The Global Positioning System generates signals that normally are intended for precise navigation. The signals can also be used for precise geodetic work, which has revolutionized the field of geodesy in the last two decades. It is now a routine exercise to locate geodetic benchmarks with uncertainties of only a few millimeters. This technology is rapidly evolving. This opens new possibilities in the measurements of crustal movements. Two kinds of surveying are applied in Iceland. 1) Repeated measurements on a relatively dense network of survey points, to determine the deformation field over an area. 2) Continuous measurements at a limited number of survey points to find and time displacement events. An instrument is permanently installed for prolonged operation. The methods compliment each other and allow the determination of deformation both in space and time. These techniques have been applied in Iceland to determine plate movements, deformation around the plate boundaries, crustal upheaval due to unloading of glaciers, deformation in the source areas of large earthquakes, deformation around active volcanoes, intrusions etc.
Recent publications of the Institute of Earth Sciences on this topic:
Decriem, J., T. Árnadóttir (2011). Transient crustal deformation in the South Iceland Seismic Zone observed by GPS and InSAR during 2000–2008, Tectonophysics, Available online 12 October 2011, doi: 10.1016/j.tecto.2011.09.028.
Geirsson, H., Thóra Árnadóttir, Sigrún Hreinsdóttir, Judicael Decriem, Peter C. LaFemina, Sigurjón Jónsson, Richard A. Bennett, Sabrina Metzger, Austin Holland, Erik Sturkell, Thierry Villemin, Christof Völksen, Freysteinn Sigmundsson, Páll Einarsson, Matthew J. Roberts and Hjörleifur Sveinbjörnsson (2010). Overview of results from continuous GPS observations in Iceland from 1995 to 2010. Jökull 60, 3-22.
Decriem, J., T. Árnadóttir, A. Hooper, H. Geirsson, F. Sigmundsson, M. Keiding, B. G. Ófeigsson, S. Hreinsdóttir, P. Einarsson, P. LaFemina, and R. A. Bennett (2010). The 2008 May 29 earthquake doublet in SW Iceland. Geophys. J. Int., 181(2), 1128-1146, doi: 10.1111/j.1365-246X.2010.04565.x
Völksen, C., Th. Árnadóttir, H. Geirsson, and G. Valsson (2009). Present day geodynamics in Iceland monitored by a permanent network of continuous GPS stations. J. of Geodynamics, 48, 270-283, doi:10.1016/j.jog.2009.09.033.
Sturkell, E., Einarsson, P., Geirsson, H., Tryggvason, E., Moore, J.G., & Ólafsdóttir, R. (2009). Precision levelling and geodetic GPS observations performed on Surtsey between 1967 and 2002, The Surtsey Research Society, Surtsey Research, 12, 39 - 47.
Sturkell, E., P. Einarsson, F. Sigmundsson, A. Hooper, B. G. Ófeigsson, H. Geirsson, H. Ólafsson (2009). Katla and Eyjafjallajökull volcanoes. In: Schomacker, A., Krüger, J. & Kjær, K.H. (Eds). 2009. The Mýrdalsjökull icecap, Iceland. Glacial processes, sediments and landforms on an active volcano.Developments in Quaternary Science 13. Elsevier, Amsterdam. 211 pp., ISBN 1571-0866, 5–21.
Pinel, V., Albino, F., Sigmundsson, F., Sturkell, E., Geirsson, H., Einarsson, P., Gudmundsson, M.T. (2009). Consequences of local surface load variations for volcano monitoring: Application to Katla subglacial volcano, Iceland. In: The VOLUME Procect, VOLcanoes: Understaning subsurface mass moveMEnt, ed. C.J. Bean, A.K. Braiden, I. Lokmer, F. Martini, G.S. O'Brien. School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland. Available at http://www.volume-project.net/
Keiding, M., Lund, B., Árnadóttir, T. (2009). Earthquakes, stress and strain along an obliquely divergent plate boundary: the Reykjanes Peninsula, southwest Iceland, J. Geophys. Res., 114, doi10.1029/2008JB006253
Hreinsdóttir, S., T. Árnadóttir, J. Decriem, H. Geirsson, A. Tryggvason, R. A. Bennett, and P. LaFemina (2009). A complex earthquake sequence captured by the continuous GPS network in SW Iceland, Geophys. Res. Lett., 36, L12309, doi:10.1029/2009GL038391.
