华北地区上地幔及过渡带电性结构研究  

Study on the conductivity structure of the upper mantle and transition zone beneath North China

作　　者：徐光晶[1] 汤吉[2] 黄清华[1] 上嶋诚 

机构地区：[1]北京大学地球与空间科学学院地球物理学系,北京100871 [2]中国地震局地质研究所,北京100029 [3]日本东京大学地震研究所

出　　处：《地球物理学报》2015年第2期566-575,共10页Chinese Journal of Geophysics

基　　金：国家杰出青年科学基金(41025014);国家自然科学基金(40974041)资助

摘　　要：采用远参考道和Robust技术,处理了华北地区14个地磁台站资料,得到了相干度超过0.8的地磁测深响应函数.并将其转换为大地电磁测深的响应函数,获取了10^5～10^7 s周期范围内的视电阻率和相位.应用ρ^＋理论对数据进行了一致性检验和反演,结果表明417km,850km深度附近可能存在电性间断面.同时采用基于一维最光滑模型的Occam反演方法得到了300～1000km范围的地幔电性结构,并与前人在其他地区的研究结果进行了对比.发现华北地区地幔过渡带的电导率在大兴安岭—太行山重力梯度带东西两侧表现不同,重力梯度带附近及西侧台站下方过渡带深度的电导率和北美的Tucson地区相当,而华北地区东部的电导率在地幔过渡带范围高出西侧约2～5倍,这很可能和太平洋板块的俯冲有关.In order to reveal the deep geodynamics of the North China,14 geomagnetic stations with long-period observation data in North China were used to obtain the electrical structure under the lithosphere,especially between the mantle transition zone. Remote reference method and robust estimation were conducted to obtain the high quality data（the data coherencies are higher than 0.8）.The Geomagnetic Deep Sounding（GDS）response of the periods 10^5～10^7 seconds was obtained and transformed into an equivalent scalar magnetotelluric（MT）transfer function.ρ^＋ theory was conducted to check the consistency of the apparent resistivity and phase.The smooth conductivity models of Occam inversion were obtained and compared with the past models.The real and imaginary parts of tipper were also analyzed. The ρ^＋ inversion indicates that conductivity discontinuity surfaces exist at depth about417 km and 850 km.Occam inversion shows that electrical conductivities in the eastern part aremuch higher than those of the western part in North China. The real and imaginary parts of tipper reveal that a high conductivity object along nearly north to south direction exists in the eastern part of North China.The conductivity of the mantle transition zone in the east and west of the North China are different.The conductivities of the mantle transition zone near the Ordos in the west of North China are similar as that of Tucson in the North America,while the conductivities of the east part are approximately 2～5times higher.This feature may correspond to the subduction of the Pacific plate.

关 键 词：地磁测深 华北地区 地幔过渡带 电性结构 

分 类 号：P631[天文地球—地质矿产勘探]