  In this paper we present a numerical discretization of the coupled
elasto-acoustic wave propagation problem based on a Discontinuous Galerkin
Spectral Element (DGSE) approach in a three-dimensional setting. The unknowns
of the coupled problem are the displacement field and the velocity potential,
in the elastic and the acoustic domains, respectively, thereby resulting in a
symmetric formulation. After stating the main theoretical results, we assess
the performance of the method by convergence tests carried out on both matching
and non-matching grids, and we simulate realistic scenarios where
elasto-acoustic coupling occurs. In particular, we consider the case of Scholte
waves and the scattering of elastic waves by an underground acoustic cavity.
Numerical simulations are carried out by means of the code SPEED, available at
http://speed.mox.polimi.it.
