Eruption frequency patterns through time for the current (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018) activity cycle at Volcán de Fuego derived from remote sensing data: Evidence for an accelerating cycle of explosive paroxysms and potential implications of eruptive activity.
AbstractVolcán de Fuego is a stratovolcano in Guatemala that has produced over 50 VEI 2 eruptions since 1524. After two decades of quiescence, in 1999 Fuego entered a new period of eruptive activity that continues until the present day, characterised by persistent Strombolian activity interspersed with occasional "paroxysmal" eruptions of greater magnitude, the most recent of which occurred in 2018. The land surrounding Fuego accommodates tens of thousands of people, so greater understanding of its eruptive behaviour has important implications for hazard assessment. Nevertheless, there is relatively little literature that studies recent (since 1999) activity of Fuego in detail.Using time-series analysis of remote sensing thermal data during the period 2000 -2018 combined with recent bulletin reports, we present evidence for a new eruptive regime beginning in 2015. We find that this regime is defined by a greater frequency of paroxysmal eruptions than in previous years and is characterized by the following sequence of events: (i) effusion of lava flows and increase in summit explosive activity, followed by (ii) an intense eruptive phase lasting 24 -48 hours, producing a sustained eruptive column, continuous explosions, and occasional pyroclastic flows, followed by (iii) decrease in explosive activity. We discuss various models that explain this increase in paroxysmal frequency, and consider its implications for hazard assessment at Fuego. We advocate the pairing of remote sensing data with monitoring reports for understanding long-term changes in behaviour of poorlyinstrumented volcanoes. The results that we present here provide a standard for informed assessment of future episodes of unrest and paroxysmal eruptions of Fuego.
KeywordsVolcán de Fuego -paroxysm -MIROVA -radiative power
Satellite radar backscatter has the potential to provide useful information about the progression of volcanic eruptions when optical, ground‐based, or radar phase‐based measurements are limited. However, backscatter changes are complex and challenging to interpret: explosive deposits produce different signals depending on pre‐existing ground cover, radar parameters and eruption characteristics. We use high temporal‐ and spatial‐resolution backscatter imagery to examine the emplacement and alteration of pyroclastic density currents (PDCs), lahar and ash deposits from the June 2018 eruption of Volcán de Fuego, Guatemala, using observatory reports and rainfall gauge data to ground truth our observations. We use a temporally dense time series of backscatter data to reduce noise and extract deposit areas. We observe backscatter changes in six drainages, the largest deposit was 11.9‐km‐long that altered an area of 6.3 normalknormalm2 and had a thickness of 10.5 ±2 m in the lower sections as estimated from radar shadows. The 3 June eruption also produced backscatter signal over an area of 40 normalknormalm2, consistent with reported ashfall. We use transient patterns in backscatter time series to identify nine periods of high lahar activity in a single drainage system between June and October 2018. We find that the characterization of subtle backscatter signals associated with explosive eruptions are best observed with (1) radiometric terrain calibration, (2) speckle correction, and (3) consideration of pre‐existing scattering properties. Our observations demonstrate that SAR backscatter can capture the emplacement and subsequent alteration of a range of explosive deposits, allowing the progression of an explosive eruption to be monitored.
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