Absolute and Relative Gravity Measurements at Volcanoes: Current State and New Developments Under the NEWTON-g Project

AbstractGravity changes associated with volcanic processes occur over a wide range of time scales, from minutes to years and with magnitudes between a few and a few hundred microGal. High-precision instruments are needed to detect such small signals and both time-lapse surveys along networks of stations, and continuous measurements at single points, are accomplished. Continuous volcano gravimetry is mostly carried out through relative gravimeters, either superconducting instruments, providing higher quality data, or the more widely used spring meters. On the other hand, time-lapse surveys can be carried out with relative (spring) gravimeters, that measure gravity differences between pairs of stations, or by absolute gravimeters, capable of measuring the absolute value of the gravitational acceleration at the observation point. Here we present the state-of-the-art of terrestrial gravity measurements to monitor and study active volcanoes and the possibilities of new gravimeters that are under development. In particular, we present data from a mini array of three iGrav superconducting gravimeters (SGs) at Mount Etna (the first network of SGs ever installed on an active volcano). A comparison between continuous gravity measurements recorded through the iGrav#016 superconducting gravimeter at Serra La Nave station (1730 m a.s.l.) and absolute gravity data collected with the Microg LaCoste FG5#238 gravimeter in the framework of repeated campaigns is also presented. Furthermore, we introduce the Horizon 2020 NEWTON-g project (New Tools for Terrain Gravimetry), funded under the FET-OPEN Research and Innovation Actions call, Work Programme 2016–2017 (Grant Agreement No 801221). In the framework of this project, we aim to develop a field-compatible gravity imager, including an array of low-costs Micro-Electro-Mechanical Systems (MEMS)-based relative gravimeters, anchored on an absolute quantum gravimeter. After the design and production phases, the gravity imager will be field-tested at Mt. Etna (Italy) during the last 2 years of the project.

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Estimating saturation and density changes caused by CO2 injection at Sleipner — Using time-lapse seismic amplitude-variation-with-offset and time-lapse gravity

Interpretation ◽

10.1190/int-2016-0120.1 ◽

2017 ◽

Vol 5 (2) ◽

pp. T243-T257 ◽

Cited By ~ 11

Author(s):

Martin Landrø ◽

Mark Zumberge

Keyword(s):

Gravity Data ◽

Time Lapse ◽

Co2 Injection ◽

Injection Point ◽

Amplitude Variation With Offset ◽

Seismic Method ◽

Seismic Amplitude ◽

Gravity Measurements ◽

Measured Time ◽

Best Fit

We have developed a calibrated, simple time-lapse seismic method for estimating saturation changes from the [Formula: see text]-storage project at Sleipner offshore Norway. This seismic method works well to map changes when [Formula: see text] is migrating laterally away from the injection point. However, it is challenging to detect changes occurring below [Formula: see text] layers that have already been charged by some [Formula: see text]. Not only is this partly caused by the seismic shadow effects, but also by the fact that the velocity sensitivity for [Formula: see text] change in saturation from 0.3 to 1.0 is significantly less than saturation changes from zero to 0.3. To circumvent the seismic shadow zone problem, we combine the time-lapse seismic method with time-lapse gravity measurements. This is done by a simple forward modeling of gravity changes based on the seismically derived saturation changes, letting these saturation changes be scaled by an arbitrary constant and then by minimizing the least-squares error to obtain the best fit between the scaled saturation changes and the measured time-lapse gravity data. In this way, we are able to exploit the complementary properties of time-lapse seismic and gravity data.

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

10.5194/egusphere-egu21-15186 ◽

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

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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Gravity reference at the Argentinean–German Geodetic Observatory (AGGO) by co-location of superconducting and absolute gravity measurements

Journal of Geodesy ◽

10.1007/s00190-020-01402-7 ◽

2020 ◽

Vol 94 (9) ◽

Author(s):

Ezequiel D. Antokoletz ◽

Hartmut Wziontek ◽

Claudia N. Tocho ◽

Reinhard Falk

Keyword(s):

