The significant group effort made within the Quake Project has highly faciliated my part of work, e.g., the initial 3-D model trial [28], the construction and improvement of the FEM tool-chain Archimedes, and the 2-D modeling and simulations of real earthquakes [49]. Based on that, we have designed a 3-D FEM simulator. Due to the complexity of the 3-D problems which involve arbitrarily heterogeneous materials with large contrasts and complicated seismic sources, at first we concentrated on a problem that was simplified with respect to geometry, materials and source model. Our starting point was to solve a 3-D problem, which represented an idealization, yet it was complete in all aspects to test our algorithms and methodology in analyzing 3-D seismic effects using a plane incident SV wave as excitation. Subsequently, we developed a source model for aftershocks, which are usually considered as a point source. The model was implemented in our 3-D FEM code to simulate a real earthquake aftershock, one of the 1994 Northridge aftershocks and it yielded meaningful results. A summary of completed work is given below.