Temporal Variations in the Depth Estimate of Mass Density Changes at Mt Etna Volcano

2021 ◽  
Author(s):  
Thomas King ◽  
Daniele Carbone ◽  
Filippo Greco
Keyword(s):  
Amplitude Ratio ◽  
Mass Density ◽  
Sampling Rate ◽  
Summit Crater ◽  
Temporal Variations ◽  
Mass Source ◽  
Depth Estimate ◽  
Effusive Activity ◽  
Superconducting Gravimeters ◽  
Mt Etna

<p>Continuous gravity measurements at Mt. Etna, Sicily demonstrate spatio-temporal variations that can be related to volcanic processes. Two iGrav superconducting gravimeters (SGs) were installed in 2014 and 2016 at Serra La Nave Astrophysical Observatory (SLN; 1,730 m elevation; ~6.5 km from the summit craters) and La Montagnola hut (MNT; 2,600 m asl; ~3.5 km SE of the summit crater). Since their installation both stations have been continuously recording, resulting in high-resolution (1 Hz sampling rate) time series. The persistent activity of Etna is maintained by a regular supply of magma to the shallower levels of the plumbing system. The bulk mass redistributions induced by the newly injected material result in minor variations in the local gravity field that are recorded by the two stations. By assuming that the observed gravity changes are due exclusively to mass changes in an almost spherical-shaped source, located beneath the craters, the amplitude ratio between the two signals can be used to estimate the depth to potential mass changes beneath the surface.</p><p>This study reports on the time-dependent nature of mass changes located beneath the craters of the volcano during 2019. Results highlight distinct periods of stability at different depths, as well as potential periods of transitory activity, where the predominant mass source switches between storage zones at different depth. These events are correlated to phases of strombolian and effusive activity, highlighting the potential of continuous gravimetry for the detection of eruption precursors.</p>

Deploying and operating an Absolute Quantum Gravimeter on the summit of Mount Etna volcano

2021 ◽  
Author(s):  
Daniele Carbone ◽  
Laura Antoni-Micollier ◽  
Filippo Greco ◽  
Jean Lautier-Gaud ◽  
Danilo Contrafatto ◽  
...  
Keyword(s):  
Gravity Data ◽  
Volcanic Tremor ◽  
Mount Etna ◽  
Quality Data ◽  
Etna Volcano ◽  
High Quality ◽  
Absolute Gravimetry ◽  
Superconducting Gravimeters ◽  
Mt Etna ◽  
Absolute Quantum

<p>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].<br>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.<br>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 μGal, even during intense volcanic activity.<br>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  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.<br>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.</p><p>[1] www.newton-g.com</p><p>[2] D. Carbone et al., “The NEWTON-g Gravity Imager: Toward New Paradigms for Terrain Gravimetry”, Front. Earth Sci. 8:573396 (2020)</p><p>[3] V. Ménoret et al., "Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)</p>

First 2-D intrinsic and scattering attenuation images of Mt Etna volcano and surrounding region from active seismic data

2019 ◽  
Vol 220 (1) ◽  
pp. 267-277 ◽  
Author(s):  
Jesús M Ibáñez ◽  
Ignacio Castro-Melgar ◽  
Ornella Cocina ◽  
Luciano Zuccarello ◽  
Stefano Branca ◽  
...  
Keyword(s):  
Summit Crater ◽  
Volcanic Complex ◽  
High Attenuation ◽  
Intrinsic Attenuation ◽  
Scattering Effects ◽  
Seismicity Rates ◽  
Intrinsic And Scattering Attenuation ◽  
Mt Etna ◽  
Upper South ◽  
Work Supports

SUMMARY We present 2-D attenuation images of the Mt Etna volcanic region on the basis of separation of intrinsic and scattering effects. The analysis presented here exploits a large active seismic database that fully covers the area under study. We observe that scattering effects dominate over intrinsic attenuation, suggesting that the region is very heterogeneous. Comparison with analyses conducted at other volcanoes reveals that the Mt Etna region is characterized by high intrinsic attenuation, resulting from the presence of large volcanoclastic deposits at shallow depth. The 2-D distributions of intrinsic and scattering anomalies show the presence of regions characterized by high and low attenuation effects, corresponding to several tectonic and volcanic features. In particular, we identify a high attenuation region in the SW sector of the Mt Etna volcanic complex, which is correlated with high seismicity rates and volcanism. This work supports the hypothesis of a link between the dynamics of the SW flank and the recharge of the volcano in the last decades, occurring under the summit crater and, secondarily, the upper South rift zone.

