On the full-waveform inversion of Lamé parameters in semi-infinite solids in plane strain

Abstract

We are concerned with imaging the spatially varying Lamé parameters of semi-infinite, arbitrarily heterogeneous solids, when probed by elastic waves in the time domain. We use a full-waveform inversion approach to tackle the inverse medium problem, and seek the Lamé distributions that minimize the misfit between measured and computed responses, subject to the governing PDEs. As is commonly the case, the resulting inverted profiles of the second Lamé parameter (μ) are of better quality than those of the first (λ). To improve the resolution of both Lamé parameters, we discuss the use of three robustifying schemes, namely, source-frequency continuation, regularization factor continuation, and a search direction-biasing scheme. We demonstrate with numerical experiments the effect the schemes have on the inversion process and conclude with an application of the robustified full-waveform method to a challenging adaptation of the Marmousi2 model.