宜宾,沐川4次5级地震前后的地震活动特征

1993年至1996年四川宜宾、沐川地区发生了4次5级地震。给出了这4次5级地震的基本参数，震源机制解和地震活动性分析结果。4次5级地震前的小震活动特征表现为成团成丛，震群活动，频度变化和低b值异常等，但异常出现情况在4次5级地震前有明显差异。4次5级地震的余震分布区较窄。计算了4次5级地震的10种序列参数．并与1970年至1973年马边、雷波地震序列参数类比，出现明显异常的均在震群序列的首进序列中表现显著．有一定的震兆意义。最后对四川盆地南缘附近地区未来地震势态进行了初步推论。

SEISMIC ACTIVE CHARACTERISTICS FROM THE PRE-EARTHQUAKES AND POST-EARTHQUAKES OCCERED IN YIBIN-MUCHUAN

There were 4 earthquakes (M>= 5.0) occured in the region of Yibin-Muchuan from 1993 to 1996. Basic earthquake parameters, focal mechanism solutions and seismic activities for these earthquakes are put forward. The main characteristics of these earthquakes show that small earth quakes happened in the form of group; Earthquake cluster activities, frequency changes and b values are anomaly but the anomalies are not same. Compared with the anomalies of earthquake series of Yibin--Leibo from 1970 to 1973, the anomalies of Yibin-Muchuan earthquakes are mainlyin the first swarm earthquakes. This is very useful for the prediction of earthquake. At the sametime the seismic tendency of south part of Sichuan basin is also put forward.