SIAMIS-GT

One of the unsolved challenges for deep geothermal projects is how to mitigate unacceptably large, induced earthquakes. Unfortunately, the processes and conditions underpinning induced seismicity are still not sufficiently well understood to make useful predictions of the likely seismic response to geothermal reservoir development and exploitation. This predictability is further reduced by the sparse knowledge of the hydro-mechanical and geological conditions in the deep underground, and our lacking ability to map them well enough with current technologies. The seismic response to deep geothermal operations can, however, be monitored in real-time by seismological methods. These methods are, therefore, the core element of any traffic light system (TLS) for induced seismicity that was proposed in recent years.

In this project SIAMIS-GT (Improvement of SeIsmological Analysis Methods to better support cantonal authorities in questions related to Induced Seismicity in deep GeoThermal projects), we want to improve seismological analysis methods for monitoring induced seismicity by taking advantage of the waveform similarity observed in these earthquake sequences. The goal is to enable the SED to inform authorities, project developers and the population faster and more accurately about induced earthquakes that may occur during geotechnical projects (e.g., geothermal, mining, tunneling, etc.). We plan to apply similarity and repeating earthquake analysis to induced seismicity to improve the understanding of the source mechanics (i.e., distinction of natural versus induced seismicity, improved detection, localization and characterization). With these methods we also hope to be able to resolve aseismic changes in the subsurface that cannot be resolved using classical methods in real-time.

Figure on the left: Illustration of the basic principles of similarity location. Upper left: waveforms of 7 template earthquakes used for template matching of the Diemtigen swarm. Upper right: Epicenter map of 306 relocated earthquakes color-coded by highest similarity to the 7 templates. Red diamonds indicate the location of the templates. Notice that earthquakes cluster closely around the template they are associated to by waveform similarity. Bottom: Relationship between inter-event distance and waveform similarity for each template with respect to the 306 relocated earthquakes. Color indicates the reference template. It can be clearly seen that similarity decreases strongly with inter-event distance and that individual relationships can be derived for every reference template.