The role of attenuation on acoustic emission amplitude distributions and b-values

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An analysis is presented that allows the evaluation of the effect of attenuation on acoustic emission amplitude distributions and b-values obtained during the deformation of geomaterials in laboratory experiments. It is shown that initial amplitude distributions can be strongly affected by attenuation. Therefore, the interpretation of recorded distributions or b-values, in terms of damage, distribution of microcrack sizes, or the comparison of the microseismicity at a small scale with earthquakes dynamics in the Earth's crust has to be taken with caution. The analysis allows one to ascertain, in some cases, whether a b-value calculated from a measured distribution was modified by attenuation. The procedure can be theoretically reversed in order to estimate the original distribution (at the source) from the recorded distribution. However, in practice, lack of precision on attenuation coefficients and source radii makes it difficult to perform.