龙门山断裂带地震活动的月尺度频度分布特征

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M_L≥3.0地震活动半年频度符合正态分布, 而2000年以来M_L≥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M_S5.0地震前和汶川M_S8.0地震前, 龙门山断裂带M_L≥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M_L≥2.0地震活动月频度分布出现异常变化。

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

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 M_L≥3.0 earthquakes occurred since 1970 agrees with normal distribution, and that of the monthly number for M_L≥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 M_S5.0 in September and November of 1999 and the Wenchuan M_S8.0 earthquake, the distribution of the semi-annual number for M_L≥3.0 earthquakes changes abnormally, and the distribution of the monthly number for M_L≥2.0 earthquakes changes obviously prior to the Wenchuan M_S8.0 earthquake.