  Power-law type probability density functions spanning several orders of
magnitude are found for different avalanche properties. We propose a
methodology to overcome empirical constrains that limit the power-law range for
the distributions of different avalanche observables like amplitude, energy,
duration or size. By considering catalogs of events that cover different
observation windows, maximum likelihood estimation of a global power-law
exponent is computed. This methodology is applied to amplitude and energy
distributions of acoustic emission avalanches in failure-under- compression
experiments of a nanoporous silica glass, finding in some cases global
exponents in an unprecedented broad range: 4.5 decades for amplitudes and 9.5
decades for energies. In the later case, however, strict statistical analysis
suggests experimental limitations might alter the power-law behavior.
