  We study numerically the propagation of seismic waves in a three-dimensional
block medium. The medium is modeled by a spatial lattice of masses connected by
elastic springs and viscous dampers. We study Lamb's problem under a surface
point vertical load. The cases of both step and pulse load are considered. The
displacements and velocities are calculated for surface masses. The influence
of the viscosity of the dampers on the attenuation of perturbations is studied.
We compare our numerical results for the block medium with known analytical
solutions for the elastic medium.
