What makes a volcano tick—A first explanation of deep multiple seismic sources in ascending magma

Thomas, Mark; Neuberg, Jürgen

doi:10.1130/g32868.1

Cited by 56 publications

(66 citation statements)

References 23 publications

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“…An example of a spatially extended source generating seismicity within a volcanic environment is a volcanic conduit through which magmatic fluids move. In these instances, the generation of low frequency seismicity may be related to the brittle failure of magma itself Lavallée et al 2008;Thomas and Neuberg 2012) or through a stick-slip motion at the conduit edge (Iverson et al 2006). In either case, shallow source depths (1-2 km) and short epicentral distances to seismic receivers (a few kilometers) suggest that a spatially extended source is more realistic than a single point source.…”

Section: The Source Mechanisms Of Low Frequency Earthquakesmentioning

confidence: 99%

“…The trigger mechanism of such seismic energy is further disputed, with suggestions that it may be generated by: (1) a stick-slip motion along the conduit walls as magma ascends (e.g. Iverson et al 2006); (2) the brittle failure of magma itself either through an increase in viscosity and strain rates (Lavallée et al 2008), which may be due to an increase in the ascent rate of magma through the conduit , changes in the crystal and/or bubble concentration in the magma (Goto 1999), or through a change in the geometry of the conduit (Thomas and Neuberg 2012); (3) the interaction between the magmatic and hydrothermal system at depth (e.g. Nakano and Kumagai 2005); or (4) through slow rupture and failure of unconsolidated material on volcanic slopes (Bean et al 2014).…”

Section: Classification By Frequency Contentmentioning

confidence: 99%

“…Other spatially extended sources which may evoke the generation of low frequency seismicity include: the upward movement of magma through a narrow dyke, numerically modelled by two oppositely directed double couple sources; slip along distinct segments of the volcanic conduit i.e. due to geometry changes (Thomas and Neuberg 2012), numerically modelled with double couple sources on distinct segments; or the generation of a number of seismic swarms of families of earthquakes occurring simultaneously (Salvage and Neuberg 2016), which can be numerically modelled by movement on two or more simultaneously acting ring fault structures. Green and Neuberg (2006) suggested that accelerated magma movement at Soufrière Hills volcano can be linked to observed deformation cycles through low frequency seismic swarms, and that seismicity is only generated if significant magma movement takes place.…”

Section: The Source Mechanisms Of Low Frequency Earthquakesmentioning

confidence: 99%

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Volcano Seismology: Detecting Unrest in Wiggly Lines

Salvage¹,

Karl

Neuberg

2017

Advances in Volcanology

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Seismology is a useful tool to gain a better understanding of volcanic unrest in real time as it unfolds. The generation of seismic signals in a volcanic environment has been linked to a number of different physical processes occurring at depth, including fracturing of the volcanic edifice (producing high frequency seismicity) and movement of magmatic fluids (producing low frequency seismicity). Further classification of seismic signals according to their waveform similarity, in addition to their frequency content, allows greater detail in temporal and spatial changes of seismicity to be detected. At Soufrière Hills volcano, Montserrat, one of the target volcanoes of the VUELCO project, families of similar waveforms provided valuable insight into evaluating the significance of ongoing unrest. In June 1997 over 6000 more events were able to be identified over a 5 day period of interest (22 to 25 June) by using families of seismic events, rather than a standard amplitude-based detection algorithm. In total, 11 families were identified, with the events clustering into a number of swarms, suggesting a repeating and non destructive cyclic source mechanism. Since each family is believed to represent a distinct source location and mechanism, identifying 11 coexisting families R.O. Salvage (&)

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Section: The Source Mechanisms Of Low Frequency Earthquakesmentioning

confidence: 99%

Section: Classification By Frequency Contentmentioning

confidence: 99%

Section: The Source Mechanisms Of Low Frequency Earthquakesmentioning

confidence: 99%

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Volcano Seismology: Detecting Unrest in Wiggly Lines

Salvage¹,

Karl

Neuberg

2017

Advances in Volcanology

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“…Neuberg et al (2006) further modelled magma ascent in confined geometry and showed that a De $ 1 is met at a depth of 830 m below the surface using parameters typical for recent eruptions at Soufriere Hills volcano and the magma thereof. Thomas and Neuberg (2012) predicted a deeper source of 1500 m using the same model approach but by invoking a conduit restriction (see Chap. 9), consistent with inversions for low-frequency sources using seismic data.…”

Section: Laboratory-scale Unrest Signalsmentioning

confidence: 99%

“…However, knowledge of the physics of the source leads to a more diverse range of tools being deployed to understand the evolution of volcanic systems into the future. In the context of low-frequency earthquakes at volcanoes, once a source mechanism is identified (Tuffen et al 2003;Neuberg et al 2006), numerical models of magma ascent in the conduit beneath volcanoes can be used to reproduce the depths of the source from first principles (Thomas and Neuberg 2012) and could eventually make forecasts of other observables at the surface that would be consistent with impending eruption.…”

Section: Introductionmentioning

confidence: 99%

When Does Magma Break?

