运用InSAR技术解算四川长宁M_(S)6.0地震三维形变场及时间序列形变分析

Calculation of 3D deformation field and time series deformation of Changning M_(S)6.0 earthquake in Sichuan Province using InSAR technique

运用升、降轨Sentinel-1A卫星的差分干涉影像,获取2019-06-17四川宜宾长宁M_(S)6.0地震的三维同震形变场。在此基础上,以升降轨同震形变数据为约束条件,基于Okada弹性半空间位错模型反演得到发震断层符合走滑和逆冲特征,断层破裂尺度约为15 km×20 km,断层滑动角为44.37°,断层倾角为56.42°,震源深度约为10.2 km,矩震级为M_(W)5.8。最后,采用SBAS-InSAR技术获取该地区2019-04-05至2019-08-03各时间段的累计形变,结果认为该区域在震前近场形变波动较小,震后一段时间累积形变增长,分析原因可能是余震分布使得地表变化处于不稳定状态。通过与已有研究文献的比较和对该区域断层构造的分析,推测此次长宁地震发震断层由反演出的断层滑动引起,滑动面上缘接近地表,主震引起的次级断层活动触发短期内强余震频发。

In this paper,the three-dimensional coseismic deformation field of Changning M_(S)6.0 earthquake in Yibin,Sichuan Province on June 17,2019 was obtained by using the differential interferogram images of ascending and descending Sentinel-1A satellite.Then,the coseismic deformation data was taken as the constraint condition,and the inversion results based on the Okada elastic half-space dislocation model show that the seismogenic fault conforms to the characteristics of strike slip and thrust.The fault rupture scale of the M_(S)6.0 earthquake is about 15 km×20 km;the dip and rake angles are 44.37°and 56.42°,respectively;the focal depth is about 10.2 km,and the moment magnitude is M_(W)5.8.Finally,the SBAS-InSAR technique was used to obtain the cumulative deformation of the study region from April 5 to August 3,2019.The results show that the near-field deformation fluctuation of this region is small before the earthquake,and the cumulative deformation increases after the earthquake.The reason may be that the distribution of aftershocks makes the surface change in an unstable state.Through a comparison with the existing research literature and the analysis of the fault structure in the study area,this study inferred that the Changning earthquake is caused by the sliding of seismogenic fault.The upper edge of the sliding surface is close to the ground surface,and the secondary fault activity caused by the mainshock triggers frequent strong aftershocks in a short time.