| Abstract |
On November 15, 2017, a magnitude 5.4 earthquake occurred near a geothermal project under construction in Pohang, South Korea. Based on the information available and its own analysis of the situation, Geo-Energie Suisse (GES) decided to immediately inform the Government of the Canton Jura. The Government reacted on November 28, 2017, by asking Geo-Energie Suisse to provide a report on the Pohang events and their possible implications on the Haute-Sorne EGS project. Therefore, based on information available through our participation in the DESTRESS project, we evaluated micro-seismicity and hydraulic data from the stimulation campaigns, geological well data, well logging data, information from borehole drilling and information on the regional stress field. Only by an integration of all this information, we were able to derive a plausible conceptual model for the basic understanding of the Pohang EGS reservoir and the probable triggering of the magnitude 5.4 earthquake. The Pohang EGS project has had a well-defined traditional magnitude based traffic light system. However, our evaluation highlights the need for advanced traffic light systems taking into account the spatial distribution of seismicity and integrating continuously throughout all project stages information about fault structures. Such a procedure has been the basis for the permit by the authorities of the Canton Jura for the Haute-Sorne project 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 in 2017. With our contribution we want to sensitize the geothermal community to understand seismic risk assessment as an accompanying process through all project stages and as a multidisciplinary task, and we want to stress the importance for an advanced traffic light system allowing a timely and qualitatively good localization of micro-seismic events, especially in the case that EGS projects are close or within fault structures. |