基于变密度模型的位场界面反演

在波数域中用重力反演莫霍面深度时通常假定壳幔密度差为一常数，但这只是一种近似的密度模型，本文采用了密度随深度呈指数变化的变密度模型来反演莫霍面深度，给出了利用指数密度模型在波数域中计算重力异常的正演公式及界面深度的反演公式.利用指数密度模型及重力资料反演了青藏高原莫霍面的深度，分析了莫霍面的特征.结果表明，青藏高原莫霍面呈现出边缘浅、中部深的特点，边缘变化快、梯度大，中间变化梯度趋缓.中心地带的羌塘地体莫霍面深度达74 km，向四周慢慢变浅至67 km左右，边缘地区突然变浅至50km左右.通过常密度模型、变密度模型及地震反演得到的莫霍面的比较，证实变密度模型更适合于莫霍面结构的反演.

Interface depths inversion of potential field data with variable density model

The constant density model for conventional Moho depths inversion in wave-number domain from gravity data is just an approximate density model.A variable density model with exponential density contrast is used for inverting Moho depths instead of constant density model.The method is introduced and some formulae are derivated for forward calculating gravity anomaly and Moho depths inversion.The Moho depths of Tibet plateau are inverted from gravity data with exponential density model.The inversion result demonstrates that the Moho depths of Tibet plateau are shallow around the edges,and deep at the center.The gradients at the edges are steeper than at the center.The Moho depth of Qiangtang block situated at the central Tibet plateau is 74 km,and changed to 67 km slowly outward,but changed to 50km rapidly at the margins.The variable density model is more suitable for inversion of Moho depths structures than constant density model by comparison of Moho depth from seismic inversion.