Abstract: Based on calculation results of 11 parameters of 294 aftershock sequences with mainshock magnitude greater than or equal to 5.0 occurred in Chin′s mainland, Fisher discriminant functions in different period since the mainshock, taking different sequence parameters as the independent variables, have been established, which could be used for synthetical judgment of sequence types. Besides routine sequence parameters, the rake of the mainshock has also been introduced into the Fisher discriminant functions to make them containing messages of fracture mode of the mainshock. Statistical results show that the accurate ratio of discriminant on types of aftershock sequences increases with the increment of time period since the mainshock and there is something different for different sequence types. The accurate ratio is greater than 0.93 for isolated earthquake type, is from 0.73 to 0.95 for mainshock-aftershock type and is from 0.57 to 0.86 for multiple mainshock type. All of them are highly greater than stochastic corresponding ratio, 0.33, and therefore its forecasting score should be positive.

Key words: Synthetical judgment of types of aftershock sequences, Fisher discriminant function, Isolated earthquake type, Mainshock-aftershock type, Multiple mainshock type, Sequence parameters