Using earthquake catalog from 1975 to April 2010 recorded by Shandong Earthquake Net, the minimum magnitude of completeness in the study area is determined. Then the after shocks are eliminated from catalog in Shandong Province and its neighboring areas. The distribution of monthly number for small earthquakes after pretreatment and the function relationship between the monthly number and the accumulative frequency of the monthly number are tested. The results show that the distribution of the monthly number agrees with normal distribution, the relationship between the monthly number and the accumulative frequency resembles the G-R law. The changes of Kurtosis, Skewness, value and value of the monthly frequency with time are analyzed. It is shown that before the 13 earthquakes with ML≥5. 0 in Shandong Province and its neighboring areas, the distribution of the small earthquake monthly number changes up and down obviously.%采用1975-2010年4月山东区域地震台网地震目录,确定研究区地震震级下限,剔除余震,对预处理后的小震活动月频次进行Kolmogorov-Smirnov分布检验,及小震月频次(X)与累计次数之间的函数拟合.结果表明,山东地区小震活动月频次符合正态分布,月频次与其累计次数之间存在类似G-R关系.对小震月频次分布的峰度Ku、偏度Sk、Cv值以及bm值随时间的变化进行分析,结果表明,研究区内13次ML≥5.0地震前,月频次分布表现出明显起伏变化.
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