Obtain The Depth Of Lab Beneath Northeast China By S Receiver Function

The P-wave receiver function has been widely used in researches on the cr ust and upper mantle structure.However,it is still difficult to accurately measure the depth ofLithosphere-Asthenosphere-Boundary(LAB)only by considering PS converted seismic phases because of the interference of the multiple reflection seismic phases in Moho and crust velocity discontinuities.The method of extracting S-wave receiver functionby S-to-P converted phase is similar to method of obtaining the P-wave receiver function.Compared with P-wave receiver function,the S-wave receiver function is immune to the effects of the multiple reflection phases of the discontinuities which has great advantages on the researches on Lithosphere-Asthenosphere-Boundaryand has been widely used in the researches on LAB.In this paper,we use the large number of seismic data in the northeast of China recorded by the 127 broadband seismic stations which were set in the 2009.9~2011.8 international cooperation projects to study the depth of LAB,includ ing three main parts: extraction of receiver function,time-depth conversion and depth stacking.By comparing the depth of Moho using S wave receiver function and P wave receiver function of the 127 stations,deleting the data with a deviation less than 5km,then obtain the depth of LAB below the 70 stations left.Results show that the thickness of lithosphere beneath the northeast area is obvious differentin East-West.The lithosphere of Greater K hingan Range block in the west is thicker and its thickness is within 100~160km.The thickness of lithosphere in Zhang Guangcai Ridge area is 90~140km.The thickness of the lithosphere in Jiamusi block is 70~100km.The lithosphere of Songliao basin is significantly thin,which is 50~90km.We speculate this phenomenon is related to the subduction of the Pacific plate in the later period of the Mesozoic era,the eastern side of ancient Pacific plate diving to the Asian mainland,resulting in stretching and thinning of lithosphere in the area,and then this area suffered a thermal subsidence and late compression.Concrete structure evolution process still needs to be further explored.