北部湾6．1、6．2级地震的前兆异常

PRECURSOR ANOMALY OF THE M_s6.1 AND M_s6.2 EARTHQUAKES IN BEIBUWAN

通过对北部湾６．１、６．２级地震前的震兆分析，认为地震是在区域地震活动出现中期异常背景的情况下发生的。前兆观测的趋势异常较为突出，但短临异常极少。地震活动性和前兆观测手段的趋势异常变化具有稳定性和准同步性，反映了震前区域应力场的变化。

By analyzing the earthquake precursor anomalies that presented before the Ms6.1 and Ms6.2 earthquakes occurred in the gulf of Beibuwan,it is considered that the earthquake sequence occurred against the background of the local seismicity of medium-term anomaly.The tendency anomalies on precursor observation are marked but the short-impending anomalies are less;and the former have stability and quasi-simultaneity with seismicity.The variation of the regional stress field before earthquake is the main representation.