Insights into lava fountain eruptions at Mt. Etna by improved source location of the volcanic tremor

The NEWTON-g project [1] proposes a paradigm shift in terrain gravimetry to overcome the limitations imposed by currently available instrumentation. The project targets the development of an innovative gravity imager and the field-test of the new instrumentation through the deployment at Mount Etna volcano (Italy). The gravity imager consists in an array of MEMS-based relative gravimeters anchored on an Absolute Quantum Gravimeter [2]. The Absolute Quantum Gravimeter (AQG) is an industry-grade gravimeter measuring g with laser-cooled atoms [3]. Within the NEWTON-g project, an enhanced version of the AQG (AQGB03) has been developed, which is able to produce high-quality data against strong volcanic tremor at the installation site. After reviewing the key principles of the AQG, we present the deployment of the AQGB03 at the Pizzi Deneri (PDN) Volcanological Observatory (North flank of Mt. Etna; 2800 m elevation; 2.5 km from the summit active craters), which was completed in summer 2020. We then show the demonstrated measurement performances of the AQG, in terms of sensitivity and stability. In particular, we report on a reproducible sensitivity to gravity at a level of 1 &#956;Gal, even during intense volcanic activity. We also discuss how the time series acquired by AQGB03 at PDN compares with measurements from superconducting gravimeters already installed at Mount Etna. In particular, the significant &#160;correlation with gravity data collected at sites 5 to 9 km away from PDN proves that effects due to bulk mass sources, likely related to volcanic processes, are predominant over possible local and/or instrumental artifacts. This work demonstrates the feasibility to operate a free-falling quantum gravimeter in the field, both as a transportable turn-key device and as a drift-free monitoring device, able to provide high-quality continuous measurements under harsh environmental conditions. It paves the way to a wider use of absolute gravimetry for geophysical monitoring.[1] www.newton-g.com[2] D. Carbone et al., &#8220;The NEWTON-g Gravity Imager: Toward New Paradigms for Terrain Gravimetry&#8221;, Front. Earth Sci. 8:573396 (2020)[3] V. M&#233;noret et al., "Gravity measurements below 10&#8722;9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol.&#160;8,&#160;12300 (2018)

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Volcanic tremor wave field during quiescent and eruptive activity at Mt. Etna (Sicily)

Journal of Volcanology and Geothermal Research ◽

10.1016/0377-0273(94)90006-x ◽

1994 ◽

Vol 61 (3-4) ◽

pp. 239-251 ◽

Cited By ~ 17

Author(s):

Davide Ereditato ◽

Guiseppe Luongo

Keyword(s):

Wave Field ◽

Volcanic Tremor ◽

Eruptive Activity ◽

Mt Etna

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Integrated monitoring of soil gases, plume SO2 and volcanic tremor to detect impulsive magma transfer at Mt. Etna volcano (Italy)

10.5194/egusphere-egu2020-14698 ◽

2020 ◽

Author(s):

Susanna Falsaperla ◽

Tommaso Caltabiano ◽

Alessia Donatucci ◽

Salvatore Giammanco ◽

Horst Langer ◽

...

Keyword(s):

