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In the last few decades dense large-scale seismic networks showed their importance in studying the structure of the lithosphere and the upper mantle. The better understanding of the Apennines-Alps-Carpathian-Dinarides system is the main target of the AlpArray European international initiative in which more than 50 institutes are involved. The core of AlpArray is the AlpArray Seismic Network (AASN). With its $ 600 broadband seismic stations ( $ 280 of which are temporary) the AASN is, so far, the largest passive seismic experiment in Europe. The MTA CSFK Geodetic and Geophysical Institute, as a Core Member of the AlpArray project, contributes to the AlpArray Seismic Network with its entire permanent network as well as with 11 temporary broadband seismic stations deployed in Western Hungary. Three additional station equipment were provided by the Swiss-AlpArray SINERGIA program. The average station distance together with the permanent stations is around 40 km in the area of interest. The temporary network has been installed between December 2015 and July 2016 and the planned operation period is 3 years. In this paper we describe the characteristics of the 29 permanent and temporary stations, introducing not only the equipment, but the location, housing and geological setting, as well. We present median power spectral density curves in order to characterise the noise conditions at each station.

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.