GEOMAGNETIC LOW-POINT DISPLACEMENT PHENOMENA AND THEIR RELATION TO EARTHQUAKES
DING JIANHAI, HUANG XUEXIANG, XING RUYING, AND ZHANG SHULAN(Centre for Analysis and Prediction, State Seismological Bureau)
On the basis of data recorded for many years by the network of geomagnetic observatories in China, the anomalous features of appearance time of the minima of diurnal variations (i.e. low-point time) of the geomagnetic vertical component and the variation of their spatial distribution (i e. phenomena of low-point displacement) have been studied. Such rare phenomena of geomagnetic anomalies are an objective reality, being well-correlated with the occurrence of earthquakes. It has been found that most earthquakes occur in the vicinity of the boundary line of sudden change of the low-point displacement and generally within four days before or after the 27th or 41st day counting from the day of appearance of the anomaly.The low-point displacement is one of the complicated geophysical phenomena which is affected by many factors and its mechanism is still under study.