地震活动周期表及其预报意义

本文以地震在空间上的区域性位移,作为时间上的分幕标志,提出了一种与作M-t图不同的周期表式的分期方法,按照这种方法,用华北、华南和西部特定地区近二千年的较大地震排列的地震活动周期表,周而复始地重现时、空、强特征相似的九个地震幕。其中华南和华北地区每个周期的最大地震——周期主震(简称主震),都排在位于同一横栏的主震幕内。在此基础上,研究了我国大陆东部上述两个强震区地震活动的周期特征与相互关系,阐明了周期前震(简称前震)的识别方法和前兆意义,得出未来数百年乃至更长时期内,华北不可能发生大于7.8级地震的结论。最后用地震震源区雪崩式不稳定裂隙形成模式,对周期成因作了解释。

THE PERIODIC TABLE OF SEISMICITY AND ITS APPLICATION TO EARTHQUAKE PREDICTION

In this paper, the episodes of seismicity are determined from the spatialregional migration of earthquakes. A method to divide periodically thestages of seismicity is proposed, which differs from the M-t diagram. Inthis way, the periodic table of seismicity of larger earthquakes whichoccurred during the past two thousand years in the given regions of NorthChina, South China and West China can be made. In this table nine episodesof seismicity can be recognized, which have similar characters in times ofoccurrence, spatial distributions and magnitudes. The largest earthquakesat each period in North China and South China, which called periodicmainshocks, are listed on the same horizontal columns of the table. Fromthis, the periodic characters of seismicity in the two regions and theircorrelations are studied, the identification of periodic foreshocks and theirprecursory implications are expounded. It is concluded that earthquakeswith M>7.8 may not occur within the coming hundreds of years or morein North China. Finally, the formation of seismicity periods is explainedby the forming mode of unstable cracks in the earthquake hypocenter region.