  The dynamical facilitation scenario, by which localized relaxation events
promote nearby relaxation events in an avalanching process, has been suggested
as the key mechanism connecting the microscopic and the macroscopic dynamics of
structural glasses. Here we investigate the statistical features of this
process via the numerical simulation of a model structural glass. First we show
that the relaxation dynamics of the system occurs through particle jumps that
are irreversible, and that cannot be decomposed in smaller irreversible events.
Then we show that each jump does actually trigger an avalanche. The
characteristic of this avalanche change on cooling, suggesting that the
relaxation dynamics crossovers from a noise dominated regime where jumps do not
trigger other relaxation events, to a regime dominated by the facilitation
process, where a jump trigger more relaxation events.
