Crustal structure in eastern areas of South China block based on P-wave receiver functions

The South China block is composed of the Yangtze block and Cathaysia block and has undergone several stages of late transformation. It is of great significance to study the deep structural differences among the blocks for understanding the tectonic evolution history of the South China block. Based on the data of the broadband seismic array located in the eastern South China block, we calculated the P-wave radial receiver functions, and obtained the crustal anisotropy based on the Pms harmonic analysis. The results show that the crustal anisotropy of the seismic array has obvious regional characteristics. The fast wave directions near JSF (JiangShao fault) are consistent with the strike of the fault, indicating that the JSF may cut through the entire crust. In the Qinling-Dabie orogenic belt, the Yangtze block and the southern Cathaysia block, the fast wave directions are nearly perpendicular to the regional principal compressive stress direction, reflecting that the crustal deformation in this region may be influenced by the remote effect of subduction of the Philippine Sea plate and the Pacific plate. We also measured the crustal thickness and the average V-p/V-s ratio using H-kappa-c stacking method. The crustal thickness of the Yangtze block is thinner than that of the Cathaysia block and the Qinling-Dabie orogenic belt with lower V-p/V-s ratios of approximately 1. 7, which indicates that the crust is dominated by felsic and acidic rocks. The crustal thickness obtained by Airy isostasy theory shows that the crustal density is lower in the south of 29 degrees N than that in the northern regions. The low density and low V-P/V-s ratio in the south of 29 degrees N may be related to the vertical differentiation and delamination of crustal material caused by the northwestward subduction of the Philippine Sea plate and the westward subduction and retreat of the Pacific plate.