中强震前地磁谐波振幅比的趋势性变化特征初步研究

PRELIMINARY STUDY ON THE CHARACTERISTICS OF LONG AND MEDIUM TERM VARIATION FOR THE AMPLITUDE RATIO OFGEOMAGNETIC HUMOROUS WAVE BEFORE MODERATE-STRONG EARTHQUAKES

摘要:

应用最大似然谱分析技术,获得了上海佘山台和崇明台1982年至1999年的地磁三分量之间的短周期谐波振幅比。经初步分析发现,在中强地震前后谐波振幅比的趋势性异常表现为下降-转折-恢复的过程,持续时间为1~3年。同时变化还具有由长周期(深部)向短周期(浅部)迁移的特征。

Abstract:

The amplitude ratios of short-period geomagnetic humorous wave among the three compnents from Sheshan and Chongming geomagnetic stations, Shanghai city, from 1982 to 1999 are obtained, with the technology of maximum-likelihood method (MLM).By preliminary analysis, the characteristics of long and medium term anomalous variation of the ratio in seismogenic process of moderate-strong earthquakes are declining,turning,then resuming,and the duration is about 1~3 years.Meanwhile the migration characteristics of the anomalous variation from long-period to short-period are found.