Multiparameter Full Waveform Inversion Based on Automatic Differentiation for Acoustic–Viscoelastic Fluid–Solid Coupled Equations and Its Application to Actual OBN Seismic Data

In marine seismic exploration, the seismic wave propagation environment is considered a fluid–solid coupled medium, where the upper layer is a fluid medium, and the lower layer is a solid medium. Traditional full waveform inversion (FWI) techniques neglect the effects of fluid–solid coupling, whereas recent developments in FWI for fluid–solid coupled media fail to achieve multiparameter inversion, including the quality factor (Q). The present study constructs fluid–solid coupled equations using acoustic–viscoelastic wave equations and implements multiparameter FWI under an automatic differentiation framework. In the proposed approach, gradients are directly computed through the chain rule, avoiding the explicit calculations and backpropagation of adjoint sources, considerably simplifying the application of multiparameter FWI to fluid–solid coupled equations. Model experiments indicate that the proposed multiparameter FWI algorithm based on acoustic–viscoelastic wave fluid–solid coupling can simultaneously invert P-wave velocity, S-wave velocity, and Q models. Furthermore, the method proves suitable for the FWI of actual ocean-bottom node data.