The shear-wave splitting study of Sichuan Zipingpu reservoir region

Using seismic data recorded by Zipingpu reservoir Digital Seismic Network from Aug. 17, 2004 to May 11, 2008, the dominant polarization directions of fast shear-waves are obtained at 8 digital seismic stations in this region by SAM technique. The results show that dominant directions of polarizations of fast shear-waves are mainly in nearly NE or NW direction in Zipingpu reservoir region. The dominant polarization directions of fast shear-waves are consistent with the strikes of active faults, or regional principal compressive stress. The direction variety of polarization of fast shear-wave are related with the enhancement of regional stress and micro-cracking of Longmenshan fault before Wenchuan earthquake, and there are correlation between delay time of slow shear-wave and water level of Zipingpu reservoir.