2-D, frequency-domain waveform inversion of coupled acoustic-elastic media with an irregular interface

Most seismic exploration is carried out at sea, where the acoustic layer (water) covers an elastic layer (solids). The resulting data contains many elastic signals. As the sea bottom is usually not flat, inversion algorithms for a marine environment must be capable of dealing with an irregular interface between the fluid and solid layers. We have developed a conventional frequency-domain modeling algorithm for coupled media with an irregular interface, as well as the corresponding waveform inversion algorithm. The interface is represented by tessellating square and triangular finite elements. We exploit the usual backpropagation algorithm for inversion in the frequency domain, using the pseudo-Hessian matrix to normalize the gradient. Numerical experiments on synthetic models show that our algorithm can be applied successfully to both marine exploration data and OBC data.