Seismogenic structure identification of the 2013 Eryuan M_S5.5 and M_S5.0 earthquake sequence

The Eryuan M_S5.5 and M_S5.0 earthquake sequence are relocated by using absolute location (Hypo2000) and double-difference earthquake location (HypoDD) methods. The results show that the dominant direction of relocated aftershocks concentrated at 160°. Focal mechanisms of the M_S5.5 and M_S5.0 earthquakes are inverted by CAP method. The inversion result shows that the strike angles of the nodal plane Ⅱ were 158° and 157°, respectively, which are consistent with dominant distribution direction of aftershocks. Field survey suggests that the major axis of the meizoseismal region was also in NW direction. The above three directions were consistent with the NNW strike orientation of Weixi--Qiaohou fault, which can be considered as the seismogenic structure of the Eryuan earthquake sequence. Focal mechanisms of the sequence indicate that different focal dislocations and different orientations of principal compression stresses, may have relationship with the complex regional structural stress field of Weixi--Qiaohou fault.