Field data map. Historical and instrumental earthquakes (Cara et al., 2015; Masson et al., 2021; Jomard et al., 2021). Focal mechanisms are extracted from the FMHex20 database (http://www.oreme.org; Mazzotti et al., 2021) associated with the Action Transverse Sismicité of the national research infrastructure Résif (https://www.resif.fr/). Hydrothermal mapping: sources are represented (Tab. 1) with their main recharge area, and deep hydrothermal flow into the Devonian reservoir is indicated by red arrows (from the Alet branch of the Mouthoumet Massif following the plunge of the Devonian Geothermal reservoir to the West and SW). Transects of the three serried balanced cross-sections are indicated by black lines (Figs. 9–11). Dip data are only represented on the Figure 2b to improve the readability of this map.