Skip to content

Exploring the 2018 Kilauea Caldera Collapse with a New Benchmarked 3D Distinct Element Method Model

^^Thomas W. Austin1,2,^^Claire E. Harnett1,2, Eoghan P. Holohan1,2, Alexis Hrysiewicz1,2, Martin Schöpfer3

  • Affiliations: 1 UCD School of Earth Sciences, University College Dublin, Dublin, Ireland, 2 SFI Research Centre for Applied Geoscience (iCRAG), Dublin, Ireland, 3 Department of Geology, University of Vienna, Vienna, Austria

  • Presentation type: Talk

  • Presentation time: Thursday 15:00 - 15:15, Room R380

  • Programme No: 3.11.8

  • Theme 3 > Session 11

Abstract

When investigating volcanic unrest and eruptions, analytical and numerical solutions are useful tools in linking surface displacements to deformation sources at depth. These solutions, however, are limited by simulation of the host rock as an elastic or viscoelastic continuum. These material assumptions limit our ability to explore discontinuities such as fracturing and complex faulting, typical of caldera collapse events. By using 3D Distinct Element Method (DEM) Models one can simulate non-elastic (frictional-plastic) behaviour, as the breakage of elastic bonds between model elements allows for fracture localization, propagation and slip. To be confident to interpret our non-elastic behaviour, we must first benchmark our models against previous elastic solutions. We have therefore developed a 3D DEM model of a pressurised cavity within an initially linear-elastic, homogenous half-space, for which we can induce and under- or over-pressure. Surface displacements from this DEM model were benchmarked against the McTigue analytical solution and Finite Element Method (FEM) solutions without and with gravity. Benchmarking shows that all solutions fall within 10% of the analytical solution, with this difference decreasing with increasing depth, highlighting how a DEM model can yield reasonable displacements in the low strain, elastic phase of deformation. We use this newly benchmarked 3D gravity DEM model to forward model the chamber geometry of the 2018 Kilauea Caldera Collapse by analysing the surface displacement of the pre-collapse elastic deformation. Using this predicted chamber geometry, we then go one step further to model non-elastic deformation and explore the complex internal fracture geometries associated with the collapse