为了有效解决目前大地电磁和天然地震资料单方法反演结果一致性不好的问题，同时克服基于岩石不同物性参数间关系耦合约束联合反演的局限性，本项目提出开展交叉梯度耦合约束的大地电磁与天然地震走时资料三维联合反演研究。以较为成熟的天然地震走时资料三维正反演和大地电磁三维正反演算法为基础，开发出以交叉梯度结构耦合约束，能同时获得电阻率和速度模型的大地电磁和天然地震走时资料三维联合反演算法和程序。利用相容和不相容理论模型合成数据进行反演试算，以检验算法的稳定性和可靠性；将开发的联合反演算法应用于西藏南迦巴瓦地区实测资料反演，检验联合反演的有效性和适用性。研究成果将形成实用的大地电磁与天然地震三维联合反演方法技术，提高深部地球物理探测结果的可靠性。

In order to effectively overcome the weak consistency of single inversion of magnetotelluric and teleseismic travel time data, and also to solve the limitations of petrophysical approach, we study a 3-D joint inversion algorithm of magnetotelluric and natural seismic travel time data by cross-gradient method. Based on well-developed 3-D teleseismic and magnetotelluric forward and inversion algorithms, we develop the 3-D joint inversion algorithm, which has a common inversion mesh, the structural cross-gradient coupling, and can simultaneously obtain a resistivity model and a velocity model. The joint inversions algorithm is performed by generated data of compatible and incompatible theoretical models to check the robustness and reliability. The joint inversion algorithm is applied to observed data from Namche Barwa in Tibet to the validity and applicability. This research will form a practical method and technique of 3-D joint inversion by magnetotelluric and teleseismic travel time data, which is able to increase the reliability of geophysical results from detecting deep structure of the solid earth.