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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。
Using the Long-Period Earth-Electromagnetic Sounding Network (Network-MT) and other techniques, the conductivity of the upper mantle in the Pacific plate arc was detected in Changchun and Sanchahe areas. The long baseline electric field is received by land telephone line or cable, and the magnetic field changes are recorded by the three-component fluxgate magnetometer set at Changchun geomagnetic station. The longest period of observation data such as Network-MT is up to 10 5 ~ 10 6 s, The depth of inversion results can reach about 100 km. 1) there are electrical discontinuities near the depths of 10 0 ~ 2 0 0, 30 0, 50 0 ~ 600 km in the two regions; 2) there is an electrical discontinuity at 850 km depth in Changchun; 3) The conductivity increases monotonically with the increase of depth. 4) The depth of 660 km in Sanchahe River reaches 1 S / m at 850 km depth in Changchun. The above results show that there are discontinuous interfaces and inhomogeneities in the mantle, and some of the results can be compared with those of petrology.