摘要
壳幔过渡带是地壳和地幔之间的分界区域,其精细结构特征,包括过渡带的厚度和跨越过渡带的速度和密度变化,对理解下地壳和上地幔顶部之间的物质和能量交换过程具有重要约束作用.传统研究将壳幔过渡带简化为一阶间断面(即莫霍面)来估计其上下介质的地震学性质差异,可能导致显著偏差.基于数值试验,本文提出了利用多频段接收函数提取的Pms转换波振幅来同时确定壳幔过渡带S波速度跃变和厚度的方法,并将该方法运用于川滇地区47个固定台站记录的远震数据.研究结果显示,四川盆地壳幔过渡带较薄、速度跃变较小,表现出克拉通地区的典型特征,推测该区域下地壳和上地幔物质差异较小;松潘—甘孜块体壳幔过渡带较薄、速度跃变较大,推测该区域地壳底部存在部分熔融;康定块体和滇中块体西侧壳幔过渡带较厚,推测该区域存在地幔物质上涌和底侵作用;四川盆地西南缘的峨眉山地区壳幔过渡带速度跃变较大,推测该区域下地壳存在部分熔融;井研台(JYA)下方壳幔过渡带较厚,可能是壳幔过渡带深度的剧烈横向变化导致其上下边界变得模糊.
The crust-mantle transition zone is the boundary layer between the crust and mantle.The fine structure feature of the transition zone,including its thickness,velocity and density contrast across it,provides important constraints on the material and energy exchange between the lower crust and the top of the upper mantle.Conventional studies simplify the crust-mantle transition zone as a first-order discontinuity(i.e.,Moho)to estimate seismic property differences between adjacent media,yet this simplification may introduce substantial bias.Based on numerical experiments,this study proposes a method to simultaneously determine the S-wave velocity contrast across the crust-mantle transition zone and the transition width using amplitude of Pms converted phase from multiband receiver functions.We apply the method to teleseismic data recorded by 47 permanent stations in the Sichuan–Yunnan area.The results show that the crust-mantle transition zone in the Sichuan basin is thin with a low velocity contrast,indicative of typical cratonic characteristics,suggesting that little difference between the lower crust and upper mantle materials in this area.The crust-mantle transition zone in the Songpan–Garzêblock is thin with a high velocity contrast,suggesting partial melting near the bottom of the crust.The Kangding block and the west side of the Central Yunnan block are characterized by a thick crust-mantle transition zone,suggesting the existence of mantle material upwelling and bottom intrusion in this area.The crust-mantle transition zone in the Emei Mountain area on the southwestern edge of the Sichuan basin has a high velocity contrast,suggesting that there is partial melting in the lower crust in this area.The crust-mantle transition zone under the JYA station is thick,which may be due to the drastic lateral variation of the crust-mantle transition zone depth which blurred its upper and lower boundaries.
作者
彭雪峰
冯麟淇
邓凯
梁春涛
PENG XueFeng;FENG LinQi;DENG Kai;LIANG ChunTao(Key Laboratory of Earth Exploration and Information Technology of Ministry of Education,Chengdu University of Technology,Chengdu 610059,China;College of Geophysics,Chengdu University of Technology,Chengdu 610059,China)
出处
《地球物理学报》
北大核心
2025年第10期3766-3778,共13页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(41804081)资助.
关键词
莫霍面
壳幔过渡带
速度跃变
多频段接收函数
Moho
Crust-mantle transition zone
Velocity contrast
Multiband receiver functions
作者简介
第一作者:彭雪峰,男,成都理工大学在读研究生,主要从事地球深部结构研究.E-mail:pengxf1999@outlook.com;通讯作者:邓凯,博士,成都理工大学教授,从事地震学研究.E-mail:dengkai17@cdut.edu.cn。
