【摘要】 <正> 本文对我国56次5级以上地震的前兆资料做了初步的统计分析,并对地震前兆的一般特征、前兆异常的持续时间、前兆异常的地区差异性及前兆异常的强度与空间分布等几个问题进行了讨论,试图进一步描述地震前兆的特征,以期对地震前兆的深入研究起到一定的参考作用。更多还原

【Abstract】 The authors conduct a preliminary statistic analysis on about 600 items of selected precursory data obtained from 56 earthquakes (M>5) from 1962 through 1980, and make studies on the general features of seismic precursors, such as the time duration, the regional difference, the intensity and spacial distribution of the precursory anomalies. Therefore, the following understandings are obtained:1. The phenomena of seismic precursors have a property of diversity, especially, the precursors before strong shocks are very abundant.2. The seismic precursors have a property of continuity in the time distribution, and there is a rather definite proportion between precursory duration and seismic severity, which reflects the dependence between precursory anomalies and seismogenic process. The statistical formulas given in this paper are as follows:seismic precursors: Log T1=1.07+0.27 M other precursors: Log T2=0.17+0.32 M3. The precursory anomalies have marked various features in different stages of a seismogenic process, indicating that the precursory phenomina are featured with physically different genesis in different periods of source medium variations and under different stress conditions. 4.There is a relative stability and a certain proportional relation between the time progress and the morphology for various precursory anomalies,indicating a relative uni-fiability for various precursory mechanisms.Two sets of simple models for precursory progress are shown in this article.5.The precursory anomalies have obvious regional differences, and the analysis results demonstrate that the precursory duration, in North China is longer than that in Southwest China. It is suggested that seismic precursors behave differently under different tectonic conditions, stress levels, seismicity levels and earthquake categories. This is an important expression of individuality and complexity of earthquake precursors.6.The spatial distribution of precursory anomalies is related with the seismic severity, but the relation between the two is complex due to the inhomogeneity of the regional stress field and the mutual effects of different sources. So it is still difficult to give the definite relations between the seismic severity and the precursory distribution.7.The relationship between the intensity of precursors and the magnitude of earthquakes is more complicated. Because the intensity of precursors are not only constrained by the size of the focus, and the seismic severity, but also closely affected by the factors of tectonic conditions, stress staus, instrument function, observation conditions, environments of a observatory and so on. For this reason, it is difficult to discuss the regular features of the precursory intensity under the same conditions.The above-mentioned results are statistically significant, since they are established on the basis of extensive seismic case histories and rich precursory data. Thus these understandings may have generality, providing a valuable reference for the practical work of earthquake prediction research.更多还原