• Marcin Rajner Marcin Rajner assistant professor Department of Geodesy and Geodetic Astronomy (FGC/DGGA)Faculty of Geodesy and Cartography (FGC)
• Tomasz Olszak Tomasz Olszak assistant professor Department of Geodesy and Geodetic Astronomy (FGC/DGGA)Faculty of Geodesy and Cartography (FGC)
• Jerzy Rogowski Jerzy Rogowski Department of Geodesy and Geodetic Astronomy (FGC/DGGA)Faculty of Geodesy and Cartography (FGC)
• Janusz Walo Janusz Walo associate professor Department of Geodesy and Geodetic Astronomy (FGC/DGGA)Faculty of Geodesy and Cartography (FGC)

In order to utilize the absolute gravity (AG) measurements in terms of tectonic study it is necessary to reduce all disturbing environmental and instrumental effects. Many of those can be easily modelled and this step is done routinely during measurements (i.e. tide, polar motion, ocean tidal loading). Other remains in data and there is a lack of conventional models for them. Significant gravity variation is associated with changes of soil water at global scale. We study this effect for the Lower Silesia (South-western Poland) territory. Computed gravity changes can reach up to 2 μgal peak-to-peak amplitude with seasonal time scale. This effect is beyond of accuracy of modern ballistic gravimeter. Using real data collected with FG5 gravimeter we show here that neglecting of this phenomenon can lead to serious misinterpretation in term of secular gravity changes. This is emphasized especially when only sparse data of a few year time span is at our disposal. No attempt of modelling of local hydrology impact on effect was made, while in this study we concentrate on large scale water storage influence on measured gravity.

Keywords

absolute gravity, FG5 instrument, hydrology loading, Lower Silesia