LAUSR

S U M M A R Y The Ordos Block and the Qinling Orogen in central China are key regions that have been affected by Indo-Eurasian collision, convergence of the North China, South China and Siberian cratons, and subduction of the Pacific oceanic plate during the Phanerozoic. Investigation of the crustal structure in this area can therefore provide significant insights into the interactions among these tectonic blocks and plates. The Chinese Academy of Geological Sciences deployed ca. 249 portable broad-band seismic stations in this area from 2011 to 2016, and we retrieved P-wave receiver functions (RFs) from these new stations, and also from all other available permanent and portable seismic stations in China. Crustal thicknesses beneath the stations were retrieved using 1-D S-wave velocity models, which were obtained by linearized inversion of the RFs with initial reference models from regionalized S-wave velocities of surface wave inversions. We demonstrate with synthetic tests that this inversion scheme is superior to a jointly linearized inversion of RFs and surface waves. The results show that crustal thicknesses generally correlate with tectonic domains in the study region. Thus, thick crust is present beneath the Daba Shan region and the area close to the northeastern Tibetan Plateau, intermediate-thickness crust is present beneath the Ordos Block and the central North China Craton, and thin crust exists beneath the North China Plain. However, some notable exceptions exist. The crust beneath the central Qinling is thinner than that beneath the neighbouring Daba Shan region and even the Weihe Basin, implying that subduction and collision of the North China and South China cratons in the Palaeozoic did not produce a thick crust beneath the suture. The relatively thin crust beneath the eastern and central Qinling must be denser than that beneath neighbouring areas. All the basins around the Ordos Block have been considered to be graben. However, our results show that the crust beneath the basins along the southern and northern margins of the Ordos Block is thicker or the same thickness as the crust beneath the flanks of the basins, which suggests these basins are (or were) foreland basins.