Abstract: The activity of microearthquake swarm is limited in an area of coal mine. There are two types of microearthquakes: one is the microearthquakes the first motion of which distributed in a quadrant belongs to double-couple sliding focal mechanism, with S wave energy higher than P wave energy. The other is the extreme-low microearthquakes, with P wave energy higher than S wave energy. The focal mechanisms are the nondouble-couple. Both they are coal-mine tremors, which can not be considered as an evidence for the northern extension of the Xiannushan fault.

Key words: Yangtze Gorges, Yanguan, Microearthquake swarm, Near-field observation, Coal-mine tremors

摘要： 盐关微地震群的活动局限在矿区内,地震都是微震和极微震。地震分两种类型:一种是微震活动,初动呈象限分布的双力偶滑动型震源机制,S波能量高于P波能量。另一种是极微震,初动几乎全负,P波能量高于S波能量,呈非双力偶的张破裂向内爆炸型的震源机制。两种地震的成因都是采矿诱发地震,不能做为仙女山断层向北延伸的证据。

关键词: 长江三峡, 盐关, 微震群, 近场观测, 矿山地震