Variable explosive energy partitioning during open vent activity at Fuego volcano, Guatemala 2007-2009: constraining explosion source processes and implications for monitoring
Abstract
Fuego volcano, Guatemala is a 3800 m-high stratovolcano that has displayed open vent behavior since 1999, and has had several periods of historic open vent activity as well as more than 60 historical subplinian eruptions. Two years of continuous visual observations (2005-2007) and six months of seismic and acoustic data (2007) showed a repeating cycle of eruptive behavior that consisted of 1) passive lava effusion and minor strombolian explosions, 2) paroxysmal eruptions lasting 24-48 hours, and 3) degassing explosions with no associated effusion. The strombolian explosions that occurred during periods of passive lava effusion are characteristically distinct from degassing explosions. In this study, we quantify the ratio of radiated infrasound to seismic energy for each class of eruption during study periods in 2007, 2008 and 2009 to distinguish between potential models for the events. More than 25,000 people inhabit the high hazard zone around Fuego volcano, and the potential to track activity using explosive energy partitioning has monitoring and hazard implications. Strombolian explosions during passive effusion typically occur several times per hour, eject incandescent bombs, and produce ash-poor eruptive clouds. Degassing explosions characteristically occur once per hour, produce ash-rich eruptive clouds, and eject primarily lithic blocks. Two general types of degassing explosions are observed, 1) impulsive events with high excess pressure and 2) emergent, lower pressure transients in the acoustic traces without clear ground-coupled airwaves in the seismic data. On the other hand, strombolian explosions are nearly always impulsive in the acoustic traces but the seismic expressions of these events are variable. During the 2007 experiment, degassing explosions recorded at ~7 km from the vent show stable seismic-to-acoustic amplitude ratios ranging over less than an order of magnitude, while the energy partitioning during strombolian explosions varies widely with an overall higher seismic to acoustic amplitude ratio and range of ratios spanning two orders of magnitude. The opposite relationship is observed for explosions recorded during 2008 and 2009 at ~1 km from the vent. At this stage of the analysis, we have not fully explored the sensitivity of the 2007 explosive energy partitioning data to variable atmospheric conditions and variable background seismic tremor. The variations in the explosive energy partitioning in the 2008 and 2009 data, however, likely reflect changes in the depths of the sources.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.V23D2124L
- Keywords:
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- 7280 SEISMOLOGY / Volcano seismology;
- 8419 VOLCANOLOGY / Volcano monitoring;
- 8428 VOLCANOLOGY / Explosive volcanism;
- 8488 VOLCANOLOGY / Volcanic hazards and risks