Geological Society, London, Special Publications, 2016
Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges wit... more Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges with respect to monitoring and forecasting eruptions, but they also provide new opportunities to enhance our understanding of magmatic–hydrothermal processes. Their lakes and hydrothermal systems serve as reservoirs for magmatic heat and fluid emissions, filtering and delaying the surface expressions of magmatic unrest and eruption, yet they also enable sampling and monitoring of geochemical tracers. Here, we describe the outcomes of a highly focused international experimental campaign and workshop carried out at Kawah Ijen volcano, Indonesia, in September 2014, designed to answer fundamental questions about how to improve monitoring and eruption forecasting at wet volcanoes.
Awu is a remote and little known active volcano of Indonesia located in the northern part of Molu... more Awu is a remote and little known active volcano of Indonesia located in the northern part of Molucca Sea. It is the northernmost active volcano of the Sangihe arc with 18 eruptions in less than 4 centuries, causing a cumulative death toll of 11,048. Two of these eruptions were classified with a Volcanic Explosivity Index (VEI) of 4. Since 2004, a lava dome has occupied the centre of Awu crater, channelling the fumarolic gas output along the crater wall. A combined Differential Optical Absorption Spectroscopy (DOAS) and Multi-component Gas Analyzer System (Multi-GAS) study highlight a relatively small SO2 flux (13 t/d) sustained by mixed magmatic–hydrothermal emissions made-up of 82 mol.% H2O, 15 mol.% CO2, 2.55 mol.% total S (ST) and 0.02 mol.% H2. The CO2 emission budget, as observed during a short observation period in 2015, corresponds to a daily contribution to the atmosphere of 2600 t/d, representing 1% of the global CO2 emission budget from volcanoes. The gas CO2/ST ratio of 3...
Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used... more Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used to monitor the propagation of the waves in the atmosphere, recorded at several hundred of kilometers away. While Lopevi is only producing significant infrasonic waves when an eruptive column of several kilometers high is emplaced in the atmosphere, Marum and Benbow both on Ambrym island and Yasur on Tanna island are permanently generating infrasonic waves. We initially installed, in 2008, an acoustic triangular network on Ambrym volcano to detect strong volcanic explosions, relatively 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 IS22 installed at Noumea (New Caledonia), at several hundred of kilometers away. However, the comparison between measurements performed at 2 km with those performed for 3 days at a few hundred of meters from Benbow quantifies the potential of using a triangular acoustic network at a safe distance for monitoring volcanic activity even when very small. Yasur volcano is an outstanding source of infrasonic waves, as its explosions are always sufficiently strong to be recorded at Noumea (New Caledonia). One microbarometer, installed at 300 m from its crater since october 2003, has now recorded several years of activity. The volcanic sound reaches the station IS22 at Noumea during the austral summer, allowing us to compare near-field and far-field signals for a very long period. Our observations in the far-field shows that its volcanic activity is relatively stable, as confirmed by our near-field measurements. We have also performed for a week infrasonic measurements almost directly above the crater to further explore the quality of our continuous measurements in a safe location at a distance of 300 m. In the absence of appropriate modelling of the sound wave, we have used a dimensionless analysis, which relates acoustic power and the velocity of gas-ejecta mixture. Our multi-years recordings show several sudden increases in gas flux over one week as well as a more progressive evolution, over several months. The gas flux varies between 280 m3/s and 1100 m3/s, in agreement with visual observations. The acoustic time series is analysed by detecting explosions with a method based on wavelet decomposition. The frequency is remarkably constant, showing that the gas volume at the vent does not change significantly over the years. However huge variations exist in the number of explosions (up to a factor 5) and in the mean acoustic pressure (up to a factor 4). Furthermore three different regimes can be distinguished and a sharp transition exists between them (less than a day). In the first one, the activity is quiet with both a low number of explosions (20 per hour) and a low acoustic pressure (50 Pa). The second regime is characterised by a high acoustic pressure and a low number of explosions, while the third one is exactly the opposite. Regimes 2 and 3 are found in alternation, showing that the transition is reversible. We suggest that the different regimes reflect sudden variations of the gas volume fraction in the conduit. Our near-field and far-field measurements, when combined, show the potential of infrasound from volcanoes as a natural and continuous source of sound to estimate more precisely how large the errors in the upper wind models are, in a region where there is a lack of routine measurements.
