北部湾6.1,6.2级地震序列的环境应力场

Ambient stress field of the M 6 1 and 6 2 earthquakes sequence in Beibuwan

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。

In this paper, the ambient shear stress values of the middle and the small earthquakes around the M 6 1 and 6 2 earthquakes in Beibuwan are determined by using the method of the P-wave first impulse half period. Therefore, the ambient stress field characteristics in Beibuwan earthquakes sequence are analyzed. The results show that the ambient shear stress average value is about 18 MPa after the M 6 1 earthquake in Beibuwan ,and the value decrease rapidly to 6 0 MPa after the M 6 2 and two M 5 0 earthquakes. Based on these, the tendency of seismic activity in the future in Beibuwan is estimated