Analysis of Anomalous Characteristics of Geomagnetic Change before and after Eryuan M5.5 Earthquake

In this paper,the author uses two kinds of mobile geomagnetic data before and after Eryuan M5.5 earthquake on Mar.3,2013,to analyze the characteristics of anomalous change in total geomagnetic intensity and geomagnetic vectors.( 1) The observation results of total geomagnetic intensity show that before the Eryuan M5.5 earthquake,in the surveying area,for the successive surveying periods,the positive zones were approximately equal to the negative ones.Then,the whole surveying area gradually evolved into the positive one,and the high gradient belt appeared,which evolved into the high-gradient zone containing positive and negative values.The epicenter of the Eryuan M5.5 earthquake was located at the edge of positive high-gradient zone.After the earthquake occurred,the high gradient belt containing the positive and negative values was located far from the epicenter,and the positive and negative areas became balanced again.( 2) The observed geomagnetic vector show that before the Eryuan M5.5 earthquake,the horizontal and vertical vectors of lithosphere magnetic field had significant variations in earthquake area.The zero lines of the declination,inclination and total intensity all crossed near the earthquake area.After the earthquake occurred,in the earthquake area,the significant variations of these vectors disappeared,and the high-gradient zone containing the positive and negative values gradually disappeared.The inclination and total intensity also disappeared,and the zero line of the declination did not appear in the earthquake area.