Numerical investigation of temporal changes in volcanic deformation caused by a gas slug ascent in the conduit

Kawaguchi, Ryohei; Nishimura, Takeshi

doi:10.1016/j.jvolgeores.2015.06.002

Cited by 12 publications

(34 citation statements)

References 30 publications

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“…In a recently published study of Kawaguchi and Nishimura [2015] the normal stresses were derived from the original model of James et al [2008] in a similar but simplified manner. Because of this and the use of a constant Newtonian viscosity, the results cannot be expected to be identical, but qualitatively, they agree well.…”

Section: Reference Scenariomentioning

confidence: 99%

“…The influence of a more viscous body of degassed, cooled, and crystallized magma capping the top of the conduit (thus termed viscous plug) on the slug's burst has only recently been investigated experimentally and by modeling [e.g., Del Bello et al, 2015;Kawaguchi and Nishimura, 2015;Capponi et al, 2016], although its presence in nature is generally deemed plausible. The algorithm for the slug's ascent described in section 2 does not pose any restrictions on the rheological model, and the specific one documented in Appendix B can readily be adapted to incorporate a viscous plug at the top of the conduit in a consistent way.…”

Section: Viscous Plugmentioning

confidence: 99%

“…While the downward shear stresses associated with the film stay essentially the same, the upward ones above the slug decrease slightly to 0.11 bar due to the slower decompression. Kawaguchi and Nishimura [2015] model the effect of a viscous plug on the normal stresses on the conduit by direct manipulation of the differential equations. They predict that given a 10 m thick high-viscosity layer being 10 times more viscous than the magma below, the positive stresses above the slug increase by a factor of 1.3 and the negative stresses below it decrease and might actually become positive shortly before the burst.…”

Section: Viscous Plugmentioning

confidence: 99%

“…The original model has since been further studied and extended, e.g., to examine the cause of low-intensity explosions (puffing) or to allow for the overflow of magma over the crater rim as the magma level rises Table 2 for the different symbols. [James et al, 2009;Del Bello et al, 2012], but the constraint to a constant viscosity has only been recently addressed by Kawaguchi and Nishimura [2015] and Del Bello et al [2015] who investigate the effect of a region of higher viscosity (viscous plug) at the top of the conduit and the stresses acting during the slug ascent.…”

Section: Introductionmentioning

confidence: 99%

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Slug ascent and associated stresses during strombolian activity with non‐Newtonian rheology

Lieth

Hort

2016

JGR Solid Earth

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Strombolian activity is generally assumed to be driven by overpressurized gas slugs that rise through the magma‐filled volcanic conduit and burst at the surface. We develop an analytical model for this process that incorporates a generic, depth‐dependent, and non‐Newtonian magma rheology. Our model also describes the film draining after the burst and allows for the computation of the stresses exerted on the conduit walls using a new analytical solution for the thickness of an annular film flow. Using Stromboli volcano, Italy, as reference, it was evaluated with a specifically designed, non‐Newtonian rheological model based on petrochemical data. The results show the importance of using a realistic magma viscosity model when modeling the slug ascent: A 100 kg gas slug attains its maximum overpressure of 2.1 bars about 40 s before it rapidly expands and finally bursts at only 1.4 bars. This preburst pressure drop is not reproduced by constant viscosity models. The normal stresses on the conduit wall are generally dilatational above and adjacent to the slug and constrictive below it and after the burst. In both cases their maximum values exceed 3 bars, whereas the shear stresses stay negligible. Furthermore, it was found that the slug needs to start deeper than 25 m to build up its full burst pressure. At greater depth, the burst pressure decreases because of the adiabatic slug gas. Finally, a viscous plug at the top of the conduit is shown to increase the explosive potential of the volcano significantly.

