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

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

<p>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’s summit craters; Italy).</p><p>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.</p><p>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,  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).</p><p>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.</p><p>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.</p>

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

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.

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

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.

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

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

<p>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. 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.</p><p>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.</p><p>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 2009–2018.</p><p>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.</p><p>The application of the proposed approach could led to an improved capability to identify processes heralding eruptions.</p>

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

2020 ◽  
Author(s):  
F. Greco ◽  
D. Carbone ◽  
F. Cannavò ◽  
A. A. Messina ◽  
G. Siligato
Keyword(s):  
Gravity Data ◽  
Time Lapse ◽  
Active Volcano ◽  
Superconducting Gravimeter ◽  
Mount Etna ◽  
Micro Electro Mechanical Systems ◽  
Horizon 2020 ◽  
Research And Innovation ◽  
Gravity Measurements ◽  
Mt Etna

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.

scholarly journals Twelve Years of High Frequency Absolute Gravity Measurements at the UK’s Space Geodesy Facility: Systematic Signals and Comparison with SLR Heights

2021 ◽  
Author(s):  
Victoria Anne Smith ◽  
Graham Appleby ◽  
Marek Ziebart ◽  
Jose Rodriguez
Keyword(s):  
Time Series ◽  
Gravity Data ◽  
International Comparisons ◽  
Vertical Motion ◽  
Space Geodesy ◽  
Global Navigation Satellite Systems ◽  
Absolute Gravity ◽  
Soil Parameters ◽  
Satellite Systems ◽  
Gravity Measurements

AbstractAbsolute gravity measurements taken on a near-weekly basis at a single location is a rarity. Twelve years of data at the UK’s Space Geodesy Facility (SGF) provides evidence to show that the application of results from international comparisons of absolute gravimeters should be applied to data and are critical to the interpretation of theSGF gravity time series of data from 2007 to 2019. Though residual biases in the data are seen. The SGF time series comprises near weekly data, with exceptions for manufacturer services and participation in international instrument comparisons. Each data set comprises hourly data taken over 1 day, with between 100 and 200 drops per hour. Environmental modelling indicates that the annual groundwater variation at SGFof some 2 m influences the gravity data by 3.1 μGal, based upon some measured and estimated soil parameters. The soil parameters were also used in the calculation of the effect of an additional telescope dome, built above the gravity laboratory, and have been shown to be realistic. Sited in close proximity to the long-established satellite laser ranging (SLR) system and the global navigation satellite systems (GNSS) the absolute gravimetry (AG) measurements provide a complimentary geodetic technique, which is non space-based. The SLR-derived height time series provides an independent measurement of vertical motion at the site which may be used to assess the AG results, which are impacted by ground motion as well as mass changes above and below the instruments.

scholarly journals Measuring gravity changes for decades

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

<p>Being sensitive to any phenomena associated with mass transfer, terrestrial gravimetry allows the monitoring of many phenomena at the 10<sup>-10</sup> g level (1 nm/s²) 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.</p><p>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.</p><p>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 3–4 nm/s²/yr. Concurrently, using superconducting gravimeter time series longer than 10 years, we also investigated the time variations of tidal parameters.</p><p>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/s² (<=> 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 km².</p><p>Extracting and interpreting those elusive signals could only by achieved throughout multi-instrumentation, multi-disciplinary collaborative studies, and 25 years of hard work.</p>

Can we use regional runoff models for correcting time series of absolute gravimetry?

2020 ◽  
Author(s):  
Brian Bramanto ◽  
Vegard Ophaug ◽  
Christian Gerlach ◽  
Kristian Breili
Keyword(s):  
Time Series ◽  
Gravity Data ◽  
Outer Zone ◽  
Subsurface Water ◽  
Absolute Gravity ◽  
Periodic Pattern ◽  
Hydrological Models ◽  
Land Uplift ◽  
Absolute Gravimetry ◽  
Lower Amplitude

<p>Absolute gravity time series are available at various stations in Norway. The data have mainly been used for investigation of secular variations due to glacial isostatic adjustment. Previous work indicates that some of the estimated gravity trends suffer from unmodeled geophysical effects, like hydrological mass variations. Here we try to correct for hydrological effects by employing a combination of global and regional hydrological models. We use gravity data at two locations in the Norwegian network (NMBU and TRYC) which have frequently been observed with the absolute gravimeter FG5-226. </p><p>For computing the gravity corrections, we test various Global Hydrological Models (GHMs) and combine them with a Regional Runoff Model (RRM) for Norway, run by the Norwegian Water Resources and Energy Directorate (NVE). We distinguish between an outer and an inner zone. In the outer zone, Newtonian attraction and loading effects are derived from the GHMs, while the RRM is used in the inner zone. Both types of models provide information on soil moisture and snow layers. The RRM provides groundwater variations in addition. Furthermore, we try to consider the ‘umbrella effect’ that accounts for local disturbances in subsurface water flow caused by the existence of the building in which the gravity site is located.  </p><p>Neglecting the GIA trend, both NMBU and TRYC gravity time series show different amplitude and pattern. NMBU shows a lower amplitude, and with no prominent periodic pattern in the data, while TRYC shows the opposite. Significant discrepancies occurring in the NMBU gravity dataset between 2014 and 2015 are likely due to an instrumental effect, such as maintenance. The total modelled hydrological signal ranges from -4 and 4 µGal. Application of the correction reduces the standard deviation in the gravity time series, at its best, by about 33% or 0.8 µGal for NMBU, and by about 43% or two µGal for TRYC. Secular gravity rates have been derived from both, the uncorrected and the corrected time series. We find that application of the hydrological correction improves the fit of the computed secular gravity rates as compared to rates derived from the state-of-the-art Fennoscandian land uplift model NKG2016LU_abs. The uncorrected trends are 75% and 50% of the expected trend (0.77 and 1.12 µGal/year), while the hydrological corrections improve the fit to 82% and 93% for NMBU and TRYC, respectively.</p>