Volcanic Tremor ◽

Easy Access ◽

Geochemical Data ◽

Integrated Monitoring ◽

Seismic Stations ◽

Geochemical Parameters ◽

Mt Etna ◽

Magma Migration ◽

Soil Gases ◽

Rms Amplitude

Magma transfer in an open-conduit volcano is a complex process that is still open to debate and not entirely understood. For this reason, a multidisciplinary monitoring of active volcanoes is not only welcome, but also necessary for a correct comprehension of how volcanoes work. Mt. Etna is probably one of the best test sites for doing this, because of the large multidisciplinary monitoring network setup by the Osservatorio Etneo of Istituto Nazionale di Geofisica e Vulcanologia (INGV-OE), the high frequency of eruptions and the relatively easy access to most of its surface. We present new data on integrated monitoring of volcanic tremor, plume sulphur dioxide (SO2) flux and soil hydrogen (H2) and carbon dioxide (CO2) concentration from Mt. Etna. The RMS amplitude of volcanic tremor was measured by seismic stations at various distances from the summit craters, plume SO2 flux was measured from nine stations around the volcano and soil gases were measured in a station located in a low-temperature (T &#8764; 85 &#176;C) fumarole field on the upper north side of the volcano. During our monitoring period, we observed clear and marked anomalous changes in all parameters, with a nice temporal sequence that started with a soil CO2 and SO2 flux increase, followed a few days later by a soil H2 spike-like increase and finally with sharp spike-like increases in RMS amplitude (about 24 h after the onset of the anomaly in H2) at all seismic stations. After the initial spikes, all parameters returned more or less slowly to their background levels. Geochemical data, however, showed persistence of slight anomalous degassing for some more weeks, even in the apparent absence of RMS amplitude triggers. This suggests that the conditions of slight instability in the degassing magma column inside the volcano conduits lasted for a long period, probably until return to some sort of balance with the &#8220;normal&#8221; pressure conditions. The RMS amplitude increase accompanied the onset of strong Strombolian activity at the Northeast Crater, one of the four summit craters of Mt. Etna, which continued during the following period of moderate geochemical anomalies. This suggests a cause-effect relationship between the anomalies observed in all parameters and magma migration inside the central conduits of the volcano. Volcanic tremor is a well-established key parameter in the assessment of the probability of eruptive activity at Etna and it is actually used as a basis for a multistation system for detection of volcanic anomalies that has been developed by INGV-OE at Etna. Adding the information provided by our geochemical parameters gave us more solid support to this system, helping us understand better the mechanisms of magma migration inside of an active, open-conduit basaltic volcano.

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Volcanic tremor at Mt. Etna: State-of-the-art and perspectives

Pure and Applied Geophysics ◽

10.1007/bf00879369 ◽

1987 ◽

Vol 125 (6) ◽

pp. 1079-1095 ◽

Cited By ~ 10

Author(s):

S. Gresta ◽

S. Imposa ◽

D. Patan� ◽

G. Patan�

Keyword(s):

State Of The Art ◽

Volcanic Tremor ◽

Mt Etna

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“Failed” eruptions revealed by pattern classification analysis of gas emission and volcanic tremor data at Mt. Etna, Italy

International Journal of Earth Sciences ◽

10.1007/s00531-013-0964-7 ◽

2013 ◽

Vol 103 (1) ◽

pp. 297-313 ◽

Cited By ~ 12

Author(s):

S. Falsaperla ◽

B. Behncke ◽

H. Langer ◽

M. Neri ◽

G. G. Salerno ◽

...

Keyword(s):

Pattern Classification ◽

Volcanic Tremor ◽

Gas Emission ◽

Classification Analysis ◽

Mt Etna

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Relationship between soil CO2 flux and volcanic tremor at Mt. Etna: Implications for magma dynamics

Environmental Earth Sciences ◽

10.1007/s12665-009-0359-z ◽

2009 ◽

Vol 61 (3) ◽

pp. 477-489 ◽

Cited By ~ 15

Author(s):

Andrea Cannata ◽

Gaetano Giudice ◽

Sergio Gurrieri ◽

Placido Montalto ◽

Salvatore Alparone ◽

...

Keyword(s):

Volcanic Tremor ◽

Co2 Flux ◽

Soil Co2 ◽

Soil Co2 Flux ◽

Magma Dynamics ◽

Mt Etna

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Volcanic Tremor of Mt. Etna (Italy) Recorded by NEMO-SN1 Seafloor Observatory: A New Perspective on Volcanic Eruptions Monitoring

Geosciences ◽

10.3390/geosciences9030115 ◽

2019 ◽

Vol 9 (3) ◽

pp. 115

Author(s):

Tiziana Sgroi ◽

Giuseppe Di Grazia ◽

Paolo Favali

Keyword(s):

