用大地电磁网法在长春等地探测上地幔电导率结构  

MEASUEMENT OF NETWORK-MT IN TWO AREAS OF NE CHINA FOR STUDY OF UPPER MANTLE CONDUCTIVITY STRUCTURE OF THE BACK-ARC REGION

作　　者：赵国泽[1] 汤吉[1] 梁竞阁[1] H.Utada M.Uyeshina M.Ichiki 马明志[3] 黄之维[3] 王洪歧[3] 

机构地区：[1]中国地震局地质研究所,北京100029 [2]日本东京大学地震研究所 [3]吉林省地震局,长春130022

出　　处：《地震地质》2001年第2期143-152,共10页Seismology and Geology

基　　金：中国地震局地质研究所论著2001B0013。

摘　　要：使用长周期大地电磁测深网 (Network -MT)等技术 ,在长春和三岔河等地对太平洋板块弧后的上地幔电导率结构进行了探测。用陆地电话线或电缆接收长基线的电场 ,由设置在长春地磁台的三分量磁通门磁力仪记录磁场变化 ,得到Network -MT等观测资料的最长周期可达 10 5～10 6 s,反演结果的深度可达约 10 0 0km。 1)在两个区的 10 0～ 2 0 0 ,30 0 ,50 0～ 6 0 0km深度附近存在电性间断面 ;2 )长春测区的 850km深度存在电性间断面 ;3)平滑模型的电导率随深度增大而单调增加 ;4 )三岔河测区 6 0 0km深度、长春测区 850km深度的电导率达到 1S/m。上述结果表明 ,地幔内存在不连续界面和不均匀性 ,有些结果可与岩石学的研究结果对比。The upper mantle electrical conductivity structure of the Pacific back-arc beneath northeastern China was investigated by the long-period magnetotelluric (Network-MT) at Changchun city and Sanchahe site. Time series data of the long baseline electric field were collected by using land telephone line cables and three component magneic field variations were recorded at Changchun observatory by digital flux magnetometer. Network-MT responeses have been obtained up to 10 5～10 6s, which were inverted to one-dimensional model down to depths of about 1 000km. Resulted models show that: (1) The discontinuity were detected at 100～200km, and in mantle transition zone for around 300 km and 500～600 km depth, respectively. (2) The discontinuity appears at 850km for the lines in Changchun. (3) The conductivity almost monotonically increases with depth in the smooth conductivity models. (4) The conductivity reaches 1 S/m at 600 km depth in Sanchahe sites and at 850 km in Changchun sites, respectively. The above results indicate the discontinuity and the heterogeneity of the mantle and can be compared with the results obtained by petrology studies.

关 键 词：大地电磁网 上地幔 电导率 地下岩石 资料处理 平滑模型 

分 类 号：P319.2[天文地球—固体地球物理学]