Háskóli Íslands

InSAR - interferometry by synthetic aperture radar in satellites

Several satellites in Earth orbit take radar images of the surface of the Earth, mainly for the purpose of mapping. The radar images are insensitive to cloud coverage and weather and show both the phase and the amplitude of the reflected signal. Repeated images of the same area may be used to map the topographic changes that have taken place during the intervening time. One phase image is then subtracted from the other. If the reflected signal is strong enough the resulting map shows the changes in the length of the line of sight to the satellite with a resolution of a few millimeters. Snow cover, blowing sand, and vegetation disturb these measurements, but otherwise the technique works very well under Icelandic conditions. Scientists at the Institute of Earth Sciences have been in the forefront in utilizing this state-of-the-art technique for studies of crustal deformation. It has been used to study deformation around the plate boundaries, around areas of geothermal power extraction, in earthquakes source areas, at active volcanoes, uplift due to glacier retreat, etc. The methos is particularly powerful if applied in conjunction with GPS-surveying of the same area.


Crustal deformation associated with the M6.3 earthquake, and associated events, in South Iceland on May 29, 2008.

Recent publications of the Institute of Earth Sciences on this topic:

E. de Zeeuw-van Dalfsen, Rikke Pedersen, Andrew Hooper, Freysteinn Sigmundsson (2012). Subsidence of Askja caldera 2000–2009: Modelling of deformation processes at an extensional plate boundary, constrained by time series InSAR analysis. Journal of Volcanology and Geothermal Research 213–214, 72–82.  doi:10.1016/j.jvolgeores.2011.11.004

Ofeigsson, B. G., A. Hooper, F. Sigmundsson, E. Sturkell, and R. Grapenthin (2011). Deep magma storage at Hekla volcano, Iceland, revealed by InSAR time series analysis, J. Geophys. Res., 116, B05401, doi:10.1029/2010JB007576.

Hooper, A., B. G. Ofeigsson; F. Sigmundsson; B. Lund; H. Geirsson; P. Einarsson; E. Sturkell (2011). Increased capture of magma in the crust promoted by ice-cap retreat in Iceland. Nature Geoscience, doi:10.1038/NGEO1269.

Sigmundsson, F., S. Hreinsdóttir, A. Hooper, T. Árnadóttir, R. Pedersen, M. J. Roberts, N. Óskarsson, A. Auriac, J. Decriem, P. Einarsson, H. Geirsson, M. Hensch, B. G. Ófeigsson, E. Sturkell, H. Sveinbjörnsson, K. L. Feigl (2010). Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption, Nature, 468, 426-430, doi:10.1038/nature09558.

Grapenthin, R., B. G. Ófeigsson, F. Sigmundsson, E. Sturkell, and A. Hooper (2010). Pressure sources versus surface loads: Analyzing volcano deformation signal composition with an application to Hekla volcano, Iceland, Geophys. Res. Lett., 37, L20310, doi:10.1029/2010GL044590.

Pedersen, R., Sigmundsson, F., Masterlark,T. (2009). Rheologic controls on inter-rifting deformation of the Northern Volcanic Zone, Iceland, Earth and Planetary Science Letters, 281, 14-26, doi:10.1016/j.epsl.2009.02.003.

Auriac, A., F. Sigmundsson, Past and future investigations on present-day glacio-isostatic rebound near Vatnajökull, Iceland, from InSAR and GPS data, In: Proceedings of the IGS Nordic Branch Meeting, Höfn, Iceland, Oct. 29-31 2009 (S. Gudmundsson & Th. Thorsteinsson, eds.), p. 8-10, 2009.

Hooper A., B. Ofeigsson, F. Sigmundsson and H. Geirsson (2008). Recent Deep-Seated Magmatic Activity and the 2008 M6.3 Earthquake:  Applicability of ALOS/PALSAR in Iceland, Proceedings ALOS Workshop, Rhodes.

Hooper, A. (2008). A multi-temporal InSAR method incorporating both persistent scatterer and small baseline approaches, Geophys. Res. Lett., 35, L16302, doi:10.1029/2008GL034654. 

Pagli, C., F. Sigmundsson, B. Lund, E. Sturkell, H. Geirsson, P. Einarsson, Th. Árnadóttir, and S. Hreinsdóttir (2007). Glacio-isostatic deformation around the Vatnajökull ice cap, Iceland, induced by recent climate warming: GPS observations and Finite Element Modeling, J. Geophys. Res., 112, B08405, doi:10.1029/2006JB004421.

Pagli, C., F. Sigmundsson, R. Pedersen, P. Einarsson, Th. Árnadóttir and K. L. Feigl (2007). Crustal deformation associated with the 1996 Gjálp subglacial eruption, Iceland: InSAR studies in affected areas adjacent to the Vatnajökull ice cap, Earth and Planetary Science Letters, 259, 24-33, doi:10.1016/j.epsl.2007.04.019.

Pedersen, R., F. Sigmundsson, Hooper, A. J. and Feigl, K. L. (2007).  Extending the temporal coverage of Icelandic crustal deformation measurements through ENVISAT InSAR images, paper ESA SP-636, Proc. of the 2007 ENVISAT Symposium, Montreux, Switzerland, 23-27 April. 

Hooper, A., P. Segall, and H. Zebker (2007). Persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis, with application to Volcán Alcedo, Galápagos, J. Geophys. Res., 112, B07407, doi:10.1029/2006JB004763.

Hooper, A. and H. A. Zebker (2007). Phase unwrapping in three dimensions with application to InSAR time series, J. Optical Soc. of America. A 24, 2737-2747.

Pagli C., Sigmundsson, F., Árnadóttir, T., Einarsson, P., Sturkell, E. (2006). Deflation of the Askja volcanic system: contraints on the deformation source from combined inversion of satellite radar interferograms and GPS measurements, Journal of Volcanology and Geothermal Research, 152, 97-108.

Pedersen, R., Sigmundsson, F. (2006). Temporal development of the 1999 intrusive episode in the Eyjafjallajökull volcano, Iceland, derived from InSAR images, Bull. Volc., 68, 377-393.

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