Gravity Waves ◽

Volcanic Tremor ◽

Volcanic Eruptions ◽

Seismic Signal ◽

High Amplitude ◽

Sea Waves ◽

Spectral Content ◽

Mt Etna ◽

New Perspective ◽

Seafloor Observatory

The NEMO-SN1 seafloor observatory, located 2100 m below sea level and about 40 km from Mt. Etna volcano, normally records a background seismic signal called oceanographic noise. This signal is characterized by high amplitude increases, lasting up to a few days, and by two typical 0.1 and 0.3 Hz frequencies in its spectrum. Particle motion analysis shows a strong E-W directivity, coinciding with the direction of sea waves; gravity waves induced by local winds are considered the main source of oceanographic noise. During the deployment of NEMO-SN1, the vigorous 2002–2003 Mt. Etna eruption occurred. High-amplitude background signals were recorded during the explosive episodes accompanying the eruption. The spectral content of this signal ranges from 0.1 to 4 Hz, with the most powerful signal in the 0.5–2 Hz band, typical of an Etna volcanic tremor. The tremor recorded by NEMO-SN1 shows a strong NW-SE directivity towards the volcano. Since the receiver is underwater, we inferred the presence of a circulation of magmatic fluids extended under the seafloor. This process is able to generate a signal strong enough to be recorded by the NEMO-SN1 seafloor observatory that hides frequencies linked to the oceanographic noise, permitting the offshore monitoring of the volcanic activity of Mt. Etna.

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Magma Budget From Lava and Tephra Volumes Erupted During the 25-26 October 2013 Lava Fountain at Mt Etna

Frontiers in Earth Science ◽

10.3389/feart.2018.00116 ◽

2018 ◽

Vol 6 ◽

Cited By ~ 3

Author(s):

Daniele Andronico ◽

Boris Behncke ◽

Emanuela De Beni ◽

Antonino Cristaldi ◽

Simona Scollo ◽

...

Keyword(s):

Lava Fountain ◽

Mt Etna

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A model for gravity changes induced by lava fountaining at Mt Etna

10.5194/egusphere-egu21-9186 ◽

2021 ◽

Author(s):

Luigi Passarelli ◽

Mehdi Nikkhoo ◽

Eleonora Rivalta ◽

Corine Frischknecht ◽

Costanza Bonadonna ◽

...

Keyword(s):

Magma Chamber ◽

Foam Layer ◽

Lava Fountain ◽

Gas Accumulation ◽

Lava Fountaining ◽

Gravity Changes ◽

Gravity Measurements ◽

Mt Etna ◽

Lava Fountains ◽

Gravity Signal

<div> Lava fountains represent a common eruptive phenomenon at basaltic volcanoes, which consist of jets of fluid lava ejected into the atmosphere from active vents or fissures. They are driven by rapid formation and expansion of gas bubbles during magma ascent. The dynamics of lava fountains is thought to be controlled by the gas accumulation in the foam layer at the top of a shallow magmatic reservoir, which eventually collapses triggering the lava fountaining. Gravity measurements taken from a location close to summit of Mt. Etna during the 2011 lava fountain episodes showed a pre-fountaining decrease of the gravity signal. The interplay between gas accumulation in the foam layer and its subsequent exsolution in the conduit has been interpreted as the mechanism producing the gravity decrease and eventually leading to the foam collapse and onset of the lava fountaining activity. Gravity measurements have proved helpful in recording the earliest phases anticipating the lava fountain episodes and inferring the amount of gas involved. However, more accurate estimates of the accumulating and ascending gas volume and total magma mass require considering the possible effect of non-spherical magma chamber geometries and magma compressibility. </div><div> Under task 4.4 of the H2020 NEWTON-g project, we are accomplishing a detailed study aimed to simulate the gravity signal produced in the stage prior to a lava fountain episode, through a magma chamber - conduit model. We use a prolate ellipsoidal chamber matching the inferred shape of the shallow chamber active at Mt. Etna during the lava fountain episodes, and calculate the surface gravity changes induced by inflow of new magma into the chamber-conduit system. We use a two-phase magma with fixed amount of gas mass fraction and account for magma compressibility. We find that a realistic chamber shape and magma compressibility play a key role and must be considered to produce realistic gravity changes simulations. We combine our physical model with empirical distributions of recurrence time and eruption size of the past lava fountains at Mt. Etna to stochastically simulate realistic time series of gravity changes. The final goal of this study is to develop a prediction model for the amount of magma and duration of lava fountains at Mt. Etna. </div>

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