Abstract

Magma intrusions grow to their final geometries by straining the Earth’s crust internally and displacing the Earth’s surface. Interpreting that volcanic unrest is key to forecasting a volcanic eruption. While scaled laboratory models enable us to study the relationships between surface displacement and intrusion geometry, past approaches entailed limitations regarding imaging of the model interior or simplicity of the simulated rheology.

This talk presents results from combining state-of-the-art wide beam X-ray Computed Tomography (CT) and Digital Volume Correlation (DVC) to quantify in 4D the deformation induced in laboratory models by an intrusion of a magma analogue (golden syrup) in a granular Mohr-Coulomb host material (sand and plaster). The evolution of the extracted surface deformation and strain field of the entire experimental volume in 3D over time shows how contrasting geometries – cryptodomes, cup shapes, cone sheets and dikes – form in host material of different strength. Moreover, contrasting geometries induce contrasting propagation modes and strain field characteristics in the host.

Our results demonstrate how the combination of CT and DVC can greatly enhance the utility of optically non-transparent crustal rock analogues in obtaining insights into crustal deformation processes. This unprecedented inside perspective helps understanding the limitations of simple elastic rheology used in geodetic and inversion modeling of crustal deformation processes.