Abstract:We calculate the radial receiver functions of each station using the dense broadband seismic array data across the Xiangfan-Guangji fault and measure the crustal anisotropy based on Pms converted phases. The crustal thickness and the average VP/VS values are estimated by a new H-κ-c method. The average delay time of the entire survey is 0.275 s and the anisotropy is larger in the Yangtze block (the mean value is 0.344 s) than in the Dabie orogenic belt (the mean value is 0.226 s). The crustal anisotropy intensity of the Dabie orogenic belt varies greatly, with a maximum value of 0.46 s and a minimum value of 0.06 s, and the fast polarization directions (FPDs) are scattered. In the Yangtze block, the FPDs and anisotropy intensity are concentrated, indicating a stable crustal structure. The average FPDs in this area is NW-SE, which has an angle with the strike of the fault and the GPS direction. We suppose the FPDs may be related to the northward subduction of the Yangtze block. The H-κ-c stacking results show that the Dabie orogenic belt has a thicker crust (the mean value is 33.2 km) and a lower VP/VS value (the mean value is 1.74), indicating that the crust is dominated by felsic and intermediate rock compositions, which may be related to the delamination of the lower crust. The Yangtze block has a thinner crust (the mean value is 32.6 km) and a higher VP/VS value (the mean value is 1.78), indicating that it is a stable continental core, and still retains the iron-magnesium composition in the lower crust.
TAN Ping,DUAN Yonghong,TAN Yujuan et al. Study on the Composition and Deformation Characteristics of the Crust on Both Sides of the Xiangfan-Guangji Fault[J]. jgg, 2023, 43(6): 627-632.