A large-N passive seismological experiment to unravel the structure and activity of the transcrustal magma system of the Eifel Volcanic Field

The Quaternary east (EEVF) and west Eifel volcanic fields consist of hundreds of distributed scoria cone and explosive maar-diatreme volcanoes fed from reservoirs in the upper mantle and lower crust. Uplifting of the larger EVF region of up to 2 mm/yr is resolved today with modern GNSS and InSAR processing, and the distribution of deformation rates correlate with seismic anomalies and topography at Moho level. The EEVF developed additionally explosive volcanic centres, with a VEI 6 Plinean eruption at the Laacher See volcano (LSV) only 13,000 years ago. The LSV is the second youngest silicic-carbonatitic magma system in the world, with CO2-rich melt erupting from a long-lived (>30.000 years) zoned silicic reservoir at a depth of 5-6 km. The phonolitic centres are today characterised by high CO2 fluxes, fossil CO2-driven diatremes and short-term short wavelength uplift and subsidence. Deep low-frequency earthquakes have been observed beneath the LSV since 2013, suggesting a channel-like connection between the upper mantle and the suspected LSV reservoir, through which magmatic volatiles and possibly fresh melts could migrate upwards.

As a uniquely accessible site in central Europe, the Eifel is a prime location to study the transcrustal magma system of intraplate distributed volcanic fields and their appearance in seismological and geodetic data. Therefore, in September 2022 we started a large-scale field experiment with more than 350 temporary seismological stations (Eifel Large-N) complementing the permanent seismic networks, a 100 km long dark fibre DAS campaign for a period of three months, and further densified the network of continuous GNSS and multiparameter stations at the LSV. We report on pre-studies to design the Large-N experiment, the logistical and technical approach to handle the network and data, and show first examples for selected earthquakes, local noise conditions and ambient noise correlations.