Study On The Joint Inversion Of The Receiver Function And Gravity Data For Crustal Thickness And Poisson's Ratio In The North China-Northeast China

The North China-Northeast China,with complex geological structure and crustal deformation,lies between two tectonic units of the North China Craton and the Central Asian Orogenic Belt.Crust thickness and Poisson's ratio are two important parameters for understanding the crustal structure,composition and deformation of the North China-Northeast China.The conventional receiver-function H-? stacking method is a common method to estimate the crustal thickness and Poisson's ratio.However,due to the complexity of the crustal structure and the low signal-to-noise ratio of the teleseismic waveform,the conventional receiver-function H-? stacking method has uncertainty in the estimation of some stations in the study area,which affects the accuracy and reliability of crust thickness and Vp/Vs ratio.In this paper,the joint inversion method of receiver function and gravity is applied to reduce the uncertainty of estimation under the constraints of gravity data,and obtain more reliable crustal thickness and Poisson's ratio distribution in the study area.The main work and understanding of this article are as follows:(1)We preprocessed the waveform data of 626 seismic stations in the North China and Northeast China,and obtained the initial crustal thickness and Vp/Vs ratio of each station by using the receiving function H-? stacking method.Then we conduct joint inversion of the receiver function and gravity by combining gravity vertical gradient.Finally,the distribution of crustal thickness and Poisson's ratio in the study area are obtained through the optimization selection of joint inversion parameters.The quality evaluation analysis shows that the results of the joint inversion in this paper are effective and reliable.(2)The thickness of the crust in the study area,ranging 27.5?58.5km,is thick in the West and thin in the East,and its variation is gentle.The whole crust is in a state of gravity isostasy.There is a gradient zone of crustal thickness thinning from west to east along the line of the Da Hinggan-Taihang Mountain,which is basically consistent with the gravity gradient zone.It is obvious that the crustal thinning in the east of the gradient zone,which is supposed to be closely related to the westward subduction of the western Pacific plate.(3)The crustal Poisson's ratio in the study area has large-range variation with values between 0.21?0.32,which in the Songliao Basin,western North China Craton and Sichuan Basin is relatively high,while in the North China Basin and Qilian Block is relatively low.The crustal Poisson's ratio on both sides of the Da Hinggan-Taihang Mountain gravity gradient zone is different.There are low value belts of crustal Poisson's ratio in the south and north sides of the North China Craton,which are basically consistent with the tectonic trend.(4)At the junction of the northern margin of the North China Craton and the Central Asian orogenic belt,there is an EW-trending low-value belt of crustal Poisson's ratio,which is along the line of Tonghua-Shenyang-Chifeng-Hohhot.Combined with previous studies,it represents the possible location of the suture zone in the eastern segment of the Central Asian Orogenic Belt.