50,822 earthquakes in the alps since 1987 : a catalog to improve seismic hazard characterization

The western Alpine arc is characterized by moderate but constant seismic activity. Numerous studies (geodynamic and seismological, etc.) highlight the persistent scientific questions linked to Alpine dynamic processes and the associated rate of deformation (resulting from late continental collision phases), and to the assessment of seismic hazard and associated risks. Seismic monitoring in the northern French Alps was launched in 1987 with the installation of the first Sismalp seismological network, hosted by the Observatoire des sciences de l’Univers de Grenoble (OSUG) and managed by the Institut des Sciences de la Terre (ISTerre/OSUG).

Since 1987, the network has been updated over the years, keeping pace with technical developments in instrumentation, monitoring and data management. The homogenization of information over the period 1987-2023 was motivated by the need for a single instrumental seismic catalog. The final SISMalp-1987-2023 catalog contains 50,822 earthquakes with a completeness magnitude of less than 1, and can be used as a basis for all general seismotectonic studies and seismic risk assessments in the Alpine region.

The database and the strategy for harmonizing information over the period 1987-2023 are described in Langlais et al. (2024).

Technical validation is described in Virieux et al. (2024) via an in-depth study of the influence of parameters and choices for local seismic tomography (LET), which inverts local-regional earthquake arrival time selections for P- and S-wave velocities in conjunction with hypocenter parameters.

► Go to the SISMalp-1987-2023 catalog : the 1987-2023 catalog of earthquakes in the western (French) Alps north of 43.5°N.

References

Virieux J., Paul A., Langlais M., Janex G., Guéguen P., Helmstetter A., Stehly L. 2024. Assessing the reliability of local earthquake tomography for crustal imaging : 30 years of records in the Western Alps as a case study, Geophysical Journal International, 236(1):99–118. doi :10.1093/gji/ggad378

The database is available at Data Terra, via doi : https://doi.org/10.57932/bba3b3a3-e92e-4d90-92db-9b045684ed5d