Analysis on the seismogenic fault of Lushan M_S7.0 earthquake by using epicenters of its aftershocks

The absolute earthquake location method (Hypo71) was used to locate micro- and small-aftershocks of 2013 M_S7.0 Lushan earthquake，which were recorded by 29 stations around the mainshock region for more than one year. Finally we got the epicentral location of about 1960 aftershocks. Results reveal that aftershocks laterally distribute along Shuangshi-Dachuan branch fault and its surrounding area，and vertically concentrate on two intersecting aftershock belts in depth range of ~5—20 km. One aftershock belt dips towards NW，and its dip angle becomes steeper at depth about 12 km. This belt’s extrapolation coincides with the buried fault between Shuangshi-Dachuan branch fault and Xinkaidian fault at surface. The other aftershock belt dips towards SE. Its extrapolation is close to Shuangshi-Dachuan fault at surface; however，its dipping direction is opposite to that of Shuangshi-Dachuan fault. The hypocenter of the Lushan main shock locates close to intersect of the two aftershock belts. Two nodal planes of focal mechanism of the main shock correspond well to the geometry of the two aftershock belts，respectively. This seismogenic structural feature implies that Lushan earthquake probably is resulted from simultaneous movement of two faults along the two aftershock belts.