Gravity Data ◽

Total Error ◽

International Comparisons ◽

Superconducting Gravimeter ◽

Calibration Factor ◽

Absolute Gravity ◽

Absolute Level ◽

Gravity Measurements ◽

Instrumental Drift

AbstractThe Argentinean–German Geodetic Observatory (AGGO) is a fundamental geodetic observatory located close to the city of La Plata, Argentina. Two high-precision gravity meters are installed at AGGO: the superconducting gravimeter SG038, which is in operation since December 2015, and the absolute gravimeter FG5-227, which has provided absolute gravity measurements since January 2018. By co-location of gravity observations from both meters between January 2018 and March 2019, calibration factor and instrumental drift of the SG038 were determined. The calibration factor of the SG038 was estimated by different strategies: from tidal models, dedicated absolute gravity measurements over several days and a joint approach (including the determination of the instrumental drift) using all available absolute gravity data. The final calibration factor differs from the determination at the previous station, the transportable integrated geodetic observatory, in Concepcion, Chile, by only 0.7‰, which does not imply a significant change. From the combined approach also the mean absolute level of the SG was determined, allowing to predict absolute gravity values from the SG at any time based on a repeatability of $$12\,\hbox {nm}/\hbox {s}^{2}$$ 12 nm / s 2 for the FG5-227 at AGGO. Such a continuous gravity reference function provides the basis for a comparison site for absolute gravimeters in the frame of the international gravity reference frame for South America and the Caribbean. However, it requires the assessment of the total error budget of the FG5-227, including the link to the international comparisons, which will be subject of future efforts.

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Optical readout design for a MEMS semi-absolute pendulum gravimeter

10.5194/egusphere-egu21-5045 ◽

2021 ◽

Author(s):

Phoebe Utting ◽

Giles Hammond ◽

Abhinav Prasad ◽

Richard Middlemiss

Keyword(s):

Microelectromechanical Systems ◽

Gravity Data ◽

Oscillation Period ◽

Mems Sensor ◽

Optical Readout ◽

Gravity Measurements ◽

Gravity Sensor ◽

Mt Etna ◽

Current Design ◽

Set Up

Gravimetry has many useful applications from volcanology to oil exploration; being a method able to infer density variations beneath the ground. Therefore, it can be used to provide insight into subsurface processes such as those related to the hydrothermal and magmatic systems of volcanoes. Existing gravimeters are costly and heavy, but this is changing with the utilisation of a technology most notably used in mobile phone accelerometers: MEMS &#8211;(Microelectromechanical-systems). Glasgow University has already developed a relative MEMS gravimeter and is currently collaborating with multiple European institutions to make a gravity sensor network around Mt Etna - NEWTON-g. A second generation of the MEMS sensor is now being designed and fabricated in the form of a semi-absolute pendulum gravimeter. Gravity data for geodetic and geophysical use were provided by pendulum measurements from the 18th to the 20th century. However, scientists and engineers reached the limit of fabrication tolerances and readout accuracy approximately 100 years ago. With nanofabrication and modern electronics techniques, it is now possible to create a competitive pendulum gravimeter again. The pendulum method is used to determine gravity values from the oscillation period of a pendulum with known length. The current design couples two pendulums together. Here, an optical shadow-sensor pendulum readout technique is presented. This employs an LED and split photodiode set-up. This optical readout can provide measurements to sub-nanometre precision, which could enable gravitational sensitivities for useful geophysical surveying. If semi-absolute values of gravity can be measured, then instrumental drift concerns are reduced. Additionally, the need for calibration against commercial absolute gravimeters may not be necessary. This promotes improved accessibility of gravity measurements at an affordable cost.

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An integrated approach for understanding long-term volcano dynamics based on absolute gravity and GNSS measurements

10.5194/egusphere-egu2020-18949 ◽

2020 ◽

Author(s):

Alessandro Bonforte ◽

Filippo Greco ◽

Daniele Carbone

Keyword(s):

