Elastic wave CT with multistage inversion process based on improved SIRT

Elastic wave computerized tomography (CT) is a commonly used physical exploration technique. This paper proposes a multistage inversion imaging method based on improved simultaneous iterative reconstruction technique (SIRT) to obtain better reconstructed images. In this inversion stage, the distance relationships between sources and receivers are used to improve the poor matching between ray path matrix L and travel time residual Δt, which is called numerical fitting inversion. After outer loop is finished, the principal component weighting method is utilized to pretreat the matrix L to reduce its ill-posedness, and the result of numerical fitting inversion is taken as the initial value to inverse again, which is called the model refinement inversion. Results of simulation and field test indicate that the method can effectively suppress the problem of overcorrection of SIRT and has better convergence accuracy and reconstructed image.