  We show that the divergent acoustic energy release rate in a quasi-statically
compressed nano-porous material can be used as a precursor to failure in such
materials. A quantification of the inequality of the energy release rate using
social inequality measure indices help constructing a warning signal for large
bursts of energy release. We also verify similar behavior for simulations of
viscoelastic fiber bundle models that mimic the strain-hardening dynamics of
the samples. The results demonstrate experimental applicability of the
precursory signal formulation for any diverging response function near a
transition point using social inequality indices.
