Salt Reconstruction in Full Waveform Inversion with a Parametric Level-Set Method

Seismic full-waveform inversion tries to estimate subsurface medium parameters from seismic data. Areas with
subsurface salt bodies are of particular interest because they often have hydrocarbon reservoirs on their sides or
underneath. Accurate reconstruction of their geometry is a challenge for current techniques. This paper presents a
parametric level-set method for the reconstruction of salt-bodies in seismic full-waveform inversion. We split the
subsurface model in two parts: a background velocity model and the salt body with known velocity but undetermined
shape. The salt geometry is represented by a level-set function that evolves during the inversion. We choose radial
basis functions to represent the level-set function, leading to an optimization problem with a modest number of
parameters. A common problem with level-set methods is to fine tune the width of the level-set boundary for
optimal sensitivity. We propose a robust algorithm that dynamically adapts the width of the level-set boundary to
ensure faster convergence. Tests on a suite of idealized salt geometries show that the proposed method is stable
against a modest amount of noise. We also extend the method to joint inversion of both the background velocity
model and the salt-geometry