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Section: Reference Scenariomentioning

confidence: 99%

Section: Viscous Plugmentioning

confidence: 99%

Section: Viscous Plugmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Slug ascent and associated stresses during strombolian activity with non‐Newtonian rheology

Lieth

Hort

2016

JGR Solid Earth

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“…The parameters include the varying mass of gas involved ( M ), and the physical parameters defining the volcanic system: density ( ρ ) and viscosity ( μ ) of the magma, shear modulus ( G ) of the host rock, radius of the conduit ( r c ), and the depth of the magma free surface ( c ). The model used incorporates both the conduit model, developed by Bonaccorso and Davis () and further improved by Kawaguchi and Nishimura (), and the model of slug ascent process in an open conduit based on the one proposed by James et al (, ) which consider the slug dynamic described by Llewellin et al () (Table ).…”

Section: Introductionmentioning

confidence: 99%

A Bayesian Approach to Infer Volcanic System Parameters, Timing, and Size of Strombolian Events From a Single Tilt Station

Manta

Taisne

2019

JGR Solid Earth

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Persistently active volcanoes are characterized by frequent eruptions, in which volatiles dissolved in magma play an important role in controlling the explosivity. Inverting techniques on geodetic data sets have been used to retrieve information about key controlling parameters of these eruptions. However, up to date, several data sets are combined to obtain reliable estimates of the physical parameters using a physical model, hindering the possibility to provide forecasting tools for time and magnitude of eruptions at volcanoes with limited monitoring network. In this work, we propose an approach to extract valuable information out of limited data sets through inverting techniques dealing with limited number of sensors, but high frequency of events. Our method exploits time series of tilt signals recorded by a single station to estimate, by mean of the Bayesian statistics and a physics-based model, the range of the controlling parameters. The method was developed and tested on a synthetic volcanic system before being applied on data from Semeru volcano (Indonesia). Finally, we tested the possibility to forecast explosion magnitude and timing using data recorded by a single tilt station. Results show that data from a limited network or even a single tilt station is sufficient to estimate the controlling parameters. The information obtained is shown to be useful for estimating the time and magnitude of future events, which can enhance the monitoring systems of those volcanoes characterized by frequent, potentially dangerous events.

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The implications of gas slug ascent in a stratified magma for acoustic and ground deformation source mechanisms in Strombolian eruptions

Capponi

Lane

James

2017

Earth and Planetary Science Letters

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The interpretation of geophysical measurements at active volcanoes is vital for hazard assessment and for understanding fundamental processes such as magma degassing. For Strombolian activity, interpretations are currently underpinned by first-order fluid dynamic models which give relatively straightforward relationships between geophysical signals and gas and magma flow. However, recent petrological and high-speed video evidence has indicated the importance of rheological stratification within the conduit and, here, we show that under these conditions, the straightforward relationships break down. Using laboratory analogue experiments to represent a rheologically-stratified conduit we characterise the distinct variations in the shear stress exerted on the upper sections of the flow tube and in the gas pressures measured above the liquid surface, during different degassing flow configurations. These signals, generated by varying styles of gas ascent, expansion and burst, can reflect field infrasonic measurements and ground motion proximal to a vent. The shear stress signals exhibit timescales and trends in qualitative agreement with the near-vent inflation-deflation cycles identified at Stromboli. Therefore, shear stress along the uppermost conduit may represent a plausible source of nearvent tilt, and conduit shear contributions should be considered in the interpretation of ground deformation, which is usually attributed to pressure sources only. The same range of flow processes can produce different experimental infrasonic waveforms, even for similar masses of gas escape. The experimental data resembled infrasonic waveforms acquired from different vents at Stromboli associated with different eruptive styles. Accurate interpretation of near-vent ground deformation, infrasonic signal and eruptive style therefore requires detailed understanding of: a) spatiotemporal magma rheology in the shallow conduit, and b) shallow conduit geometry, as well as bubble overpressure and volume.

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Numerical investigation of temporal changes in volcanic deformation caused by a gas slug ascent in the conduit

Cited by 12 publications

References 30 publications

Slug ascent and associated stresses during strombolian activity with non‐Newtonian rheology

Slug ascent and associated stresses during strombolian activity with non‐Newtonian rheology

A Bayesian Approach to Infer Volcanic System Parameters, Timing, and Size of Strombolian Events From a Single Tilt Station

The implications of gas slug ascent in a stratified magma for acoustic and ground deformation source mechanisms in Strombolian eruptions

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