2021年9月16日四川泸县M_(S)6.0地震震区三维S波精细速度结构  

Three-dimensional fine S-wave velocity structure around the source area of the Sichuan Luxian M_(S)6.0 earthquake on September 16,2021

作　　者：吴萍萍[1] 李大虎[2,3] 詹艳[4] 郭慧丽[1] 刘雪华 徐微 杨歧焱 鲁来玉[1] 丁志峰[1] WU PingPing;LI DaHu;ZHAN Yan;GUO HuiLi;LIU XueHua;XU Wei;YANG QiYan;LU LaiYu;DING ZhiFeng(Institute of Geophysics,China Earthquake Administration,Beijing100081,China;Chengdu Institute of the Tibetan Plateau Earthquake Research,China Earthquake Administration(Chengdu Base of China Seismic Experimental Site),Chengdu610039,China;Sichuan Earthquake Agency,Chengdu610039,China;Institute of Geology,China Earthquake Administration,Beijing100029,China;Key Laboratory of Intelligent Detection and Equipment for Underground Space of Beijing-Tianjin-Hebei,Hebei GEO University,Shijiazhuang050031,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局成都青藏高原地震研究所(中国地震科学实验场成都基地),成都610039 [3]四川省地震局,成都610039 [4]中国地震局地质研究所,北京100029 [5]河北地质大学,京津冀城市群地下空间智能探测与装备重点实验室,石家庄050031

出　　处：《地球物理学报》2023年第6期2386-2403,共18页Chinese Journal of Geophysics

基　　金：中央级公益性科研院所基本科研业务专项(IGCEA2103);中国地震局地球物理研究所基本业务专项(DQJB22B19,DQJB22B26);四川省地震局地震科技专项(LY2218)联合资助。

摘　　要：近年来,四川盆地南缘(川南)中强地震频次增多和地震活动性增强,2021年9月16日四川省泸州市泸县M_(S)6.0地震的发生再次引起国内外学者对川南地区深部孕震环境和潜在地震危险性的密切关注.为了探究泸县6.0级地震震区的深部结构特征,本文基于最新布设于震区70个短周期密集地震台站的观测资料,采用背景噪声成像法构建了泸县M_(S)6.0震区三维S波精细速度结构.研究结果表明,研究区内喻家寺向斜和华蓥山断裂带东/西支深部速度结构表现明显非均匀性,喻家寺向斜构造区在深度3.0 km内表现为低速,随着深度增加,速度逐渐增大.华蓥山断裂带东、西支除了存在局部低速非均匀体,整体上表现为NE-SW展布的高速特征.泸县震源区西侧4.0~6.0 km深度呈现低速异常,东侧则表现高速异常分布,主震位于高低速分界带,震区周边存在大范围的明显线状几何特征的地震分布,震源深度优势分布层位主要集中在3.0~5.0 km之间.综合已有的资料分析,主震西侧的低速异常区指示着该处可能存在流体,推测泸县6.0级地震可能是在区域构造应力和流体扰动的作用下,泸县震区的先存隐伏断层发生错动所致.In recent years,the frequency of moderate and strong earthquakes and the intensity of seismicity in the southern margin of Sichuan Basin increase significantly.The occurrence of the Luxian M_(S)6.0earthquake on 16September 2021,located in Luzhou City of Sichuan Province,have once again attracted the attention of domestic and foreign researchers for the seismogenic environment and potential seismic hazards in southern Sichuan.In order to explore the deep structure around the source area of the Luxian M_(S)6.0earthquake,based on the dense array composed of 70short-period seismic stations,a high-resolution 3-D S wave velocity model is constructed with the method of ambient noise tomography.The results show that the velocity varies significantly beneath Yujiasi syncline and Huayingshan fault′s eastern/western branches.The velocity structure beneath the Yujiasi syncline exhibits low within the depth of 3.0km,and as the depth increases,the velocity gradually increases.The eastern and western branches of the Huayingshan fault zone shows high velocity in the NE-SW direction generally,except for several local low velocity anomaly zones.It shows low velocity anomaly to the west of the Luxian earthquake source area at depths of 4.0~6.0km,and high velocity to the east.The Luxian earthquake epicenter is located at the boundary of the high and low velocity zone.The focal depth of the aftershock sequences are mainly between 3.0and 5.0km.Combined with the previous studies,the low-velocity zone located west of the epicenter may be interpreted as the effect of fluids.It is speculated that the occurrence of the Luxian M_(S)6.0earthquake may due to the dislocation of the pre-existing hidden fault under the action of regional tectonic stress and fluids disturbance.

关 键 词：泸县地震 背景噪声成像 S波速度结构 华蓥山断裂带 孕震环境 

分 类 号：P315[天文地球—地震学]