Abstract: The Jiujiang-Ruichang earthquake sequence (M_S5.7), occurred in Jiujiang, Jiangxi Province, on November 26, 2005 is relocated by the main shock location method using the data of arrival time of P, S and Pn waves recorded by Nanchang regional digital seismic station networks and temporary seismic stations, and the rupture process is analyzed. The epicenters of aftershocks of this sequence are distributed along a direction of N37°W. This consists with the N35°W node plane of focal mechanism of the mainshock determined from the seismic wave data by the Harvard university, also consists with the NW-striking Yangjishan-Wushan-Tongjiang fault, and the epicenter is located at the southeast end of the fault. The rupture extended before 19:00, 30, Nov 2005, and then remained relatively stable. The main shock located on the northwestern margin of the region where aftershocks distributed, it seems that this earthquake ruptures unilaterally towards the southeast. The focal depth of after shocks increases in four hours after the main shock, and then remains stable at a depth of about 15 km gradually. The process of rupture can be divided into the following two phases: Phase 1, from the main shock to 16:22:0.8, 26, Nov 2005 lasting for about 7.54 hours. The size of rupture zone is around 13.8 km.The mean velocity of rupture is approximately 50.8 cm/sec. Phase 2, from 11:35:21.7, 29, Nov 2005 to 19:57:58, 30, Nov 2005 lasting for about 32.4 hours. The size of rupture zone reaches to 17.9 km. The mean velocity of rupture is approximately 15.4 cm/sec. The rupture totally propagates for a distance of 31.7 km with a mean velocity of 22 cm/sec.The velocity of the former phase is obviously greater than that of the latter one, and the rupture is retardatory.

Key words: The Jiujiang-Ruichang earthquake, Main shock location method, Process of rupture