Structural Controls on Geothermal Reservoir Deformation at Stillwater, Nevada From InSAR and GPS Data

Abstract

Surface rupture traces of the 1954 Rainbow Mountain earthquake coincide with the western and eastern boundaries of subsidence associated with pumping at the Stillwater, Nevada geothermal plant. Space-based Interferometric Synthetic Aperture Radar (InSAR) provides precise and detailed measurements of surface deformation associated with movement of sub-surface fluids. Maximum peak-to-peak subsidence displacement along satellite radar line of site is near 120 mm for the period March 1, 2009 to August 23, 2009. The oblique-dextral earthquake rupture was consistent in style and orientation with active extension and shear strain accumulation detected with GPS networks in the western Great Basin. The subsidence pattern we detect with InSAR had a compact time-variable subsidence with three distinct lobes, one near the Stillwater, Nevada geothermal plant, another 3 km north of the plant near a well that draws water for the plant, and a third south of the plant that is of unknown origin and of opposite sign. Time series analysis of the interferometric pairs indicates that the most rapid subsidence began before March, 2009. The patterns of subsidence provide evidence that structures related to contemporary tectonic deformation and seismicity play a controlling factor in the location and response to pumping of economically important geothermal resources. earthquake coincide with the western and eastern boundaries of subsidence associated with pumping at the Stillwater, Nevada geothermal plant. Space-based Interferometric Synthetic Aperture Radar (InSAR) provides precise and detailed measurements of surface deformation associated with movement of sub-surface fluids. Maximum peak-to-peak subsidence displacement along satellite radar line of site is near 120 mm for the period March 1, 2009 to August 23, 2009. The oblique-dextral earthquake rupture was consistent in style and orientation with active extension and shear strain accumulation detected with GPS networks in the western Great Basin. The subsidence pattern we detect with InSAR had a compact time-variable subsidence with three distinct lobes, one near the Stillwater, Nevada geothermal plant, another 3 km north of the plant near a well that draws water for the plant, and a third south of the plant that is of unknown origin and of opposite sign. Time series analysis of the interferometric pairs indicates that the most rapid subsidence began before March, 2009. The patterns of subsidence provide evidence that structures related to contemporary tectonic deformation and seismicity play a controlling factor in the location and response to pumping of economically important geothermal resources.