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本文对于1970年7月到1983年12月四川地区16组5级以上地震前,分别统计Δ≤30km,30km<Δ≤50km,50km<Δ≤100km范围内(对于7级以上地震另加100km<ΔA≤150km和150hm<Δ≤200km)弱震活动逐月频度的变化。其中15组震前弱震活动出现较明显的变化。 临震前震中附近弱震活动频度变化的主要特征,大体可以分为两类:一种在临震前一段时间里,震中附近以平静或弱震活动减弱为主要特征。另一种在临震前,震中附近弱震活动增强。如果观察的时间尺度放长一点,可以发现,大多经历过起伏。凡是有较长观测资料的,一般都有增强一减弱,或增强一减弱一增强(有的再稍下降)的过程。 本文借鉴陈顒、耿乃光、姚孝新和马瑾等岩石破裂实验研究成果,对上述强震前弱震活动频度变化特征进行了初步的定性解释。
In this paper, before the earthquakes of magnitude 16 or above M5 in Sichuan Province from July 1970 to December 1983, respectively, within the range of Δ≤30km, 30km <Δ≤50km, 50km <Δ≤100km (for the magnitude 7 earthquakes plus 100km < ΔA ≤ 150km and 150hm <Δ≤200km). Among them, 15 groups of weak earthquakes occurred more obvious changes. The main features of the frequency of the earthquakes near the epicenter before the quake epicenters can be divided into two types: one is the period before the epicenter, the epicenter near the epicenter of weak or weak earthquake activity as the main feature weakened. The other before the epicenter, weak earthquakes near the epicenter activity increased. If you observe a longer time scale, you can see that most have experienced ups and downs. For those who have long observation data, there is generally a process of increasing or decreasing, or increasing or decreasing (and then decreasing slightly). Based on the research results of rock fracture experiments such as Chen Huan, Geng Nai-guang, Yao Xiao-xin and Ma Jin, the paper qualitatively explained the characteristics of the frequency of the weak earthquakes before the strong earthquakes.