  The statistical properties of failure are studied in a fiber bundle model
with thermal noise. We show that the macroscopic failure is produced by a
thermal activation of microcracks. Most importantly the effective temperature
of the system is amplified by the spatial disorder (heterogeneity) of the fiber
bundle. The case of a time dependent force and the validity of the Kaiser
effects are also discussed. These results can give more insight to the recent
experimental observations on thermally activated crack and can be useful to
study the failure of electrical networks.