Ambrym volcano is presenting one of the rare examples for which 2 volcanic edifices, build at a f... more 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.
Ambrym volcano is presenting one of the rare examples for which 2 volcanic edifices, build at a f... more 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 ...
PELLETIER Bernard (1); ALLARD Patrick (2); AIUPPA Alexandro (3); BATTAGLIA Jean (4); BANI Philips... more PELLETIER Bernard (1); ALLARD Patrick (2); AIUPPA Alexandro (3); BATTAGLIA Jean (4); BANI Philipson (5); BERTAGNINI Antonella (6); BURTON James (6); DONNADIEU Franck (4); FINIZOLA Anthony (7); GALLOIS Francis (5); GARAEBITI Esline (8); GAUTHIER Pierre ...
ABSTRACT Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which ca... more ABSTRACT Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used to monitor the propagation of the waves in the atmosphere, recorded at several hundred of kilometers away. While Lopevi is only producing significant infrasonic waves when an eruptive column of several kilometers high is emplaced in the atmosphere, Marum and Benbow both on Ambrym island and Yasur on Tanna island are permanently generating infrasonic waves. We initially installed, in 2008, an acoustic triangular network on Ambrym volcano to detect strong volcanic explosions, relatively close to the vents, at 2 km. The lack of strong explosions during our 6 months of recordings, with recorded acoustic pressure &lt; 10 Pa, prevented us to use these explosions as natural sources for tracing the propagation path in the atmosphere towards the station IS22 installed at Noumea (New Caledonia), at several hundred of kilometers away. However, the comparison between measurements performed at 2 km with those performed for 3 days at a few hundred of meters from Benbow quantifies the potential of using a triangular acoustic network at a safe distance for monitoring volcanic activity even when very small. Yasur volcano is an outstanding source of infrasonic waves, as its explosions are always sufficiently strong to be recorded at Noumea (New Caledonia). One microbarometer, installed at 300 m from its crater since october 2003, has now recorded several years of activity. The volcanic sound reaches the station IS22 at Noumea during the austral summer, allowing us to compare near-field and far-field signals for a very long period. Our observations in the far-field shows that its volcanic activity is relatively stable, as confirmed by our near-field measurements. We have also performed for a week infrasonic measurements almost directly above the crater to further explore the quality of our continuous measurements in a safe location at a distance of 300 m. In the absence of appropriate modelling of the sound wave, we have used a dimensionless analysis, which relates acoustic power and the velocity of gas-ejecta mixture. Our multi-years recordings show several sudden increases in gas flux over one week as well as a more progressive evolution, over several months. The gas flux varies between 280 m3/s and 1100 m3/s, in agreement with visual observations. The acoustic time series is analysed by detecting explosions with a method based on wavelet decomposition. The frequency is remarkably constant, showing that the gas volume at the vent does not change significantly over the years. However huge variations exist in the number of explosions (up to a factor 5) and in the mean acoustic pressure (up to a factor 4). Furthermore three different regimes can be distinguished and a sharp transition exists between them (less than a day). In the first one, the activity is quiet with both a low number of explosions (20 per hour) and a low acoustic pressure (50 Pa). The second regime is characterised by a high acoustic pressure and a low number of explosions, while the third one is exactly the opposite. Regimes 2 and 3 are found in alternation, showing that the transition is reversible. We suggest that the different regimes reflect sudden variations of the gas volume fraction in the conduit. Our near-field and far-field measurements, when combined, show the potential of infrasound from volcanoes as a natural and continuous source of sound to estimate more precisely how large the errors in the upper wind models are, in a region where there is a lack of routine measurements.
