Abstract: Using seismic data recorded by permanent stations in Ningxia province from January 2009 to September 2014, this study analyzed the crustal anisotropy in west of the Ordos block locating at northeastern margin of Tibetan Plateau by Systematic Analysis Method (SAM method) of shear-wave splitting, and obtained 19 available data from 7 stations. The results show that, influenced by the complicated local tectonics, stress field and a large number of faults, the spatial distribution of crustal anisotropy are different in west of the Ordos block. Owing to the regional tectonic stress field, the polarization directions of fast shear-wave at most stations are consistent with the regional tectonic compressive stress field. Moreover, the distribution of polarization directions varies in different regions. Structurally, the study region can be divided into north and south parts roughly by Sanguankou-Niushoushan fault at the middle of the region. According to the spatial distribution feature of the polarization directions, we divided the research region into north and south parts roughly bounded by 37°N. In the north part, the polarization directions are nearly N-S, consistent with the regional compressive stress field at the north of west of the Ordos block, divided by tectonics. In the south part, the polarization directions are nearly E-W, consistent with the regional compressive stress field at the south west of the Ordos block, also divided by teconics.

Key words: Crustal anistropy, Shear wave splitting, Ordos block