关键词: 华北, 地震断层面解, 应力场

Abstract: Based on the first motion data of more than 4000 small earthquakes from 115 seismic station, the stress fields of small earthquakes in the North China were determined by the method by which compositive fault plane solution is solved from first motion data of p wave. It is suggested that on the same seism otectonic zone, the directions of principal compressional stress of fault plane solution of small earthquakes are consistent. Before and after a large earthquake, regional stress field may change. The dynamic variation characteristics of stress field of small earthquakes before Heze 5.9 earthquake of 1981 were analysed. It is suggested that regional stress field variation with the occurrence of large earthquakes is the base for forming complicated and multi-level seismic activity. Finally, the stress field characteristics of the North China and the areas with high stress background are discussed.

Key words: North China, Earthquake, Fault plane solution, Stress field