The 1998 Valhall microseismic data set: An integrated study of relocated sources, seismic multiplets, and S-wave splitting

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. B183-B195 ◽  
Author(s):  
K. De Meersman ◽  
J.-M. Kendall ◽  
M. van der Baan
Keyword(s):  
Seismic Anisotropy ◽  
Amplitude Ratio ◽  
Temporal Variations ◽  
Oil Field ◽  
P Wave ◽  
Wave Form ◽  
S Wave ◽  
Data Set ◽  
Wave Splitting ◽  
Source Mechanisms

We relocate 303 microseismic events recorded in 1998 by sensors in a single borehole in the North Sea Valhall oil field. A semiautomated array analysis method repicks the P- and S-wave arrival times and P-wave polarizations, which are needed to locate these events. The relocated sources are confined predominantly to a [Formula: see text]-thick zone just above the reservoir, and location uncertainties are half those of previous efforts. Multiplet analysis identifies 40 multiplet groups, which include 208 of the 303 events. The largest group contains 24 events, and five groups contain 10 or more events. Within each multiplet group, we further improve arrival-time picking through crosscorrelation, which enhances the relative accuracy of the relocated events and reveals that more than 99% of the seismic activity lies spatially in three distinct clusters. The spatial distribution of events and wave-form similarities reveal two faultlike structures that match well with north-northwest–south-southeast-trending fault planes interpreted from 3D surface seismic data. Most waveform differences between multiplet groups located on these faults can be attributed to S-wave phase content and polarity or P-to-S amplitude ratio. The range in P-to-S amplitude ratios observed on the faults is explained best in terms of varying source mechanisms. We also find a correlation between multiplet groups and temporal variations in seismic anisotropy, as revealed by S-wave splitting analysis. We explain these findings in the context of a cyclic recharge and dissipation of cap-rock stresses in response to production-driven compaction of the underlying oil reservoir. The cyclic nature of this mechanism drives the short-term variations in seismic anisotropy and the reactivation of microseismic source mechanisms over time.

Seismic anisotropy time variations at Mt Etna

2019 ◽  
Vol 220 (1) ◽  
pp. 450-460
Author(s):  
Lucia Nardone ◽  
Francesca Bianco ◽  
Lucia Zaccarelli ◽  
Domenico Patanè
Keyword(s):  
Time Delay ◽  
Stress Field ◽  
Shear Wave ◽  
Local Stress ◽  
Temporal Variations ◽  
Fast Wave ◽  
Polarization Direction ◽  
Stress Changes ◽  
Mt Etna ◽  
Local Stress Field

SUMMARY The aim of this paper is to study the temporal variations in the seismic wavefield associated with the stress changes in the dynamic features of the Mt Etna volcanic activity. We used shear wave splitting analysis on a huge data set of local earthquakes, in order to identify changes of the local stress field at Mt Etna during the time interval from 2006 to 2011. This analysis allows us to obtain two parameters: the polarization direction of the fast shear wave (φ) and the time delay of the slow shear wave (Td,time delay between the split shear waves). Orientation of φ generally provides information about the anisotropic symmetry and stress direction whereas Td provide information about the average crack density along the ray path. Based on our findings it is possible to divide Etna Volcano in three different sectors, each one distinguished by typical fast wave polarization direction. We find that the western part of the volcano is controlled by the regional tectonic stress field having a NS and EW directions. Instead, the eastern part of the volcano is mainly controlled by the local volcanic stress, particularly an EW local stress field in the NE sector (Pernicana), and a quasi NS local stress field in the SE sector (Mascalucia, Timpe), where previous studies evidenced: (i) some low-Qp anomaly regions between 0 and about 6 km depth, probably associated with high pore pressure and the intense faulting and (ii) by magnetotelluric surveys, several high conductivity zones, up to 8 km depth, related to a diffuse presence of hydrothermal activity and fluid circulation. Temporal variations in time delay, mostly before the 2008–2009 lateral eruption, can be interpreted as stress accumulation increase with a consequent release of stress due to coalescing of microcracks in the conduit for the eruption of magma.

