The multi-scale roughness of a fault interface is responsible for
multiple asperities that establish a complex and discrete set of real
contacts. Since asperities control the initiation and evolution of the
fault slip, it is important to explore the intrinsic relationships
between the collective behavior of local asperities and the frictional
stability of the global fault. Here we propose a novel analog
experimental approach, which allows us to capture the temporal evolution
of the slip of each asperity on a faulting interface. We find that many
destabilizing events at the local asperity scale occurred in the
frictional strengthening stage which is conventionally considered as the
stable regime of a fault. We compute the interseismic coupling to
evaluate the slipping behaviors of asperities during the
fault-strengthening stage. We evidence that the interseismic coupling
can be affected by the elastic interactions between asperities through
the embedding soft matrix. Scaling laws of natural slow slip events are
reproduced by our setup in particular the moment-duration scaling. We
also evidence an unexpected persistency of a disordering of the
asperities through the seismic cycles despite the relaxation effects of
the large slip events.