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

摘要： 本文采用地震学P 波初动资料求解小地震综合断层面解方法,使用115个地震台的4000余个小地震初动资料,测定了华北地区近年小震应力场。提出在同一地震构造带上,小震断层面解的主压应力方向具有一致性。大地震前、后区域应力场可能发生变化。分析了1981年菏泽5.9级地震前小震应力场的动态变化特征等。指出随着大地震的发生,区域应力场发生变化是形成复杂的多层次的地震活动性的基础。最后,对华北地区应力场特征及高应力背景区等做了讨论。

关键词: 华北, 地震断层面解, 应力场