The 2019 eruptive phase of Stromboli volcano through multiparametric geophysical observations.

2020 ◽  
Author(s):  
Massimo Orazi ◽  
Flora Giudicepietro ◽  
Carmen López ◽  
Giovanni Macedonio ◽  
Salvatore Alparone ◽  
...  
Keyword(s):  
Pyroclastic Flow ◽  
Seismic Station ◽  
Volcanic Tremor ◽  
Summit Crater ◽  
Seismic Signal ◽  
Sea Surface ◽  
Effusive Activity ◽  
Eruptive Column ◽  
Borehole Strainmeter ◽  
Sciara Del Fuoco

<p>In summer 2019, two paroxysmal explosions occurred in Stromboli. The first one occurred on July 3, when the Strombolian ordinary eruptive activity did not show a significant intensification. The explosion formed an eruptive column more than 3 km high. A pyroclastic flow ran down the “Sciara del Fuoco” slope causing a victim and some injuries. Moreover, the pyroclastic flow spread over the sea surface for about one kilometer. On August 28, a second paroxysmal explosion occurred, similar to the previous one. Also in this case the eruption formed an eruptive column of more than 3 km and a pyroclastic flow that expanded along the “Sciara del Fuoco” slope and traveled about 1 km on the sea surface. In the period between the two paroxysms, effusive activity occurred from the summit crater area. The eruptive phase of summer 2019, which began with the paroxysm of 3 July, was not preceded by significant changes in the routinely monitored parameters, such as the hourly frequency (daily average) of the VLP events (typical of Stromboli) and the amplitude of the seismic signal (RSAM). For this reason, we have analyzed the seismic and dilatometric data, which were recorded by the INGV geophysical network in the period November 2018 - September 2019, focusing our attention on other parameters that can give indications on the activity state of the volcano. In particular, we analyzed the data of the broadband seismic stations, equipped with the Guralp CMG40T sensors, and the data of one Sacks-Evertson borehole strainmeter. We defined the "VLP size", which takes into account the waveform of the VLP events, in terms of both amplitude and duration. We also applied time varying Fractal Dimension (FD) analysis to the seismograms of a seismic station close to the crater area and we analyzed the polarization of the same signal. We carried out the polarization analysis both without applying a filter and by filtering the seismic signal in the typical frequency bands of the Stromboli volcanic tremor (1-3 Hz) and of the VLPs (0.5-0.05 Hz). We found that the "VLP size", the FD and the polarization parameters showed significant changes about one month before the paroxysm of July 3. In the short term, we applied an appropriately tuned STA/LTA algorithm to the data of the borehole strainmeter, which is installed on the island at about 2km from the craters, and we obtained an automatic detection of the paroxysmal events 10 and 7.5 minutes before the explosion of July 3 and August 28, respectively.</p>

scholarly journals Distribution of meteoric smoke – sensitivity to microphysical properties and atmospheric conditions

2006 ◽  
Vol 6 (12) ◽  
pp. 4415-4426 ◽  
Author(s):  
L. Megner ◽  
M. Rapp ◽  
J. Gumbel
Keyword(s):  
Middle Atmosphere ◽  
Mass Density ◽  
Temporal Variations ◽  
Vertical Wind ◽  
Noctilucent Clouds ◽  
Atmospheric Conditions ◽  
Smoke Particles ◽  
Microphysical Properties ◽  
Meteoric Smoke ◽  
Atmospheric Phenomena

Abstract. Meteoroids entering the Earth's atmosphere experience strong deceleration and ablate, whereupon the resulting material is believed to re-condense to nanometre-size "smoke particles". These particles are thought to be of great importance for many middle atmosphere phenomena, such as noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. The properties and distribution of meteoric smoke depend on poorly known or highly variable factors such as the amount, composition and velocity of incoming meteoric material, the efficiency of coagulation, and the state and circulation of the atmosphere. This work uses a one-dimensional microphysical model to investigate the sensitivities of meteoric smoke properties to these poorly known or highly variable factors. The resulting uncertainty or variability of meteoric smoke quantities such as number density, mass density, and size distribution are determined. It is found that the two most important factors are the efficiency of the coagulation and background vertical wind. The seasonal variation of the vertical wind in the mesosphere implies strong global and temporal variations in the meteoric smoke distribution. This contrasts the simplistic picture of a homogeneous global meteoric smoke layer, which is currently assumed in many studies of middle atmospheric phenomena. In particular, our results suggest a very low number of nanometre-sized smoke particles at the summer mesopause where they are thought to serve as condensation nuclei for noctilucent clouds.

