Application of PP cluster method in the earthquake swarm analysis

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Application of PP cluster method in the earthquake swarm analysis

Taking 98 earthquake swarms occurred in Xinjiang during 1972-1992 as examples,and & parameters (e. g. U,K, p and the maximum energy rate of earthquake sequence etc.)as the characteristic quantity in earthquakeswarrn pattern observation, the author made a numerical cluster by PP cluster analysis method. The results indicate that those 98 earthquake swarms can be divided into 4 types as A, B, C, D. There are 24 swarms in typeA, among which strong shocks occur nearby after 18 swarms in the coming 12 months.Among 61 earthquakeswarms in type C and D, strong shocks occur nearby only after 7 swarms in the same time period. The occurrence rate of strong shocks only takes 3/11 in type B swarms. No doubt, PP cluster analysis method can effectively distinguish precursory swarms (type A) and correctly judge the short-and medium-term trend in the areaaround the earthquake swarms. Being a new and useful classification, PP cluster provides a wide application tothe identification of the type of earthquake sequence.