Microgravimetric measurements at the 1994 International Comparison of Absolute Gravimeters

Becker, Matthias; Balestri, Lorenzo; Bartell, R.; Berrino, Giovanna; Bonvalot, Sylvain; Csapó, G.; Diament, M.; D’Errico, Marco; Gerstenecker, C.; Gagnon, C.; Jousset, Philippe; Kopaev, A.; Liard, J.; Marson, I.; Meurers, Bruno; Nowak, I.; Nakai, S.; Rehren, F.; Richter, B.; Schnüll, M.; Somerhausen, André; Spita, W.; Szatmári, G; Ruymbeke, M. Van; Wenzel, H.-G.; Wilmes, H.; Zucchi, M.; Zürn, W.

doi:10.1088/0026-1394/32/3/002

Cited by 28 publications

(27 citation statements)

References 2 publications

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“…The calibration factors of the gravimeters used in this study were checked in the same measurement range using the calibration line of the Bureau International des Poids et Mesures (BIPM), Sèvres, France. This line was established in 1994 during the fourth intercomparison of absolute and relative gravimeters (Becker et al . 1995) using fourteen LaCoste & Romberg relative gravimeters (D and G models).…”

Section: Gravimeter Calibrationmentioning

confidence: 99%

Continuous gravity recording with Scintrex CG-3M meters:a promising tool for monitoring active zones

Bonvalot¹,

Diament²,

Gabalda³

1998

Geophys. J. Int.

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We acquired continuous series of microgravity measurements using several Scintrex CG‐3M gravity meters for several weeks in 1997. The meters with 1 μGal resolution were installed side by side in a stable reference station at the ORSTOM research centre to perform identical data acquisition. We present and compare the instrumental responses obtained for the various gravity meters (measurement series of gravity field, standard deviation, internal temperature, tilts) and analyse their correlation with simultaneous recordings of meteorological parameters. The data have been processed in order to (1) establish the mid‐ to long‐term relative stability and the accuracy of the instruments, (2) estimate the contribution of instrumental effects to gravity data measurements and (3) quantify the amplitude of the time variations of the gravity field that might be detected with such instruments. This study emphasizes the sensitivity of some instrumental responses of the Scintrex CG‐3M gravity meters (such as internal temperature or tilt) to local atmospheric‐pressure variations. This sensitivity can lead to non‐negligible perturbations of the gravity measurements through automatic corrections applied in real‐time mode by the integrated software. We show that most of these instrumental artefacts can be easily removed in data post‐processing by using simultaneous atmospheric‐pressure data. After removal of an accurate Earth tide model, the instrumental drift and the instrumental effects, the temporal series are compared by computing differential signals. These residual signals obtained over a period of several weeks exhibit the following characteristics: (1) the gravity residuals have a maximum amplitude ranging from 5 to 10 μGal and from 10 to 15 μGal for filtered and unfiltered data, respectively; and (2) the standard error, tilts and internal temperature measurements of the various gravity meters are very consistent; their respective residual amplitudes are ±2 μGal, ±3 arcsec and ±0.05 mK. In order to calibrate the gravity meters precisely in the measurement range used in this study, we have measured a calibration line established in the framework of the fourth intercomparison of absolute and relative gravity meters. This calibration was achieved with an accuracy of 5 μGal. This result is consistent with other field tests already performed with such gravity meters. In addition, we also checked the accuracy of the tilt sensors by increasing the electronic read‐out by a factor of 10. The tilt response of the whole gravity meter to a small induced inclinometric variation indicates that the precision of the tilt measurements is about a few tenths of an arc second. This study reveals that temporal variations of the gravity field could potentially be detected in the field with an accuracy of about 5–15 μGal by permanent networks of Scintrex CG‐3M gravity meters set up a few kilometres apart. This result is of particular interest in field surveys of temporal gravity changes related to some environmental or geodynamical processes, ...

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Section: Gravimeter Calibrationmentioning

confidence: 99%

Continuous gravity recording with Scintrex CG-3M meters:a promising tool for monitoring active zones

Bonvalot¹,

Diament²,

Gabalda³

1998

Geophys. J. Int.

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“…In earlier RGCs [4][5][6][7][8][9][10]12], participation was open to the wider scientific community. Some participants could not perform the full and rigorous schedule demanded by earlier RGCs due to limits on their time or other conditions.…”

