地震类型与震源机制

本文分析了我国14次地震序列的主要地震断层面解和错动性质。结果表明:震群型序列中较强地震的断层面解基本相同,其错动性质或相同或互为共轭错动;双震型序列中两次主震的断层面解明显的不同,其错动性质也有差异,它们的较大余震断层面解分别相似于两次主震的断层面解。在这种情况中,有意义的是第一主震至第二主震中间均有与第二主震断层面解相似的地震发生;主震型序列中早期较强余震断层面解多与主震相同,也有少数较杂乱,总的看来这种一致性劣于震群型序列。最后讨论了不同震型地震断层面解的差异在实用中的意义。

TYPES OF EARTHQUAKES AND FOCAL MECHANISM

The fault-plane solutions of some large earthquakes sequences that occurred in China are analysed. The results can be summarized as follow: 1. The P-wave nodal planes solutions of the stronger earthquakes in an earthquake swarm are essentially the same. Their parameters of the fault planes are the same or conjugate to each other. 2. In the twin-quake tipe earthquake sequence, there are two sets of noticeably different fault plane solutions which correspond respectively with those of the two main shocks. It is noticed that the fault plane solutions of some earthquakes which occurred during the interval between the occurrences of the first and second main shocks, are the same as those of the second main shock. 3. For the main shock-after shock sequances, the fault plane solutions of strong after-shocks in earlier stage of the sequence are essentially the same as those of the main shock, but in the later stage, noticeable changes may take place. Finally, the use of focal mechanism to discriminate earthquake tipes are discussed.