The Crust And Upper Mantle Structure Study Beneath Northeast China

We stacked of approximately 47500 radial receiver functions recorded at about 175 broadband seismic stations. We removed the effects of losse sedimentary layer in Songliao Basin. Then we calculated Sub-sediment Crustal thickness and Vp/Vs measurements and got the Moho depth map and lateral variation Vp/Vs map. Surface topography can be used to explain the major but not complete reason for the large depth variations of the Moho. There is a difference between Moho depth calculated results based on the Airy’s isostasy model and the Moho depth got from receiver function. The difference indicates that the Moho is dynamically uplifted beneath the Changbaishan region. The results also showed that some parts of Great khingan Range and Changbaishan area have higher Vp/Vs value than their surrounding areas. It is suggested that a mantle upwelling might be the reason for the uplift.Based on the shear wave splitting analysis of SKS, SKKS and PKS from 129 broadband seismic stations in northeast China, a total of 993 pairs of high-quality anisotropic parameters are calculated and mapped. Combined with previous results, the upper mantle anisotropy was analyzed. Results of complex anisotropy analysis and anisotropy depth analysis suggest that the observed anisotropy mostly resides in the lithosphere-asthenosphere coupling area. Based on the splitting measurements and previous seismic tomography studies, we propose a model mainly controlled by the mantle flow resulting from the northwestwards subduction of the Pacific Plate. For some local areas, anisotropy is related to different mechanisms: the tearing of Pacific Plate leads to the splitting parameters observed beneath Jiamusi massif; Anisotropy beneath Songliao Basin is controlled by the depleting of partial lithosphere and two-layer anisotropy was observed around Yanshan belt.The Moho map from receiver function study and the anisotropy interpretation model from Shear wave splitting indicate that the evolution of crust and upper mantle structure were mainly controlled by Pacific plate.