中文摘要：

在地震电磁学研究中,电流在地下流动特征与构造关系是一个非常重要的问题.多个强电流源的存在和大范围地电场观测站的分布格局为我们研究这个问题提供了更好的机会.本文通过利用上海及其周边地区4个地点不同的高压换流站接地极向地下注入的大电流（1200~4780A）信号,研究了华东地区8个台站组成的地电场观测台网接收到的附加地电场信号,推进了对地电流在地下传播特征的认识.研究显示：1从幅度特征而言,对于源自不同的大电流信号,各台站观测到的附加地电场信号幅度特征有很大不同,而近处的浦东台只能观测到南桥大电流源的信号而观测不到其他3个大电流源发出的信号,存在着所谓的＂敏感点＂效应;2对于上海地区4个接地极大电流而言,能够观测到源自它们的附加地电场的台站最远为350km,在更远的台站则观测不到.3从均匀度方面而言,在每个台站对于不同的信号源,记录到的附加地电场信号在各方向上的长极距和短极距信号幅度之比可以有很大变化;4在方位特征上,只有崇明台站接收到的同里接地极和华新接地极大电流信号的计算方位度数与实际方位度数误差最小,分别为0.2°和0.8°.而在距离各个信号源最近的青浦台,这种误差要比崇明台站的大;5极化方向特征显示,在青浦台和崇明台所观测到的附加地电场信号中,存在着同一方向上长、短极距信号极化方向是反向的现象,这与常理相悖,怎样解释该现象有待于今后进一步研究.本文从点电流源与台站测线布局构成的装置系统、大区域介质非均匀性、台站测区以及附近地区的介质细结构的影响三个方面,对上述特征进行了较深入的分析和解释.

英文摘要：

In the study of seismo-electromagnetics, the relationship between the flowing characteristics of electric current and the geological structure is a very important problem. The arrangement of four heavy currents from different place injected into the underground and the distribution of many geoelectric field stations offer us a golden opportunity to study the scientific problem further. In this paper, by studying the signals originated from grounding electrodes 1200 - 4780 A current of four converter stations in different places around the Shanghai area and recorded at eight geoelectric field stations in the Huadong area in China, we could promote the understanding of ground current in underground transmission characteristics further. The study shows that （1） as for the magnitude characteristics, the magnitude of the additional geoelectric field recorded at different stations varies greatly for different current sources. Only the signals originated from Nanqiao grounding electrode are observed at Pudong station which is near the heavy current sources, but that from Tongli, Huaxin and Fengxian grounding electrodes are not recorded at this station, which means the so-called sensitive site phenomenon （2） The furthest distance is 350km between the source and the station that could observe the signals originated from these four heavy current sources, and at the stations more than 350 kilometers away no any additional geoelectric signals from the sources could be recorded （3） The uniformity degree of the geoelectrie field in the area does not follow the regular patterns of homogeneous medium, which illustrates that the characteristics of inhomogeneous medium and anisotropy are obvious at many stations in the area. At each station for the different heavy current source the amplitude ratio value of the additional geoelectric field on long dipole to short dipole could vary bigly （4） For the azimuth characteristics, only at Chongming station the errors are minimum between the actual bearing degree and the