1988年澜沧-耿马地震前地磁异常变化特征

Variation features of geomagnetic anomalies before lancang-gengmaearthquake in 1988

分析了澜沧－耿马地震前地磁异常时间进程中的阶段性，根据形态和速率，可把异常分为趋势性异常和突发性异常。在空间上，压磁、感磁等机制引起的震磁效应主要分布在震中附近的有限区域内，震级越大，展布范围也越大。受区域应力场及构造展布控制的地磁异常则出现的远场或较大的范围内，７级以上地震的震磁效应可达６００ｋｍ。

Stage features of geomagnetic anomalies. before Lancang-Gengma earthquake have been analysed in this paper. According to forms and rate , the anomalies can be divtided into tenden- cy anomaly and mutation anomaly. Spatially , seismomagnetic effect caused by piezomagnetism and induced magnetism.is mainly distributed in the limited areas near epicenters , the bigger of the magnitude , the wider of the range. Geomagnetic anomalies controlled by regional stress field. and structure spreading appeared in the range of far field or larger scope. The seismomag- netic effect of earthquake with M ≥7 can reach as far as 600 km.