提取地震同震形变场特征的最佳雷达波段问题研究

利用弹性形变模型, 并以走滑型断层为例, 对地震同震形变场进行了模拟研究。 结合雷达成像几何关系, 得到干涉雷达的LOS向形变场以及干涉相位条纹图像。 对比分析了不同雷达波段(X波、 C波、 L波)以及不同雷达入射角(30°和50°)的同震形变场和干涉相位图。 结果表明, 同一雷达波段不同雷达入射角的LOS向形变场会有不同的效果, 入射角逐渐增大时, LOS向形变量随之增大, 体现了发震断层走滑特征; 采用不同雷达入射角, 其探测到的地表形变垂向分量和水平分量信息量不同, 表明入射角较大或较小时能够分别较好地对地表形变的水平变化和垂向变化进行监测; 同一雷达入射角, 不同雷达波段的干涉相位条纹有明显区别, 波长越短, 干涉条纹越密集, 容易出现去相关现象, 长波长的干涉相位条纹比较清晰。 从某种意义上讲, 尽管长波长的干涉相位反映地表形变信息的细节会减少, 但受噪声影响较小, 抗干扰性能较短波长的强, 干涉像对相干性高。 地表形变表现为长期缓慢的小幅度渐变性形态, 也表现为短期迅速的大面积突发性形态。 不同雷达波长探测到的地表形变有效信息不同, 为了更好地利用干涉雷达对各种尺度和不同变化速率的地表形变进行监测, 需要在满足精度的条件下尽可能地选择波长较长及多样化的雷达数据。

Study on Optimal SAR Band for Mapping Co-seismic Deformation

In this paper,we modeled earthquake co-seismic deformation field using a linear elastic model in half-space with a strikeslip earthquake fault. Afterward, we got coseismic deformation field in LOS direction, descending and ascending pass InSAR results with two kinds of radar imaging geometry respectively, and made comparative analysis of results with different SAR bands (X, C and L) and different SAR incidence angles (30°and 50°). The results show that, in the same band, the InSAR results contains different effective information with different incidence angles. The deformation field in LOS direction increases with the increase of incidence angle, reflecting the characteristics of the seismic fault. The detected vertical component and horizontal component of the surface deformation by InSAR differ with different incidence angle. Larger or smaller incidence angle can be used to well detect horizontal deformation or vertical deformation respectively. In the same incidence angle, fringes of the InSAR results are obviously different with different wavelengths. With shotee wavelength, the rate of the fringe is higher, resulting in incoherence phenomena. In contrast, the fringe with longer wavelength is relatively clear. In a sense, using longer wavelength may result in more usable interferometric pairs, and the InSAR result are less affected by noise, although it may contain less precise crustalmotion measurements. The surface deformation is not only embodied as long-term, slow and gradual change, but also embodied as shortterm, rapid and large change. Radar with different wave length can detect different effective information about surface deformation. In order to better detect surface deformation with different rate and various scale of changes by using InSAR, it is necessary to use the longest radar wavelengths possible within some limits, and multiple observations.