Section: Participantsmentioning

confidence: 99%

Relative Gravity Measurement Campaign during the 8th International Comparison of Absolute Gravimeters (2009)

et al. 2011

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The 8th International Comparison of Absolute Gravimeters (ICAG-2009) and the associated Relative Gravity Campaign (RGC2009) took place at the Bureau International des Poids et Mesures (BIPM) between July and October 2009. Altogether 24 institutes with 22 absolute gravimeters and 9 relative gravimeters participated in the ICAG/RGC campaign. Accurate absolute and relative gravity measurements as well as precision levelling measurements were performed on the micro-gravity 3D-grid at the BIPM. The 2009 comparison was the first to be organized as a Comité International des Poids et Mesures (CIPM)metrological Key Comparison under the CIPM MRA (Mutual Recognition Arrangement), which means that the result will be officially recognized by the governmental organizations responsible. As a consequence, the relative gravimeters employed were carefully selected and the measurement schedules were rigorously enforced compared to earlier campaigns. Thus the quality of the RGC2009 and the determination of the BIPM local gravity network were improved.After thirty years and eight successive ICAGs, the BIPM has decided to transfer its role to the National Metrological Institutes, although the CIPM will continue to organize the key comparison as ICAGs. The background to the RGC2009, and the organization, data processing and final results of the gravity and vertical gravity gradients are presented in this paper. This report is more detailed than previous final reports of the RGCs. Notation ICAG: International Comparison of Absolute Gravimeters RGC: Relative Gravity Campaign organized in association with ICAG AG: absolute gravimeter RG: relative gravimeter KC: CIPM key comparison WB: BIPM watt balance 1 µGal = 10 -8 m s −2 g: measured absolute acceleration due to gravity in µGal (minus a constant value of 980 900 000 µGal) G: adjusted g value KCRV: KC reference value of G δg, δG: differences of g or G H: height in meters above the ground benchmark γ H : average gradient corresponding to the height H RMS: root mean square error given by a least-squares adjustment (1-σ statistic estimation) Mean: mean value of a data set Std: standard deviation u: standard uncertainty Site, Station and point: The BIPM gravity network comprises indoor and outdoor relative measurement ties between 5 sites (A, B, C1, C2 and WB) and 12 stations (Figures 2.2.1, A, B, B1-B6, C1, C2, W1 and W2). The WB site is used for the BIPM watt balance project. Results at the WB site are not discussed in this paper. This paper therefore is limited to 4 sites and 10 stations. At each station, 3 points are defined at 0.30 m, 0.90 m and 1.30 m above the ground benchmark (C1 and C2 have only 2 points at 0.90 m and 1.30 m). There are 28 points in total. Naming convention is by station plus height in cm, e.g. A.030, A.090 and A.130.

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“…In addition, gravity meters have been calibrated periodically at the Bureau International de Poids et Mesures (BIPM) at Sèvres-Paris [41]. During the last calibration in 1994, the differences obtained between readings from all participating gravity meters were in the range ±2 Gal to ±5 Gal.…”

Section: Gravity Network and Gravity-height Data Processingmentioning

confidence: 99%

Hazard assessment during caldera unrest at the Campi Flegrei, Italy: a contribution from gravity–height gradients

Gottsmann

Berrino

Rymer

et al. 2003

Earth and Planetary Science Letters

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(2003). Hazard assessment during caldera unrest at the Campi Flegrei, Italy: a contribution from gravity-height gradients. Earth and Planetary Science Letters, AbstractHazard assessment and risk mitigation at restless calderas is only possible with adequate geophysical monitoring. We show here how detailed long-term microgravity and deformation surveys may contribute to hazard assessment at the Campi Flegrei caldera (CFc) in Italy by evaluating gravity-height change (∆g/∆h) gradients obtained during ground inflation and deflation between 1981 and 2001. Such gradients provide a framework from which to assess the likelihood and type of volcanic eruptions. Our new analysis of unrest at the CFc allows us to separate 'noise' during the gravity survey from the signal of deep-seated magmatic processes. This facilitates identification of the dynamics within the magma reservoir beneath the CFc. We found that magma replenishment during rapid uplift between 1982 and 1984 was insufficient, probably by one to two orders of magnitude, to trigger an eruption similar to the 1538 Monte Nuovo eruption, the most recent volcanic eruption within the CFc. Furthermore, our interpretation of ∆g/∆h gradients for the ongoing period of deflation since 1984 suggests that eruptive volcanic activity is not imminent. Short periods of minor inflation associated with large gravity changes since 1981 are interpreted to reflect noise, which to some degree is probably due to sub-surface mass/density changes within shallow hydrothermal systems beneath the CFc, indicating no risk of eruptive volcanic activity. We propose that monitoring ∆g/∆h gradients at restless calderas is essential as a caldera develops from a state of unrest to a state where volcanic eruptions have to be anticipated. Adoption of this method for the several tens of restless calderas world-wide will provide early warning of changes in or increase of activity at these supervolcanoes.

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Microgravimetric measurements at the 1994 International Comparison of Absolute Gravimeters

Cited by 28 publications

References 2 publications

Continuous gravity recording with Scintrex CG-3M meters:a promising tool for monitoring active zones

Continuous gravity recording with Scintrex CG-3M meters:a promising tool for monitoring active zones

Relative Gravity Measurement Campaign during the 8th International Comparison of Absolute Gravimeters (2009)

Hazard assessment during caldera unrest at the Campi Flegrei, Italy: a contribution from gravity–height gradients

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