Deformation derived from GPS geodesy associated with Bárðarbunga 2014 rifting event in Iceland

• Main Authors: Ofeigsson, Benedikt Gunnar, Hreinsdóttir, Sigrún, Sigmundsson, Freysteinn, Friðriksdóttir, Hildur, Parks, Michelle, Dumont, Stephanie, Árnadóttir, Þóra, Geirsson, Halldór, Hooper, Andrew, Roberts, Matthew, Bennett, Rick, Sturkell, Erik, Jónsson, Sigurjón|
• Other Authors: Crustal Deformation and InSAR Group, Earth Science and Engineering Program, Physical Science and Engineering (PSE) Division, Icelandic Meteorological Office, Iceland, GNS Science, New Zealand, Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania, USA, Centre
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: Ice cap; Iceland; Vatnajökull
• Online Access: http://hdl.handle.net/10754/595109

On August 16, 2014 an intense seismic swarm started below the eastern part of Bárðarbunga Caldera in the north-western corner of Vatnajökull ice-cap, Iceland, marking the onset of the first rifting event in Iceland since the Krafla fires (1975-1984). The migration of the seismicity was corroborated by ground deformation in areas outside the ice cap and on nunataks within the ice cap suggesting a lateral propagation of magma, from the Bárðabunga system. The sesimicity migrated out of the caldera forming a dyke with roughly three segments, changing direction each time until August 28 when the migration stopped around 10 km south of Askja Volcano, eventually leading to a short lived eruption in Holuhraun north of Dyngjujökull. A second fissure eruption started in Holuhraun on August 31 which is still ongoing at the time of this writing. In the months prior to the onset of the activity, subtle signs of inflation where observed on continuous GPS sites around the Bárðarbunga indicating a volume increase in the roots of the volcanic system. When the activity started on August 16, the deformation pattern indicated a simultaneous deflation centered within the caldera and a lateral growth of a dyke also reflected in the migration of seismicity along segments of variable strike. A maximum widening of 1.3 m occurred between stations on opposite sides of the dyke spaced 25 km apart. Significant movements where detected on GPS site more then 80 km away from the tip of dyke. Displacements indicated the fastest rate of widening at any time in the most distal segment of the dyke throughout its evolution. After the dyke stopped propagating, the inflation continued, decaying exponentialy with time. On September 4, five days into the second fissure eruption, the movements associated with the dyke where no longer significant. As the fissure eruption continues, a slowly decaying contraction is observed around the Bárðarbunga central volcano, both shown in the piston like subsidence of the caldera floor, observed on a GPS instrument ...