Abstract: Using correlation coefficient method, a study of shear wave splitting is made through the recording of aftershocks of the Anqing M_S4.8 earthquake, Anhui province in 2011. The results show that the preponderant polarization of the fast shear wave is NNW. It accords with the regional predominant direction of principal compressional stress. By analyzing the change of S wave time delay, obvious stress relaxation could be seen after the M_S4.8 earthquake. The time delay basically increases before strong aftershocks. However, it was observed that the time delay decreased abruptly immediately before one strong aftershock. It is coincident with the conclusion that long-term stress accumulation and short-term stress relaxation existed before earthquakes. It is significant for the short-term earthquake prediction that the time delay decreases before strong earthquakes. The result suggests that parameters of shear wave splitting may reflect the dynamic change of regional stress field and provide useful information for the study of stress field and earthquake prediction.

Key words: Shear wave splitting, Time delay, the 2011 Anqing M_S4.8 earthquake