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为了从区域地震的尾波中提取强震的前兆信息,我们以江苏溧阳1979年7月9日6.0级地震前后的一系列马鞍山爆破资料为基础,探讨了三个固定台站上的记录尾波,包括走时持续时间特性、频率随时间的变化特性及振幅衰减特性等的变化情况。其结果表明这些特性的变化与直达波的传播途径无关。我们又进一步以天然地震的资料为对象,讨论了尾波振幅衰减特性α的变化情况和尾波频率随时间的变化特性。天然地震的资料分两类,一是用内部(强震震源区)发生的小震资料,二是用邻区(强震震源区以外)发生的中小震资料。两类地震均由同一组台站记录。结果表明,物理参量特性的变化与途径无关,这些参量的变化是一致的,天然震源、人工震源和实验三者的尾波参量变化吻合良好。因此,尾波特征参量携带强震前兆信息是可能的。在以上参变量的基础上,提出一个品质因素相对变化趋势的简易估讨。
In order to extract the precursory information of strong earthquakes from the coda of the regional earthquake, based on a series of Ma’anshan blasting data before and after the 6.0 magnitude earthquake on July 9, 1979, in Liyang, Jiangsu Province, we discussed the recording coda on three fixed stations , Including the duration of travel time characteristics, the frequency of changes with the characteristics of time and amplitude attenuation characteristics of changes. The results show that these characteristics are not related to the direct wave propagation. Based on the data of natural earthquakes, we further discuss the variation of coda amplitude attenuation characteristic α and the variation of coda frequency with time. There are two types of information on natural earthquakes. One is the use of small earthquakes in the interior (strong earthquakes) and the second is the use of small and medium earthquakes in the adjacent areas (other than the strong earthquakes). Both types of earthquakes are recorded by the same group of stations. The results show that the changes of physical parameters have nothing to do with the way, and the changes of these parameters are consistent. The variation of the coda parameters of the natural source, artificial source and experiment are in good agreement. Therefore, it is possible that the coda parameter carries the information of precursors of strong earthquakes. Based on the above variables, a simple estimation of the relative change trend of quality factor is proposed.