Seismic-acoustic energy partitioning during a paroxysmal eruptive phase of Tungurahua volcano, Ecuador

Abstract

S U M M A R YStudies of discrete volcanic explosions, that usually last less than 2 or 3 min, have suggested that the partitioning of seismic-acoustic energy is likely related to a range of physical mechanisms that depend on magma properties and other physical constraints such as the location of the fragmentation surface. In this paper, we explore the energy partition of a paroxysmal eruptive phase of Tungurahua volcano that lasted for over 4 hr, on 2006 July 14-15, using seismicacoustic information recorded by stations on its flanks (near field). We find evidence of a linear scaling between seismic and acoustic energies, with time-dependent intensities, during the sustained explosive phase of the eruption. Furthermore, we argue that this scaling can be explained by two different processes: (1) the fragmentation region ultimately acts as the common source of energy producing both direct seismic waves, that travel through the volcanic edifice, and direct acoustic waves coming from a disturbed atmosphere above the summit; (2) the coupling of acoustic waves with the ground to cause seismic waves. Both processes are concurrent, however we have found that the first one is dominant for seismic records below 4 Hz. Here we use the linear scaling of intensities to construct seismic and acoustic indices, which, we argue, could be used to track an ongoing eruption. Thus, especially in strong paroxysms that can produce pyroclastic flows, the index correlation and their levels can be used as quantitative monitoring parameters to assess the volcanic hazard in real time. Additionally, we suggest from the linear scaling that the source type for both cases, seismic and acoustic, is dipolar and dominant in the near field.

Phreatic eruption dynamics derived from deposit analysis: a case study from a small, phreatic eruption from Whakāri/White Island, New Zealand

“…In contrast, a number of studies have examined the partitioning of seismic and acoustic energies (e.g. Hagerty et al 2000;Palacios et al 2016;Taddeucci et al 2010). More recent analysis of eruption energetics through combined field and laboratory analysis provides some basis for comparison, especially for relatively small, multi-pulse, phreatic eruptions (e.g.…”

Geophysical examination of the 27 April 2016 Whakaari/White Island, New Zealand, eruption and its implications for vent physiognomies and eruptive dynamics

“…The volcanic acoustic-seismic ratio (VASR) is the ratio between the acoustic energy and the seismic energy of an eruption or eruption sequence. VASR was first shown by Johnson and Aster (2005) on Karymsky, Russia and Erebus, Antarctica, and later used on Redoubt Volcano, Alaska (McNutt et al 2013), Te Maari, New Zealand (Jolly et al 2014a), and at Tungurahua, Ecuador (Palacios et al 2016). We use VASR on the Whakaari eruption sequence as a means to investigate the partition of energy between the ground and atmosphere to give an idea what the eruption source characteristics might be, as well as, other differences between the multiple pulses (e.g., energy transfer, conduit size, and source area).…”

A simple method to evaluate the seismic/infrasonic energy partitioning during an eruption using data contaminated by air-to-ground signals

“…The Volcanic Acoustic-Seismic Ratio (VASR) that is the infrasonic power over the seismic power [Johnson and Aster, 2005], has been used to investigate the energy partitioning between seismic waves and infrasonic waves. The energy partitioning allows us to infer the change of eruptive behaviors [Sciotto et al, 2011;Johnson and Aster, 2005;Ichihara, 2016, Palacios et al, 2016. When the same eruption mechanism is kept, the seismic and infrasonic eruption tremors tend to vary their amplitudes with the eruption parameter, like plume height, keeping their ratio constant [Ichihara, 2016;Fee et al, 2016;Haney et al, 2018;Sciotto et al, 2019].…”