Anthropogenic and natural ground deformation in the Hengill geothermal area, Iceland

D. Juncu, Th. Arnadottir, A. Hooper, G. Gunnarsson

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


We investigate crustal deformation due to the extraction of water and steam from a high-enthalpy geothermal reservoir; a common occurrence, yet not well understood. The cause of this deformation can be a change in pressure or in temperature in the reservoir, both of which can be caused by extraction or injection of geothermal fluids. Our study area, the Hengill mountains in SW Iceland, is an active volcanic center and a plate triple junction that hosts two power plants producing geothermal energy. This combination of natural and anthropogenic processes causes a complex displacement field at the surface. We analyze geodetic data—Global Navigation Satellite System and Interferometric Synthetic Aperture Radar—to obtain the surface velocity field, which we then simulate using an inverse modeling approach. We focus on the deformation around the geothermal power plants but need to model the regional tectonic and volcanic deformation as well, because the signals are overlapping. We find that plate motion and a deep contracting body can explain the broad scale signal in the area. Local deformation near the two power plants, Hellisheidi and Nesjavellir, can be explained by extraction of geothermal fluids. We estimate reservoirs extending from 0.6 to 3.0 km depth at Hellisheidi, and 1.0 to 3.0 km depth at Nesjavellir for observed pressure decrease rates of 0.25 MPa/yr and 0.1 MPa/yr, respectively. We find that the main cause for the subsidence in the geothermal area is the observed pressure drawdown.
Original languageEnglish (US)
Pages (from-to)692-709
Number of pages18
Issue number1
StatePublished - Jan 28 2017
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-02
Acknowledgements: The authors would like to thank Einar Gunnlaugsson from Reykjavik Energy (RE) for providing production data from Hellisheidi and Nesjavellir; Bjarni Reyr Kristjánsson (RE) for discussions and advice regarding the geothermal power plant operations; RE and ÍSOR for GNSS data from the dense Hengill network; the Icelandic Meteorological Office (IMO) for operating the cGPS network in Iceland; Sigrún Hreinsdóttir (GNS, New Zealand) for global GNSS solutions; Tabrez Ali (University of Wisconsin, Madison, USA) for help and ideas regarding deformation in geothermal areas; Halldór Geirsson (IES) for helpful comments on the work in progress; Sarah Minson (U.S. Geological Survey) for help with CATMIP and letting us use her code; David Bekaert (University of Leeds, UK) for helpful advice on the InSAR processing; Sigurjón Jónsson (King Abdullah University of Science and Technology, KSA) for providing his Quadtree code; Guðni Axelsson (ÍSOR) for helpful discussions concerning geothermal reservoirs; the crustal deformation group at IES for help with the GNSS measurements in SW Iceland and discussions on the work in progress. For computing the elastic half-space models we use DMODELS [Battaglia et al.,]. Many of the figures were prepared using the GMT software [Wessel and Smith, Wessel et al.,]. The earthquake locations in Figure were provided by IMO. The intermediate TanDEM-X digital elevation model used in the InSAR processing was provided by DLR under project IDEM_GEOL0123. COMET is the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics. This work was supported in part by grants from the Iceland Research Fund and the University of Iceland Research Fund. The data for this paper are available by contacting the corresponding author at
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


Dive into the research topics of 'Anthropogenic and natural ground deformation in the Hengill geothermal area, Iceland'. Together they form a unique fingerprint.

Cite this