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Crustal thickness and composition are closely related to geology and tectonic evolution of the region. Studying the differences in the crustal thickness and composition of the South China Block (SCB) is important to gain a comprehensive understanding of multi-phase amalgamation, breakup, reworking, and regional geodynamic processes. In this study, teleseismic data from 135 high-density portable broadband stations from SinoProbe were processed using Common Conversion Point (CCP) stacking and H-κ stacking methods. The Moho depth and P-wave and S-wave velocity ratio (Vp/Vs) were studied. Our results revealed several insights about the tectonic processes in the SCB. First, the crustal structure and Vp/Vs ratios of the Cathaysia Block, Jiangnan Orogenic Belt, and Yangtze Block were significantly different. The average depth of the Moho in the Cathaysia Block was approximately 31 km, and the Vp/Vs ratios increased from the inland area (1.66) to the coastal area (1.78), indicating the oceanward increase of mafic proportion in the lower crust, which is related to the influence of the Paleo-Pacific Plate westward subduction. Second, the crustal thickness of Jiangnan Orogenic Belt deepens from east ca. 31 to the west ca. 42 km and the Vp/Vs ratios varied from 1.75 to 1.64, illustrating a relatively felsic crust, which could have been related to the Mesozoic upper crustal thickening under compression followed by the lower crust removal under the extensional background. Third, the average crustal thickness of the Yangtze Block was 42 km, and the Vp/Vs ratios ranged from 1.64 to 1.84, presenting a positive correlation between the Moho depth and the Vp/Vs ratio, which is explained by the relatively thick mafic lower crust. Based on the variations in the crustal structure and Vp/Vs ratios of the profile, we inferred that the central part of the Jiangnan Orogenic Belt was bounded by the Jiangshan-Shaoxing-Hengyang in the east and the Jiujiang-Shitai-Jishou in the west. The small-scale Moho depth undulations at the intersection of the Cathaysia Block and the Jiangnan Orogenic Belt could be related to the Mesozoic compression-extension geodynamic transformation. [ABSTRACT FROM AUTHOR]

The seismic investigation achievements from three kinds of methods have revealed the lithospheric structure and the deep process of deformation caused by collision. It is found that convergent collision and deep subduction of the continental lithosphere are in progress along the northern margin of the Tibetan Plateau. The deep process of due collision and deformation is different from that of oblique collision. It is revealed in the study that the deep process of the collision and deformation on the northern margin is different from that on the southern margin of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]