Geological Society, London, Special Publications, 2016
Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges wit... more Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges with respect to monitoring and forecasting eruptions, but they also provide new opportunities to enhance our understanding of magmatic–hydrothermal processes. Their lakes and hydrothermal systems serve as reservoirs for magmatic heat and fluid emissions, filtering and delaying the surface expressions of magmatic unrest and eruption, yet they also enable sampling and monitoring of geochemical tracers. Here, we describe the outcomes of a highly focused international experimental campaign and workshop carried out at Kawah Ijen volcano, Indonesia, in September 2014, designed to answer fundamental questions about how to improve monitoring and eruption forecasting at wet volcanoes.
Awu is a remote and little known active volcano of Indonesia located in the northern part of Molu... more Awu is a remote and little known active volcano of Indonesia located in the northern part of Molucca Sea. It is the northernmost active volcano of the Sangihe arc with 18 eruptions in less than 4 centuries, causing a cumulative death toll of 11,048. Two of these eruptions were classified with a Volcanic Explosivity Index (VEI) of 4. Since 2004, a lava dome has occupied the centre of Awu crater, channelling the fumarolic gas output along the crater wall. A combined Differential Optical Absorption Spectroscopy (DOAS) and Multi-component Gas Analyzer System (Multi-GAS) study highlight a relatively small SO2 flux (13 t/d) sustained by mixed magmatic–hydrothermal emissions made-up of 82 mol.% H2O, 15 mol.% CO2, 2.55 mol.% total S (ST) and 0.02 mol.% H2. The CO2 emission budget, as observed during a short observation period in 2015, corresponds to a daily contribution to the atmosphere of 2600 t/d, representing 1% of the global CO2 emission budget from volcanoes. The gas CO2/ST ratio of 3...
Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used... more Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used to monitor the propagation of the waves in the atmosphere, recorded at several hundred of kilometers away. While Lopevi is only producing significant infrasonic waves when an eruptive column of several kilometers high is emplaced in the atmosphere, Marum and Benbow both on Ambrym island and Yasur on Tanna island are permanently generating infrasonic waves. We initially installed, in 2008, an acoustic triangular network on Ambrym volcano to detect strong volcanic explosions, relatively 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 IS22 installed at Noumea (New Caledonia), at several hundred of kilometers away. However, the comparison between measurements performed at 2 km with those performed for 3 days at a few hundred of meters from Benbow quantifies the potential of using a triangular acoustic network at a safe distance for monitoring volcanic activity even when very small. Yasur volcano is an outstanding source of infrasonic waves, as its explosions are always sufficiently strong to be recorded at Noumea (New Caledonia). One microbarometer, installed at 300 m from its crater since october 2003, has now recorded several years of activity. The volcanic sound reaches the station IS22 at Noumea during the austral summer, allowing us to compare near-field and far-field signals for a very long period. Our observations in the far-field shows that its volcanic activity is relatively stable, as confirmed by our near-field measurements. We have also performed for a week infrasonic measurements almost directly above the crater to further explore the quality of our continuous measurements in a safe location at a distance of 300 m. In the absence of appropriate modelling of the sound wave, we have used a dimensionless analysis, which relates acoustic power and the velocity of gas-ejecta mixture. Our multi-years recordings show several sudden increases in gas flux over one week as well as a more progressive evolution, over several months. The gas flux varies between 280 m3/s and 1100 m3/s, in agreement with visual observations. The acoustic time series is analysed by detecting explosions with a method based on wavelet decomposition. The frequency is remarkably constant, showing that the gas volume at the vent does not change significantly over the years. However huge variations exist in the number of explosions (up to a factor 5) and in the mean acoustic pressure (up to a factor 4). Furthermore three different regimes can be distinguished and a sharp transition exists between them (less than a day). In the first one, the activity is quiet with both a low number of explosions (20 per hour) and a low acoustic pressure (50 Pa). The second regime is characterised by a high acoustic pressure and a low number of explosions, while the third one is exactly the opposite. Regimes 2 and 3 are found in alternation, showing that the transition is reversible. We suggest that the different regimes reflect sudden variations of the gas volume fraction in the conduit. Our near-field and far-field measurements, when combined, show the potential of infrasound from volcanoes as a natural and continuous source of sound to estimate more precisely how large the errors in the upper wind models are, in a region where there is a lack of routine measurements.
