Abstract
We combine geophysical and experimental observations to interpret preeruptive unrest at Volcán de Colima in 1998. 17,893 volcanic earthquakes were detected between 1 October and 31 December 1998, including 504 clusters. Using seismic ambient noise interferometry, we observe a drop in velocity prior to the eruption linked to damage accumulation during magma ascent. This is supported by experimental observations where static stress causes a velocity decrease prior to failure. Furthermore, we observe acoustic emission clusters during the experiments, with lower porosity samples producing higher numbers of repeaters. This behavior introduces tensile failure as an additional viable mechanism for clusters during magma ascent. The findings suggest that preeruptive magma ascent may be monitored to variable degrees of accuracy via descriptions of damage accumulation and associated seismic velocity changes.
Highlights
An important aspect of volcano monitoring is assessing whether a period of unrest will portend an eruption
The findings suggest that preeruptive magma ascent may be monitored to variable degrees of accuracy via descriptions of damage accumulation and associated seismic velocity changes
We observe an unsteady rise in the amplitude ratios of EZV4/EZV3 and EZV7/EZV3 that indicates the relative movement of earthquake sources toward stations EZV4 and EZV7 prior to the eruption on 20 November (Figure 2b)
Summary
An important aspect of volcano monitoring is assessing whether a period of unrest will portend an eruption. Recent studies have shown that seismic interferometry, using either the coda waves of repeating earthquakes or ambient noise, holds considerable potential as a tool for monitoring active volcanoes [e.g., Brenguier et al, 2008; Hotovec-Ellis et al, 2015]. Seismic velocity is frequently observed to decrease prior to eruption and subsequently increase as the eruption ensues, a pattern often attributed to cycles of static stress due to magma movement [e.g., Ratdomopurbo and Poupinet, 1995; Wegler et al, 2006; Brenguier et al, 2008; Duputel et al, 2009; Hotovec-Ellis et al, 2015]. AEs have been demonstrated to precede material failure under temperature and stress conditions typical of shallow volcanic conduits [e.g., Lavallée et al, 2008]. The recent advances in experimental rock mechanics have improved our understanding of field-scale volcanic processes
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