Assessment of possible volcanic hazards in Germany with regard to repository site selection

Abstract. In the context of selecting a site for the long-term disposal of radioactive, heat-generating waste in deep geological formations, the potential for future volcanic activity within the next 1 million years must be systematically evaluated. This assessment draws upon an integrated analysis of geological, geochemical, and geophysical datasets, as well as isotopic measurements of crustal and mantle-derived gases. Relevant data sources include teleseismic imaging, long-term seismic and microseismic monitoring—particularly deep earthquake patterns—and geodetic observations of vertical crustal movements. Additional insights are provided by geological and mineralogical studies that inform the spatial distribution and petrogenesis of volcanic rocks. When combined with geophysically derived mantle anomalies and radioisotopic age data for volcanic centers, these datasets enable the delineation of areas with an elevated probability of future volcanism. Special focus is given to the Quaternary volcanic provinces of the Eifel and Vogtland, which are identified as regions with a significantly increased likelihood of renewed activity. The outermost volcanic centers in these regions are used to define preliminary hazard perimeters. A conservative safety buffer of 25 km beyond these limits is adopted to define the exclusion zone boundary for deep geological repositories. In the Vogtland region, known for its characteristic earthquake swarms, seismic epicenters are equated with volcanic centers to delineate zones of potential recurrence. The extent of this area is adjusted accordingly based on seismic swarm distribution and geophysical data. A major secondary hazard associated with volcanism in the Eifel is the potential damming of the Rhine River within its narrow Middle Rhine Valley by lava flows or tephra deposits. Prolonged blockage of the river would result in extensive upstream flooding, affecting the Upper Rhine Graben and its tributary valleys. Two regions in Germany—north of the Westerwald and east of the Black Forest—are classified as having a low probability of future volcanism within the next 1 million years. In the Tertiary volcanic fields, no volcanic activity is expected within the next 1 million years due to their advanced age and normal mantle and gas compositions.