Passive seismic exploration with a dense network of 700 sensors in the Canton of Jura, Switzerland

As part of the Net Zero climate strategies of the European Union and Switzerland, deep geothermal power production is given an important role to play as a baseload energy resource. In Switzerland, the Haute Sorne project of Geo-Energie Suisse is the first EGS geothermal project to take place since the unsuccessful project of Basel terminated in 2010. The Canton of Jura, where Haute Sorne is located, gave the green light to Geo-Energie Suisse in January 2022. To minimize the risk of damaging induced seismicity as in 2017 during the Pohang EGS project, innovative state-of-the-art exploration and monitoring methods at Haute Sorne are being implemented to reduce subsurface uncertainty and de-risk the project as much as possible.

In this context, the University of Geneva is deploying a seismic network of 700 nodal sensors in February 2024 in a radius of 12 km around the planned Haute Sorne EGS site. The sensors will record continuous 3-component seismic velocity data passively over 30 days. Using ambient noise tomography techniques, this study aims to image at up to 5 kilometres depth regional-scale structures relevant to seismic hazard assessment and to understand the local seismo-tectonic context. Particular interest is given to basement-related structures including a nearby presumed Permo-Carboniferous trough. By examining anomalies in shear-wave velocity, radial anisotropy and/or attenuation, we aim to elucidate the presence of deep faults and/or deep fluid reservoirs. In this presentation, we will report the outcomes of the nodal deployment campaign, the quality of the data collected, preliminary ambient noise observations and the methods to be applied. Passive seismic campaigns with temporary nodal networks have great potential for geothermal exploration due to their low cost, easier permitting process, and ability to image basement-related structures with appropriately designed networks.