Abstract
In this paper we describe all the field operations and the robust post-processing proceduresto determine the height of the new absolute gravimetric station purposely selected to belong to a new absolute gravimetric network and located in the Science Faculty of the L’Aquila University. This site has been realized indoor in the Geomagnetism laboratory, so that the height cannot be measured directly, but linking it to the GNSS antenna of AQUI benchmark located on the roof of the same building, by a classical topographic survey. After the topographic survey, the estimated height difference between AQUI and the absolute gravimetric site AQUIgis 14.9700.003 m. At the epoch of the 2018 gravimetric measures, the height of AQUI GNSS station was 712.9740.003 m, therefore the estimated ellipsoidalheight of the gravimetric site at the epoch of gravity measurements is 698.0040.005 m. Absolute gravity measurements are referred to the equipotential surface of gravity field, so that the knowledge of the geoidal undulation at AQUIg allows us to infer the orthometric height as 649.32 m.
Highlights
Gravity changes measured on the Earth’s surface consist of two terms: the effect of ground vertical displacement and internal mass redistribution
We will give a description of AQUI and the methodology followed to obtain the precise coordinates referred to the Antenna Reference Point (ARP, Figure 1); we will describe AQUIg and the absolute gravity measurements; in the end, we will describe the classical topographic survey to estimate the height difference between the ARP of AQUI and the gravimetric benchmark AQUIg located four floors below the roof of the same building
In this paper we describe how we determined the height of the absolute gravimetric station of L’Aquila, AQUIg, located indoor the Geomagnetism laboratory of L’Aquila University
Summary
Gravity changes measured on the Earth’s surface consist of two terms: the effect of ground vertical displacement and internal mass redistribution. The medium-long-term gravity and ground deformation variations related to post-seismic relaxation are expected as consequence of vertical deformation of the Earth surface and/or of the internal boundaries separating layers at depth with different densities Another interesting geophysical process active in the L’Aquila area is the deformation induced by ground water level changes in the aquifers: the filtered time series of long-term deformations correlate well with the time series of rainfall excess and gravity field variations in term of equivalent water height (EWH) from GRACE data [Riguzzi et al, 2020]. We will give a description of AQUI and the methodology followed to obtain the precise coordinates referred to the Antenna Reference Point (ARP, Figure 1); we will describe AQUIg and the absolute gravity measurements; in the end, we will describe the classical topographic survey to estimate the height difference between the ARP of AQUI and the gravimetric benchmark AQUIg located four floors below the roof of the same building
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