  When materials are loaded below their short-term strength over extended
periods, a slow time-dependent process known as creep deformation takes place.
During creep deformation, the structural properties of a material evolve as a
function of time. By means of a generic coarse-grained mesoscopic elastoplastic
model which envisages deformation as a sequence of stochastically activated
discrete events, we study the creep deformation of disordered materials. We
find that the structural evolution of the material during creep modifies not
only the average material properties but also changes the statistics of those
properties. We analyze the emergence of correlations in the strain localization
and deformation activity patterns, the variation of the event rate and the
evolution of the inter-event time distribution. We find that the event rate
follows the Omori law of aftershocks, which is the discrete counterpart of
Andrade's transient creep law, and that the exponent of these laws only depends
on the microstructural heterogeneity. Finally, we find during the initial
stages of transient creep a transition from Poisson distributed inter-event
times towards a non-trivial power law distribution.