Gravity Data ◽

General Pattern ◽

Integrated Approach ◽

Absolute Gravity ◽

Gravity Measurements ◽

Mt Etna ◽

Elevation Changes ◽

Spatio Temporal ◽

Gnss Measurements ◽

Relative Measurements

Here we present the results of repeated Absolute Gravity and GNSS measurements, collected at Mt. Etna (Italy) between 2009 and 2018. We aim at investigating the capabilities of this integrated approach for understanding the dynamics of magmatic sources over time-scales of months to years.&#160;The absolute gravity and GNSS campaign measurements were repeated roughly once a year; in order to improve the time resolution of gravity data, in some stations we performed, besides absolute gravity measurements, also relative measurements at intervals shorter than 1 year.After being corrected for the effect of elevation changes, gravity data reveal an increase/decrease cycle, well spatio-temporal correlated with a general pattern of uplift/subsidence, during a period of intense lava fountains from the summit craters.Our results provide insight into the processes that controlled the transfer of the magma from deeper to shallower levels of the plumbing system of Mt. Etna volcano, in periods preceding/accompanying the eruptive activity during 2009&#8211;2018.Specifically, we propose that coupled changes in height-corrected gravity and elevation might be induced either by the magma storage/withdrawal below the volcanic pile, or by fluids pressurization/depressurization, or by a combination of both processes.The application of the proposed approach could led to an improved capability to identify processes heralding eruptions.

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Measuring gravity changes for decades

10.5194/egusphere-egu2020-4432 ◽

2020 ◽

Author(s):

Michel Van Camp ◽

Olivier de Viron ◽

Bruno Meurers ◽

Olivier Francis

Keyword(s):

Gravity Data ◽

Superconducting Gravimeter ◽

Rate Of Change ◽

Earth Tides ◽

Convective Precipitation ◽

Absolute Gravity ◽

Tectonic Deformation ◽

Time Frequency ◽

Gravity Measurements ◽

The Impact

Being sensitive to any phenomena associated with mass transfer, terrestrial gravimetry allows the monitoring of many phenomena at the 10-10 g level (1 nm/s&#178;) such as Earth tides, groundwater content, tectonic deformation, or volcanic activity. This sensitivity is richness, but also a source of problems because data interpretation requires separating the signatures from the different sources, including possible measurement artefacts associated with high precision. Separating the signal from a given source requires a thorough knowledge of both the instrument and the phenomena.At the Membach geophysical laboratory, Belgium, the same superconducting gravimeter has monitored gravity continuously for more than 24 years. Together with 300 repeated absolute gravity measurements and environmental monitoring, this has allowed us to reach an unprecedented metrological knowledge of the instrument and of its sensitivity to hydrological and geophysical signals.Separation is possible whenever the phenomena exhibit distinct time/frequency signatures, such as (pseudo)periodic phenomena or long-term processes, so that the signatures from other sources average out by stacking. For example, when performing repeated gravity measurements to evidence slow tectonic deformation, the easiest way to mitigate hydrological effects is to accumulate measurements for many years, at the same epoch of the year: the impact of seasonal variations is then minimized, and the interannual variations cancel out. Using 10 repeated absolute gravity campaigns at the same epoch of the year, we showed that the gravity rate of change uncertainty reaches on average 3&#8211;4 nm/s&#178;/yr. Concurrently, using superconducting gravimeter time series longer than 10 years, we also investigated the time variations of tidal parameters.It is also possible to separate phenomena by observing them by both gravity and some other techniques, with a different transfer function. By using 11 year-long times series from the gravimeter and soil moisture probes, and by stacking the observations, we measured directly the groundwater mass loss by evapotranspiration in the forest above the laboratory of Membach. Always with a precision better than 1 nm/s&#178; (<=> 2.5 mm of water), we also monitored ground partial saturation dynamics and combining the gravity data with a weather radar allowed measuring convective precipitation at a scale of up to 1 km&#178;.Extracting and interpreting those elusive signals could only by achieved throughout multi-instrumentation, multi-disciplinary collaborative studies, and 25 years of hard work.

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Comparison between a six-year (2015-2020) continuous time series from an iGrav superconducting gravimeter and absolute gravity data at Mt. Etna volcano (Italy).

10.5194/egusphere-egu21-9119 ◽

2021 ◽

Author(s):

Filippo Greco ◽

Daniele Carbone ◽

Alfio Alex Messina ◽

Danilo Contrafatto

Keyword(s):

