  We are concerned with the linearized, isotropic and homogeneous elastic
scattering problem by (possibly many) small rigid obstacles of arbitrary
Lipschitz regular shapes in 3D. Based on the Foldy-Lax approximation, valid
under a sufficient condition on the number of the obstacles, the size and the
minimum distance between them, we show that any of the two body waves, namely
the pressure waves P or the shear waves S, is enough for solving the inverse
problem of detecting these scatterers and estimating their sizes. Further, it
is also shown that the shear-horizontal part SH or the shear vertical part SV
of the shear waves S are also enough for the location detection and the size
estimation. Under some extra assumption on the scatterers, as the convexity
assumption, we derive finer size estimates as the radius of the largest ball
contained in each scatterer and the one of the smallest ball containing it.
  The two estimates measure, respectively, the thickness and length of each
obstacle.
