中文摘要：

通过对单层模型反射和透射系数的推导，提出了利用接收函数一次转换波和多次波确定Moho面速度和密度跃变的速度-密度跃变（δβ -δρ）扫描叠加方法.利用反射率法计算了不同模型的远震理论地震图，按照与处理实际观测波形一致的方法和流程计算了理论接收函数；根据不同模型数值试验结果，深入分析了界面速度和密度跃变对接收函数震相幅度的影响.利用（δβ -δρ）扫描叠加方法，对理论接收函数进行了数值试验，结果证明了该方法的可行性.最后将该方法应用于位于青藏高原东北缘的高台（GTA）台和兰州（LZH）台，确定了两个台站下方Moho面的速度跃变分别约为（19±1）%和（20±1）%，密度跃变最小值为（4±2）%和（6±2）%.

英文摘要：

Based on the theoretical analyses of the reflection and refraction coefficients of the one-layer model, the velocity-density contrast （δβ-δρ） scan stacking algorithm was proposed to constrain the velocity and the density contrasts of the Moho by using the P-to-S conversion and multiples of the receiver functions. Teleseismic seismograms of different models were calculated with the reflectivity method, and then the same method and procedures were applied to the observational waveforms to construct the synthetic receiver functions. According to the numerical tests with different models, we analyzed the influences of velocity and density contrasts on the amplitudes of receiver functions. The method was firstly applied to the synthetic receiver functions, and the results indicated the reliability and stability of the method. Finally, this method was applied to the GTA and LZH stations in the northeastern margin of the Tibetan Plateau. The results suggest that the S-wave velocity contrast across the Moho is about （19±1）% below GTA station and （20±1）% below LZH station, respectively, while the minimum of the density contrast is （4±2）% below GTA station and （6±2）% below LZH station, respectively.