Earthquakes in a classical sense originate from the rapid release of elastic energy caused by the rupture of rock in the earth. Damaging effects due to an earthquake arise (i) from a source outcropping directly at the earths surface, (ii) from the radiated seismic waves. In practice the second effect is the most important. It occurs more frequently and the area shattered by seismic waves is by far larger than the zone which could be hit by an outcropping source. In ShakyGround we focus, therefore, on the effects caused by the radiation of seismic waves. The simulation of the seismic source in ShakyGround follows a stochastic concept as it has been proposed by Hanks & McGuire (1981) and Boore (1983). The source signal, in terms of ground acceleration, is generated as a sequence of gaussian distributed random numbers. The general characteristics of the seismic source are represented by applying a window function in the time domain and filtering the signal with respect to the spectral properties of the seismic source. The concept thus reflects the high variability typically in most accelerograms, which can be reconducted to heterogeneities of the source (the so-called 'barriers' or 'asperities', schematically indicated by the red spots in the figure). On the other hand, the deterministic frame parameters, like source dimension (represented here by the length L and the width W) and the average dislocation D, are accounted for by the window function and the spectral filtering.