【摘要】 本文考察了1966年邢台大震后我国大陆上(只限东部地区,不包括台湾省)25个6级以上地震的余震序列,指出这些序列主震后三天内余震数量集中,衰减迅速,衰减规律与其后的余震有所区别;且这部分余震在时间上控制着以后余震的发展,在空间上已经大体勾划出余震区。根据这些特征,可把余震分为直接余震和间接余震两类。文中分析了直接余震的特点,统计了间接余震与直接余震的关系,并提出根据直接余震特点来估计间接余震,预报序列发展的想法。文中还初步探讨了直接余震和间接余震的物理机制。更多还原

【Abstract】 In this paper, aftershock sequences of 25 large earthquakes, M ≥ 6, which occurred in China continent since the M=7.2 Xingtai (邢台) earthquake of 1966, are analyzed. It is found that in these sequences a great number of aftershocks followed the main-shocks in two or three days. The frequencies of these aftershocks decreased rapidly and exhibited a time decay law different from that governing the later aftershocks. These early aftershocks governed the temporal variation of the later aftershocks and had already roughly sketched out the aftershock regions. Based on these characteristics, aftershocks are considered to be of two kinds, say direct aftershocks and indirect aftershocks. The characteristics of direct aftershocks are examined, and the relationships between indirect and indirect aftershocks are derived. A suggestion is made to estimate indirect aftershocks and predict the development of the aftershock sequences which rely on the direct aftershocks. Finally, a preliminary discussion is made on the machanism of the two kinds of aftershocks.更多还原