Seismogenic structure of the 20 April 2014 Huoshan M_S4.3 earthquake in Auhui region

A M_S4.3 earthquake occurred in Huoshan region，Anhui Province on 20 April 2014，which is the largest earthquake in Huoshan region in recent 41 years. Several inversion methods such as Hypo2000，CAP and PTD methods，were used to get the focal depth of this earthquake, and the result shows the focal depth is about 8 km. Based on the local broadband waveform data of available stations in Anhui Province and its adjacent province regional seismic networks，we relocated precisely the main shock and aftershock sequence with the Hypo2000 and HypoDD methods. The relocation results indicate that the earthquake sequence distributes along NE direction and most aftershocks are situated in the southwest of the main shock location. The focal mechanism soloutions of Huoshan M_S4.3 earthquake obtained with FOCMEC and CAP methods are basically consistent with each other，which is 135°/70°/-30° for nodal plane I and 230°/60°/-160° for nodal plane Ⅱ. The major axis of field seismic intensity distribution map extends also along NE direction. Combined with history earthquakes and the regional geological structure data，it is deduced that this earthquake is likely related to the NE-wards Luo’erling--Tudiling fault. In addition，the azimuth and plunge of the maximum principal (compressive) stress axis of this region are 267° and 5° respectively，and 358° and 4° for the minimum principal (tensile) stress axis. Referring to the focal mechanism and the seismogenic structure，it is inferred that the Huoshan M_S4.3 earthquake is a dextral-slip normal event under regional stress field.