2021-09-15
Ten researchers from the Swiss Seismological Service (SED) at ETH Zurich went to Iceland in June and August 2021 to support two projects with a seismic measurement campaign. In a collaborative effort with the German Research Centre for Geoscience (GFZ) and Reykjavik Energy (ON Power), the team set up a network of 500 seismic nodes across the Hengill geothermal field. It is the largest and densest network of measuring stations installed in the country so far.
This fieldwork in Iceland was part of a seismic measurement campaign for a geothermal project in Iceland and "DEEPEN" (DErisking Exploration for geothermal Plays in magmatic ENvironments), a European research project in the field of geothermal energy. DEEPEN aims at establishing an approach to minimise the risk of field exploration in deep geothermal energy and at contributing to a higher probability of success when drilling for geothermal fluids in magmatic systems.
Read more...The seismic nodes that were used are 5Hz geophones with integrated battery and digitiser (SOLOS provided by the University of Geneva) and 5Hz geophones with external digitiser and batteries (provided by the Geophysical Instrument Pool of the GFZ). Data from such dense seismic node deployments allow the researchers to gain a better understanding of the sub-surface. Thanks to the small size of the nodes, the research team finished the deployment within two weeks in June, despite the tough weather condition, steep terrain and long hikes to reach each dedicated site.
With the network, a special focus was given to the Northern region around Nesjavellir and the Southern Hverahlid, where the most productive boreholes of the geothermal field are located. A vehicle called vibrotruck (see fig. 2) passed through the Northern array and provided an additional source signal during the deployment time. Typically used in seismic exploration, the vibrotruck pressed a vibrating plate onto the earth’s surface. The low-frequency vibrations propagate underground and are reflected by the rock strata. These seismic waves were recorded by the installed geophones and gave further insights into the geological sub-surface.
After the deployment, the network was running successfully for two months and overlapped with another seismic network (COSEISMIQ), which is also operated by the SED. In August 2021, the research group travelled again to Iceland to dismantle both networks. The researchers expect that the high-density seismic imaging will allow them to illuminate the sub-surface in unprecedented detail.