Full-waveform inversion in acoustic-elastic coupled media with irregular seafloor based on the generalized finite-difference method

Abstract

The marine environment can be considered as a fluid-solid coupled media governed by the acoustic-elastic coupled equation (AECE). For complex fluid-solid coupled models with irregular seabeds, the well-known finite-difference method (FDM) often causes ripple-shaped scattering due to the rectangular grid. To overcome this problem, a meshless method (MM), called the generalized finite-difference method (GFDM), for irregular node distributions is developed and applied to AECE forward modeling by using a body-fitted node-generation method, which provides robust node distributions for GFDM. Compared with the FDM, our GFDM improves modeling accuracy and eliminates divergence. Furthermore, our MM was applied to an AECE-based elastic full-waveform inversion (EFWI). Owing to the well-matched irregular seabed, our EFWI can invert the accurate elastic model for ocean-bottom cable and pressure data. Numerical examples demonstrate that this method can efficiently improve the numerical accuracy and build an accurate velocity model even using noisy data, which is helpful for high-precision seismic exploration in the complex marine environment.