The planning and field work for the large-N passive seismological experiment in the Eifel Volcanic Field

In September 2022 we launched a large-scale seismic experiment in Germany with more than 350 seismological stations (Eifel large-N), to study the Eifel volcanic system. The temporary network is complementing the permanent seismic networks in the region. The deployed instruments used include both 4.5 Hz 3C, 1 Hz short-period, and broadband instruments. DIEGOS Cube³ digitizers are used for data sampling and 9 V electrical fence batteries provide autarch energy at each site. Most of the instruments were borrowed from the GFZ GIPP Instrument Pool for 1 year. In a second phase of the project, half of the installed stations will be re-deployed along linear profiles with a station spacing of 1 km. In 2023, continuous distributed acoustic sensing measurements along a 100 km dark telecommunication fiber optical cable will begin, for a period of three months. These measurements will complete the campaign. We report on preliminary studies on the design of the Large-N experiment, the logistical and technical approach to handling the network and the data, and show first examples for selected local earthquakes, local noise conditions and noise correlations.

The Eifel region in Germany is characterized both as a recreational area with villages, agriculture, forestry and parks, as well as with cities, industrial centers, motorways, railway lines, windmill energy parcs and quarries. The site selection phase was carried out with up to three groups, and began half a year before the network deployment. At the same time, the district administrators and mayors of cities and municipalities who provide valuable support for the project were contacted.

Site selection information was organized in a geo information system (GIS). The fieldwork was orchestrated using the mobile QField App. In September 2022, we started to install the large-N network, which covers an area of ​​approximately 150 x 110 km². Around the scientific target, the Laacher See, is a high station density with inter-station distance of less than 1 km, the inter-station distances increase with distance from the Laacher See. During the installation phases in September and October 2022, the international project partners formed up to 8 groups that installed the nodal stations in the sectors. Each group was equipped with a smartphone or tablet running the QField app also, updating the station information database independently. The QField app provided instant information about the network status via online synchronization.