An Adjoint-Based Hybrid Computational Method for Crosswell Seismic Inversion

Waveform tomography, or full waveform inversion (FWI), is in general better than ray tomography; however, a reliable initial model is usually required to ensure success. Here, the authors designed a cascade-like hybrid tomography technology to solve the crosswell seismic inversion problem. The new method is a combination of several widely used tomography technologies, implemented in a sequence, where the cheaper method is used as the initial model feeder for the more expensive method. They start with the Radon-transform-based back-projection method; then the Linear Iterative Reconstruction method, such as selective internal radiation therapy, is adopted to update this initial model; which is further improved by the nonlinear, Gradient-based Eikonal Equation Tomography method. Finally, the velocity model reconstructed from the previous multiple ray tomography methods is used as the initial model for the FWI.