Yamasaki, T, Kobayashi, T, Wright, TJ orcid.org/0000-0001-8338-5935 et al. (1 more author) (2018) Viscoelastic crustal deformation by magmatic intrusion: A case study in the Kutcharo caldera, eastern Hokkaido, Japan. Journal of Volcanology and Geothermal Research, 349. pp. 128-145. ISSN 0377-0273
Abstract
Geodetic signals observed at volcanoes, particularly their temporal patterns, have required us to make the correlation between the surface displacement and magmatic process at depth in terms of viscoelastic crustal rheology. Here we use a parallelized 3-D finite element model to examine the response of the linear Maxwell viscoelastic crust and mantle to the inflation of a sill in order to show the characteristics of a long-term volcano deformation. In the model, an oblate-spheroidal sill is instantaneously or gradually inflated in a two-layered medium that consists of an elastic layer underlain by a viscoelastic layer. Our numerical experiments show that syn-inflation surface uplift is followed by post-inflation surface subsidence as the viscoelastic substrate relaxes. For gradual inflation events, the magnitude of inflation-induced uplift is reduced by the relaxation, through which the volume of a magma inferred by matching the prediction of an elastic model with observed surface uplift could be underestimated. For a given crustal viscosity, sill depth is the principal factor controlling subsidence caused by viscoelastic relaxation. The subsidence rate is highest when the inflation occurs at the boundary between the elastic and the viscoelastic layers. The mantle viscosity has an insignificant impact unless the depth of the inflation is greater than a half the crustal thickness. We apply the viscoelastic model to the interferometric synthetic aperture radar (InSAR) data in the Kutcharo caldera, eastern Hokkaido, Japan, where the surface has slowly subsided over a period of approximately three years following about a two-year period of inflation. The emplacement of a magmatic sill is constrained to occur at a depth of 4.5 km, which is significantly shallower than the geophysically imaged large-scale magma chamber. The geodetically detected deformation in the caldera reflects the small-scale emplacement of a magma that ascended from the deeper chamber, but not the inflation of the chamber itself. The observed ground displacement is controlled by a lower-crustal viscosity of 4 × 1017 Pa s, which is lower than that inferred from some studies of post-seismic deformation, perhaps due to higher temperatures beneath the active caldera. Our results suggest that geodetic signals observed during and following magmatic intrusions need to be revisited.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | (c) 2017 Elsevier B.V. This is an author produced version of a paper published in Journal of Volcanology and Geothermal Research. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Volcano deformation; Viscoelasticity; Magma intrusion; Viscosity of the crust; Kutcharo caldera; Geodetic data |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 26 Oct 2017 14:23 |
Last Modified: | 24 Oct 2018 00:38 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.jvolgeores.2017.10.011 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:123138 |