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| Titel |
Probing the magma plumbing of Ambrym volcano, by a triangular acoustic network |
| VerfasserIn |
Philipson Bani, Sylvie Vergniolle, Christelle Zielinski, Michel Lardy, Alexis Le Pichon, Damien Ponceau, Francis Gallois, Pascal Herry, Sylvain Todman, Esline Garaebiti |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037518
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| Zusammenfassung |
| Ambrym volcano is presenting one of the rare examples for which 2 volcanic edifices, build
at a few kilometers from one another, are simultaneously erupting. Their volcanic activity,
quasi permanent, vary between exhibiting weak to strong strombolian explosions. Both
volcanoes may also produce eruptive columns reaching a few kilometers in the atmosphere.
We initially installed, in 2008, an acoustic triangular network on Ambrym volcano to detect
strong volcanic explosions, relativeley close to the vents, at 2 km. The lack of strong
explosions during our 6 months of recordings, with recorded acoustic pressure < 10 Pa,
prevented us to use these explosions as natural sources for tracing the propagation path in the
atmosphere towards the station installed at Noumea, 650 km away. Our acoustic
network on Ambrym could also have been very useful to monitor an eruption on a
nearby volcano, Lopevi, distant by 10 km, and compare the signals close to the
volcano, 1 km, with those recorded at a intermediate distance from the source, 10 km.
Unfortunately Lopevi did not produce any significant eruptive column during the recording
period.
However our acoustic triangular network installed in 2008 on Ambrym volcano have been
proven suitable to distinguish the volcanic activity in Benbow and Marum. More than
hundred thousand acoustic events have been recorded within a 6 month period (longest data
series ever obtained on Ambrym) indicating a quasi continuous magmatic activity in both
Benbow and Marum craters. 60 % of the acoustic events occurred in Marum with several
periods marked by significant bursts and some periods of quiescence, while Benbow exhibits
minor explosions continuously. The first period with strong explosions at Marum is preceded
by an increase in number and duration of acoustic events in both craters as well as a
shift in frequency. This suggests that either both volcanic edifices share the same
magma reservoir or that an efficient connection exists in their magma plumbing
systems. The rapid return of Benbow to its normal activity after a period of strong
explosions at Marum compared to that of Marum may indicate that Benbow crater is
the closest to the magmatic source, hence probably directly above it. This is also
compatible with the existence of periods of quiescence solely at Marum and not at
Benbow. This new approach in volcanic studies and monitoring has revealed valuable
information of the edifice plumbing system of Ambrym, which is of a key to understand
its eruptive behaviour. It is also a promising tool for volcanic monitoring as our
acoustic network detects precursory events 1-2 days prior to major explosions. |
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