Some statistical features of avalanche dynamics preceding extreme events can be related to the onset of a phase transition. Other features are more difficult to reproduce at the conceptual level. This is the case of temporal correlations in the form of aftershock sequences as observed in earthquakes, interface deppining, acoustic emission experiments and structural phase transitions. Different micromechanical models reproduce such features by introducing physically-based mechanisms: rheology of structural materials and internal fluids; rate-and-state friction; dynamic stress transfer, inertia, etc.. Recent studies also revealed non-trivial effects caused by small and large-scale heterogeneities in numerical simulations and experiments.
This section is a follow-up of Section 3, focused on the experimental observation and modelling of second-order features such as precursors, sporadic or driven regime transitions, and the effects of temporal scales and heterogeneity.