Acoustic sounder measurements of the vertical velocity of volcanic jets at Stromboli Volcano

Weill, Alain; Brandeis, G.; Vergniolle, S.; Baudin, François; Bilbille, Jacques; Fèvre, Jean-François; Piron, Brigitte; Hill, Xavier

doi:10.1029/92gl02502

Cited by 54 publications

(38 citation statements)

References 17 publications

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“…The median of v ej represents a first order approximation for U. Gas ejection velocities v ej reported on Strombolian explosions are in the range of (20-112) m/s (Chouet et al 1974;Weill et al 1992;Ripepe et al 2001Ripepe et al , 2002. For vulcanian explosions at Soufriere Hills, jet velocities varying from 40 to 140 m/s were measured (Formenti et al 2003).…”

Section: Analysis Of Source Locationsmentioning

confidence: 99%

Source constraints of Tungurahua volcano explosion events

2005

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The most recent eruptive cycle of Tungurahua volcano began in May 2004, and reached its highest level of activity in July 2004. This activity cycle is the last one of a series of four cycles that followed the reawakening and major eruption of Tungurahua in 1999. Between June 30 and August 12, 2004, three temporary seismic and infrasonic stations were installed on the flanks of the volcano and recorded over 2,000 degassing events. The events are classified by waveform character and include: explosion events (the vast majority, spanning three orders of pressure amplitudes at 3.5 km from the vent, 0.1-180 Pa), jetting events, and sequences of repetitive infrasonic pulses, called chugging events. Travel-time analysis of seismic first arrivals and infrasonic waves indicates that explosions start with a seismic event at a shallow depth (<200 m), followed ∼1 s later by an out-flux of gas, ash and solid material through the vent. Cluster analysis of infrasonic signals from explosion events was used to isolate four groups of similar waveforms without apparent correlation to event size, location, or time. The clustering is thus associated with source mechanism and probably spatial distribution. Explosion clusters do not exhibit temporal dependence.

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Section: Analysis Of Source Locationsmentioning

confidence: 99%

Source constraints of Tungurahua volcano explosion events

2005

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“…The fluid could be gas or bubbly magma with a very wide range of variability of velocity. If air or pure hot gas are considered, their wave velocity are equal to 0.34 and 0.704 km/s (WEILL et al, 1992), respectively. If we take into account bubbly magma, the wave velocity ranges from 0.3 km/s (AKI et al, 1977) to 2.5 km/s (MURASE and MCBIRNEY, 1973), according to different flow conditions and magma properties (above all the gas fraction).…”

Section: Discussionmentioning

confidence: 99%

Towards an Automatic Monitoring System of Infrasonic Events at Mt. Etna: Strategies for Source Location and Modeling

Montalto

Cannata

Privitera

et al. 2010

Pure Appl. Geophys.

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Active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models:(1) Strombolian bubble; (2) resonating conduit and (3) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters.

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“…At the onset of each explosion, V +max displays a sharp peak increase followed by a slower decay with time. Smaller peaks of V +max are superimposed on the decay trend; although these could result from parasitic effects, their amplitude suggests that they might be due to pressure oscillations during each jet, as already detected by photoballistic ) and acoustic (Weill et al 1992) studies of individual explosions at Stromboli. Note that when the backscattered power is very low (lack of activity), the signal to noise ratio is low too so that background noise fluctuations may lead to underestimation of V +max (e.g.…”

Section: Explosion Sequencesmentioning

confidence: 90%

“…These are mainly based on photographic Blackburn et al 1976;Ripepe et al 1993), video (Sparks and Wilson 1982;Neuberg et al 1994; or acoustic (Mauk 1983;Ripepe et al 1996) techniques. Recently, active remote sensors based on Doppler radar principle and commonly used in atmospheric research have been successfully operated at Stromboli volcano (Weill et al 1992;Hort and Seyfried 1998;Seyfried and Hort 1999). The main advantage of these systems is to selectively probe inside a specific volume of the jet generally just above the crater.…”

Section: Introductionmentioning

confidence: 99%

Doppler radar sounding of volcanic eruption dynamics at Mount Etna

et al. 2003

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Besides their common use in atmospheric studies, Doppler radars are promising tools for the active remote sensing of volcanic eruptions but were little applied to this field. We present the observations made with a mid-power UHF Doppler radar (Voldorad) during a 7-h Strombolian eruption at the SE crater of Mount Etna on 11-12 October 1998. Main characteristics of radar echoes are retrieved from analysis of Doppler spectra recorded in the two range gates on either side of the jet axis. From the geometry of the sounding, the contribution of uprising and falling ejecta to each Doppler spectrum can be discriminated. The temporal evolution of total power backscattered by uprising targets is quite similar to the temporal evolution of the volcanic tremor and closely reproduces the overall evolution of the eruption before, during and after its paroxysm. Moreover, during the sharp decrease of eruptive activity following the paroxysm, detailed analysis of video (from camera recording), radar and seismic measurements reveals that radar and video signals start to decrease simultaneously, approximately 2.5 min after the tremor decline. This delay is interpreted as the ascent time through a magma conduit of large gas slugs from a shallow source roughly estimated at about 500 m beneath the SE crater. Detailed analysis of eruptive processes has been also made with Voldorad operating in a high sampling rate mode. Signature of individual outburst is clearly identified on the half part of Doppler spectra corresponding to rising ejecta: temporal variations of the backscattered power exhibit quasi periodic undulations, whereas the maximum velocity measured on each spectrum displays a sharp peak at the onset of each outburst followed by a slow decay with time. Periodicity of power variations (between 3.8 and 5.5 s) is in agreement with the occurrence of explosions visually observed at the SE vent. Maximum vertical velocities of over 160 m s 1 were measured during the paraoxysmal stage and the renewed activity. Finally, by using a simplified model simulating the radar echoes characteristics, we show that when Voldorad is operating in high sampling rate mode, the power and maximum velocity variations are directly related to the difference in size and velocity of particles crossing the antenna beam.

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Acoustic sounder measurements of the vertical velocity of volcanic jets at Stromboli Volcano

Cited by 54 publications

References 17 publications

Source constraints of Tungurahua volcano explosion events

Source constraints of Tungurahua volcano explosion events

Towards an Automatic Monitoring System of Infrasonic Events at Mt. Etna: Strategies for Source Location and Modeling

Doppler radar sounding of volcanic eruption dynamics at Mount Etna

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