联合光学遥感和SAR影像青海玛多Ms 7.4地震同震形变场分析

Coseismic Deformation Analysis of Qinghai Maduo Ms 7.4 Earthquake Based on Optical Remote Sensing and SAR Images

    摘要
  • 摘要: 2021-05-22青海省果洛藏族自治州玛多县发生Ms 7.4地震,作为近年来少有的发生在巴颜喀拉块体内部的强震,研究其同震形变场特征是十分必要的。收集了玛多地震前后Sentinel-2和Landsat 8影像,利用光学像素追踪(pixel offset tracking,POT)技术获得了该地震东西向和南北向形变；基于地震前后Sentinel-1升、降轨影像,利用合成孔径雷达干涉测量技术获取了该地震升、降轨雷达视线向（line of sight,LOS）形变,利用合成孔径雷达（synthetic aperture radar,SAR）POT技术获得该地震距离向和方位向形变,联合解算得到其三维同震形变场,并对提取的同震形变场结果进行对比交叉验证。结果表明,此次玛多地震为左旋走滑型地震,同震形变以东西向水平运动为主,发震断裂为江错断裂。基于光学遥感影像,得到该地震东西向和南北向形变大约集中在±1.60 m和±0.60 m；基于SAR影像,得到升轨最大LOS向抬升和沉降量分别约为1.29 m和-1.12 m,降轨最大LOS向抬升和沉降量约分别为1.15 m和-1.26 m；解算的三维同震形变场中,东西向形变约为-2.00~1.70 m,南北向形变主要集中在-1.00~0.50 m,垂直向上沿断裂带两侧呈升降交替运动,形变约在±0.3 m。地震北侧形变量级相较于南侧更大,得到的地表破裂带长约176 km,在东南末端（34.48°N,99.04°E）、西北末端（34.76°N,97.61°E）和西段鄂陵湖南侧（34.74°N,97.75°E）存在分支破裂。基于光学遥感和SAR影像提取的玛多地震同震形变场具有一致特征,且多平台、多技术为获取该地震完整同震形变场补充了更多地表破裂带分支等特征,该研究为光学遥感和SAR影像在地震同震形变监测中的应用提供一些参考。

     

    Abstract:
    Objectives An Ms 7.4 earthquake occurred in Maduo, Qinghai Province,China on May 22, 2021, which is a rare powerful earthquake that occurred in Bayan Har block in recent years, it is essential to study the characteristics of its coseismic deformation field.
    Methods Based on Sentinel-2 and Landsat 8 images before and after Maduo earthquake, east-west and south-north two-dimensional coseismic deformation fields were obtained by optical pixel offset tracking (POT). Interferometric synthetic aperture radar (InSAR)was utilized to obtain line of sight (LOS) coseismic deformation based on Sentinel-1 ascending and descending images, and synthetic aperture radar (SAR) POT was utilized to obtain range and azimuth directions coseismic deformation of the earthquake, meanwhile, 3D coseismic deformation field of this earthquake is calculated, moreover, the results of coseismic deformation field extracted are compared and verified.
    Results The experimental results show that coseismic deformation field characteristics of Maduo earthquake based on optical and SAR images are great consistent. Maduo earthquake is a typical left-lateral strike-slip event, the coseismic deformation is dominated by east-west horizontal movements, and the seismogenic fault is Jiangcuo fault. Based on optical images, it is obtained that east-west and north-south deformations of the earthquake are about ±1.60 m and ±0.60 m,respectively. Based on SAR images, the maximum LOS uplift and subsidence of ascending are about 1.29 m and -1.12 m, and descending are about 1.15 m and -1.26 m. In the 3D coseismic deformation field, the east-west deformation is about -2.00 m to 1.70 m, north-south deformation is mainly concentrated in -1.00 m to 0.50 m, and it moves alternately up and down along both sides of the fault zone in vertical direction, the deformation is about ±0.3 m. The magnitude of deformation values on north side of the earthquake is larger than that on south side. Branch ruptures are shown at the end of the southeast (34.48°N, 99.04°E) and northwest (34.76°N, 97.61°E) of the surface rupture, and south side of Eling Lake (34.74°N, 97.75°E), and aftershock sequence is distributed near these branch ruptures.
    Conclusions InSAR and POT technologies complement each other, which provide an effective way to obtain the complete coseismic deformation field, and multi-platform, high-resolution optical and SAR images provide important datasets.

     

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