The physics of an earthquake is a subject with many unknowns. It is true that we have a good understanding of the propagation of seismic waves through the Earth and that given a large set of seismographic records we are able to reconstruct a posteriori the history of the fault rupture (the origin of the waves). However, when we consider the physical processes which lead to the initiation of a rupture with a subsequent slip and its growth through a fault system to give rise to an earthquake, then our knowledge is really limited. Not only the friction law and the rupture evolution rules are largely unknown, but the role of many other processes such as plasticity, fluid migration, chemical reactions, etc., and the couplings between them, remain unclear [1, 2]. © 2006 Springer.