中文摘要：

通过求解引力相等原则下的Fredholm积分方程,可以得到不规则单一密度界面（Moho面）的起伏.本文充分参考了前人的理论研究,推导出扰动垂直重力梯度确定Moho面深度的频谱域表达式,该式具有二次项迭代精度.运用此公式进行了全球Moho面的恢复计算,并将该结果与CRUST1.0模型和GEMMA Moho模型进行了对比和验证.

英文摘要：

In classical gravity research,the determination of Moho is mainly based on the Vening Meinesz-Moritz（VMM）method.This approach assumes that terrain and seawater can be considered as the load on the elastic crust.The Moho depth or crustal thickness can be obtained by solving the Fredholm integral equation which requires a form of expression for gravity gradient observations.However,there is no such accurate expression available now.In this work,the Fredholm integral equation of Moho depth is converted into the one in the spectrum domain.By considering the second-item influence,we provide a simple and general expression that is applicable for the vertical gravity gradients.In the investigation,we utilize the new methodology to calculate the global Moho depth.The method of the spherical harmonic synthesis is applied to raw gravity gradient data and step-by-step stripping of Moho signal from the GOCO03 smodel and the prior crust information,respectively.The global crustal thickness is from 6km to 79 km.The land crust is usually thicker than the normal value.The minimum thickness of the crust is located in the ocean.Especially,because of the collision between in the India and the Eurasian plates,the Tibetan plateau has a very thick crust.With respect to the African region,the crust in the north continent is thinner than the one in the south.Finally,bycomparison with CRUST1.0and GEMMA model,it is demonstrated that our Moho solutions have a good consistency on the global scale with standard deviations of 4.6km and 3.4km,respectively.