MS8.0 earthquake, with cutoff magnitude ML3.0. The declustering of the original earthquake catalogue(cat_chundian.txt) utilizes the space-time ETAS model developed by zhuang (2002),a probability file (probs.dat)obtained. In the second column of the prob.dat, the probability (0~1) of each earthquake as an independent earthquake/background earthquake is given. So, you can the background earthquake events according to your own defined criterion whether its probabilityis larger than a prescribed threshold value(for example, 0.5),or using the ‘probability weighted’ catalogue, that is, the probability as the weight of a certain physical quantity corresponding to each earthquake event (JiangWu, 2011; 2013).  Zhuang, J., Ogata, Y.Vere-Jones, D. (2002). Stochastic declustering of space-time earthquake occurrences. J. Amer. Stat. Assoc., 97: 369~380.  Jiang, C. S.Wu, Z. L. (2011). PI forecast withwithout de-clustering: an experiment for the Sichuan-Yunnan region. Nat. Hazards Earth Syst. Sci., 11(3): 697~706, doi: 10.5194/nhess-11-697-2011.  Jiang, C. S.Wu, Z. L. (2013). Intermediate-term medium-range precursory accelerating seismicity priori to the May 12, 2008, Wenchuan earthquake. Pure appl. Geophys., 170(1): 209~219, doi: 10.1007/s00024-011-0413-0.