Joint inversion of magnetotelluric and fullwaveform seismic data based on alternating cross-gradient structural constraints

Magnetotelluric(MT) inversion and seismic inversion are important methods for the interpretation of subsurface exploration data, but separate inversion of MT and seismic produces ambiguous and non-unique results due to various factors. In order to achieve accurate results, the authors propose a joint inversion method of two-dimensional MT and seismic data in the frequency domain. The finite element method is used for numerical simulation of electromagnetic data in the forward modelling, and the Gauss-Newton method is used for the inversion. The 9-point-finite-difference method is used to solve the seismic wave field in the acoustic wave equation, and the inverse problem of seismic data is solved by full waveform inversion with a conjugate gradient, a simple and fast method. Cross gradient functions are used to provide constraint structure between resistivity and velocity parameters to carry out the joint inversion. The joint inversion algorithm is tested by double-rectangular model synthesis data, and the accuracy of the algorithm is verified. The results show that the joint inversion results are better than those from separate inversion. The algorithm is applied to a geophysical model of a metalliferous deposit in Jinchuan and is compared with the separate inversion results. It shows that the results obtained with joint inversion are much closer to the real model.