Abstract: Using the isoseismal data of greater than M_S6.5 since 1985 and aftershocks energy field, we base on particle swarm algorithm to create the smallest area ellipse which includes all the main excitation aftershocks 6 hours after the quake as the estimated magistoseismic area. We statistically analyse the distances among the estimated epicenter, the micro- and macro- epicenters of different fracture types in each period, as well as the angle among orientations of the estimate influence field, fault strike and direction of meizoseismal region of different fracture types in each period. The results show that aftershock particle swarm algorithm effectively narrows the deviations of micro- and macro- epicenters. The optimal estimation epicenters of strike-slip type earthquake appear 2 hours after the quake. The optimal estimated epicenters of dip-slip type appear 6 hours after the quake.The study reveals that the mean angle between the direction and orientation of meizoseismal region of the estimated influence field 2 hours after the quake is less than the mean angle of fault strike and orientation of meizoseismal area. The optimal estimation orientations of strike-slip type earthquake appear 1 hour after the quake, while the optimal estimated orientations of dip-slip type appear 2 hours after the quake.

Key words: Aftershocks energy field, Particle swarm algorithm, Magistoseismic area, Macroscopic epicenter