Publication Date:
2022-06-08
Description:
Magmatic degassing, typically measured as SO2 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 SO2 emission rates and volcanic tremor on
Mt. Etna, track rapid variability in eruptive dynamics. Correlations between SO2 flux
and tremor are explored in both quiescent and eruptive periods, comparing the two
parameters at both long and short time-scales (〈 〈 1 day) for 2 years. Our analysis
reveals that over month-long timescales passive degassing of SO2 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.
Description:
Published
Description:
Article 157
Description:
5V. Processi eruttivi e post-eruttivi
Description:
JCR Journal
Keywords:
Mt. Etna
;
SO2 flux
;
volcanic tremor
;
eruptive and quiescent degassing
;
volcano monitoring
;
04.08. Volcanology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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