Time Series ◽

Continuous Time ◽

Gravity Data ◽

Total Error ◽

Superconducting Gravimeter ◽

Repeated Measurements ◽

Absolute Gravity ◽

Data Sets ◽

Gravity Changes ◽

Mt Etna

Since September 2014, iGrav#016 superconducting gravimeter (SG; by GWR) has recorded continuously at the Serra La Nave Astrophysical Observatory (SLN; 1730 m elevation; ~6.5 km from the Etna&#8217;s summit craters; Italy).Here we present results of a comparison between a six-year (2015-2020) time series from iGrav#16 and absolute gravity data collected through the Microg LaCoste FG5#238 absolute gravimeter (AG), in the framework of repeated measurements that were performed at the same installation site of the SG. Both AG and SG records have been corrected for the local tides, local atmospheric pressure and for the polar motion effect.The comparison allows to estimate the long-term drift of the SG, defined as the total SG trend minus the observed trend in AG measurements, which is of the order of 9 microGal/year. Once the drift effect is removed,&#160; there is a remarkably good fit between the two data sets. The differences between absolute gravity changes and corresponding relative data in the continuous time series from the SG are within 1-2 microGal (the total error on AG measurements at this station is typically +/- 3 microGal).After being corrected for the effect of instrumental drift, the time series from the SG reveals gravity changes that are due to hydrological and volcanological effects.Our study shows how the combination of repeated AG measurements and continuous gravity observations through SGs can be used to obtain a fuller and more accurate picture of the temporal characteristics of the studied processes.

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Forty-three years of absolute gravity observations of the Fennoscandian postglacial rebound in Finland

Journal of Geodesy ◽

10.1007/s00190-020-01470-9 ◽

2021 ◽

Vol 95 (2) ◽

Author(s):

Mirjam Bilker-Koivula ◽

Jaakko Mäkinen ◽

Hannu Ruotsalainen ◽

Jyri Näränen ◽

Timo Saari

Keyword(s):

Gravity Data ◽

Gravity Change ◽

Global Navigation Satellite Systems ◽

Absolute Gravity ◽

Data Sets ◽

Postglacial Rebound ◽

Land Uplift ◽

Satellite Systems ◽

Gravity Measurements ◽

Global Navigation Satellite

AbstractPostglacial rebound in Fennoscandia causes striking trends in gravity measurements of the area. We present time series of absolute gravity data collected between 1976 and 2019 on 12 stations in Finland with different types of instruments. First, we determine the trends at each station and analyse the effect of the instrument types. We estimate, for example, an offset of 6.8 μgal for the JILAg-5 instrument with respect to the FG5-type instruments. Applying the offsets in the trend analysis strengthens the trends being in good agreement with the NKG2016LU_gdot model of gravity change. Trends of seven stations were found robust and were used to analyse the stabilization of the trends in time and to determine the relationship between gravity change rates and land uplift rates as measured with global navigation satellite systems (GNSS) as well as from the NKG2016LU_abs land uplift model. Trends calculated from combined and offset-corrected measurements of JILAg-5- and FG5-type instruments stabilized in 15 to 20 years and at some stations even faster. The trends of FG5-type instrument data alone stabilized generally within 10 years. The ratio between gravity change rates and vertical rates from different data sets yields values between − 0.206 ± 0.017 and − 0.227 ± 0.024 µGal/mm and axis intercept values between 0.248 ± 0.089 and 0.335 ± 0.136 µGal/yr. These values are larger than previous estimates for Fennoscandia.

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DRIvE Project Unlocks Demand Response Potential with Digital Twins

Proceedings ◽

10.3390/proceedings2020065014 ◽

2020 ◽

Vol 65 (1) ◽

pp. 14

Author(s):

Laura Pérez ◽

Juan Espeche ◽

Tatiana Loureiro ◽

Aleksandar Kavgić

Keyword(s):

Knowledge Transfer ◽

Demand Response ◽

Low Carbon ◽

Distribution Grid ◽

Horizon 2020 ◽

Research And Innovation ◽

Digital Twins ◽

Future Workshop ◽

Innovative Solutions ◽

Innovation Project

DRIvE (Demand Response Integration Technologies) is a research and innovation project funded under the European Union’s Horizon 2020 Framework Program, whose main objective is unlocking the demand response potential in the distribution grid. DRIvE presented how the use of digital twins de-risks the implementation of demand response applications at the “Flexibility 2.0: Demand response and self-consumption based on the prosumer of Europe’s low carbon future” workshop within the conference “Sustainable Places 2020”. This workshop was organized to cluster and foster knowledge transfer between several EU projects, each developing innovative solutions within the field of demand response, energy flexibility, and optimized synergies between actors of the built environment and the power grid.

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