Source rupture process of Yutian, Xinjiang, M_S7.3 earthquake on 21 March 2008

This paper studied the source rupture process of the M_S7.3 earthquake occurred in Yutian, Xinjiang on March 21, 2008, by using digital teleseismic P wave seismograms recorded by long-period seismograph stations of the Global Seismic Network. Then we got the rupture pattern of the earthquake and analyzed the relationship between distribution of aftershocks and fault slip of the main shock. The rupture process inversion result shows that the co-seismic deformation affected a big area (about 100 km×20 km) and that the total rupture duration is about 40 s. One large rupture behavior on the seismogenic fault almost constitutes the whole rupture process of this earthquake； the scalar moment tensor is 4.23×10¹⁹ N·m and its moment magnitude is M_W7.02. The distribution of static slip on the main-shock fault shows that the rupture zone is dominated by sinistral strike-slip normal motion， suggesting a bilateral rupture process. The maximum slip is 151 cm, which is located at the surface above the initial rupture point. The projection results of the relocated aftershocks on the main shock fault plane show that more than 80% of the aftershocks with 4.0≤M_L≤4.9 and all of M_L≥5.0 aftershocks occurred near the initial rupture point and its southwestern region， where the sliding displacement resulted from the main shock reduces rapidly. It may reflect the heterogeneity of fault medium strength in the source region.