Modelling soil response at the national scale for Switzerland in the framework of risk assessment of induced seismicity

Risk modelling is a key tool for mitigating the seismic risk associated with geo-energy applications and CO₂ storage. Prior estimation of potential damages and mapping of affected communities enable, among other things, the feasibility assessment of geothermal projects in their planning phase and the allocation of appropriate resources for damage compensation. This promotes societal preparedness and acceptance towards such applications.  

With rising interest in geothermal energy in Switzerland, the Federal Office of Energy tasked the Swiss Seismological Service (SED) to extend the national Earthquake Risk Model ERM-CH23 (Papadopoulos et al., 2024) to include induced seismicity associated with geo-energy applications and CO₂ injection projects. Since these activities typically trigger shallow earthquakes with low-to-moderate magnitudes, the need arose to extend the range of modelled intensity measures towards intermediate periods, which are more sensitive to potential damage from the expected scenario ruptures. As ERM-CH23 already covers PGV and PSA at 1, 0.6 and 0.3 s, it was decided to additionally integrate PSA(0.4s) and PSA(0.2s). From the perspective of soil amplification modelling, we first verified that the existing ERM-CH23 local response layers (Bergamo et al., 2023) are suitable for induced seismicity scenarios. We then applied the procedure of Bergamo et al. (2023), i.e., combining empirical amplification factors with site proxies via geostatistical interpolation, to generate the additional soil response layers for PSA(0.4, 0.2s). Leveraging an extended ground motion database and proven site condition indicators, the maps cover the whole of Switzerland while achieving a fine spatial resolution (250 m); the high quality of the input datasets contributes to keeping the associated (and mapped) epistemic uncertainty (ϕ_S2S) within reasonable limits.

In addition to seismic risk modelling, the complete set of national soil amplification maps for PSA(0.2 - 1.0s) has also been incorporated into the GRID approach of the current revision of SED's Good-Practice Guide for managing induced seismicity in deep geothermal projects (Kraft et al., 2025). GRID (Geothermal Risk of Induced seismicity Diagnosis, Trutnevyte & Wiemer 2017) is a diagnostic tool developed to classify a project's induced seismicity risk. The PSA(0.2 - 1.0s) amplification maps have been collated to consistently chart soft soil areas (soil types D, E and F of the Swiss building code SIA 261) at the national scale, contributing to GRID’s “local amplification” indicator.

 

References

Bergamo, P., et al. (2023). A site amplification model for Switzerland based on site-condition indicators and incorporating local response as measured at seismic stations. Bull Earthquake Eng 21, 5831–5865. https://doi.org/10.1007/s10518-023-01766-z

Papadopoulos, A. N., et al. (2024). The Earthquake Risk Model of Switzerland, ERM-CH23, Nat. Hazards Earth Syst. Sci., 24, 3561–3578, https://doi.org/10.5194/nhess-24-3561-2024

Kraft, T., et al. (2025). Good-Practice Guide for Managing Induced Seismicity in Deep Geothermal Energy Projects in Switzerland, Version 3, Report of the Swiss Seismological Service (SED) at ETH Zurich, pp. 80, https://10.3929/ethz-b-000714220

Trutnevyte, E., & S. Wiemer (2017). Tailor-made risk governance for induced seismicity of geothermal energy projects: An application to Switzerland, Geothermics, 65, 295-312, https://doi.org/10.1016/j.geothermics.2016.10.006.