Dynamic Poroelastic Finite Element Deformation Modelling of the Bárðarbunga Volcano, Iceland, 2015-2024

Monitoring and modelling of ground deformation at volcanoes provides key insights into how a subsurface magmatic system is evolving due to magma movements at depth. Here, we present a dynamic poroelastic-reservoir Finite Element (FE) volcano deformation model. This thesis aims to reproduce the observed post-eruptive (2015 – 2024) deformation of the Bárðarbunga volcano to constrain the likely magma supply and storage characteristics. Initial exploratory modelling was undertaken using 2D-axisymmetric FE models to investigate the general effects on surface deformation of poroelastic reservoir geometry, poroelastic parameters, and the inclusion of a caldera ring fault. Exploratory models demonstrated that poroelastic effects influence deformation even at high reservoir melt fractions, and that a sill-shaped geometry and inclusion of a caldera ring fault focus and amplify deformation directly above the magma reservoir. Analytical (inverse) deformation models provided a preliminary range of likely parameters to inform a more complex FE modelling grid search. Following this, a 3D FE volcano deformation model of the Bárðarbunga volcano was constructed, incorporating independent geological, geophysical, and geochemical data to be as realistic as possible within computational constraints. The model incorporates: a heterogeneous crust informed by a 1D seismic velocity model; real surface topography; a poroelastic magma reservoir informed by past eruptive deposits; and a caldera ring fault which simulates active slip. Our optimal FE model provides a good statistical fit to the horizontal GNSS data. Optimal model parameters suggest a sill-shaped magma reservoir at 12 km depth, with a melt fraction of 85%, and a volume of accumulated magma of ~0.36 km^3 over a nine-year period, equivalent to an average inflow rate of 1.25 m^3/s. Of the 1.9 km^3 of magma extruded during the previous eruption, our models suggest that ~19% has been resupplied, and, assuming a continued linear melt flux, will take ~47 years to be fully resupplied.<p></p>

Author dc:creator

• Dan Manns (21044948)

• Volcanology
• Geophysics
• Geodesy
• Geology
• Iceland
• Numerical Modelling
• Ground Deformation

Statement dc:rights

• All rights reserved

Identifier

10779/exe.32804315.v1

OAI identifier oai:identifier

oai:figshare.com:article/32804315