Dynamics of foreshocks and pre-slip during the nucleation of laboratory earthquakes

2020 ◽  
Author(s):  
Alexandre Schubnel ◽  
Samson Marty ◽  
Blandine Gardonio ◽  
Harsha Bhat ◽  
Eiichi Fukuyama ◽  
...  
Keyword(s):  
Source Parameters ◽  
Scaling Law ◽  
Sampling Rate ◽  
Acoustic Emissions ◽  
Slip Rate ◽  
Absolute Magnitude ◽  
Temporal Variations ◽  
P Wave ◽  
Time Data ◽  
Stick Slip

<p>Over the past decades, an increasing number of seismological observations and improvement in data quality have allowed to better detect <span>foreshock sequences prior to earthquakes. However, due to strong spatial and temporal variations of foreshock occurrence, their underlying physical processes and their links to earthquake nucleation are still under debate. Here we address these issues by looking at precursory acoustic activity during laboratory earthquakes (stick-slip instabilities).<br></span></p><p><span>Here, laboratory earthquake experiments were performed on saw-cut Indian metagabbro under upper crustal stress conditions ranging from 30 to 60 MPa confining pressure. Using a high-frequency monitoring system and calibrated piezoelectric acoustic sensors we continuously record particle velocity field at 10 MHz sampling rate during the experiments. Based on a trigger logic we identify acoustic emissions (AE) within continuous data. From P-wave arrival-time data and from spectral analysis we are able to estimate the following seismological parameters for each AE: location, </span>absolute magnitude, stress-drop and size.</p><p>First, we show that the source parameters of AE (Mw -9.0 to Mw -7.0) follow the same scaling relationship as natural earthquakes justifying the use of acoustic precursors as proxy to foreshocks. We observe that foreshock triggering is systematically related to aseismic slip and that the dynamics of foreshocks mirrors the acceleration of slip-rate preceding failure. Experimental scalings demonstrate that : i- the nucleation evolves  from an aseismic process into a cascading one, and ii) the duration and magnitude of the pre-seismic moment correlates with the magnitude of the mainshock, at least at the scale of the laboratory. Finally, using Hertz contact theory, we find a scaling law between the seismic energy released by foreshocks, the fault roughness  and the normal stress acting on the fault interface.</p>

scholarly journals Sensitivity of meteoric smoke distribution to microphysical properties and atmospheric conditions

2006 ◽  
Vol 6 (3) ◽  
pp. 5357-5386 ◽  
Author(s):  
L. Megner ◽  
M. Rapp ◽  
J. Gumbel
Keyword(s):  
Middle Atmosphere ◽  
Mass Density ◽  
Temporal Variations ◽  
Vertical Wind ◽  
Noctilucent Clouds ◽  
Atmospheric Conditions ◽  
Smoke Particles ◽  
Microphysical Properties ◽  
Meteoric Smoke ◽  
Atmospheric Phenomena

Abstract. Meteoroids entering the Earth's atmopsphere experience strong deceleration and ablate, whereupon the resulting material is believed to re-condense to nanometre-size "smoke particles". These particles are thought to be of great importance for many middle atmosphere phenomena, such as noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. The properties and distribution of meteoric smoke depend on poorly known or highly variable factors such as the amount, composition and velocity of incoming meteoric material, the efficiency of coagulation, and the state and circulation of the atmosphere. This work uses a one-dimensional microphysical model to investigate the sensitivities of meteoric smoke properties to these poorly known or highly variable factors. The resulting uncertainty or variability of meteoric smoke quantities such as number density, mass density, and size distribution are determined. It is found that the two most important factors are the efficiency of the coagulation and background vertical wind. The seasonal variation of the vertical wind in the mesosphere implies strong global and temporal variations in the meteoric smoke distribution. This contrasts the simplistic picture of a homogeneous global meteoric smoke layer, which is currently assumed in many studies of middle atmospheric phenomena. In particular, our results suggest a very low number of nanometre-sized smoke particles at the summer mesopause where they are thought to serve as condensation nuclei for noctilucent clouds.

