云南大姚6.2级、6.1级地震前电磁异常特征分析

对2003年云南大姚6．2级、6．1级地震前云南磁电资料分析研究，结果表明，震前地磁Z、D分量及地电阻率、自然电位出现明显异常。6．1级地震前出现的异常比6．2级地震前出现的异常更为显著，两次地震发生前均出现多组相对速率变化超差异常。6．1级地震前一周，元谋自然电位NS、EW向同时出现大幅度下降的临震异常。分析总结这些异常特征，对云南地区未来中强地震的震情分析和短临跟踪有一定的预报意义。

Analysis on characteristics of geoelectric and geomagnetic anomaly be fore the Dayao Earthquake with Ms 6.2 and Ms 6.1 in Yunnan province

Based on the geoelectric and geomagnetic data of Yunnan province in 2003,Dayao earthquakes,with magnitude M S 6.2 and M S 6.1,are analyzed.It shows that there appear short term and imminent anomalies in D and Z component of geomagnetism and apparent resistivity as well as spontaneous potential.The anomalies appear before the earthquake with M S= 6.1 are more significance than that of the earthquake with M S= 6.2.Several groups of Mean Square Deviation anomalies of relatively changeable velocity appear before the two earthquakes. A week before the earthquake with M S 6.1,the NS and EW components of spontaneous potential at Yuanmou station simultaneously descend in large scale. The above characteristics are meaningful to analyze and trace the occurrence of the moderate earthquake.