Abstract
The rapid discharge of gas and rock fragments during volcanic eruptions generates acoustic infrasound. Here we present results from the inversion of infrasound signals associated with small and moderate gas‐and‐ash explosions at Santiaguito volcano, Guatemala, to retrieve the time history of mass eruption rate at the vent. Acoustic waveform inversion is complemented by analyses of thermal infrared imagery to constrain the volume and rise dynamics of the eruption plume. Finally, we combine results from the two methods in order to assess the bulk density of the erupted mixture, constrain the timing of the transition from a momentum‐driven jet to a buoyant plume, and to evaluate the relative volume fractions of ash and gas during the initial thrust phase. Our results demonstrate that eruptive plumes associated with small‐to‐moderate size explosions at Santiaguito only carry minor fractions of ash, suggesting that these events may not involve extensive magma fragmentation in the conduit.
Highlights
Volcanoes are efficient sources of infrasonic acoustic waves with frequencies below 20 Hz [Johnson et al, 2004; Fee and Matoza, 2013; Garcés et al, 2013]
It has been shown that propagation of the acoustic wavefield over terrain with variable topography may result in diffraction, attenuation, or focusing effects beyond the predictions of geometrical spreading [Lacanna et al, 2014]
Multidisciplinary, approach can help to improve our understanding of the mechanisms of volcanic explosions and the dynamics of plume rise
Summary
Volcanoes are efficient sources of infrasonic acoustic waves with frequencies below 20 Hz [Johnson et al, 2004; Fee and Matoza, 2013; Garcés et al, 2013]. Several authors used infrasound to assess the strength of volcanic explosions measuring either gas velocity or volume flux at the vent. Kim et al [2012] recently proposed a waveform inversion workflow based on a representation of the acoustic source as a combination of multipole terms, using analytical Greens functions in a half-space. This method can simultaneously retrieve the time history of mass outflow at the vent and account for directivity effects on the acoustic wavefield.
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