Shear-wave splitting in the crust in Eastern Songpan-Garze block, Sichuan-Yunnan block and Western Sichuan Basin

In eastern Tibetan Plateau, there are eastern Songpan-Garze block, Sichuan-Yunnan block and western Sichuan Basin, where is one of the areas with strong seismic activity in China. In this study, the polarization of fast shear waves (PFS) and time delay of slow shear-wave beneath the 44 stations in this area were computed using shear-wave Splitting Analysis Method (SAM) based on the seismic data during January 2000 to April 2010, recorded by Sichuan Regional Digital Seismic Network. Due to the impact of the regional principal compressive stress and local geological structure, the spatial distribution of polarization of the fast shear-wave shows the localized characteristic. The dominant PFS beneath the northeast and southwest segment of Longmenshan fault belt exhibits the North-East and North-West direction, respectively. PFS beneath the northwest and southeast part of the Sichuan-Yunnan block shows nearly East-West and North-Northwest direction, respectively. The dominant direction of PFS beneath the north and south side of Qingchuan fault respectively are nearly North-South and East-West. The time delay beneath north side is larger than that in the south side of Qingchuan fault. This study suggests that the localized distribution of shear-wave splitting parameter could be caused by complex geological structure and the geometry of active faults.