Modelling of ground deformation at Eyjafjalljökull volcano 2011-2015

Abstract

Measurements and modeling of volcano deformation can be used to gain a better understanding of how volcanoes behave, and which magmatic processes take place under the surface that could trigger eruptions. Modeling can reveal the location, shape and volume change of magma bodies. In 2010 a 'touristy' flank eruption at Eyjafjallajökull was followed by an explosive summit eruption that caused unprecedented disruption of air traffic over most of Europe. In 1994, 1999, 2009 and 2010 sill intrusions formed under the volcano, causing uplift that was measured by GNSS stations surrounding the volcano and InSAR measurements. During the summit eruption gradual deflation was measured, where a distinct deflation source was activated. After the eruption ceased in May 2010, deflation continued until 2011. From 2011 to 2015 small inflation was measured. In this thesis, a Bayesian inversion is applied to the GNSS data of the inflation during that period. Two types of models can broadly fit the data; both assume a source of deformation within a half-space that behaves as an elastic material. One of the models assumes a spherical point source of pressure, where pressure increases within a spherical volume with a small radius compared to the depth of the center of the source. The other model is a rectangular plane with constant opening (magma dike or sill) These models give an estimate of the location, depth, geometry and volume change of the inferred magma accumulation under the volcano with 95\% confidence interval. The results of these models are quite different, except for the depth which is from 2.5 - 2.6 km. The location of the point source is north of Gígjökull, and its optimal volume change is 3.9 x 10^6 m^3 The location of the sill is close to the center of the volcano and the optimal volume is 15 x 10^6 m^3