| 27 Dec 2025
South East France Potentially Active Faults: A database for seismic hazard assessment
Abstract. The South-East of France has been structured by numerous tectonic episodes resulting in a complex compound of crustal deformations. This fallouts in a large network of faults which have evolved throughout subsequent tectonic events. Nevertheless, the present-day tectonic deformation is slow and of debated origin, giving place to a low to moderate seismicity. This seismotectonic context is a challenge for seismic hazard analysis, specifically for the identification and characterisation of potentially active faults. In this study we present a fault-related data compilation, named South-East France Potentially Active Faults (SEFPAF, Mowbray et al., 2025, https://doi.org/10.5281/zenodo.17235395), which integrates structural components from geological maps, previous neotectonic databases and fault-specific studies. Our objective is to provide a new, well documented, and modular fault database. Multiple structural representations per fault are presented, allowing the end-user to choose from the various parameter value options. With an end purpose of identifying the most relevant faults for seismic hazard assessment, we build a series of indices which allow fault prioritization: the Importance index (I), the Documentation index (D) and, the Seismogenic Potential index (SP). The first classifies faults into major, secondary and minor based on the source's description of the structure; the second analyses the quantity of information known for each fault; the last intends to decipher seismically active faults by integrating the age of the last documented rupture, the spatial correlation with seismic flux and, the spatial correlation with geodetic strain. SEFPAF may have various applications, amongst them we illustrate the first step towards the development of a fault model for seismic hazard analysis: we identify relevant faults to model by adjusting the index criteria and, propose idealized geometries for a set of 20 faults which can subsequently be used as composite seismogenic sources.
General comments:
This manuscript provides detailed development of a new database of potentially active faults in South-east France, called South-East France Potentially Active Faults (SEFPAF), for seismic hazard assessment.
Significance: The newly developed database has a broad potential utility and is a long-awaited improvement to the “BDFA” (Base de Données de Failles Actives) from Jomard et al. (2017), which aims to map active faults in the 50 km vicinity of nuclear facilities within metropolitan France. built with a different purpose and with a different geographical extension.
Presentation: the manuscript has sections that read more like a user manual than a journal publication. I feel that this is to some extent inevitable, as the purpose of the paper is to develop a new database, however I suggest new Appendices to facilitate the reading.
Specific comment on the La Rouvière Fault (Thomasset et al., 2024) :
As described in the supplement image, the location of the La Rouvière fault (in red) of SEFPAF is not consistent with the cited publication of Thomasset et al. (2024). This location is also not consistent with surface ruptures indices from Ritz et al. ( 2020) observed just after the Le Teil earthquake (Mw 4.9, 2019/11/11, France).
I suggest to add in SEFPAF database the secondary surface-rupturing Bayne-Rochrenard fault described in the publication of Burnol et al. (2023) in MDPI Remote sensing.