广西陆川小震群特征的初步研究

一九七七年冬,广西陆川县乌石附近发生一起小震群。这次震群活动从77年12月开始,到78年7月结束,共发生小震和微震880余次,释放的地震波总能量为1.3×10~(17)尔格。广西是少震区,地处桂东南的陆川县地震活动水平稍高一些。据史料记载,陆川周围八个县自明朝以来六百年间,共发生五级以上破坏性地震五次。陆川近年的小震活动平均每年

PRELIMINARY STUDY OF CHARACTERISTICS OF THE SMALL EARTHQUAKE SWARMS IN THE LUCHUAN OF GUANGXI

In this paper the main characteristics of the small earthquake swar-ms in the Luchuan have been investigated by comparing with the fore-shocks of the Haicheng earthquake (M_s=7.3).It is found that seis-mic activity process of the small earthquake swarms may be divided into two stages which are distinguished by maximum earthquake.The first stage is basically in agreement with foreshocks.There are clear differences between the late stage sequence and the foreshocks in manner of frequency attenuation,the rate of strain release and the stationary of focal mechanism.It is believed that these differences are criterion of distinguishing foreshocks from small earthquake swarms.It is shown that the messages of judging small earthquake swarms or foreshocks can be found by comparing small earthquake swarms with foreshocks.These messages are useful in earthquake prediction.