应用 Ｐ 波初动半周期直接测定环境剪应力值的方法， 测定了北部湾６１ ，６２ 级地震前后中小地震的环境剪应力值τ０ ， 由此分析了北部湾地震过程的环境应力场特征。结果表明， 北部湾６１ 级地震后平均剪应力值较高， 达１８ Ｍ Ｐａ 左右； ６２ 级地震及两次５ 级余震后剪应力值下降很快， 降至目前的６ Ｍ Ｐａ 左右。在此基础上对北部湾的地震活动趋势作了初步分析 The environmental shear stress values ​​of medium and small earthquakes before and after Beidou Bay 61 and 6 2 earthquakes were measured by the method of direct measurement of environmental shear stress values ​​during the first half cycle of P wave. The environmental stress of Beibuwan seismic process was analyzed Field characteristics. The results show that the average shear stress value of Beibuwan 61 earthquake is high, which is about 18 M Pa. The shear stress decreases sharply after 62 earthquakes and two aftershocks of 5 aftershocks to 6 M Pa about. Based on this, the trend of seismic activity in Beibu Bay is analyzed