Árnadóttir, Th., B. Lund, W. Jiang, and H. Geirsson, H. Björnsson, P. Einarsson and T. Sigurdsson (2009). Glacial rebound and plate spreading: Results from the first countrywide GPS observations in Iceland. Geophys. J. Int., 177(2), 691–716, doi: 10.1111/j.1365-246X.2008.04059.x
Sturkell, E., Einarsson, P., Roberts, M.J., Geirsson, H., Gudmundsson, M.T., Sigmundsson, F., Pinel, V., Guðmundsson, G.B., Ólafsson, H., & Stefánsson, R. (2008). Seismic and geodetic insights into magma accumulation at Katla subglacial volcano, Iceland: 1999 to 2005, Journal of Geophysical Research, 113, B03212, doi:10.1029/2006JB004851.
Sturkell, E., Sigmundsson, F., Geirsson, H., Ólafsson, H., & Theodórsson, Th., 2008.Multiple volcano deformation sources in a post-rifting period: 1989-2005 behaviour of Krafla, Iceland constrained by levelling, tilt and GPS observations. Journal of Volcanology and Geothermal Research, 177 (2), 405-417, DOI:10.1016/j.jvolgeores.2008.06.013
Dubois, L., K. L. Feigl, D. Komatitch, Th. Árnadóttir, F. Sigmundsson, 2008. Three-dimensional mechanical models for the June 2000 earthquake sequence in the south Iceland seismic zone, Tectonophysics, 457, 12-29, doi: 10.1016/j.tecto.2008.05.020.
Árnadóttir, TH., Halldór Geirsson and Weiping Jiang (2008). Crustal deformation in Iceland: Plate spreading and earthquake deformation, Jökull (58), 59-74.
Pinel, V. Sigmundsson, F. Sturkell, E. Geirsson, H. Einarsson, P. Gudmundsson, M. T. Högnadóttir, T. (2007). Discriminating volcano deformation due to magma movements and variable surface loads: application to Katla subglacial volcano, Iceland. Geophysical Journal International, Volume 169, Number 1, pp. 325-338(14).
Trota, A., Houlié, N., Briole, P., Gaspar, J.L., Sigmundsson, F., and K. L. Feigl, (2006). Deformation studies at Furnas and Sete Cidades Volcanoes (Sao Miguel Island, Azores). Velocities and further investigations, Geophys. J. Int., 166, 952-956.
Sturkell, E., F. Sigmundsson, and R. Slunga (2006). 1983-2003 decaying rate of deflation at Askja caldera: Pressure decrease in an extensive magma plumbing system at a spreading plate boundary, Bull. Volc., 68, 727-735.
Sturkell, E., P. Einarsson, F. Sigmundsson, H. Geirsson, H. Olafsson, R. Pedersen, E. de Zeeuw-van Dalfsen, A. L. Linde, I. S. Sacks, and R. Stefansson (2006). Volcano geodesy and magma dynamics in Iceland, J. Volc. Geotherm. Res., 150, 14-34.
Grapenthin, R., F. Sigmundsson, H. Geirsson , T. Arnadottir, V. Pinel (2006). Icelandic rhythmics: Annual modulation of land elevation and plate spreading by snow load, Geophys. Res. Lett., 33, L24305, doi:10.1029/2006GL028081.
Geirsson, H., Th. Árnadóttir, C. Völksen, W. Jiang, E. Sturkell, T. Villemin, P. Einarsson, F. Sigmundsson and R. Stefánsson (2006). Current plate movements across the Mid-Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland, J. Geophys. Res., 111, B09407.
de Zeeuw-van Dalfsen, E., Rymer, H., Williams-Jones, G., Sturkell, E., & Sigmundsson, F. (2006). The integration of micro-gravity and geodetic data at Krafla Volcano, N Iceland.Bulletin of Volcanology, 68, 420-431.
Arnadóttir, Th., Jiang, W., Feigl, K.L., Geirsson, H., & Sturkell, E. (2006). Kinematic models of plate boundary deformation in southwest Iceland derived from GPS observations. Journal of Geophysical Research, 111, B07402.