The Central Asian Orogenic Belt (CAOB) between the Siberia paleo-continent and the North China paleo-continent has a close relationship with the evolution of the Paleo-Asian Ocean. The Xing'an-Mongolia Orogenic Belt (XMOB) as eastern part of the CAOB is located in North China. It is generally considered that the closure of the Paleo-Asian Ocean resulted in the formation of the XMOB, but there remain some disputes about the tectonic attribute of the northern margin of the North China Craton and where the Paleo-Asian Ocean finally closed and how it behaves due to complex evolution process, extensive coverage of Cenozoic sediments and the lack of high resolution deep exploration data. Structures and some major discontinuities beneath stations can be imaged by the receiver function method. In recent years, this method has become a mature and effective tool for studying the velocity structure of the crust and upper mantle. By the H-kappa stacking method, the P-to-S converted waves at the Moho discontinuity and their multiple reflections are used to calculate crust thickness and V-p/V-s ratio, which provide a way to study the rock composition of the crust and stress condition under stations. Funded by National Natural Science Foundation of China, Institute of Geology, Chinese Academy of Geological Sciences deployed 41 portable broadband seismic stations from Huailai county in northern North China to Bayinondor town near the China-Mongolia border. The profile extends along the reflection and refraction profile funded by Sinoprobe project, crossing the Yinshan-Yanshan orogenic belt, the Inner Mongolia paleo-uplift, the Bainaimiao arc, the Ondor sum subduction accretion complex, the Solonker suture zone (the Solonder suture zone, located between the North China plate and Siberia plate, representing the closure of the Paleo-Asian Ocean), the Baolidao arc accretion complex, the Hegenshan ophiolite arc accretion complex and the Uliastai active continental margin from south to north. Recorders were set to the continuous recording mode and the sampling frequency was set to 50 Hz. The average distance between two neighbouring stations is 15 km and the length of the profile is about 650 km. Up to December 2014, we got 421 GB raw data in total. First, we select 746 teleseismic events of m(b) > 5 from 30 to 95 degrees and obtain their P waveforms from -20 s to 100 s with respect to the first P arrival time. Then, 3-component waveform data with high signal-noise ratio are pre-processed (including mean removal and linear removal) and pre-filtering at 0.02 similar to 2 Hz and then rotated Z-N-E to the Z-R-T coordinate system. Finally we obtain 1844 P-wave receiver functions by the time domain iterative deconvolution method. After that we obtain the crustal thicknesses, V-p/V-s ratios and Poisson ratios beneath the profile by the H-kappa stacking method and image extension of the Moho interface by the Common Coversion Point (CCP) stacking method. The results are as follows: (1) The Moho depth on average is 40 km along the profile. The crust thickness changes little across different tectonic blocks but shows evident variation at the boundaries between the blocks. The Moho dips southward beneath the Ondor sum belt and the Bainaimiao belt, while dips northward beneath the Baolidao belt and the Hegenshan belt. The Linxi fault seems to be as the boundary dividing the northern margin of North China Craton (NCC) and the southern CAOB. (2) The Poisson ratio shows a correlation with the tectonic unit along the profile. The averaged Poisson ratio in the northern margin of NCC is larger than the southern part of CAOB. The Poisson ratio changes little within the blocks except nearby the boundaries of different blocks. (3) There is a negative correlation between the crust thickness and the Poisson ratio that indicates the lateral heterogeneities of the crust structure resulted from the tectonic deformation. (4) Poisson ratio of the crust along the profile presents an approximately nonlinear symmetric shape relating to the south margin of Solonker suture zone. The characteristics of the crust and mantle structure and distribution of Poisson ratio along the profile support the geodynamic model that the Paleo-Asian Ocean subducted and closed at the southern margin of the Solon suture zone (along the Linxi fault).
