四川大岗山水库蓄水对2022年泸定M_(S)6.8地震及余震的影响  

The impact of the Dagangshan Reservoir impoundment in Sichuan Province on the 2022 Luding M_(S)6.8 earthquake and its aftershocks

作　　者：朱家正 孙玉军 谢志远 吴刚 ZHU Jiazheng;SUN Yujun;XIE Zhiyuan;WU Gang(Sanya Institute of South China Sea Geology,Guangzhou Marine Geological Survey,China Geological Survey,Sanya 572000,Hainan,China;SinoProbe Laboratory,Beijing 100037,China;Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]广州海洋地质调查局三亚南海地质研究所,海南三亚572000 [2]自然资源部深地科学与探测技术实验室,北京100037 [3]中国地质科学院,北京100037

出　　处：《地质力学学报》2024年第2期363-376,共14页Journal of Geomechanics

基　　金：国家自然科学基金项目(42022029,41874114);国家重点研发项目(2022YFC2805503)。

摘　　要：2022年9月5日四川省泸定县发生M_(S)6.8地震,2023年1月发生MS 5.6余震。该次地震发生在鲜水河断裂南段,位于泸定地震震中东南部70 km的大岗山水库。该水库自建成蓄水后,引起库区北西侧磨西断裂的地震活动性显著变化:2014年11月水库达到预定水位之前的3年内,磨西段地震震级较小,多为0~2级微震;11月之后的3年内该区域地震震级和数量明显增加。文章利用高精度DEM数据、精准的地表断裂信息和地层地质信息,建立了三维孔隙弹性有限元数值模型,并根据震源机制解得到断层参数,定量计算了水库水位变化对地层孔隙压力、断层库仑应力的影响。在相关参数约束下的结果表明:水库蓄水造成M_(S)6.8地震震源位置在发震时刻的地层孔隙压力增加5 kPa,库仑应力增加3.6 kPa,对其发生具有一定促进作用。对于MS 5.6正断层型余震,水库蓄水造成其震源位置孔隙压力增加0.32 kPa,库仑应力降低0.69 kPa,对其所处断层面的滑动具有抑制作用。[Objective]The M_(S)6.8 earthquake that struck Luding County,Sichuan Province,on September 5,2022,and its aftershocks have drawn widespread attention,especially concerning the potential risks of induced seismicity associated with the construction of high-dam reservoirs in regions with high seismic intensity.Previous studies have explored the possible link between reservoirs and seismic activity,without reaching a definitive conclusion.This study aims to assess the impact of water storage in the Dagangshan Reservoir on the surrounding strata and its correlation with recent seismic events.[Methods]Numerical simulation methods were employed using high-precision digital elevation model(DEM)data,fault data,and reservoir water level information to develop a three-dimensional poroelastic finite element numerical model extending from the surface to a depth of 25 km.By analyzing the hydrogeological conditions,lithology of rock masses,and groundwater dynamic changes,this study evaluated the seismic hazard risk of major faults,such as the Moxi Fault,and calculated variations in Coulomb stress and strata pore pressure at the hypocenter during the occurrence of the earthquake.[Results]The study indicates that,during the M_(S)6.8 Luding earthquake on September 5,2022,the pore pressure at the epicenter reached 5 kPa,and the Coulomb stress increased by 3.6 kPa,suggesting that the impoundment of the Dagangshan Reservoir contributed to an increased risk along the Moxi Fault on the northwestern side of the reservoir.Using the source parameters of the MS 5.6 aftershock that occurred on January 26,2023,it was observed that the impoundment caused a change in Coulomb stress at the epicenter of-0.69 kPa and a pore pressure of approximately 0.32 kPa.It is evident that the reservoir impoundment had a relatively minor impact on the fault activity where the MS 5.6 aftershock occurred and even exhibited a certain inhibitory effect.Moreover,seismic activity was mainly concentrated in two areas on the western side of the reservoir,with both th

关 键 词：泸定地震 水库地震 库仑应力 孔隙压力 有限元数值模拟 

分 类 号：P584[天文地球—岩石学]