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Modelling Stress and Strain Rates of Dynamic Magma Mush Reservoirs: Insights into Reservoir Stability and Failure.

Lorenzo Mantiloni 1, James Hickey1, Rami Alshembari1, Brendan McCormick Kilbride2, Karen Pascal3,4

  • Affiliations: 1 Department of Earth and Environmental Sciences, University of Exeter, Cornwall, TR10 9FE; 2 Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL; 3 Montserrat Volcano Observatory (MVO), Flemmings, Montserrat; 4 Seismic Research Centre, University of West Indies, Republic of Trinidad and Tobago

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 185

  • Programme No: 1.8.16

  • Theme 1 > Session 8

Abstract

Volcanoes can enter phases of unrest that may or may not culminate in an eruption. Assessing the stability of magma reservoirs is essential for understanding what differentiates these outcomes. Over the last decades, magma reservoir modelling has been shifting from simple, static models of melt-filled magma chambers to dynamic magma-mush reservoirs (DMMRs), where magma is stored in and moves through a permeable crystal matrix. DMMRs can be approached as poroelastic reservoirs, where failure within or at the reservoir boundary is likely influenced by strain rates from magma migration/accumulation, and the state of stress in the surrounding rocks and elastic matrix. Determining the latter requires consideration of the medium's response to gravity. Recent progress in numerical modelling of DMMRs has provided new insights into the dynamic processes of magma injection and withdrawal. However, most models lack detailed analysis of reservoir failure and often overlook the role of gravity. We address these aspects in our study. Specifically, we examine the steady state of stress within and around a DMMR arising from the gravitational force and load of the surrounding rocks. Then, using Finite-Element numerical models, we study the evolution of strain rates and stress patterns in both the reservoir and the host rocks and the deformation over time and space when magma is supplied to the reservoir. We consider mush reservoirs of various geometries and different assumptions on the initial state of stress and pore pressure of the system, discussing the locations and timing where reservoir failure may become more likely.