Context:

Stressed rocks produce acoustic emission signals. Acoustic emission and seismic information are complementary in their applications as well as on their theoretical basis. Thus, studying characteristic frequencies in acoustic emission signals is relevant to understanding the seismic wave propagation on the Earth.

Method:

A uniaxial compression test was performed on cylindrical samples of andesite rock, which were stressed up to breakage. Acoustic emission signals were recorded during the test. Frequency analysis in these signals may be carried in the context of an elementary seismic focus model. This model describes the fracture advance and propagation during brittle material fracture. The corner frequency is obtained from the Fourier spectrum of the signals, conveniently represented in log scale. This parameter accounts for the size of fissures as damage progresses when the material is stressed.

Results:

The corner frequency was determined on a first analysis. On a second analysis, the signals were filtered on different bands with the Wavelet Transform and the corresponding wavelet energy b-value was obtained.

Conclusions:

Studying the evolution of the wavelet energy b-value in different frequency bands allowed the determination of characteristic frequencies which can be associated with different fracture regimes in rocks.