A magnitude 7.0 earthquake occurred in Lushan county, Sichuan province on April 20, 2013. According to the initial position of the earthquake and tectonic setting of Longmenshan fault system, based on the fault strike of Longmenshan and the preliminary focal mechanism, with the finite fault inversion method developed by Ji et al., we inverted the rupture process of Lushan earthquake using the teleseismic data.

  Figure 1  Rupture process of Lushan earthquake

The slip model is shown in figure 1. The main shock is dominated by a thrust fault mechanism with the focal depth of about 12.3km. The majority slip of the Lushan earthquake occurred in a relatively compact area with the peak slip of about 1.5 m; The majority slip is just in the hypocenter, a circular region with a radius of 10 kilometers, and the range is about 12~30km along dip. The main rupture duration is about 30s and the total of seismic moment of whole fault is 1.01×1019 Nm, but most of the energy released at the first 10s, and there are two small asperities after 18s. The map view of the rupture is shown in figure 2. Seeing from Waveform fitting (figure 3), the predicted waveforms are very similar to the actual records. So the results are very reliable.

Seeing from the inverted results, the surface rupture is not significant. Some surface rupture may occur in the range of 10km in the south of hypocenter, and the rupture mainly occurred in the range of 10km from the around the epicenter (103.0oE, 30.3oN). The location of this earthquake is just in the area of coulomb stress increase. Thus, we deduce that Wenchuan earthquake could promotes the occurrence of the Lushan earthquake.

　　  Figure 2  The map view of the slip model

 

　 Figure 3  Comparison of the teleseismic records and synthetic seismograms inverted by the slip model