The Research Of Relationship Between Regional Geomagnetic Anomalous And The Earthquake

With the further research on seismo-magnetic relationship, it has already been an indisputable fact that the earthquake arises the abnormal change of geomagnetic filed. As the geomagnetic filed change process for earthquake is complex and with a weak repeatability of the rule currently there are many different theories and different research methods of all directions to explore the representation and correlation between the earthquake and geomagnetic abnormal change, such as conversion function, the minimum value displacement, spectral function etc.The paper is based on the geomagnetic vector data accumulated of the"2005.0 China geomagnetic chart"project, studies the repeated observation data after the Ms=5.7 JiangXi Jiujiang earthquake and the Ms=8.0 Wenchuan earthquake. It uses the spherical cap harmonic model, surface spline model and other means to calculate models, which gets the region abnormal geomagnetic lithosphere field models before and after the earthquake. Combining the seismogeologic and seismicity of the research area,the change characteristics of abnormal geomagnetic lithosphere field before and after the earthquake are studied.The research shows the following points: first, earthquake can influence the abnormal lithosphere geomagnetic field of epicenter, the representation is abnormal changes on one component or more components of the abnormal lithosphere geomagnetic field; second, there are some relativities between the epicenter and the zero-value-line in positive-negative abnormal boundary of the abnormal geomagnetic lithosphere field. Based on the previous research, a further study was made on the relativities between epicenter distribution and the zero-value-line of abnormal geomagnetic lithosphere field. We build the buffer zones with a 30km radius to the zero-value-line distribution of all components in the abnormal geomagnetic lithosphere field of north China seismic region, and statistical analysis is done on all the Ms≥4.0 earthquakes in the buffer zones since 1900.Statistical analysis results indicate, there are close relativities between the epicenters distributions of large earthquake above Ms7.0 and the geomagnetic declination, north component, east component and vertical component zero-value-line of the abnormal geomagnetic lithosphere field, epicenter distribution is more relate to the geomagnetic declination, the proportion is up to 83.3%. For the other magnitude earthquakes, the epicenter distribution and the zero-value-line positions of all components have their own characters. For example, Ms4.0 to Ms4.9 earthquake epicenters distributions are more relate to the magnetic inclination zero-value-line, while Ms5.0 to Ms5.9 earthquake epicenters distributions are more relate to the north component zero-value-line.