Bardarbunga Eruption Response: Monitoring of post-rifting deformation and activity at Askja Volcano with continuous GPS

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Earth's lithosphere is broken up into tectonic plates that move relative to one another. At the plate interfaces their motion determines the character of the plate boundary zone: convergent (subduction), transform (strike-slip), or divergent (spreading). Rifting episodes indicate periods of active spreading of tectonic plates at divergent plate boundaries (here Eurasia and North America). Such events are incredibly rare and difficult to observe as most rift zones are covered by ocean. This RAPID award assists with the prompt installation of continuous GPS (cGPS) stations to record crustal motions in response to the ongoing eruption of the Icelandic Bárðarbunga Caldera at the Holuhraun rift in Central Iceland. The period of unrest initiated on August 16, 2014 as a magma intrusion propagated ~40 km from Bárðarbunga Caldera and approached to within about 10 km of Askja Caldera to the north. The dike likely caused a M4.6 earthquake on August 26, 2014, and associated microseismicity at Askja. The investigator joins an international collaboration of scientists at the Icelandic Meteorological Office; the University of Iceland; GNS Science, New Zealand; and the University of Arizona who collectively record crustal motions induced by this rifting episode. After installation of the new sites, the Icelandic Meteorological Office will use the telemetered data for hazard mitigation and civil protection purposes. Activity and possible changes at Askja will, for the first time, be monitored continuously with geodetic instruments. Due to Askja?s caldera lake and the likelihood of reactivation of shallow magma reservoirs, explosive activity is a threat that could affect air travel and more distant populations. The data will help assess the eruptive potential of Askja, and furthermore enable the scientific community to re-evaluate observations made after the 1975-85 Krafla Fires and the 2005 Afar rifting episodes, providing a unique and rare glimpse into the mechanisms of plate spreading.The main motivation of the project is in the expansion of the existing cGPS network to capture (1) the impact of the stress changes due to the rifting event on Askja's magmatic system and (2) the onset of the nonlinear process of post-rifting relaxation of the lower crust and upper mantle around the rift. Leveraging support from all collaborators, we plan to install a total of 8 telemetered cGPS sites. 3 sites will be installed at Askja (one in the caldera, one at the eastern flank, one at the southern flank). 4 sites will be installed at different latitudes within 15-40 km to the East of the rift. The last site will fill a gap to the west of the rift; in between Askja and Bárðarbunga, about 20 km from the rift. Rapid deployment of the proposed cGPS sites will be invaluable to monitor the evolution of this event, distinguish processes that contribute to the overall deformation field, and -importantly- to interpret temporally limited observations from campaign GPS or InSAR; especially since InSAR is only effective during times of no snow cover. These data lay the foundation for detailed investigation of the rifting event by the scientific community. Analysis of the early stages of the non-linear characteristics of viscous relaxation in the lower crust and upper mantle is important to derive a model for the post-rifting transient. Such a model is crucial to correctly interpret any subsequent deformation in broader region, which is riddled with volcanic and glacial isostatic adjustment processes. Furthermore, the impact of the static and transient changes to the regional stress field induced by the regional dike intrusion and their impact on neighboring volcanic systems, their magma production and crustal storage capacity can be studied with the deformation data provided through this project.