三峡水库蓄水后,秭归盆地内部仙女山断裂北端邻近区域内发生多次3.5级以上地震,该地区的地震活动备受关注。本研究分析了该区域秭归井动水位的变化、水化学特征以及同期GNSS形变数据,结果显示:①秭归井水位的快速变化主要受该区域构造应力变化的影响,前期以拉张应力为主,后期区域应力变为挤压状态;②GNSS应变场特征显示面膨胀率高值区位于三峡库区周边及其南部,极高值区恰好位于仙女山断裂北部,且GNSS时间序列与秭归井水位的涨落存在较好的同步性;③2020年10月初开始的震群与该地区持续6个月的挤压状态有关,表明研究区应力积累已经超过岩层抗剪强度,岩层发生破裂。

After the water impoundment of the Three Gorges reservoir,several earthquakes above M3.5 occurred in the area adjacent to the northern end of the Xiannvshan fault,which has attracted much attention. In this study,a series of analyses were carried out on the change of Zigui dynamic water level,hydro-chemical characteristics and the GNSS deformation data. The results show that:①The rapid change of Zigui well water level is mainly affected by the change of tectonic stress in the region. In the early stage,the tensile stress is dominant,while in the later stage,the regional stress changes to the compression state. ②The characteristics of GNSS strain field show that the high value area of surface expansion rate is located around and in the south of the Three Gorges reservoir area,and the high value area is located in the north of the Xiannvshan fault. Moreover,the time series of GNSS is well synchronized with the fluctuation of Zigui well water level. ③The earthquake swarms started in early October 2020 are related to the compression state of the region and lasted for 6 months,indicating that the stress accumulation in the study area has exceeded shear strength of the rock,and caused the rock failure.

P315

中国地震局监测、预测、科研三结合课题(3JH-202201030)资助