Results of the first North American comparison of absolute gravimeters, NACAG-2010

Schmerge, D.; Francis, Olivier; Henton, J. A.; Ingles, D.; Jones, David; Kennedy, Jeffrey R.; Krauterbluth, K.; Liard, J.; Newell, David B.; Sands, R. W.; Schiel, A.; Silliker, J.; Westrum, Derek van

doi:10.1007/s00190-011-0539-y

Cited by 18 publications

(16 citation statements)

References 8 publications

(9 reference statements)

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“…Hence, the pillar may cause some vibration during the FG5 measurements. When we excluded the FG5 outside stations, we obtained the differences at the inside stations to be between −3.9 and 5.5 μGal which are similar to the results reported by the other researchers (Vitushkin et al 2002;Timmen 2010;Jiang et al 2011Jiang et al , 2012aFrancis et al 2010Francis et al , 2013Schmerge et al 2012).…”

Section: Comparison Of Fg5 and A10 Absolute Gravitysupporting

confidence: 91%

Absolute gravity measurements by using FG5 and A10 absolute gravimeters in the Kingdom of Saudi Arabia

Ayhan

Al-Muslmani

Kanney³

et al. 2014

Arab J Geosci

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In order to define gravity datum and gravity scale in the Kingdom of Saudi Arabia (KSA), an absolute gravity network, called KSA Absolute Gravity Network (KSA-AGN), comprising of 25 sites distributed countrywide was observed from January 2013 to February 2013. Two stations were installed at each network site: one inside the building and one outside. Micro-g A10 (#029) portable absolute gravimeter was used for data acquisition of two setups of ten sets each at both inside and outside stations. Set scatters for A10 setups are usually less than ±3 μGal, and the differences between two setups vary in the range of −8 to 5 μGal. The weighted mean of the two setups were calculated as unique absolute gravity value and its uncertainty at the stations. Seven of the stations (five inside and two outside) were collocated by Micro-g FG5 (#111) absolute gravimeter having 24 sets for each setup. Set scatters for FG5 setups are less than ±4 μGal almost like A10 setups. However, we obtained the total uncertainty of FG5 and A10 measurement about ±2 and ±6 μGal, respectively. Furthermore, to reduce measured absolute gravity from the reference height to any height, gravity gradients over both inside and outside stations were measured by using two Scintrex CG5 (#922 and #924) relative gravimeters. Average CG5 gradient at the outside stations is about 3.1 μGal/cm, satisfying the free air gradient in the country. Differences between A10 and FG5 absolute gravities at 72 cm vary between −3.8 and 9.5 μGal at seven stations. Excluding the outside stations, we obtained the differences from −3.8 to 5.5 μGal at inside stations.

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Section: Comparison Of Fg5 and A10 Absolute Gravitysupporting

confidence: 91%

Absolute gravity measurements by using FG5 and A10 absolute gravimeters in the Kingdom of Saudi Arabia

Ayhan

Al-Muslmani

Kanney³

et al. 2014

Arab J Geosci

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“…Absolute gravimeters measure the acceleration due to gravity directly by timing the acceleration of a free‐falling mass. The A‐10 used in the study has an accuracy of about 6 µGal, verified from previous gravimeter intercomparisons [ Schmerge and Francis , ; Schmerge et al ., ]. Both the iGrav and gPhone gravimeters are stationary, continuously recording instruments.…”

Section: Methodsmentioning

confidence: 99%

Time‐lapse gravity data for monitoring and modeling artificial recharge through a thick unsaturated zone

Kennedy

Ferré

Creutzfeldt

2016

Water Resources Research

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Groundwater‐level measurements in monitoring wells or piezometers are the most common, and often the only, hydrologic measurements made at artificial recharge facilities. Measurements of gravity change over time provide an additional source of information about changes in groundwater storage, infiltration, and for model calibration. We demonstrate that for an artificial recharge facility with a deep groundwater table, gravity data are more sensitive to movement of water through the unsaturated zone than are groundwater levels. Groundwater levels have a delayed response to infiltration, change in a similar manner at many potential monitoring locations, and are heavily influenced by high‐frequency noise induced by pumping; in contrast, gravity changes start immediately at the onset of infiltration and are sensitive to water in the unsaturated zone. Continuous gravity data can determine infiltration rate, and the estimate is only minimally affected by uncertainty in water‐content change. Gravity data are also useful for constraining parameters in a coupled groundwater‐unsaturated zone model (Modflow‐NWT model with the Unsaturated Zone Flow (UZF) package).

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“…[, ], or included in the uncertainty budget [ Sato et al ., ; Mémin et al ., ; Palinkas et al ., ]. Intercomparison campaigns [e.g., Francis et al ., , , , ; Jiang et al ., ; Schmerge et al ., ; Vitushkin et al ., ] showed that differences between FG5 and JILAg gravimeters are commonly of the order of 100–150 nm/s 2 . A difference as large as 461 nm/s 2 was reported for one of the A10 instruments that participated in the ICAG‐2001 intercomparison [ Vitushkin et al ., ].…”

Section: Instrumental Artifactsmentioning

confidence: 99%

“…When different AGs are used in the same study, interinstrument differences should be taken into account, as done, for example, by Lambert et al [2006Lambert et al [ , 2013b, or included in the uncertainty budget [Sato et al, 2006;Mémin et al, 2011;Palinkas et al, 2012]. Intercomparison campaigns [e.g., Francis et al, 2005Francis et al, , 2010Francis et al, , 2013Francis et al, , 2015Jiang et al, 2012;Schmerge et al, 2012;Vitushkin et al, 2002] showed that differences between FG5 and JILAg gravimeters are commonly of the order of 100-150 nm/s 2 . A difference as large as 461 nm/s 2 was reported for one of the A10 instruments that participated in the ICAG-2001 intercomparison [Vitushkin et al, 2002].…”

Section: Instrumental Artifactsmentioning

confidence: 99%

Separating climate‐induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements

Camp

Viron

Avouac

2016

Geophysical Research Letters

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We estimate the signature of the climate‐induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission. We show results at the globe scale and compare them with repeated absolute gravity (AG) time behavior in three zones where AG surveys have been published: Northwestern Europe, Canada, and Tibet. For 10 yearly campaigns, the uncertainties affecting the determination of a linear gravity rate of change range 3–4 nm/s2/a in most cases, in the absence of instrumental artifacts. The results are consistent with what is observed for long‐term repeated campaigns. We also discuss the possible artifact that can result from using short AG survey to determine the tectonic effects in a zone of high hydrological variability. We call into question the tectonic interpretation of several gravity changes reported from stations in Tibet, in particular the variation observed prior to the 2015 Gorkha earthquake.

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Results of the first North American comparison of absolute gravimeters, NACAG-2010

Cited by 18 publications

References 8 publications

Absolute gravity measurements by using FG5 and A10 absolute gravimeters in the Kingdom of Saudi Arabia

Absolute gravity measurements by using FG5 and A10 absolute gravimeters in the Kingdom of Saudi Arabia

Time‐lapse gravity data for monitoring and modeling artificial recharge through a thick unsaturated zone

Separating climate‐induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements

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