestern of the Burog Co lake in central Tibet exists a cone-shaped subsidence region of the diameter of about 2 km and with a maximum subsidence rate of about 10±2.1 mm/a in the line-of-sight (LOS) direction. The tectonic activity in the plateau produced a large sum of rivers and lakes along the fault traces; and the permafrost is widely spread in riverbed or sedimentary basins. This poses great challenges for describing accurately tectonic deformation. The results obtained in this paper can be regarded as a helpful criterion for discerning between permafrost motion and tectonic deformation; and is useful for studies on physical properties and dynamic mechanism of permafrost.

Key words: InSAR, Permafrost, Subsidence, Tectonic deformation, Tibetan Plateau

中图分类号:

P315.7

罗毅, 田云锋, 张苏, 张景发. 利用InSAR技术研究青藏高原冻土形变特征[J]. 地震, 2020, 40(3): 179-188.

LUO Yi, TIAN Yun-feng, ZHANG Su, ZHANG Jing-fa. Study on Characteristics of Permafrost Deformation in the Tibetan Plateau Using InSAR Technique[J]. EARTHQUAKE, 2020, 40(3): 179-188.

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