Numerical Models of Deformation for the Askja Volcano Complex and Rift Segment, Iceland

Interferometric synthetic aperture radar (InSAR) data reveal an unusually large magnitude (~5 cm/yr) of subsidence for the Askja volcanic complex and rift segment, Iceland. The deformation pattern, as well as GPS and gravity data, local to Askja volcano suggests a shallow contracting deformation source that is distinctly different from the regional subsidence pattern of the rift segment. Although the differing local and regional deformation patterns suggest different deformation sources, we propose to account for these observations with numerical models that couple the local volcano deformation to regional divergence of the rift segment. We develop finite element models to simulate the Askja volcano complex and rift segment as a deformational system driven by plate divergence that induces pressure gradients between the viscoelastic upper mantle and the overlying elastic crust of the rift segment. The model allows for mass flux caused by magmatic migration from a shallow magma chamber beneath Askja caldera into the mantle below via a numerical conduit. The viscous flux through the conduit, and thus transient deformation of the system, is governed by a combination of the conduit geometry, viscosity of the magma, and the pressure gradient between the two chambers. This pressure gradient is driven by the imposed plate divergence. The goal of this analysis is to calibrate magmatic flux parameters to observed InSAR, GPS, and gravity data for a model driven by specified plate divergence alone.