REGIONAL EARTHQUAKE SWARMS AND THE 1976 TANGSHAN EARTHQUAKE

A regional earthquake swarm is defined as a series of earthquake swarm events occurred under a similar geological environment during the seismogenetic stage of a major earthquake. In analysing the temporal and spatial development of regional earthquake swarms in North China since 1967, it may be seen that about 5 years before the Tangshan Earthquake of 1976, a ring-like region of earthquake swarm quiescence or gap appears around the epicenteral area, outside which is a ring-like belt of relatively active earthquake swarms. In this belt of earthquake swarm activity, certain connection with the seismogenetic process of the Tangshan Earthquake could be observed by the gradual increase of earthquake swarms in steps and at the turning points of different stages, it becomes highly intense. At the same time, within a still vast surrounding area, regional earthquake swarms migrate alternatlly between the farther and nearer areas.Before and after the Tangshan Earthquake, such temporal and spatial distribution of regional earthquake swarms, correlate also with the change of other indications of seismic activity to a certain extent. They combine together may constitute the anomalous features of the far and near surounding regions before the great earthquake. It is therefore supposed that study of the characteristics of the temporal and spatial distribution of regional earthquake swarms might possibly give some clue to the prediction of the earthquake.