Q β tomography under the crust and upper mantle in eastern China

Abstract

On the basis of data of long period Rayleigh surface wave, we select 43 two-station paths which cover the eastern China thoroughly. By using the improved method of multi-filtration, we obtain the group velocity and amplitude spectrum, and then get attenuation factor for each paths. We employ Talentola inversion method to get local attenuation factor, and further invert the three-dimension Qβ image under the crust and upper mantle in the eastern Chinese continent. The Qβ image shows the following basic characters. There is correlation between the seismic activity and Qβ structure under the crust and upper mantle in North China region. The Yangtze block begins to collide with and subduct to the North China block from the southern border of the Qinling in the southern Shaanxi. In the large part of Yangtze quasi-platform appear an obvious high Qβ area at 88 km deep. In the east of Sichuan depression platform, the juncture of Sichun and Guizhou, and the Jiangnan block near the juncture of Guizhou and Hunan, the lateral variation of Qβ in the crust is little, and there is a high-Qβ layer no thinner than 40 km in the top mantle. In the Dian-Qian fold and fracture region between Yunnan and Guizhou, the vertical variation of Qβ at the region of the crust and upper mantle is little, there is a low-Qβ layer in the top mantle, about 40 km thick, low-Qβ layer of the upper mantle begins to appear at about 95 km deep. In the east of Yangtze quasi-platform and the central and eastern part of the South China fold system, the Moho is smooth, the lateral variation of Qβ in the crust is also little, low-Qβ layer of the upper mantle begins to appear at about 85 km deep.