Crustal Seismic Characteristics In The Northeast Of North China Craton By Receiver Runctions

North China Craton is one of the most important tectonic units in the east ofchina. In the period of Paleozoic, North China Craton has all the typical characterswhich ancient craton has, until Mesozoic east of North China Craton suffered anfiercely destroy, with a phenomenon: mainly more than one hundred kilo-metres ofit’s lithosphere had thinned in a large-scale. With decenniums of research on NorthChina Craton, researcher has presented many kinds of theories and hypothesis toexplain the process of North China Craton’s destroy, and the process which has adriect relationship with the crust is delamination. A part of lower crust delaminate andfallen down to asthenosphere mantle with lithosphere mantle, then the hotasthenosphere material gushed up to the depth of lower crust and replace the coldupper mantle, meanwhile the lower crust has been heated and cause a series ofgeologic process such as partial melting of crust, metamorphism and fluid circulationin a large scale.Studuy region locates in the northeast of North China Craton, and itcovers the Beijing，Tianjin and Tangshan where the economy and culture are mostdeveloped the people are most densely. So study the structure and physical property ofthe crust in this area, will give us some advice to the sustainable development of thisarea and help us know more about evolution process of North China Craton.The tele-sesimc events we used in this research were recorded by broadbandseimic stations which are located in Shangdong, Hebei, Liaoning, Beijing, Tianjingprovince. We investigate the crustal thickness and averaged poisson’s ratios beneath101means of the grid stacking search method of receiver functions, then we using theresult to do S wave volocity structure inverstion and got92results. We had analysisrecerver functions form36stations, but by data selection we just got results from4stations.Our inverstion results show that: the crustal thickness varies from30km to46km, and the crustal thickness has thinned gradually from mountain to basin which shows a good corelation between surface terrain and crustal thickness. In the middleand west of North China Craton the S wave velocity beneath the stations was step upsteadily, and rarely had low velocity layers, it suggest that the crust beneath thisstations had a relative stable state and suffer a weaker geological transformation. Thedepth of Moho in Beijing area is undulating, and the S wave velocity structure showna Strong Consistency with P wave velocity structure.Distribution of the Poisson’s ratio over the middle and the west region aredispersed and it is suggest that east of North China Craton suffered a most fiercelydestroy. The region beneath the east part of Yanshan has a low poisson’s ratios, mightrelate to the delamination of North China Craton. The Poisson’s ratio over transitionzone between the Taihang-mountain and North China Plain has two differentperformances when the crust become thick it will get smaller or bigger, and it shouldbe relate to different geological transformation. The region beneath east part ofTancheng-Lujiang fault zone has a complex distribution of both low and highpoisson’s ratios, and that might be with relation to volcanic activity.A part of stationsnear the western segment of Zhangjiakou-Bohai seismic active belt andTancheng-Lujiang fault zone has a little higher poisson’s ratios,which might be causedby both broken rocks and the partial fusion of rocks near seismic active belt.We have extracte the whole crustal seismic anisotropy parameter of4stationsnear Zhangjiakou-Bohai seismic active belt and Tancheng-Lujiang fault zone by usingReceiver Runction. The result of fast shear-waves polarization direction near theZhangjiakou-Bohai seismic active belt are consistent to the trend ofZhangjiakou-Bohai seismic active belt, and the station near the Tancheng-Lujiangfault zone are mainly consistent to the of trend of Tancheng-Lujiang fault zone. Itsuggests that the fault mainly control the anisotropy feature of this area. The delaytime between fast and slow wave are long. Each station has a delay time longer than0.3seconds, it means that the degree of crustal seismic anisotropy is high. Wecompare our result with upper crust S wave split result and SKS wave split in ZJKstation and found that our result are more consistent with upper crust S wave splitresult. Preliminarily we consider the crust and mantle anisotropy formation mechanism may be different in Zhangjiakou.