Insights Into the Stress Field Around Bár ðarbunga Volcano From the 2014/2015 Holuhraun Rifting Event

The two weeklong rifting event at Bárðarbunga volcano in 2014 led to the Holuhraun eruption,which produced 1.5 km3of lava and was the largest in Iceland in over 200 years. Predicting when andwhere an intrusion will lead to eruption requires detailed knowledge of the underlying stress field. Previousstudies have explained the dike propagation path with a model that includes a tectonically induced stressfield set up by a uniform amount of plate spreading across a straight rift axis. Here we test this hypothesisby modeling the tractions acting on the dike walls, constrained by data from Global Navigation SatelliteSystem and Interferometric Synthetic Aperture Radar. Our results show that the majority of the opening andshearing in the final two dike segments is due to stresses built up by plate spreading since the last eruptionat Holuhraun, as expected, but that the tectonically induced stress magnitude must be much lower toexplain the movement of the dike walls further south. This result implies that most of the tectonicallyinduced stress beneath the ice cap has been released, presumably due to intrusions associated with theBárðarbunga volcanic system and the nearby Grímsvötn volcanic system, which have not been detected dueto their subglacial nature. Modeling of the 2014 Bárðarbunga rifting event therefore not only yields insightsinto the event but also provides a window into undetected volcanic activity in the past.