南黄海6.4级地震的短临前兆及其震源过程

研究了1996年11月9日南黄海6．4级地震前地震时空分布、应变能释放的异常变化,发现震前地震活动时空分布的异常变化清楚地反映出南黄海6．4级地震的震源过程一“三级跳跃”模式。即早期地震活动增强,形成大的孕震空区;中期在上述背景上地震活动再次向外围扩散并收缩,地震活动逐渐减弱,晚期在孕震空区内形成临震空区和临震小震条带。孕震空区缩小;晚期地震活动出现短期平静（4个月无≥2．0级地震）,显示临震“平静”异常,由R（t）图可以对64级地震的发震时间进行预测。

SHORT-TERM AND IMPENDING PRECURSORY AND SOURCE PROCESS OF THE SOUTH YELLOW SEA ML 6. 4 EARTHQUAKE

The anomalous spatial and temporal distribution of the seismic activity. earthquake strainenergy release before the occurrence of the SYSML6. 4 earthquake on November, 9, 1996 hasbeen studied in this paper. The results show that the anomalous variation of the spatial andtemporal distribution of seismicity fully reflected the source process of the SYS ML6. 4 earthquake "three stage jump" pattern. During the early stage, a broad seismic gap emerged whilethe earthquake activity becomes stronger; in the middle stage, the seismicity extrended outward, then retreated and turned weaker; in the late stage, the impending seismic gap and thesmall earthquake belt appeared. A short quiet period (no M>2 earthquakes in 4 months ), namely, the impending earthquake "quiet" abnormality occurred in this stage. The occurrencetime could be predicted by utilizing the R(t) diagram of the SYS M.6' 4 earthquske.