2022年青海门源M_(W)6.6地震InSAR同震形变场与震源特征

InSAR coseismic deformation monitoring and source characteristics of the 2022 Qinghai Menyuan M_(W)6.6 earthquake

本文利用合成孔径雷达差分干涉(Differential Interferometric Synthetic Aperture Radar,D-InSAR)技术处理哨兵卫星升降轨影像,获取了2022年青海门源M_(S)6.9地震的同震变形场,变形结果显示此次地震导致冷龙岭断裂西段两侧约30 km×20 km范围明显变形,卫星视线向最大同震位移达50 cm.基于有限断层模型,本文构造断层滑动分布模型,反演同震变形场数据.模型显示,冷龙岭断裂的破裂以左旋走滑为主,破裂长度约23 km,主要分布在10 km以上深度,整体形态表现为不规则椭圆盘,其中约3.9 m的最大破裂位于5~6 km深度的椭圆中心.基于反演模型估算的地震平均应力降约5.9 MPa,地震标量矩为1.0×10^(19) N·m,对应矩震级为MW6.6.本文计算了1927年古浪地震、1986年及2016年门源地震对本次地震破裂面的同震静态库仑应力扰动,结果表明冷龙岭断裂西段受到历次地震的库仑应力加载作用,库仑应力增加累积达0.12 MPa,对本次发震断层的破裂有促进作用,其中以1927年古浪地震的应力加载最为显著.本次地震导致周边托莱山断裂应力变化,形成一段长约30 km超过发震阈值的库仑应力增加区,未来托莱山东段断层发生破裂的风险较高.

Using the Differential Interferometry Synthetic Aperture Radar(D-InSAR)technology,coseismic deformation field of the 2022 Qinghai Menyuan M_(S)6.9 earthquake was obtained by processing the Sentinel-1A satellite ascending and descending images.The interferograms exhibit an obviously deformed area of 30 km×20 km in range on both sides of the west Lenglongling fault,from which the maximum coseismic displacement of the line of sight is inferred at 50 cm.Based on the finite fault dislocation,a geodetic inversion for the fault slip model was carried out.The resolved slip distribution shows that the 2022 Menyuan earthquake's rupture on the Lenglongling fault is dominated by left-lateral strike-slip with the rupture length of~23 km and at depth above~10 km.The rupture plane features an elongated ellipses in which the maximum rupture of~3.9 m is located nearly at the center of the ellipse at a depth of 5~6 km.The earthquake gives an average stress drop of~5.9 MPa and the scalar moment of 1.0×10^(19) N·m,corresponding moment magnitude of M_(W)6.6.Coseismic static Coulomb stress disturbances induced by the 1927 Gulang earthquake,1986 and 2016 Menyuan earthquakes on the fault of this earthquake are calculated.The result shows that the western segment of the Lenglongling fault has been hastened by the Coulomb stress of these previous earthquakes with the cumulative stress increase of~0.12 MPa.Among them,the stress loading of the 1927 Gulang earthquake is the most significant and may have prompted this event.The 2022 Menyuan earthquake leads to a change of the stress level in the surrounding Tuolaishan fault,causing Coulomb stress increases that exceeding the seismic threshold on the segment of~30 km in length,which suggests a higher risk of potential earthquake along the Tuolaishan fault.