利用P波接收函数方法研究华北克拉通西部地壳和上地幔间断面  

Investigation on crustal and upper mantle discontinuities in western part of North China Craton using P wave receiver functions

作　　者：原世豪[1] 陈永顺[1] 

机构地区：[1]北京大学地球与空间科学学院地球物理研究所,北京100871

出　　处：《地球物理学进展》2015年第6期2589-2595,共7页Progress in Geophysics

基　　金：国家自然科学基金委的资助(NSFC grants:91128210;90814002)

摘　　要：本文利用北京大学在华北克拉通西部布设的一条东西方向流动地震观测台阵记录的远震资料,提取各台站P波接收函数,然后通过倾斜叠加(H|κ)、共转换点叠加(CCP)和偏移成像获得了横跨华北克拉通西部鄂尔多斯块体和祁连块体下方地壳和上地幔速度间断面的形态分布.研究结果显示,Moho面从东向西逐渐加深,与地形大致呈镜像关系,东部华北克拉通内部(鄂尔多斯地块)的地壳厚度为~40km,而最西部青藏高原内部(柴达木盆地)的地壳厚度为~65km.在祁连块体下方出现了剧烈地Moho面阶跃,我们推断这是因为柴达木盆地受到南北方向印度板块对欧亚板块的挤压,从而导致垂直方向上厚度的增加.对于上地幔660km速度间断面的成像显示,在30°~32°N|100~102°E范围内出现了加深,这可能与存在低温物质有关.通过对比其他学者利用体波成像和接收函数所获得的结果,我们推测660km速度间断面的加深可能是受印度板块在对应深度上的残留俯冲块体的影响所致.P wave receiver functions have been retrieved from the teleseismic data recorded by a temporal seismic array deployed by Peking University along an east-west profile in the western part of North China Craton（NCC）.The shape of the crustal and upper mantle discontinuities was acquired through the subsequent slant stacking（H｜κ）,common conversion point（CCP）stacking,and Kirchhoff migration imaging.It is shown that the depth of the Moho increases gradually from the east to west under a roughly mirroring relationship with the topography.The crustal thickness in the west of NCC（Ordos block）is^40km while in the east of the profile（Qaidam block of the Tibetan Plateau）is^65km.There is a sharp Moho step beneath Qilian block,which indicates the vertical thickening due to the north-south compression between Indian plate and Eurasian plate.The CCP stacking image of the upper mantle discontinuities indicates that the thickened transition zones probably result from low temperature in the range of 30~32°N｜100 ~ 102°E. The thickened transition zones are also concordance with the previous observations in the same region,which are interpreted as the evidence of the slab penetration of the Indian plate.

关 键 词：华北克拉通 P波接收函数 Moho面 地幔转换带 

分 类 号：P631[天文地球—地质矿产勘探] P541[天文地球—地质学]