“…inverse source problems [4,5,31], inverse obstacle scattering [20,32,33], seismic inverse scattering [41], and see e.g. [6,8,15,16,22,34,35,36,37,46] for inverse boundary value problems of determining the elastic body, [19,45] for inverse problems for nonlinear elastic wave equations, and [9,27,38,39] for identifying inclusions or cracks.…”