We performed a receiver function analysis on teleseismic data recorded along two dense seismic profiles and from 4 broadband regional seismic stations across the northeastern Tibetan plateau.The crustal thickness and vP/vS ratio were measured by the H-κ domain search algorithm.The Moho discontinuity across the Haiyuan arc fault zone was also revealed by common conversion point(CCP)imaging.Our study results show that the crustal thickness and the vP/vS ratio were 42-56 km and 1.60-1.88,respectively.The crustal thickening on the northeastern margin indicates that the crust is shortening or that there was a superimposition of crusts during the collision of the Tibetan plateau with Eurasian block.Our results suggest that Haiyuan fault likely resulted from the interactions of high temperature and pressure conditions during the collision of the Indian and Asian continents.The Moho beneath the Haiyuan tectonic region exhibits an obvious offset and a vague discontinuity according to CCP imaging.This study suggests that the Haiyuan arc fault zone is a trans-crustal fault that cuts through the Moho in the northeastern Tibetan Plateau.Moreover,there are indications of strong deformation in the intensive crustal extrusion from the interior of the Tibetan Plateau to its northeastern margin.