Abstract: In order to study the spatial and temporal change of shear-wave splitting before and after September 7 2012 Yiliang earthquake, the study uses data obtained from temporary stations in the south part of North-South Seismic Belt setting up under the project ChinArray Phase one from August 2011 to September 2013, to compute the seismic anisotropy. The result shows that the stations in the area of fault belt and nearby reveal the NE polarization directions of fast shear waves, which are consistent with the strike of faults. However, the stations in the area have no or little faults reveal the NW polarization, which are consistent with the directions of regional principal compressive stress. The result demonstrates polarization directions of fast shear waves can clearly reveal the stress states of upper crust. There is a visible change in the delay time of slow shear-wave during the observational times, especially before and after earthquake. Before the earthquake, the delay time of slow wave slowly increased, and the distribution was discrete, suggesting the stress accumulation. After the earthquake occurred, the delay time of the slow shear-wave decreased rapidly, indicating the stress in the crust releases rapidly with the earthquake occurrence, which meaned this method can be used to monitor crustal stress changes.

Key words: Yiliang earthquake, Shear-wave splitting, Crustal seismic anisotropy, Stress in the crus