The Need for Advanced Traffic Light Systems for Risk Mitigation of EGS Projects

Many enhanced geothermal systems (EGS) projects rely solely on traditional magnitude based traffic light systems in order to mitigate seismic risks. However, in several geothermal projects (e.g. Basel and St. Gallen in Switzerland, Pohang in South Korea) traditional traffic light systems have fallen short to limit induced seismicity to a predefined level of event magnitude.

Our risks studies for the planned EGS project in Haute-Sorne in Canton Jura (Switzerland) and the evaluation of the Basel case highlight the need (1) for an advanced traffic light system taking into account the spatial distribution of seismicity and integrating continuously throughout all project stages new data and especially information about fault structures and (2) to update the risk studies throughout the duration of the project.

Such a procedure has been the basis for the permit by the authorities of the Canton Jura for the planned EGS project in Haute-Sorne and is also recommended by the “Good practice guide for managing Induced Seismicity in Deep Geothermal Energy Projects in Switzerland” published by the Swiss Seismological Survey.

Firstly we list some of the conditions of the permit and secondly we discuss selected points in light of the experiences of the Basel and Pohang EGS projects.