The crack propagation dynamics is describe by the application of incubation time criterion based on fracture incubation under dynamic conditions. The rectangular specimens are loaded on the crack faces by a dynamic pulse uniformly distributed along the crack length. The temporal dependence of pressure pulse in the system is approximated by successive trapezoids and the behavior of the system is described by elasticity equations. The nodes of the crack continuum are subjected to symmetric boundary conditions until a moment is arrived where corresponding nodes are removed and a free surface is formed. The results show that varying the pressure pulse amplitude results in crack amplitudes of 5 MPa. The results also show that using the finite-element method for solving the dynamic problem of linear elasticity, it is possible to describe the propagation of dynamically loaded cracks.