Magnetotelluric closed-loop inversion

Magnetotelluric (MT) inversion constitutes a pivotal research domain within the purview of electromagnetic data interpretation, characterized by its inherent nonlinearity and illposed problem. Traditional MT inversion algorithms often require introducing an initial model as a prior constraint, and then drawing the electrical distribution of the structure based on the observed data, which has limitations such as low computational efficiency and high computational costs. This paper proposes an efficient and high-quality MT intelligent joint inversion method based on artificial intelligence (AI) control strategy to address the issues in MT inversion problems. Capitalizing on the strong nonlinear fitting capabilities of convolutional neural networks (CNNs), the closed-loop network composed of forward and inversion subnetworks is constructed to enable the closed-loop network to train in the absence of labels, thereby solving the restrictive problem of the small number of label samples faced by MT inversion. Simultaneously, the reciprocal constraint between forward and inversion subnetworks can suppress inversion multiplicity, leading to improved inversion accuracy. In addition, the uncertainty in inversion can be further reduced by mutual constraints between apparent resistivity and phase data. Finally, this paper tests and verifies the effectiveness of the closed-loop network using synthetic and measured data. The results demonstrate that the closed-loop network significantly enhances the depth resolution of inversion and elevates the reliability of inversion results. Moreover, the closed-loop network can also effectively predict the apparent resistivity and phase response data that are close to those simulated via the finite element method.