Eruption-induced modifications to volcanic seismicity at Ruapehu, New Zealand, and its implications for eruption forecasting

Bryan, Carol J.; Sherburn, S.

doi:10.1007/s00445-002-0236-z

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…Etna: Cannata et al, 2008;Bonaccorso et al, 2011b;Kilauea: Nadeau et al, 2015). Changes in the dominant tremor frequency have been commonly associated with changes in the regime and style of eruptive activity (e.g., Ereditato and Luongo, 1994;Thompson et al, 2002;Alparone et al, 2003;Bryan and Sherburn, 2003;Cannata et al, 2018). At Mt.…”

Section: Introductionmentioning

confidence: 99%

Coupling Between Magmatic Degassing and Volcanic Tremor in Basaltic Volcanism

et al. 2018

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Magmatic degassing, typically measured as SO 2 flux, plays a fundamental role in controlling volcanic eruption style and is one of the key parameters used by volcano observatories to assess volcanic unrest and detect eruption precursors. Volcanic tremor, the integrated amplitude of seismic energy release over a range of frequencies, is also a key parameter in volcano monitoring. A connection between volcanic degassing and tremor has been inferred through correlations between the signals which are often, but not always, observed during periods of unrest or eruption. However, data are often equivocal and our understanding of the physical processes, which couple degassing with tremor are still evolving. New insights into degassing-tremor coupling can be made by investigation of the long-term relationship between degassing and tremor, focusing on the frequency-dependence of tremor and passive degassing behavior. In this study, we examine how long-term SO 2 emission rates and volcanic tremor on Mt. Etna, track rapid variability in eruptive dynamics. Correlations between SO 2 flux and tremor are explored in both quiescent and eruptive periods, comparing the two parameters at both long and short timescales (< < 1 day) for ∼2 years. Our analysis reveals that over ∼month-long timescales passive degassing of SO 2 and tremor tend to be well-correlated, but these correlations are lost over shorter timescales. This reflects a coupling process between passive degassing and tremor, produced by a combination of gas flow through permeable magma and the convective flow of magma within the conduit. Short-term correlations are lost because variations in the continuous degassing process are relatively small compared with the overall degassing rate and fall below measurement noise. During eruptive periods strong correlations are observed between degassing and tremor, with a significant contribution of higher frequency signal in tremor, controlled by eruptive style. These observations suggest that in syneruptive periods the tremor source is dominated by the coupling between the eruption column and the ground through infrasonic waves, rather than conduit processes. Our results demonstrate the importance of high quality long-term observations and offer new insights into the physical mechanisms which couple degassing and volcanic tremor at active volcanoes.

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Section: Introductionmentioning

confidence: 99%

Coupling Between Magmatic Degassing and Volcanic Tremor in Basaltic Volcanism

et al. 2018

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“…More recently changes to the seismicity of Ruapehu following the 1995–1996 eruptions were noted by Sherburn et al (1999) and Bryan & Sherburn (2003). Prior to the eruptions volcanic tremor and earthquakes were dominated by a 2 Hz spectral peak and some higher frequencies.…”

Section: Introductionmentioning

confidence: 99%

Seismic tomography of the Tongariro Volcanic Centre, New Zealand

Rowlands

White

Haines

2005

Geophysical Journal International

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S U M M A R YTomographic inversion of local earthquake P-and S-wave traveltime data is used to investigate 3-D P-wave velocity (V p ) and P-wave/S-wave velocity ratio (V p /V s ) variations at the Tongariro Volcanic Centre (TgVC), New Zealand. P-wave model resolution is generally high throughout the TgVC at depths of around 3-9 km below sea level. Near-surface resolution is lower since rays at shallow depths are predominantly subparallel. Resolution decreases below 12 km depth due to clustering of seismicity at greater depths. The final 3-D V p model shows low-velocity volumes from 3 to 7 and 8 km depth, respectively beneath the active volcanoes Ruapehu and Ngauruhoe. Smaller low-velocity volumes are observed beneath the active Tongariro volcano and the extinct Tama Lakes vents. Synthetic tests indicate that the resolution of the 3-D V p /V s model is insufficient to permit any reliable interpretation.Accurate earthquake depths are determined for the first time within the TgVC. Seismicity is largely restricted to two clusters west of Ruapehu, possibly with origins on eastward striking branches of the normal Raurimu Fault, two lineations near Waiouru in the south-east of the study area and a fault belt between Tongariro and Lake Taupo in the north of the study area.Earthquake depths indicate possible shallowing of the brittle-ductile transition beneath Ruapehu and Ngauruhoe.

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“…However, a limitation for these models is that the structure and constitution of the magma-conduit system is unlikely to be the same across volcanic environments or to be preserved during an eruption. In addition to variations in volcano size, differences in conduit erosion (Bryan & Sherburn 2003;McNutt & Nishimura 2008) and magma degassing (Sparks 2003) would, according to standard models, lead to large variations in the tremor frequency, which are not observed.…”

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Volcanic tremors and magma wagging: gas flux interactions and forcing mechanism

Bercovici

Jellinek

Michaut

et al. 2013

Geophysical Journal International

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Volcanic tremor is an important precursor to explosive eruptions and is ubiquitous across most silicic volcanic systems. Oscillations can persist for days and occur in a remarkably narrow frequency band (i.e. 0.5-7 Hz). The recently proposed magma-wagging model of Jellinek & Bercovici provides a basic explanation for the emergence and frequency evolution of tremor that is consistent with observations of many active silicic and andesitic volcanic systems. This model builds on work suggesting that the magma column rising in the volcanic conduit is surrounded by a permeable vesicular annulus of sheared bubbles. The magma-wagging model stipulates that the magma column rattles within the spring like foam of the annulus, and predicts oscillations at the range of observed tremor frequencies for a wide variety of volcanic environments. However, the viscous resistance of the magma column attenuates the oscillations and thus a forcing mechanism is required. Here we provide further development of the magmawagging model and demonstrate that it implicitly has the requisite forcing to excite wagging behaviour. In particular, the extended model allows for gas flux through the annulus, which interacts with the wagging displacements and induces a Bernoulli effect that amplifies the oscillations. This effect leads to an instability involving growing oscillations at the lower end of the tremor frequency spectrum, and that drives the system against viscous damping of the wagging magma column. The fully non-linear model displays tremor oscillations associated with pulses in gas flux, analogous to observations of audible 'chugging'. These oscillations also occur in clusters or envelopes that are consistent with observations of sporadic tremor envelopes. The wagging model further accurately predicts that seismic signals on opposite sides of a volcano are out of phase by approximately half a wagging or tremor period. Finally, peaks in gas flux occur at the end of the growing instability several tens of seconds after the largest tremors, which is consistent with observations of a 30-to 50-s lag between major tremor activity and maximum gas release. The extended magma-wagging model, thus, predicts tremor frequency and its evolution before and during an eruption, as well as a driving mechanism to keep the tremor excited for long periods.

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Eruption-induced modifications to volcanic seismicity at Ruapehu, New Zealand, and its implications for eruption forecasting

Cited by 7 publications

References 28 publications

Coupling Between Magmatic Degassing and Volcanic Tremor in Basaltic Volcanism

Coupling Between Magmatic Degassing and Volcanic Tremor in Basaltic Volcanism

Seismic tomography of the Tongariro Volcanic Centre, New Zealand

Volcanic tremors and magma wagging: gas flux interactions and forcing mechanism

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