龙门山断裂带地震活动的月尺度频度分布特征

Distribution Characteristics of the Month-scale Number for Earthquakes Occurred on the Longmenshan Fault

利用Kolmogorov-Smirnov分布检验法,对龙门山断裂带地震活动的月尺度频度分布进行了检验。结果表明,1970年以来ML≥3.0地震活动半年频度符合正态分布,而2000年以来ML≥2.0级地震活动月频度符合泊松分布。对半年频度和月频度分布随时间的变化做了进一步分析,发现在1999年9月、11月四川绵竹2次MS5.0地震前和汶川MS8.0地震前,龙门山断裂带ML≥3.0地震活动半年频度分布均表现出明显的异常变化,在汶川地震前ML≥2.0地震活动月频度分布出现异常变化。

The Kolmogorov-Smirnov test is used in this paper to test the distribution of month-scale number of small earthquakes occurred in the Longmenshan fault,Sichuan,China.The results show that the distribution of the semi-anual number for ML≥3.0 earthquakes occurred since 1970 agrees with normal distribution,and that of the monthly number for ML≥2.0 earthquakes occurred since 2000 agrees with the Possion distribution.Analyzing further the changes of distributions of the monthly number and the semi-anual number with time,it is found that before the two earthquakes with MS5.0 in September and November of 1999 and the Wenchuan MS8.0 earthquake,the distribution of the semi-annual number for ML≥3.0 earthquakes changes abnormally,and the distribution of the monthly number for ML≥2.0 earthquakes changes obviously prior to the Wenchuan MS8.0 earthquake.