Abstract

Based on the teleseismic records of the dense broadband seismic array, the crustal anisotropy parameters of the west Ordos block and its adjacent regions were determined with P wave receiver functions. The results indicate that the dominant direction of the fast wave is N-S in the Alxa block, NEE-SWW in north Ordos block, N-S in south Ordos block, and E-W in the Yangtze block. The fast wave direction of crust anisotropy in north Ordos block is distinctly different from the south Ordos block and the Alxa block. The Dabashan thrust fold belt is a visible boundary of crust anisotropy, which implies that the crust anisotropy kept the information of ancient South China block and North China block. Comparing with the direction of the fast wave from the SKS splitting, we tentatively discussed the interaction mode between the crust and mantle. The crust and mantle are decoupled in south Ordos block and coupled in north Ordos block. Combining the results of previous geophysical studies, we presented a crust-mantle interaction model to explain the geophysical observations. The most prominent features of the model are the horizontal eastward expansion of the mantle material in the southern Ordos and the vertical upwelling of the mantle material in the northern Ordos. The different modes of movement of the mantle material led to the deep contrasting structures of north and south Ordos, including the crust anisotropy. The mantle upwelling also implies that north Ordos block might be currently experiencing craton destruction.