The first pan-Alpine surface-gravity database, a modern compilation that crosses frontiers

Abstract

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.

Orogenic lithosphere and slabs in the greater Alpine area – interpretations based on teleseismic P-wave tomography

“…5a, b). The occurrence of negative V p anomalies and reduced gravity anomalies (Zahorec et al, 2021) immediately below this shallow orogenic Moho in the eastern Alps (e.g. profile 12, Fig.…”

Two subduction-related heterogeneities beneath the Eastern Alps and the Bohemian Massif imaged by high-resolution P-wave tomography

“…Nevertheless, neither including pre-defined slab geometries nor accounting for compositional and thermal variations with depth brings satisfactory results, which would allow them to distinguish between their two different slab configurations. The freshly compiled pan-Alpine surface-gravity database (Zahorec et al, 2021) will undoubtedly provide new impetus for struc- Royden and Burchfiel, 1989;Royden, 1993), northward push of Adria, and European slab delamination beneath the Eastern Alps (Handy et al, 2015) could have formed complex flows in the asthenosphere, which might "transport" lithosphere fragments toward the north-west. For more details see the main text.…”

New Bouguer Anomaly Map for the Territory of the Slovenia

“…DTM25 Numerous updated national Bouguer anomaly maps are currently being created, as researchers are making the best use of the improved topographic models and the increasingly improved gravimetric data at their disposal. Various methodologies are being used [6] and several new maps have been created in the vicinity of Slovenia recently: Austria [7], Hungary [8], Italy [9], Adriatic Sea [10], Croatia [11], the pan-Alps area [12]. The existing Bouguer anomaly map for Slovenia [3] was created quite a while ago, and as has been previously stated, there are quite a few new gravimetric measurements (data) for the territory of Slovenia as well as high quality digital terrain models that are needed for creating such a map at our disposal.…”

“…At the sea surfaces, one should also take into account the density of water, which for observations on sea means that one needs to take into account the density of seawater (1027 kg/m 3 ), while for observations on fresh water, one needs to take into account the density of fresh water (1000 kg/m 3 ), and for observations on ice, the density of ice (917 kg/m 3 ). For more on this, see [12,30].…”

“…A detailed description of these available data is given in Section 2. Unfortunately, the recently created regional map of gravimetric anomalies, which encompasses the area of the Alps [12], failed to include the new gravimetric data for Slovenia as it only used the old data. Thus, it would make sense to update the national Bouguer anomaly map.…”