ANALYSIS ON BACHU-JIASHI M_S 6.8 EARTHQUAKE SEQUENCE AND SEISMIC SITUATION

An earthquake of M-S 6.8 occurred between the Bachi county and Jiashi county of Xinjiang Uygur Autonomous Region on Feb. 24, 2003. Its epicenter locates in the southeast of the seismic region in Jiashi where 9 events of M-S≥6 occurred from 1997 to 1998. The aftershocks distributed along NW direction, identical with the direction of the long axis of meizoseismal area. The maximal magnitude of aftershocks was M-S 5.8 up to Apr.15,2003. The focal mechanism solution shows that the type of focal dislocation is dip-slip reverse fault, and the main rupture surface may be the near-NS-direction nodal plane, with the NWW-direction P axis azimuth of main compressive stress. The earthquake of M-S 6.8 occurred in the 2003 forecasted danger regions of M-S 6-7 earthquakes. According to the seismic situation, the Prediction Center of Xinjiang Seismological Bureau put forward the following suggestion before the shock in February, 2003: it is probable to occur moderate-strong event in the two key seismic danger regions of Xinjiang during the February of 2003 or longer. The suggestion was proved later.