Shear-wave splitting in Qinling Orogen and its both sides

In this study, the polarization of fast shear waves (PFS) and time delay of slow shear wave beneath the 17 stations in this area were computed by shear-wave Splitting Analysis Method (SAM) based on the seismic data during January 2006 to July 2015, recorded by Shaanxi Regional Digital Seismic Network. The parameters of shear-wave splitting have a striking regional division character. In the basin of Ordos and Weihe Basin, the PFS exhibits NE-SW and NEE-SWW direction, which agree with the direction of pressure stress in North China block. In the region adjacent to South-West of Ordos basin, which is located in a transition zone and accumulates a lot of strain, the dominant direction of PFS is complex. The south Qinling orogen is separated by Mianlue belt, the north region is Qinling micro-plate and the south region is located in north of Yangtze plate. The dominant PFS in Qinling micro-plate is in NWW-SEE direction, which is according with the direction of pressure stress in South China block. In north of Yangtze plate, the dominant direction of PFS is NE-SW, which may be affected by the northeastward movement of Tibetan Plateau. The results of PFS are coincident with the division of the tectonics that Qinling orogen is separated by Shangdan suture belt and Mianlue suture belt. The time delay of slow shear-wave is the biggest in north of Yangtze plate, which probably means that the anisotropy is stronger than that of other areas in this study. The results provide a very important basis for the further understanding of the compressive stress and kinetic processes of the study area.