Jökull - 01.01.2010, Side 3

Reviewed research article
Overview of results from continuous GPS observations in
Iceland from 1995 to 2010
Halldór Geirsson1,2, Thóra Árnadóttir3, Sigrún Hreinsdóttir4,3, Judicael Decriem3,
Peter C. LaFemina2, Sigurjón Jónsson5,6, Richard A.Bennett4, Sabrina Metzger5,
Austin Holland4, Erik Sturkell7, Thierry Villemin8, Christof Völksen9, Freysteinn
Sigmundsson3, Páll Einarsson10, Matthew J. Roberts1, and Hjörleifur Sveinbjörnsson1
1Division of Processing and Research, Icelandic Meteorological Office, Reykjavík, Iceland
2Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania, USA
3Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland
4Department of Geosciences, University of Arizona, Tucson, Arizona, USA
5Institute of Geophysics, ETH Zurich, Switzerland
6Division of Physical Sciences and Engineering,
King Abdullah University of Science and Technology, Jeddah, Saudi Arabia
7Department of Earth Sciences, University of Gothenburg, Göteborg, Sweden
8EDYTEM, Universite de Savoie and CNRS, Le Bourget du Lac, France
9Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland
10Institute of Earth Sciences, Science Institute, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland
H. Geirsson (hzg5036@psu.edu), Th. Árnadóttir (thora1@hi.is), S. Hreinsdóttir (runa@hi.is)
Abstract — Iceland is a natural laboratory for a variety of processes associated with crustal deformation,
such as earthquakes, magmatic events, tectonic plate motions, and glacial load changes. Continuous GPS
(CGPS) measurements started in Iceland in 1995, and since then data from the network have helped to shed
light on many different active deformation processes. The number of CGPS sites in Iceland tripled during
2006–2008, as a result of an international collaborative effort coordinated by Icelandic scientists. By early
2010 the number of CGPS stations in Iceland had reached 64, located primarily around and within the North-
American–Eurasian plate boundary zone. Since its initiation, the CGPS network has played an important role
in monitoring volcanoes and seismogenic areas, most notably during the 2009–2010 Eyjafjallajökull volcano
unrest. Plate spreading of up to 2 cm per year usually dominates the horizontal motion observed at the CGPS
sites, while uplift is observed at many of the stations due to recent retreat of the Icelandic ice caps. Co-seismic
and post-seismic deformation of the largest earthquakes in 2000 and 2008 in the South Iceland Seismic Zone
were captured by the network, and high-rate (1 Hz) CGPS observations helped to identify two magnitude 6
mainshocks in 2008 that were separated in time by only 2–3 seconds. The CGPS network has thus enabled us
to monitor deformation occurring over days to months caused by migration of magma or fluids, post-seismic
transients, rapid deformation caused by earthquakes and eruptions, as well as the long term plate spreading
signal.
JÖKULL No. 60 3