人工源地电场空间变化区域性特征

Regional characteristics of artificial source geoelectric field spatial variations

认识地震电信号特征对地震短临预报具有重要意义.通过陕甘宁晋地区、川滇地区、山东及其周边地区和上海地区的换流站接地极向地下注入2 100—4 600A大电流,研究各地区地电场的变化特征,以深入地认识地电场信号的区域性变化实质.研究显示:(1)在陕甘宁晋地区,高沙窝大电流源的附加地电场可被分布于鄂尔多斯地块边缘弧形地带的490km范围内的10个台站观测到,而距该信号源以西150km的台站均未观测到该信号;(2)在川滇地区,丽江信号源的南部地区观测到的信号强度和距离远大于北部地区.对于西昌大电流源,只有距其10km处的小庙台和540km处的仙女山台可观测到信号,而其它十几个台站均未观测到;(3)在山东和上海地区,可被观测到的人工源信号的最远距离及其特征各不相同,亦与陕甘宁晋和川滇地区大为不同;(4)对于本文所研究的地区,信号的波形变化存在着随台站与信号源距离的增加畸变程度增大的现象,一些台站只能记录到大电流开始和结束时的尖峰脉冲信息.针对上述变化特征,本文从机理和地质条件等方面进行了一些有益的探讨,以期加深对地震电信号变化特征的认识.

Knowing the seismic electric signal characteristics will be of great importance for short-term earthquake prediction.In this paper,by studying the signals originated from grounding electrodes 2 100--4 600 Acurrent of the converter stations in Shaanxi-Gansu-Ningxia-Shanxi region, Sichuan-Yunnan region,Shandong and its surrounding areas as well as Shanghai region in China,we could have a better understanding of regional nature of the geoelectric field variation.The results show that：（1） In Shaanxi-Gansu-Ningxia-Shanxi region,the additional geoelectric field originated from Gaoshawo grounding electrode could be observed at ten stations which are distributed along the edge of the Ordos massif arc in the scope of 490 km,but it could not be observed at the stations beyond the distance of 150 km to the west of the source;（2） In SichuanYunnan region,the signal strength and the distance between the source and the station that could observe the signals originated from source in southern Lijiang grounding electrode are greater than that in the north.The additional geoelectric field originated from Xichang grounding electrode can be observed only at the stations of Xiaomiao and Xiannüshan which are 10 km and 540 km from the source respectively,and at the other twelve stations the signals could not be observed;（3） The farthest distance and characteristics are different from one another for the signals originated from heavy current observed in the regions of Shandong,Shanghai and Shaanxi-Gansu-Ningxia-Shanxi,as well as SichuanYunnan region;（4） For the studied regions in this paper,the waveform distortion degree of the additional geoelectric field gets higher with the increase of the distance between the source and station.At some stations only the spike pulses were recorded which occurred only when heavy current started and ended.For the characteristics of the additional geoelectric field mentioned above,this paper has made some interpretations from mechanism and geological conditions in order to deepen the understanding of seismic electric signals.