ALBERT

Description: For a better understanding of the sustainability of geothermal resources, we want to quantify subsurface masschanges caused by production and injection of fluids at the Theistareykir geothermal field in Northeast Iceland.For this purpose, we installed three superconducting gravity meters (iGrav006, iGrav015 and iGrav032) and twospring gravity meters (gPhone061 and gPhone128) in vicinity to the new geothermal power plant that started op-eration in October 2017.Prior to the Iceland installation, all gravity meters were setup at the gravimetric observatory J9 in Strasbourg forsimultaneous side-by-side measurements. The obtained data were used for instrumental calibration, comparisonof noise levels and tidal analysis. In Theistareykir, three of our measuring sites are set up close to the geother-mal production and injection wells. The fourth site is located outside the geothermal field, to provide referencemeasurements that are unaffected by the activities of the power plant. At each site additional physical parameters,which influence the local gravity signal, are measured. This includes the continuous monitoring of GPS-positions,rainfall, soil moisture and snow thickness. Moreover, snow weight and snow water equivalent are measured at thesite close to the production wells.Here, we present the results of the unique intercomparison of three superconducting gravity meters and twogPhones at Strasbourg and the initial time series obtained at the geothermal site in Iceland. A preliminary in-terpretation of the gravity variations with regard to the geothermal activities and the hydro-metrological dynamicsis given.