| Title | Continuous Microgravity Monitoring in a Volcanic Geothermal Field: Integrated Observational Approach in Þheistareykir, NE Iceland |
|---|---|
| Authors | Kemal ERBAS, Florian SCHAEFER, Philippe JOUSSET, ÃsgrÃmur GUðMUNDSON, Gylfi Pall HERSIR, Jacques HINDERER, Jean-Daniel BERNARD, Nolwenn PORTIER, Freysteinn SIGMUNDSSON, Vincent DROIN, Kristján ÃGÚSTSSON, Benjamin MAENNEL, Andreas GUENTNER, Christian VOIGT, Tilo SCHOENE, Arthur JOLLY, Richard WARBURTON |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | superconducting, gravimeter, passive seismic, continuous monitoring, production, injection, geothermal field |
| Abstract | In volcanic and hydrothermal geosystems, monitoring of mass and stress changes provide information for both volcanic hazard assessment and estimation of geothermal resources. The combined continuous recording of the gravity field and ground motion with sufficient accuracy in an active volcano-tectonic setting allows a better understanding of the mass and stress transfer mechanisms, that produce short term gravity changes and local seismic activity. We aim at a better understanding of geothermal system processes by addressing short-term mass changes within geothermal reservoirs in relation with external influences such as anthropogenic (reservoir exploitation) and natural forcing (local and regional earthquake activity and earth tides). This contributes to knowing the reservoir properties, structure and long-term behaviour. Þheistareykir (Northeast Iceland) where the geothermal power production started in autumn 2017 (2x45 MWe) is the site chosen for this unique experiment. The overall goal of the project is to use a network of continuously measuring gravity meters to detect small variations in gravity associated with managing a geothermal field (injection and extraction). The gravity changes are expected to be small: ~5 µgal/6 months (1 µgal=10-8 ms-2). We therefore use high performance and up-to-date instrumentation such as superconducting gravity meters (SG), spring gravity meters and broadband seismometers. To achieve these goals, we deployed in autumn 2017 a network of 5 relative gravity meters (3 iGravs and 2 gPhones) and 14 seismic stations. Three gravity monitoring sites are in close vicinity to the production and injection area, and one iGrav is set up outside the geothermal field for reference. We present here details of the infrastructure and instruments deployed and first results of more than 18 months of continuous gravity and seismicity monitoring. |