Abstract: Located in an earthquake-prone region,the geological structures in Yunnan Province are complex. Taking into account that Tonghai County is located at the intersection of Xiaojiang Fault and Honghe Fault,an F-4M ELF electromagnetic instrument was installed at Tonghai seismic station,which has produced continuous reliable data. The author collected the data and information of the year 2009 & 2010,and did analysis on the variation characteristics of both geomagnetic fields and electrical resistivity. The result shows that the 1Hz and 39Hz electromagnetic power spectra are 0.2 to 1.4 orders of magnitude higher than the normal values immediately before many earthquakes. The anomalies are represented by the abrupt changes of the electric and magnetic field power spectra in earthquake and aftershock sequences,and the amplitude of change is related to the size of earthquake magnitude and the epicentral distance. The electrical resistivity also changes obviously. So,further research on the anomalous characteristics of ELF electromagnetic data will be meaningful to the use of this instrument in earthquake prediction in the future.

Key words: ELF, electromagnetic, power spectrum, apparent resistivity, short-impending anomaly

摘要： 通过对云南省通海地震台2009年1月至2010年12月ELF电磁观测数据的处理分析,研究云南省及邻区中强地震前后,电磁场强度、视电阻率的变化特征。结果表明,1Hz、39Hz的电磁场功率谱在多次地震临震前分别比正常月份约大0.2～1.4个数量级。表现为在地震及余震序列中,电、磁场功率谱有明显的突跳,变化幅度与震级大小、震中距等有关; 同时视电阻率的异常变化也比较明显。

关键词: ELF, 电磁, 功率谱, 视电阻率, 短临异常