Vulcanian explosions in the process of building-destruction of the lava dome of andesitic volcano: Insight from the seismic signals recorded at Volcán de Colima, México

Abstract

The seismic signals associated with the Vulcanian explosive events at Volcán de Colima, México during its 1998–2014 eruption were discriminated into three types according the waveforms of their initial phases. This classification includes about 85–90% of all seismic signals associated with explosive events. It was shown that the classification of the explosive seismic signals gave a useful tool for analysis of the eruption development. Analysis was performed for two 6-month stages of the eruption, the 2003 post-effusive stage culminated with large explosions and the 2007 co-effusive stage during the beginning of new lava dome growth in the crater of the volcano. The predominance (95%) of the type 1 and 3 events with low-frequency (LF) and high+low frequency (HF+LF) initial phases in the sample of the 2003 post-effusive stage explosive events identifies the termination of the lava effusion and preparation to the stage of large explosions. The high participation (37%) of the type 2 events with high-frequency (HF) initial phases in the sample of the 2007 co-effusive stage explosive events indicates the process of the lava dome growth beginning. The introduction of multi-stage conceptual model of explosive process allows the interpretation of peculiarities of the seismic signals associated with explosive activity. Analysis of the spectral content of the initial LF phases of the seismic signals associated with the explosions showed that the sources of LF initial phases, corresponding to the ascent of magma within the volcanic conduit above the fragmentation zone, were common for post-effusive and co-effusive stages. The source of events with the HF initial phases differed from the source of events with the LF first phases. The sources of explosions at explosion level were situated at different sites during post-effusive and co-effusive stages.