Asymptotic solution of the anti-plane problem for a two-dimensional   lattice
  Propagation of unsteady waves under the effect of a step point load on a square lattice of spring-connected masses is investigated. The problem is solved by two methods. Asymptotic solutions at large time intervals, which describe the behavior of long-wave perturbations, are derived analytically. The solution over the whole time interval for the waves of the entire spectral range is derived by the finite difference method. These solutions are compared, and their good agreement is shown. 
Nadezhda Aleksandrova
math.AP physics.class-ph