In this study, we used data for one year, 2004, and we obtained much larger values of variance reduction (more than 30%). Similar or larger improvements were obtained for other years. The natural explanation for these results is a strong time variation of seismic velocities beneath the volcanoes (Koulakov et al., Variable feeding regimes of the volcanoes in the Kluchevskoy group (Kamchatka, Russia) derived from timedependent seismic tomography, manuscript in preparation, 2011).