Stress relaxation in the Earth and seismic activity

Consideration of the models described in the preceding pages shows that a sound theoretical basis exists for a physical understanding of post-seismic ground deformations and several other phenomena associated with the asthenosphere relaxation. Since the asthenosphere seems to be involved in a direct way in the seismic mechanism, the knowledge of its rheological properties becomes an essential point to understand the seismic mechanism too. Once a reasonable knowledge of the asthenosphere behaviour is achieved, the models can tell us how the system lithosphere-asthenosphere will evolve after an earthquake or a similar perturbation of the stress field. It will be necessary to compute the stress pattern not only at the Earth surface, but also at the depth where the faults lay. By knowing how stress changes in space and time through the lithosphere, one might predict, for instance, the arrival of a stress wave on a seismogenetic structure: this wave might trigger an earthquake in this zone, if favourable conditions are found.