中文摘要：

利用青海和甘肃地震台网2007—2009年记录的远震波形资料,提取多频段P波接收函数,反演得到了青藏高原东北缘及相邻地块下方0~100km深度的地壳和上地幔S波速度结构.结果表明：（1）青藏高原东北缘的上、下地壳之间普遍存在一个S波速度低速层,其深度由南端的约35km向北变浅约为20km,推测该低速层为一壳内滑脱层,表明东北缘地区的上地壳变形与下地壳解耦,从滑脱层的深度分布可以认为青藏高原东北缘的地壳缩短自南向北进行,现阶段以上地壳增厚为主;（2）昆仑—西秦岭造山带的下地壳厚度较北侧的祁连地块薄,一种推测是西秦岭造山带的下地壳抗变形能力更强,也可能这种差异在块体拼合前已经存在;（3）青藏高原东北缘及鄂尔多斯和阿拉善地块的下地壳S波速度随深度的增加而增加,这种正梯度增加的S波速度结构反映较高黏滞性的下地壳,推测青藏高原东北缘的地壳结构不利于下地壳流的发育.

英文摘要：

The northeastern（NE）Tibetan Plateau is an ideal place for investigating the far field effects of collision between the Indian and Eurasian plates.By what ways the Tibetan crust is thickened and extended is a long-term debated issue for absence of convincing evidence for proving the existence of the inner-crustal low velocity zone and its role.Using teleseimic P wave datafrom the China Seismograph Network in Qinghai and Gansu provinces recorded from 2007to2009,the crustal S-wave velocity structure beneath the NE Tibet plateau is resolved.The receiver function waveform inversion technique（PROGRAM330）is used to analyze the crustal S-wave velocity structure below seismic stations.The receiver functions are estimated by a time-domain iterative deconvolution method of Ammon（1991）with four different Gaussian coefficients（α=1.0,1.5,2.0and 2.5）.Firstly,receiver functions,which are much similar in waveforms and within a narrow range of back-azimuth（less than 10°）and ray parameter（less than 0.002）,are stacked to enhance the main signal characteristics.To maintain the intrinsical details of the receiver functions,they are stacked without normal moveout.Results of Tian et al.（2013）and Li et al.（2006）are used as the constraints in the inversion process to reduce the uncertainty.The results show thata relatively low velocity layer（LVL）exists between the upper and lower crust in the region between the East Kunlun fault and the Haiyuan fault.The depth of the LVL shallows northeastward from ~35km to ~20km along the surface movement direction,while the Moho uplifts.The variation in thickness of the upper crust is more obvious than the lower crust.The thickness of the lower crust（15~20km）beneath the Kunlun-west Qinling orogenic belt is thinner than that beneath the adjacent Qilian block（25~30km）.Beneath the NE Tibetan plateau,as well as the Alashan and Ordos blocks,the S-wave velocity in the lower crust increases with depth.The whole crustal S-wave velocity increases with depth beneath t