Time-scale wavelet patterns related to the 1998–1999 eruptions of the Colima volcano, and their possible implications for eruption forecasting

The seismic activity from one of the most active (documented) periods of the Colima volcano, from October 1998 to July 1999, was analyzed using the wavelet transform, to study the evolution in time of energy content at different scales of seismic signals preceding eruptive episodes. Time-scale analysis shows seismic energy concentrations at particular scales preceding significant eruptions; concentrations that do not appear within the same time-frame for non-eruptive stages. Quantification of the energy at each scale eases the recognition of characteristic wavelet patterns before the occurrence of significant effusive or explosive eruptions. The recognition of precursory wavelet patterns, which does not depend on the absolute level of energy release, could help to objectively identify precursors to imminent explosive eruptions, even in cases where other seismic energy-based methods are not conclusive.