盈江5.8级和缅甸7.2级地震前电磁异常

本文分析了2010年10月-2011年3月云南通海ELF地震台站观测的电磁场资料,研究发现该资料变化与2011年发生在中国大陆"3·10"盈江5.8级及"3·24"缅甸7.2级地震存在以下关系,(1)470～1 Hz的磁场自功率密度谱(PSD)在2011年盈江5.8和缅甸7.2级地震前出现了脉冲丛集异常,异常幅度分别比正常月份变化约1～3个数量级.异常的幅度与观测点的电极方位和信号的频率有密切的关系.(2)2011年3月10日盈江地震的异常变化是先从地壳的深部向浅部发展,在震前25天2.6 km处的电阻率开始发生变化,震前10天400 m处的电阻率变化,出现了勺形的变化形态,阻抗相位同步变化.3月24日的缅甸7.2级地震,震前10天深部、浅部的电阻率同步发生了大幅度变化,阻抗相位发生转折,这可能是强震的变化特性.

Electromagnetic anomaly before the Yingjiang Ms5.8 and Myanmar Ms7.2 earthquakes

In this paper we analysed the electromagnetic anomaly phenomena related to the March 10 Yingjiang M_S5.8 and March 24 Myanmar M_S7.2 earthquake occurred in 2011. The anomalies of electromagnetic data are observed in Yunnan Tonghai stations in October 2010 to March 2011. The relationship between the electromagnetic anomaly phenomena and the earthquake events is studied. The following results are obtained: (1)The pulse cluster anomalies of power spectrum density (PSD) of magnetic fields in frequency band of 470～1 Hz appeared before Yingjiang M_S5.8 and Myanmar M_S7.2 earthquakes. The anomaly of magnetic PSD is about 1～3 orders of magnitude stronger than background field. The anomaly PSD have a close relationship with orientation of electrodes at observed point and the signal frequency. (2) The anomalies were emerged from deep to shallow in the earth's crust at Yingjiang earthquake on March 10, 2011. At first,the resistivity in the depth of 2.6 km began to change 25 days before the earthquake, and at the depth of 400 meters the resistivity changed 10 days before, and the impedance phase changed synchronously. For the Myanmar M_S7.2 earthquake of March 24, 2011, the deep and shallow resistivity and impedance phase synchronously changed 10 days before the earthquake,this may be the characteristic of strong earthquakes.