  We consider the inverse boundary value problem of recovering piecewise
homogeneous elastic tensor and piecewise homogeneous mass density from a
localized lateral Dirichlet-to-Neumann or Neumann-to-Dirichlet map for the
elasticity equation in the space-time domain. We derive uniqueness for
identifying these tensor and density on all domains of homogeneity that may be
reached from the part of the boundary where the measurements are taken by a
chain of subdomains whose successive interfaces contain a curved portion.