Wadsworth¹,

Witcher²,

Vasseur³

et al. 2017

Advances in Volcanology

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Geophysical signals arriving at the Earth's surface originate from a source mechanism at depth but are not necessarily directly observable. Therefore, well-posed experiments can provide insights into source mechanics and, importantly, the parameters required to model aspects of the sources of unrest signals. In this Chapter we detail one such example of how experimental laboratory work has improved our understanding of unrest signals. We focus on the failure of single-and multi-phase magmas, demonstrating that the liquid viscosity, and therefore the temperature and volatile content of a magma of a given composition, is the limiting parameter in determining whether a magma will ascend viscously or whether it can fracture during ascent. This critical threshold is characterized by a Deborah number, the ratio of the timescale of relaxation to the timescale of local flow. We show that for single-phase magmatic liquids and for vigorously vesiculating magmas, a local Deborah number of 10 À2 is the limit above which mixed viscoelastic behaviour including fracture propagation can be expected, and a Deborah number of 1 is the limit above which magma is dominantly elastic and responds in a brittle manner to applied stresses. These thresholds can be understood in terms of the onset and peak of the Debye relaxation process for viscoelastic liquids. The apparent validity of a Maxwell model permits us to predict the maximum stress that can be supported by a volcanic liquid deforming in the high Deborah number range. We use these constraints to provide a map of timescales on which we contour dominant system responses from viscous to purely brittle; valid for all magmatic liquids. Finally, we explore the scaling necessary to extend these conceptual insights to crystal-and bubble-bearing magmas valid under specific conditions. The competing timescales of deformation and relaxation in magma are relevant to unrest source mechanisms that originate from magma deformation, such as long-period seismic signals that are used to predict eruption timing. KeywordsRheology Á Strain rate Á Experimental volcanology Á Glass transition Á Failure forecasting Á Low frequency earthquakes Á Viscous dissipation Glossary RheologyThe study of the response of a material to an applied stress or deformation. In the volcano-sciences this typically refers to magma-rheology which is dominated by the rheology of the liquid phase (a viscous or viscoelastic melt) and the additional effect of suspended phases (crystals and gases). Viscoelasticity A material response to an applied stress in which both elastic and viscous components of the deformation are observed. In magma, as the temperature decreases or the local strain rate increases, the elastic component becomes more dominant. When the viscous component is negligible, purely elastic behaviour and material-rupture can readily occur. See Rheology.

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Interpretation of resonance frequencies recorded during hydraulic fracturing treatments

Tary

Baan

Eaton

2014

J. Geophys. Res. Solid Earth

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Hydraulic fracturing treatments are often monitored by strings of geophones deployed in boreholes. Instead of picking discrete events only, we here use time‐frequency representations of continuous recordings to identify resonances in two case studies. This paper outlines an interpretational procedure to identify their cause using a subdivision into source, path, and receiver‐side effects. For the first case study, two main resonances are observed both at depth by the downhole geophones and on the surface by two broadband arrays. The two acquisition networks have different receiver and path effects, yet recorded the same resonances; these resonances are therefore likely generated by source effects. The amplitude pattern at the surface arrays indicates that these resonances are probably due to pumping operations. In the second case study, selective resonances are detected by the downhole geophones. Resonances coming from receiver effects are either lower or higher frequency, and wave propagation modeling shows that path effects are not significant. We identify two possible causes within the source area, namely, eigenvibrations of fractures or non‐Darcian flow within the hydraulic fractures. In the first situation, 15–10 m long fluid‐filled cracks could generate the observed resonances. An interconnected fracture network would then be required, corresponding to mesoscale deformation of the reservoir. Alternatively, systematic patterns in non‐Darcian fluid flow within the hydraulic fracture could also be their leading cause. Resonances can be used to gain a better understanding of reservoir deformations or dynamic fluid flow perturbations during fluid injection into hydrocarbon and geothermal reservoirs, CO2 sequestration, or volcanic eruptions.

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What makes a volcano tick—A first explanation of deep multiple seismic sources in ascending magma

Cited by 56 publications

References 23 publications

Volcano Seismology: Detecting Unrest in Wiggly Lines

Volcano Seismology: Detecting Unrest in Wiggly Lines

When Does Magma Break?

Interpretation of resonance frequencies recorded during hydraulic fracturing treatments

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