Ambrym volcano is presenting one of the rare examples for which 2 volcanic edifices, build at a f... more 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.
Ambrym volcano is presenting one of the rare examples for which 2 volcanic edifices, build at a f... more 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 ...
PELLETIER Bernard (1); ALLARD Patrick (2); AIUPPA Alexandro (3); BATTAGLIA Jean (4); BANI Philips... more PELLETIER Bernard (1); ALLARD Patrick (2); AIUPPA Alexandro (3); BATTAGLIA Jean (4); BANI Philipson (5); BERTAGNINI Antonella (6); BURTON James (6); DONNADIEU Franck (4); FINIZOLA Anthony (7); GALLOIS Francis (5); GARAEBITI Esline (8); GAUTHIER Pierre ...
ABSTRACT Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which ca... more ABSTRACT Active volcanoes in the Vanuatu archipelago are a natural source of infrasound, which can be used to monitor the propagation of the waves in the atmosphere, recorded at several hundred of kilometers away. While Lopevi is only producing significant infrasonic waves when an eruptive column of several kilometers high is emplaced in the atmosphere, Marum and Benbow both on Ambrym island and Yasur on Tanna island are permanently generating infrasonic waves. We initially installed, in 2008, an acoustic triangular network on Ambrym volcano to detect strong volcanic explosions, relatively close to the vents, at 2 km. The lack of strong explosions during our 6 months of recordings, with recorded acoustic pressure &lt; 10 Pa, prevented us to use these explosions as natural sources for tracing the propagation path in the atmosphere towards the station IS22 installed at Noumea (New Caledonia), at several hundred of kilometers away. However, the comparison between measurements performed at 2 km with those performed for 3 days at a few hundred of meters from Benbow quantifies the potential of using a triangular acoustic network at a safe distance for monitoring volcanic activity even when very small. Yasur volcano is an outstanding source of infrasonic waves, as its explosions are always sufficiently strong to be recorded at Noumea (New Caledonia). One microbarometer, installed at 300 m from its crater since october 2003, has now recorded several years of activity. The volcanic sound reaches the station IS22 at Noumea during the austral summer, allowing us to compare near-field and far-field signals for a very long period. Our observations in the far-field shows that its volcanic activity is relatively stable, as confirmed by our near-field measurements. We have also performed for a week infrasonic measurements almost directly above the crater to further explore the quality of our continuous measurements in a safe location at a distance of 300 m. In the absence of appropriate modelling of the sound wave, we have used a dimensionless analysis, which relates acoustic power and the velocity of gas-ejecta mixture. Our multi-years recordings show several sudden increases in gas flux over one week as well as a more progressive evolution, over several months. The gas flux varies between 280 m3/s and 1100 m3/s, in agreement with visual observations. The acoustic time series is analysed by detecting explosions with a method based on wavelet decomposition. The frequency is remarkably constant, showing that the gas volume at the vent does not change significantly over the years. However huge variations exist in the number of explosions (up to a factor 5) and in the mean acoustic pressure (up to a factor 4). Furthermore three different regimes can be distinguished and a sharp transition exists between them (less than a day). In the first one, the activity is quiet with both a low number of explosions (20 per hour) and a low acoustic pressure (50 Pa). The second regime is characterised by a high acoustic pressure and a low number of explosions, while the third one is exactly the opposite. Regimes 2 and 3 are found in alternation, showing that the transition is reversible. We suggest that the different regimes reflect sudden variations of the gas volume fraction in the conduit. Our near-field and far-field measurements, when combined, show the potential of infrasound from volcanoes as a natural and continuous source of sound to estimate more precisely how large the errors in the upper wind models are, in a region where there is a lack of routine measurements.
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