2022年泸定6.8级地震GNSS同震形变场及其约束反演的破裂滑动分布

2022年9月5日四川省甘孜州泸定县发生6.8级地震，地震发生在川滇菱形块体东边界鲜水河断裂磨西段西侧附近.本文基于震中350 km范围内中国大陆构造环境网络和中国地震科学实验场118个GNSS连续站数据，观测获得了精细的同震形变场，结果显示：同震形变跨发震断层呈空间对称分布，表明本次地震具有显著的左旋走滑特征；记录到的最大同震形变发生在震中距40 km的SYD5(石棉安顺场)站，东西向和南北向形变量分别达到-22.0±1.2 mm和11.6±0.9 mm，震中距100 km以外测站的水平同震形变均小于5 mm；垂向同震形变不显著.结合走向163°和倾角77°的发震断层模型，本文对发震断层面的同震破裂滑动分布进行了反演，结果显示：同震滑动主要集中在主震东南侧余震空区0~15 km深度范围内，且破裂达到了地表，同震释放的地震矩与矩震级为M_W6.57地震相当.结合理论同震形变场、主应变场和邻近区域主要活动断裂库仑应力变化的空间分布特征，本次可能导致处于强闭锁和地震空区的安宁河断裂石棉—冕宁段未来发震风险性增强.

Coseismic displacement field and slip distribution of the 2022 Luding M6.8 earthquake derived from GNSS observations

The Luding M6.8 earthquake occurred on September 5, 2022 in Garzê, Sichuan province, China. The epicenter is located west neighboring to the Moxi segment of the main Xianshuihe fault, which is one part of the eastern boundary of the Sichuan-Yunnan rhombic block. Based on GNSS observations of 118 continuous stations within the scope of 350 km from the epicenter of the earthquake, collected from the Crustal Movement Observation Network of China (CMONOC) and the China Earthquake Scientific Experiment (CSES), we obtained the coseismic displacement field. The results show that the spatial distribution of the coseismic field is axisymmetric to the seismogenic fault, indicating the sinistral strike slip pattern of the earthquake. The maximum horizontal coseismic displacement was recorded at station SYD5, 40 km epicenter distance, with the magnitudes being -22.0±1.2 mm and 11.6±0.9 mm on the east-west and north-south components, respectively. The magnitudes of displacements decline to less than 5 mm for GNSS stations with epicenter distances being larger than 100 km. There is no remarkable vertical coseismic displacement recorded at these GNSS stations. By setting the geometrical strike and dip angles of the seismogenic fault being 163° and 77°, respectively, we estimated the coseismic slip distribution with the observed coseismic displacements. The results show that the coseismic slips had ruptured to the surface, mainly distributed at the depths of 0 to 15 km within the seismic gap of aftershocks, southeast to the location of the main shock. The estimated moment magnitude is MW6.57. According to the spatial distribution of the theoretical coseismic displacement field and principal strain field, as well as the Coulomb stress changes on surrounding active faults in the epicenter area, the earthquake may enhance seismic risk at the Shimian-Mianning segment of the Anninghe fault, where it is characterized as fully coupled and located in a significant seismic gap.