ANALYSIS ON FOCAL MECHANISM AND SEISMOGENIC STRUCTURES OF YAOAN EARTHQUAKE WITH M_S6.0,2009

Using joint inversion method with amplitude ratio of P wave、SV wave and SH wave,this paper calculated focal mechanism of aftershock sequence of Yaoan earthquake with MS6.0.According to the space distribution of earthquake sequence,the author analyzed the characteristics of stress field and seismogenic fault.The result showed that:(1) seismogenic fault of Yaoan earthquake was a vertical right-lateral strike-slip fault,striking NWW—SEE.The result was reliable,also consistent with nodal plane of CMT result offered by Harvard and predominant direction of aftershocks;(2) predominant direction of principal compressive stress in NWW—SEE was consistent with regional tectonic stress,and some aftershocks were different from main shock.Stress field of main shock was controlled by regional tectonic stress,indicated diversity and complexity in seismic area;(3) analyzing the distribution of earthquake sequence、focal mechanism and fault structure in seismic area comprehensively,seismogenic structure of Yaoan earthquake belongs to Mawei-jing fault.