Absolute and Relative Gravimetry

Timmen, Ludger

doi:10.1007/978-3-642-11741-1_1

Cited by 17 publications

(12 citation statements)

References 38 publications

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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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“…The gravity meters were calibrated using the calibration line in the university tower building in Hanover, Germany (Kanngieser et al, 1983) and the Harz mountain calibration line (Torge, 1989). The estimated mean standard deviations (STD) of adjusted gravity differences are in the range of 1 µGal for Hanover and 2 µGal for Harz (Timmen, 2010;Timmen et al, 2018). Frequent calibrations have shown stable calibration factors for all used instruments.…”

mentioning

confidence: 99%

Time-lapse gravity and levelling surveys reveal mass loss and ongoing subsidence in the urban subrosion prone area of Bad Frankenhausen/Germany

Kobe¹,

Gabriel²,

Weise³

et al. 2018

Preprint

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Abstract. We present results of a sophisticated, high-precision time-lapse gravity survey that was conducted over four years in Bad Frankenhausen (Germany). To our knowledge, this is the first successful attempt to monitor subrosion-induced mass changes in urban areas with repeated gravimetry. The method provides an approach to estimate the mass of dissolved rocks in the subsurface. Subrosion, i.e. leaching and transfer of soluble rocks, occurs worldwide. Especially in urban areas, any resulting ground subsidence can cause severe damage, especially if catastrophic events, i.e. collapse sinkholes occur. Monitoring strategies typically make use of established geodetic methods, such as levelling, and therefore, focus on the associated deformation processes. In this study, we combine levelling and highly precise time-lapse gravity surveys. Our investigation area is the urban area of Bad Frankenhausen in Central Germany, which is prone to subrosion, as many subsidence and sinkhole features on the surface reveal. The city and the surrounding areas are underlain by soluble Permian deposits, which are continuously dissolved by meteoric water and groundwater in a strongly fractured environment. Between 2014 and 2018, a total of 17 high-precision time-lapse gravity and 18 levelling campaigns were carried out in quarter-yearly intervals within a local monitoring network. This network covers historical sinkhole areas, but also areas that are considered to be stable. Our results reveal ongoing subsidence of locally up to 30.4 mm a−1, with distinct spatio-temporal variations. Furthermore, we observe significant time-variable gravity changes in the order of 8 μGal over four years at several measurement points. In the processing workflow, after the application of all required corrections and least squares adjustment to our gravity observations, a significant effect of varying soil water content on the adjusted gravity differences was figured out. Therefore, we place special focus on the correlation of these observations and the correction of the adjusted gravity differences for soil water variations using the global soil water model GLDAS Noah to separate these effects from subrosion-induced gravity changes. Our investigations demonstrate the feasibility of high-precision time-lapse gravity in urban areas for sinkhole investigations. Although the observed rates of gravity changes of 1–2 μGal a−1 are small, we suggest that it is significantly associated with subterranean mass loss due to subrosion processes. We discuss limitations and implications of our approach, as well as give a first quantitative estimation of mass transfer at different depths and for different densities of dissolved rocks.

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“…A brief overview on relative and absolute gravity is given by Timmen [22]. During every relative gravimetry campaign four different gravimeters of the types Scintrex CG3, CG5, and LaCoste & Romberg (LCR) are used to optimise the network surveys.…”

Section: Gravimetrymentioning

confidence: 99%

Geodetic monitoring of subrosion-induced subsidence processes in urban areas

Kersten

Kobe

Gabriel

et al. 2017

Journal of Applied Geodesy

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The research project SIMULTAN applies an advanced combination of geophysical, geodetic, and modelling techniques to gain a better understanding of the evolution and characteristics of sinkholes. Sinkholes are inherently related to surface deformation and, thus, of increasing societal relevance, especially in dense populated urban areas. One work package of SIMULTAN investigates an integrated approach to monitor sinkhole-related mass translations and surface deformations induced by salt dissolution. Datasets from identical and adjacent points are used for a consistent combination of geodetic and geophysical techniques. Monitoring networks are established in Hamburg and Bad Frankenhausen (Thuringia). Levelling surveys indicate subsidence rates of about 4–5Here, the concept of combining geodetic and gravimetric techniques to monitor and characterise geological processes on and below the Earth's surface is exemplary discussed for the focus area Bad Frankenhausen. For the different methods (levelling, GNSS, relative/absolute gravimetry) stable network results at identical points are obtained by the first campaigns, i.e., the results are generally in agreement.

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Absolute and Relative Gravimetry

Cited by 17 publications

References 38 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 and levelling surveys reveal mass loss and ongoing subsidence in the urban subrosion prone area of Bad Frankenhausen/Germany

Geodetic monitoring of subrosion-induced subsidence processes in urban areas

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