THE EFFECT OF THE TANGSHAN EARTHQUAKE ON THE GEOMAGNETIC TOTAL FIELD IN THE PEKING AREA

In the area west (about 140×200 km) of the epicenter of the Tangshan earthquake of magnitude 7.8, repeated measurements of the geomagnetic total field, once each month, have been made since February 1975, using the proton precession magnetometers, at 108 pairs of points (Fig. 1). In analysing the data thus obtained, it is found that anomalous variations of the geomagnetic total field within the entire area are relatively slight. Higher density in the distribution of surveyed sites and more repetitions of measurements during a relatively longer period of time before and after the earthquake, make it possible to do statistical analysis with regard to time and space, so as to eliminate disturbances from all kinds of sources more effectively. From February 1975 to February 1977, the statistical results of 25 repeated measurements made at all the sites show that there exists certain correlation between the geomagnetic statistical parameters and the Tangshan earthquake, both in time and space, thus providing interesting results for the study of seismo-magnetic effect.