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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Earth Sci. | doi: 10.3389/feart.2019.00219

Combining magma flow and deformation modelling to explain observed changes in tilt

  • 1University of Leeds, United Kingdom
  • 2Instituto Geofísico, Escuela Politécnice Nacional, Ecuador

The understanding of magma ascent dynamics is essential in forecasting the scale, style and timing of volcanic eruptions. The monitoring of near-field deformation is widely used to
gain insight into these dynamics, and has been linked to stress changes in the upper conduit. The ascent of magma through the conduit exerts shear stress on the conduit wall, pulling up the surrounding
edifice, whilst overpressure in the upper conduit pushes the surrounding edifice outwards. H\sout{owever, h}ow much shear stress and pressure is produced during magma ascent, and the relative contribution of
each to the deformation, \sout{is yet
to be fully understood and quantified}\textcolor{blue}{has until now only been explored conceptually}. By combining flow and deformation modelling using COMSOL Multiphysics, we \sout{are} for the first time
\sout{able to}\textcolor{blue}{present a quantitative model that links magma ascent to deformation. We} quantify how both shear stress and pressure
vary spatially within a conduit, and show that shear stress generally dominates observed changes in tilt close to the conduit during activity at Tungurahua volcano, Ecuador, between 2013 and 2014.
However, the relative contribution of pressure is not insignificant, and \sout{the full stress tensor comprising} both pressure and shear stress must be considered when interpreting deformation data.
We demonstrate that significant changes in tilt \sout{can occur as magma refills an empty conduit, or} can be driven by changes
in the driving pressure gradient or volatile content of the magma. The relative contribution of shear stress and pressure to the tilt varies considerably depending on these
parameters. Our work provides insight into the range of elastic moduli that should be considered when modelling edifice-scale rock masses,
and we show that even where the edifice is modelled as weak, shear stress \textcolor{blue}{generally} dominates the near field deformation over pressurisation of the conduit.

Keywords: Pressure, Numerical modelling & analysis, magma ascent, tilt, Tungurahua volcano, Shear stress (fluid)

Received: 01 May 2019; Accepted: 09 Aug 2019.

Copyright: © 2019 Marsden, Neuberg, Thomas, Mothes and Ruiz. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Luke H. Marsden, University of Leeds, Leeds, United Kingdom, eelhm@leeds.ac.uk