L波段InSAR数据观测的北京及其周边2007—2010年间累计地壳形变基本特征

地壳形变是评估地震灾害和地质灾害的重要依据之一。 北京及其周边地区的形变状况一直以来缺乏全面、 可靠的观测数据, 阻碍了对该地区这两种灾害的客观认识。 本研究利用L波段InSAR形变观测数据, 调查北京及其周边190 km×150 km范围内, 约3年时间内的累积地壳形变, 详细给出北京地区2007—2010年间的地壳形变基本特征, 为认识该地区的灾害提供参考。 研究结果显示, 该地区主要地壳形变源为地下水开采造成的地面沉降, 观测时间内累积的最大雷达视线向形变达到了37.6 cm。 地面沉降的严重影响, 以及大气噪声的干扰, 造成活动构造变形很难从现有数据定量分辨出来, 但可以确定在此观测期间内较大尺度(长度>50~100 km)的断层活动及其构造变形比较微弱, 对北京地区的地壳形变贡献较小。 最重要的一点是, 北京地区的地壳形变呈条块状分布, 清晰显示地面沉降与活动构造, 特别是NW走向的南口—孙河断层, 存在较强的相关性。

Accumulated Crustal Deformation and its Characteristics in Beijing and Surrounding Regions in 2007-2010 from L-band InSAR

Crustal deformation is one of the important evidences for seismic and geological hazard assessment. The lack of comprehensive and reliable observations of Beijing and surrounding regions prevents us to understand these two kinds of hazards of this area. In this study, we utilize L-band InSAR deformation observations to investigate the accumulated deformation of this region in a range of 190 km×150 km within about a 3-year period. We show the detailed characteristics of the crustal deformation of Beijing area between 2007 and 2010, to help the assessment of nature hazards of this area. The results show that, the main source of deformation of Beijing area is subsidence induced by ground water extraction, and the accumulated maximum Line-Of-Sight deformation can be as large as 37.6 cm in the observation period. The strong affection of subsidence and atmospheric noise lead to the difficulties of separating active tectonic deformation from the InSAR data quantitatively, however, it is confirmed that the large scale deformation (length >50~100 km) of fault motion and active tectonics in the observation period is weak, and contributes little to the accumulated deformation. The most important point is that, the crustal deformation exhibits in a form of strip-and-block, and clearly shows the strong correlation between subsidence and active tectonics, especially for the NW-striking Nankou-Sunhe fault.