The first pan-Alpine surface-gravity database, a modern compilation that crosses frontiers
Authors: Zahorec Pavol , Papčo Juraj , Pašteka Roman , Bielik Miroslav , Bonvalot Sylvain , Braitenberg Carla , Ebbing Jörg , Gabriel Gerald , Gosar Andrej , Grand Adam , Götze Hans-Jürgen , Hetényi György , Holzrichter Nils , Kissling Edi , Marti Urs , Meurers Bruno , Mrlina Jan , Nogová Ema , Pastorutti Alberto , Salaun Corinne , Scarponi Matteo , Sebera Josef , Seoane Lucia , Skiba Peter , Szűcs Eszter , Varga Matej 
Published: May 2021

Abstract. The AlpArray Gravity Research Group (AAGRG), as part of the
European AlpArray program, focuses on the compilation of a homogeneous
surface-based gravity data set across the Alpine area. In 2017 10 European
countries in the Alpine realm agreed to contribute with gravity data
for a new compilation of the Alpine gravity field in an area spanning from
2 to 23∘ E and from 41 to 51∘ N. This compilation relies on existing national gravity databases and,
for the Ligurian and the Adriatic seas, on shipborne data of the Service
Hydrographique et Océanographique de la Marine and of the Bureau
Gravimétrique International. Furthermore, for the Ivrea zone in the
Western Alps, recently acquired data were added to the database. This first
pan-Alpine gravity data map is homogeneous regarding input data sets,
applied methods and all corrections, as well as reference frames. Here, the AAGRG presents the data set of the recalculated gravity fields on
a 4 km × 4 km grid for public release and a 2 km × 2 km
grid for special request. The final products also include calculated values
for mass and bathymetry corrections of the measured gravity at each grid point,
as well as height. This allows users to use later customized densities for
their own calculations of mass corrections. Correction densities used are
2670 kg m−3 for landmasses, 1030 kg m−3 for water masses above the ellipsoid and
−1640 kg m−3 for those below the ellipsoid and 1000 kg m−3 for lake water
masses. The correction radius was set to the Hayford zone O2 (167 km).
The new Bouguer anomaly is station completed (CBA) and compiled according to
the most modern criteria and reference frames (both positioning and
gravity), including atmospheric corrections. Special emphasis was put on the
gravity effect of the numerous lakes in the study area, which can have an
effect of up to 5 mGal for gravity stations located at shorelines with steep
slopes, e.g., for the rather deep reservoirs in the Alps. The results of an
error statistic based on cross validations and/or “interpolation residuals”
are provided for the entire database. As an example, the interpolation
residuals of the Austrian data set range between about −8 and +8 mGal and the
cross-validation residuals between −14 and +10 mGal; standard
deviations are well below 1 mGal. The accuracy of the newly compiled gravity
database is close to ±5 mGal for most areas. A first interpretation of the new map shows that the resolution of the
gravity anomalies is suited for applications ranging from intra-crustal- to
crustal-scale modeling to interdisciplinary studies on the regional and
continental scales, as well as applications as joint inversion with other
data sets. The data are published with the DOI
https://doi.org/10.5880/fidgeo.2020.045
(Zahorec et al., 2021) via GFZ Data Services.