Monitoring of extreme land hydrology events in central Poland using GRACE, land surface models and absolute gravity data

2019 ◽  
Vol 13 (3) ◽  
pp. 229-243 ◽  
Author(s):  
Joanna Kuczynska-Siehien ◽  
Dimitrios Piretzidis ◽  
Michael G. Sideris ◽  
Tomasz Olszak ◽  
Viktor Szabó
Keyword(s):  
Land Surface ◽  
Gravity Data ◽  
Absolute Gravity ◽  
Severe Drought ◽  
Data Sets ◽  
Land Surface Models ◽  
Multiple Sources ◽  
Central Poland ◽  
Extreme Flood ◽  
Surface Models

Abstract This study deals with the analysis of temporal gravity variations in central Poland, deduced from multiple sources and covering the period from 2002–2016. The gravity data sets used comprise GRACE monthly solutions, GLDAS land surface models and absolute gravimeter measurements from the FG-5 gravimeter located in Józefosław, Poland. All data are corrected using standard processing methods in order to include the same gravity effects. After removing the annual and semi-annual components from all data using least-squares spectral analysis and seasonal-trend decomposition, the deseasoned time series are derived and examined for signatures of extreme hydrological events. The signatures of several severe drought and flood conditions affecting Poland and central Europe are identified. A complementary correlation analysis is performed to assess the level of agreement between different data sources. A higher correlation is shown when the analysis is restricted in the 2009–2012 period that includes the 2010 extreme flood and 2011 increased precipitation events, both affecting Poland.

scholarly journals Interpretation of the Chemical and Physical Time-Series Retrieved from Sentik Glacier, Ladakh Himalaya, India

1984 ◽  
Vol 30 (104) ◽  
pp. 66-76 ◽  
Author(s):  
Paul A. Mayewski ◽  
W. Berry Lyons ◽  
N. Ahmad ◽  
Gordon Smith ◽  
M. Pourchet
Keyword(s):  
Time Series ◽  
Chemical Species ◽  
Data Sets ◽  
Reactive Iron ◽  
Physical Time ◽  
Ladakh Himalaya ◽  
Data Density ◽  
Mass Circulation ◽  
The Himalaya ◽  
Analysis Of Time Series

AbstractSpectral analysis of time series of a c. 17 ± 0.3 year core, calibrated for total ß activity recovered from Sentik Glacier (4908m) Ladakh, Himalaya, yields several recognizable periodicities including subannual, annual, and multi-annual. The time-series, include both chemical data (chloride, sodium, reactive iron, reactive silicate, reactive phosphate, ammonium, δD, δ(18O) and pH) and physical data (density, debris and ice-band locations, and microparticles in size grades 0.50 to 12.70 μm). Source areas for chemical species investigated and general air-mass circulation defined from chemical and physical time-series are discussed to demonstrate the potential of such studies in the development of paleometeorological data sets from remote high-alpine glacierized sites such as the Himalaya.

scholarly journals An edge-cloud collaboration architecture for pattern anomaly detection of time series in wireless sensor networks

2021 ◽  
Author(s):  
Cong Gao ◽  
Ping Yang ◽  
Yanping Chen ◽  
Zhongmin Wang ◽  
Yue Wang
Keyword(s):  
Time Series ◽  
Wireless Sensor Networks ◽  
Sensor Networks ◽  
Anomaly Detection ◽  
Estimation Method ◽  
Feature Representation ◽  
Sensor Data ◽  
Wireless Sensor ◽  
Data Sets ◽  
Edge Node

AbstractWith large deployment of wireless sensor networks, anomaly detection for sensor data is becoming increasingly important in various fields. As a vital data form of sensor data, time series has three main types of anomaly: point anomaly, pattern anomaly, and sequence anomaly. In production environments, the analysis of pattern anomaly is the most rewarding one. However, the traditional processing model cloud computing is crippled in front of large amount of widely distributed data. This paper presents an edge-cloud collaboration architecture for pattern anomaly detection of time series. A task migration algorithm is developed to alleviate the problem of backlogged detection tasks at edge node. Besides, the detection tasks related to long-term correlation and short-term correlation in time series are allocated to cloud and edge node, respectively. A multi-dimensional feature representation scheme is devised to conduct efficient dimension reduction. Two key components of the feature representation trend identification and feature point extraction are elaborated. Based on the result of feature representation, pattern anomaly detection is performed with an improved kernel density estimation method. Finally, extensive experiments are conducted with synthetic data sets and real-world data sets.

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