利用短周期密集台阵噪声成像研究洪泽湖浅部三维横波速度结构  

Three-dimensional shear-wave velocity structure in the shallow stratum of the Hongze Lake,with a short-period dense seismic array

作　　者：徐志萍[1] 刘巧霞[1] 段永红[1] 田晓峰[1] 周铭[1] 邱勇[1] 王宏伟[1] XU ZhiPing;LIU QiaoXia;DUAN YongHong;TIAN XiaoFeng;ZHOU Ming;QIU Yong;WANG HongWei(Geophysics Exploration Center,China Earthquake Administration,Zhengzhou 450002,China)

机构地区：[1]中国地震局地球物理勘探中心,郑州450002

出　　处：《地球物理学进展》2023年第3期1035-1046,共12页Progress in Geophysics

基　　金：国家自然科学基金项目(42074070);中国地震局地球物理勘探中心科研专项(SFGEC2021-01);国家重点研发计划项目(2018YFC1504102)联合资助。

摘　　要：我国陆内河流湖泊等水系发育,但受实施条件、成本和生态保护限制,针对陆内水域精细三维速度结构和断裂构造的探测工作相对较少,需进一步探索适合陆内水域环境的地震观测及成像技术.本文选取湖水面积大、构造环境复杂且毗邻盐矿开采区的洪泽湖水域作为试验区域,开展了短周期密集台阵地震背景噪声观测与成像试验.基于16台节点式海底地震仪(OBN)所记录的观测时长16天的地震背景噪声数据,利用基于射线追踪理论的面波频散直接反演方法获取了洪泽湖东北角0~400 m深度范围的三维横波速度结构.试验结果表明:(1)OBN仪器在水域内布设及回收方便快捷,成本相对低廉,适于在大面积水域内推广应用.(2)在洪泽湖水域下方存在较厚淤泥沉积的情况下,仍可从水域台站噪声互相关函数中获取较为清晰的Rayleigh面波信号.(3)获取了洪泽湖东北角水域0~400 m深度范围的三维横波速度结构.(4)此次试验为今后在陆内水域大规模短周期密集台阵观测储备了技术和经验,为水域下方三维速度结构和断裂构造探测提供了新技术思路,具有较高的实践参考价值.There are relatively few exploration works on fine three-dimensional velocity structure and fault structure in the inland water area due to the limitations of implementation conditions and cost as well as the ecological protection.Consequently,it is needed to develop new seismic observation and imaging techniques suitable for intercontinental waters.The Hongze Lake,which is adjacent to the salt mining area and has large area with complex tectonic environment,is chosen as our ideal experimental area to carry out seismic ambient noise observation and tomography experiment.We resolved a three-dimensional shear-wave velocity structure at the northeast corner of Hongze Lake using the sixteen-days-long seismic data recorded by temporary dense seismic array consisting of sixteen four-component Ocean Bottom Nodal(OBN)seismometers using a direct 3D surface-wave tomography method.The main findings can be summarized as following:(1)It is applicable to the inland lakes and rivers with large water area since it is proved that the OBN instruments are convenient to be placed and brought back in the water area with relatively low cost.(2)Rayleigh waves can be clearly observed in the noise cross-correlation functions even in the Hongze lake with thick silt deposits.(3)We can obtain the three-dimensional shear-wave velocity structure at the northeast corner of Hongze Lake within the depth range of 0~400 m.(4)With depth less than 100 m,the velocity structure of S wave under Hongze Lake is related to water depth.With depth greater than 100 m,the range of high speed anomaly at different depths in our study area is related to the difference of inland strata in the slope zone.(5)This experiment provides good technology practice for observation and imaging with dense seismic array to detect the velocity structure and fault structure in continental waters.Due to the low speed in the study area and small range of the experimental array,our results cannot cover the salt mine distribution range ranging from 1200 m to 2400 m.Moreover,the ear

关 键 词：短周期密集地震台阵 地震背景噪声成像 洪泽湖 三维横波速度结构 

分 类 号：P315[天文地球—地震学]