Fracturing Around Magma Reservoirs Causes Variations in Surface Uplift Rates Even at Constant Volumetric Flux

41 Pages Posted: 29 Feb 2024

See all articles by Juliet Biggs

Juliet Biggs

University of Bristol

Timothy Rafferty

University of Oxford

Jonny Macha

University of Bristol

Edna Dualeh

University of Bristol

Gregor Weber

University of Bristol

Alain Burgisser

affiliation not provided to SSRN

Finbar Carroll

University of Bristol

Lauren Hart

University of Bristol

Alison Rust

University of Bristol

Mark Gilbertson

University of Bristol

Abstract

Many volcanoes show continuous but variable deformation over timescales of years to decades. Variations in uplift rate are typically interpreted as changes in magma supply rate and/or a viscoelastic response of the host rock. Here we conduct analogue experiments in the laboratory to represent the inflation of a silicic magma body at a constant volumetric flux, and measure the chamber pressure and resulting surface displacement field. We observe that dyke intrusions radiating from the magma body cause a decrease in the peak uplift rate, but do not significantly affect the spatial pattern of deformation or spatially averaged uplift rate. We identify 4 distinct phases: 1) elastic inflation of the chamber, 2) a gradual decrease in the rate of uplift and pressurisation, associated with the formation of visible cracks 3) propagation of a dyke by mode 1 failure at the crack tip and 4) a pressure decrease within the chamber. Phase 2 can be explained by either a) crack damage, which reduces the elastic moduli of the surrounding rock or b) magma filling pre- existing cracks. Thus these experiments provide alternative mechanisms to explain observed variations in uplift rate, with important implications for the interpretation of deformation patterns at volcanoes around the world.

Keywords: surface deformation, analogue models, caldera unrest

Suggested Citation

Biggs, Juliet and Rafferty, Timothy and Macha, Jonny and Dualeh, Edna and Weber, Gregor and Burgisser, Alain and Carroll, Finbar and Hart, Lauren and Rust, Alison and Gilbertson, Mark, Fracturing Around Magma Reservoirs Causes Variations in Surface Uplift Rates Even at Constant Volumetric Flux. Available at SSRN: https://ssrn.com/abstract=4744033 or http://dx.doi.org/10.2139/ssrn.4744033

Juliet Biggs (Contact Author)

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Timothy Rafferty

University of Oxford ( email )

Mansfield Road
Oxford, OX1 4AU
United Kingdom

Jonny Macha

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Edna Dualeh

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Gregor Weber

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Alain Burgisser

affiliation not provided to SSRN ( email )

No Address Available

Finbar Carroll

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Lauren Hart

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Alison Rust

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

Mark Gilbertson

University of Bristol ( email )

University of Bristol,
Senate House, Tyndall Avenue
Bristol, BS8 ITH
United Kingdom

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