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本文分析了1981年2～5月在广东海丰地区发生的为数达1800个小震的震群特征。震群由三个子群组成,均出现典型的前、主、余序列。震源投影图显示:震群集结于莲花山断裂带南沿的F_1断层沿伸线两侧,说明F_1断层是震群的发震断层;震源机制解结果说明震源破裂方式是近东西向应力场作用下北东走向断裂面的右旋错动。进而提出“闭锁域”模式来解释海丰震群震源区破裂发展的全过程。最后,简要叙述了震群发生过程中根据震群特征作出的无强震预报,及由此得到的良好社会经济效果。
This paper analyzes the swarm characteristics of 1,800 small earthquakes that occurred in Haifeng, Guangdong, from February to May, 1981. The earthquake swarm consists of three subgroups, all of which have typical front, main and residual sequences. The projection maps show that the earthquake swarms converge on both sides of the extension along the F_1 fault along the southern edge of the Lianhuashan fault zone, indicating that the F_1 fault is a seismogenic fault of the swarm. The focal mechanism solution shows that the source rupture mode is near-EW stress field The northeast to the fault surface dextral movement. Then the “closed-field” mode is proposed to explain the whole process of the rupture in the source area of Haifeng earthquake group. Finally, a brief description of the strong earthquake prediction based on the characteristics of the swarm during the occurrence of the swarm and the good socioeconomic results obtained therefrom is given.