Numerical simulations of electromagnetic field and electric current are based on the solutions of equations for the dislocation density field with the term including self-interactions between the dislocations; the case under study concerns the charge dislocations. The equations are solved numerically for the medium with thin layers representing the faults and for the initial conditions representing two groups of dislocations of opposite signs facing each other. This case refers to stress concentration; the gradients of stress field, opposite to the central point of stress accumulation, contribute to the respective dislocation densities since the linear dislocation density for a simple 1D case becomes proportional to stress gradient. A single fault, as a zone with small resistance/friction values, is described by rigidities smaller than the bulk rigidity value, while for a fine-band structure of faults the rigidities in the layers between the adjacent faults are assumed to be higher than the bulk value. The results obtained show characteristic features in which the seismic pre-cursory activity simulates that of the main rebound processes represented in the natural time as counted in relation to the consecutive events. Our model contributes to the previous discussion and experimental data related to natural time analysis suggested recently by Varotsos and coworkers.