Pre-seismic phenomena from continuous near-field strain measurements: a brief review and the case of the 2009 L’Aquila, Italy, earthquake

After a brief (incomplete) review of pre-seismic (strain-producing) phenomena, we describe our findings about the pre-seismic phase of the the April 6, 2009 L’Aquila earthquake, giving a few more details with respect to previous papers. Most past observations of crustal strain did not detect any pre-seismic deformation and have been used to constrain the size and strength of the source of possible pre-seismic phenomena. With respect to these, we performed a rather more sophisticated approach to the physics of the model; limited the volume of the possible earthquake preparation zone to less than 100 km3; showed some evidence of dilatancy of saturated rock over the earthquake causative fault (maybe related to the foreshocks) and constrained the prerupture nucleation slip in the hypocentral region to a moment less than 0.00005% of the main shock seismic moment (lowering the previous thresholds).