Regional comparison of absolute gravimeters  SIM.M.G-K1 key comparison

Newell, D B; Westrum, D van; Francis, Olivier; Kanney, J; Liard, J; Ramirez, A E; Lucero, B; Ellis, B; Greco, Filippo; Pistorio, A; Reudink, R; Iacovone, D; Baccaro, F; Silliker, J; Wheeler, R D; Falk, Reinhard; Ruelke, A

doi:10.1088/0026-1394/54/1a/07019

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…FG5#238 is also routinely checked against other absolute gravimeters, in the framework of international and regional inter-comparisons. The results provided by FG5#238 were consistent with the Key Comparison Values (Jiang et al 2012;Greco et al 2015;Newell et al 2017;Pálinkáš et al 2017;Falk et al 2020). Absolute gravimeters are compared for the purpose of assuring their reliability and ensure the traceability of measurements to the SI units.…”

Section: Mt Etna's Gravity and Geodetic Monitoring Networksupporting

confidence: 64%

A long-term charge/discharge cycle at Mt. Etna volcano revealed through absolute gravity and GPS measurements

Greco

Bonforte

Carbone

2022

J Geod

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We present results of repeated absolute gravity and GPS measurements, carried out at Mt. Etna volcano between 2009 and 2018. Absolute gravity measurements are rarely performed along arrays of stations on active volcanoes and, through our unprecedented dataset, we highlight the possibilities of this method to track underground mass changes over long time-scales. Analysis of the residual absolute gravity data and ground deformation reveals a cycle of gravity increase and uplift during 2009 to 2011, followed by gravity decrease and subsidence during 2011 to 2014. Data inversion points to a common mass and pressure source, lying beneath the summit area of the volcano, at depth of ~ 5 km b.s.l. The bulk volume change inferred by the inversion of the deformation data can account for only a small portion of the mass change needed to explain the correspondent gravity variations. We propose that the observed relationship between gravity and vertical deformation was mostly due to the compressibility of the magma in the inferred reservoir, which, in turn, was enhanced by the presence of exsolved gas. Overall, the gravity and deformation data we present reveal a cycle of magma recharge (2009–2011) and discharge (2011–2014) to/from the inferred storage zone. During the recharge phase only degassing occurred from the summit craters of Mt. Etna. During the following phase of discharge, the magma lost from the reservoir at ~ 5 km b.s.l. fed the exceptional phase of volcanic activity during 2011–2014, when tens of lava fountaining episodes took place.

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Section: Mt Etna's Gravity and Geodetic Monitoring Networksupporting

confidence: 64%

A long-term charge/discharge cycle at Mt. Etna volcano revealed through absolute gravity and GPS measurements

Greco

Bonforte

Carbone

2022

J Geod

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“…The FG5#238 has been compared with IMGC-02 at the INRiM gravity laboratory in 2011, during several contemporary field surveys on Etna at two stations in 2009 and during several CIPM key comparisons [36][37][38][39]. The results indicated that there was no large discrepancy between the two instruments, since the measured differences were between −4.0 and +8.3 µGal [22], within the standard uncertainty.…”

Section: Results Of the A10#39 And Fg5#238 Inter-comparison Versus Imgc Gravimetermentioning

confidence: 99%

Insights into Seismogenetic Areas in Central Italy from Combined Absolute Gravity and GNSS Measurements

2021

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In this study we present and discuss gravity and ground deformation variations, at different time scales, observed in a wide mesh absolute gravity and GNSS network set up in central Italy. The network was installed in the area affected by the 2009 (L’Aquila; Mw 6.1) and 2016 (Amatrice-Norcia; Mw 6.0 and 6.5) seismic activity, in order to verify if gravity and ground deformation variations could be related to seismic effects. The new network includes 5 stations distributed between the Lazio, Umbria, and Abruzzo regions. From 2018 to 2020 three campaigns were carried out using the transportable Micro-g LaCoste FG5#238 and the portable Micro-g LaCoste A10#39 absolute gravimeters and completed with two simultaneous GNSS measurements. Topographic instruments, measurement and analysis techniques enabling accurate measurements in the positioning of the stations and to control their variations over time were applied. The high reliability and accuracy of the absolute gravity data gathered, after being corrected for known effects, showed a negative short-term (2018–2020) pattern throughout the area, up to −30 µGal. Since some stations of the new network coincided with benchmarks already measured in the past, an analysis of long-term gravity changes was carried out and a fair degree of stability was observed in two stations, while positive large variations, of approximately 70 and 157 µGal, were recorded in the other two stations in the time intervals 1954–2020 and 2005–2010, respectively. On the other hand, variations highlighted by GNSS height measurements were all below 3 cm. Here, the first long-lasting gravity measurements carried out with absolute gravimeters in a seismic area in Italy are presented, providing meaningful geophysical information. The obtained results, in terms of availability of a combined absolute gravity and GNSS network, definition of data acquisition and analysis procedures, as well as creation of a high quality data archive, lay the foundations for a multidisciplinary approach towards improving the knowledge of this seismogenetic area of Italy.

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“…The Chi-square test has not been used in published results of AG comparisons. Nevertheless, inconsistent measurements were investigated based on normalized deviations (Newell et al 2017)…”

Section: Consistency Checkmentioning

confidence: 99%

Evaluation of comparisons of absolute gravimeters using correlated quantities: reprocessing and analyses of recent comparisons

Pálinkáš

Wziontek

Vaľko

et al. 2021

J Geod

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Due to the lack of a natural reference for the absolute acceleration of free fall and gravity, absolute gravimeters are compared at international comparisons, where the gravity reference is realized based on a set of precise absolute measurements and the functional model for their processing. The main estimates of comparisons, specifically, the reference values, deviations of gravimeters (biases) and associated uncertainty estimates, are obtained by the method of constrained least squares. In this paper, based on data from six comparisons, we demonstrate and discuss the importance of several aspects that significantly influence the estimated parameters, such as the type of the constraint, the weighting schemes, the correlations between measurements or outlier detection. Following the state-of-the-art key comparisons in metrology, we are applying correlations between measurements of a particular gravimeter for the first time, showing the ability to obtain appropriate uncertainty estimates, strictly applying the law of error propagation. The processing of comparisons by the method of least squares is described step by step to provide a background for analyses of absolute gravimeter comparisons in the future, reflecting all specifics of these comparisons. Estimated parameters from uniformly elaborated comparisons represent an interesting statistical data set that has been used to analyse the significance of differences between FG5, FG5X and other types of gravimeters. We believe that the described method of processing, as well as the published results, will be especially useful in the realization of the International Gravity Reference System.

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Regional comparison of absolute gravimeters SIM.M.G-K1 key comparison

Cited by 5 publications

References 7 publications

A long-term charge/discharge cycle at Mt. Etna volcano revealed through absolute gravity and GPS measurements

A long-term charge/discharge cycle at Mt. Etna volcano revealed through absolute gravity and GPS measurements

Insights into Seismogenetic Areas in Central Italy from Combined Absolute Gravity and GNSS Measurements

Evaluation of comparisons of absolute gravimeters using correlated quantities: reprocessing and analyses of recent comparisons

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