中国地震昼夜分布和季节分布的统计分析

采用Morishita(森下)指数Iδ方法分析中国地震昼夜和季节分布特点,结果表明, M≥8地震的Iδ值分别为1.40和1.20,具有明显的丛集特点; M≥7地震Iδ值分别为1.03和1.12,为轻度丛集分布; M≥6地震Iδ值分别为0.94和1.02,为均匀分布和随机性分布; M≥5地震Iδ值分别为1.01和0.99,为随机分布和均匀分布。大地震丛集分布特点明显,中小地震随机分布和均匀分布特点明显。统计结果表明,中国内陆大地震主要集中在夜间发生。

The statistical analysis of the day and night and the season distribution of earthquakes in China

The authors apply the Morishita index IW to analyze the features of the daynigh and seasonal distribution of earthquakes in China. They found that: IW for earthquakes with M≥8 is 1.40 and 1.20, showing sw arm distribution; IW for earthquakes with M≥7 is 1.03 and 1.12, showing the feature of weakly swarming; IW for earthquakes with M≥6 is 0.94 and 1.02, distributed uniformly and sto chastically; IW for earthquakes with M≥5 is 1.01 and 0.99, distributed also uniformly and stochastically. The feature of swarming distribution for strong earthquakes is obvious, and the feature of uniform and stochastic distribution appears in small and moderate earthquakes. The statistical results indicate that occurrence of strong earthquakes in China's inland is mainly concentrated at night.