Monitoring of Merapi volcano, Indonesia based on Sentinel-1 data

2021 ◽  
Author(s):  
Virginie Pinel ◽  
François Beauducel ◽  
Raditya Putra ◽  
Sulis Sulistiyani ◽  
Gusti Made Agung Nandaka ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Displacement ◽  
Field Measurements ◽  
Summit Crater ◽  
Radar Data ◽  
Pyroclastic Flows ◽  
Mean Velocity ◽  
Merapi Volcano ◽  
Synthetic Aperture Radar Data ◽  
Effusive Activity

<p>Despite the well-established interest of Synthetic Aperture Radar data for volcanoes study and monitoring, their integration to operational monitoring activities in volcanoes observatories remains limited so far. We here describe the effort in progress to integrate in near real time the information derived from Sentinel-1 satellites into the monitoring devices at BBPTKG in charge of Merapi volcano survey as well as the use of Sentinel-1 data during the recent period of  unrest. Merapi (7°32.5’ S and 110°26.5’ E) located in the densely populated Province of Yogyakarta in Central Java is one of the most active volcanoes in Indonesia. The eruptive history of Merapi is characterized by two eruptive styles: 1) recurrent effusive growth of viscous lava domes, with gravitational collapses producing pyroclastic flows known as « Merapi-type nuées ardentes » (VEI 2); 2) more exceptional explosive eruptions of relatively large size (VEI 3-4), associated with column collapse pyroclastic flows reaching distances larger than 15 km from the summit. The eruptive periodicity is 4 to 5 years for the effusive events and 50 to 100 years for the explosive ones. The last explosive events (VEI 3-4) occurred in November 2010 and was followed by a period of limited activity. In August 2018, a new dome was observed inside the summit crater, thus marking the start of a new phase of effusive activity. A new period of unrest then started in mid-October 2020, characterized by an increase in seismic activity as well as large and localized displacements in the summit area. Magma finally reached the surface on 4<sup>  </sup>January 2021. Deformation is currently recorded by EDM and tiltmeters together with a network of 10 permanent GNSS stations. GNSS data are automatically processed and inverted for a pressure source at depth. Both displacement time series as well as spatial probability distribution are directly available through WebObs (Beauducel et al., Frontiers, 2020), an integrated web-based system for monitoring. Sentinel-1 data are acquired over the volcano every 12 days on descending track 76 and every 6 days on ascending track 127. Since mid 2017, Sentinel-1 data are automatically downloaded on a local server at BPPTKG. Interferograms and coherence images are then produced using the NSBAS processing chain (Doin et al, 2012) and automatically integrated to WebObs to enable detection of potential rapid and significant changes in signal. Mean velocity maps are also produced as well as time series of surface displacement at given location enabling direct comparison with GNSS measurements. The descending InSAR time series shows a strong displacement away from the satellite in a 1.5 km wide area located on the north-eastern part  of the crater. This signal became significant in September 2020. It is consistent with field measurements recorded and allows to map the affected area. In mid-November 2020, Sentinel-1 data thus provided the first information on the spatial extent of the ongoing surface displacements, which was useful for crisis management.</p>

scholarly journals Ground Deformation Detected by Permanent Tiltmeters on Mt. Etna Summit: The August 23-26, 2018, Strombolian and Effusive Activity Case

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Salvatore Gambino ◽  
Marco Aloisi ◽  
Giuseppe Di Grazia ◽  
Giuseppe Falzone ◽  
Angelo Ferro ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Volcanic Tremor ◽  
Mount Etna ◽  
Etna Volcano ◽  
Strombolian Activity ◽  
Summit Area ◽  
Effusive Activity ◽  
Ground Deformations ◽  
Mt Etna ◽  
Set Up

Over the last few years, three tilt deep stations (27-30 meters) have been set up in the summit area of Mount Etna volcano. The aim of this challenging project is to record the ground deformations of the summit craters activity with high precision. We considered data related to the August 23-26, 2018, Strombolian and effusive activity. In this case, tiltmeters recorded variations in the order of 10−7 radians, not observed at the other stations. These changes suggest a shallow contraction source just south of the Southeast Crater. This result, related to the volcanic tremor source, points to the presence of a gas/magma reservoir feeding the Strombolian activity at 1200 m above sea level.

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