Efficient Iterative Solution of Time-harmonic Scattering by Objects in Layered Fluid

We consider the computation of time-harmonic acoustic scattering by sound-soft or elastic objects in layered media. An example of such problem is the scattering by a mine buried in sediment. The computational domain can be tens or hundreds of meters long while the target requires modeling of details smaller than one centimeter. A discretized problem can have several billion degrees of freedom.