基于密集台阵的滇西北地区壳幔结构研究及孕震环境探讨  

Study on Crust-Mantle Structure and Seismogenic Environment in Northwest Yunnan Based on Dense Array

作　　者：茶文剑 金明培[1] 王伟君[2] 黑贺堂 CHA Wenjian;JIN Mingpei;WANG Weijun;HEI Hetang(Dali Center of China Earthquake Science Experimental Office,Yunnan Earthquake Agency,19 Binhai Road,Dali 671000,China;Institute of Earthquake Forecasting,CEA,63 Fuxing Road,Beijing 100036,China)

机构地区：[1]云南省地震局中国地震科学实验场大理中心,云南省大理市671000 [2]中国地震局地震预测研究所,北京市100036

出　　处：《大地测量与地球动力学》2024年第6期611-617,共7页Journal of Geodesy and Geodynamics

基　　金：云南省地震局科技人员传帮带培养项目(CQ3-2021004);中国地震局地球物理研究所基本科研业务费专项(DQJB23Z03-02)。

摘　　要：利用滇西北地区(25.0°~26.9°N,99.20°~100.74°E)85个地震台站记录的三分量远震波形资料提取P波接收函数,并选用H-k扫描法获取研究区莫霍面深度和泊松比,再根据接收函数共转换点(CCP)叠加方法绘制NW向和NE向共6条垂直剖面。结果表明,研究区地壳厚度在38.5~52.4 km之间变化,呈纵向差异分布;泊松比范围为0.24~0.34,多呈四象限分布特征;2013年以来云龙、洱源、漾濞等几次5级以上地震均发生在泊松比高梯度带上。从CCP剖面来看,研究区NW向莫霍面起伏相对较大,由北向南莫霍面呈变浅趋势,上隆幅度约为5~10 km;NE向莫霍面起伏相对平稳,平均深度在42 km左右;地壳内分层情况较为复杂,几乎没有较为连续的界面。漾濞地震下方中上地壳存在较宽的负幅值带,推测可能存在低速区并为地震的发生提供了孕震环境。D410间断面平均深度约为420 km,D660间断面平均深度接近660 km,地幔转换带的厚度在210~260 km之间。Using the three-component teleseismic wave shape data recorded by 85 mobile seismic stations in northwest Yunnan(25.0°N to 26.9°N,99.20°E to 100.74°E),we extract the P-wave receiving function,and obtain the Moho depth and Poisson’s ratio by H-k scanning method.Then,we apply the receiving function common transformation point(CCP)stacking method,plotting a total of 6 vertical sections NW and NE were plotted.The results show that the crust thickness in the study area varies from 38.5 to 52.4 km,with the crust thickness being thicker in the northwest and thinner in the southeast.Poisson’s ratio varied between 0.24 to 0.34,showing a four-quadrant distribution.The wave velocity ratio decreases with the increase of crustal thickness in the study area,showing a certain negative correlation.Yunlong M5.1,Eryuan M5.5 and Yangbi M6.4 earthquakes all occurred in the high gradient zone of Poisson’s ratio.According to the CCP profile,the Moho in the study area fluctuates significantly in the NW direction,becoming shallower from the north to the south.The uprise amplitude is about 5 to 10 km.The fluctuation of NE toward Moho is relatively smooth,with an average depth of about 42 km.The stratification in the Earth’s crust is complicated,and there are few continuous interfaces.There is a wide negative amplitude band in the middle and upper crust below the Yangbi earthquake,which may provide seismogenic environment for the occurrence of earthquakes.The average depth of the D410 discontinuity plane is about 420 km,the average depth of the D660 discontinuity plane is about 660 km,and the thickness of the mantle transition zone is 210 to 260 km.

关 键 词：接收函数 H-k叠加 泊松比 共转换点叠加 壳幔结构 孕震环境 

分 类 号：P315[天文地球—地震学] P313[天文地球—固体地球物理学]