Towards more realistic values of elastic moduli for volcano modelling

Michael J. Heap*, Marlène Villeneuve, Fabien Albino, Jamie I. Farquharson, Elodie Brothelande, Falk Amelung, Jean Luc Got, Patrick Baud

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

21 Citations (Scopus)

Abstract

The accuracy of elastic analytical solutions and numerical models, widely used in volcanology to interpret surface ground deformation, depends heavily on the Young's modulus chosen to represent the medium. The paucity of laboratory studies that provide Young's moduli for volcanic rocks, and studies that tackle the topic of upscaling these values to the relevant lengthscale, has left volcano modellers ill-equipped to select appropriate Young's moduli for their models. Here we present a wealth of laboratory data and suggest tools, widely used in geotechnics but adapted here to better suit volcanic rocks, to upscale these values to the scale of a volcanic rock mass. We provide the means to estimate upscaled values of Young's modulus, Poisson's ratio, shear modulus, and bulk modulus for a volcanic rock mass that can be improved with laboratory measurements and/or structural assessments of the studied area, but do not rely on them. In the absence of information, we estimate upscaled values of Young's modulus, Poisson's ratio, shear modulus, and bulk modulus for volcanic rock with an average porosity and an average fracture density/quality to be 5.4 GPa, 0.3, 2.1 GPa, and 4.5 GPa, respectively. The proposed Young's modulus for a typical volcanic rock mass of 5.4 GPa is much lower than the values typically used in volcano modelling. We also offer two methods to estimate depth-dependent rock mass Young's moduli, and provide two examples, using published data from boreholes within Kīlauea volcano (USA) and Mt. Unzen (Japan), to demonstrate how to apply our approach to real datasets. It is our hope that the data and analysis presented herein will assist in the selection of elastic moduli for volcano modelling. To this end, we provide a Microsoft Excel

Original languageEnglish
Article number106684
JournalJournal of Volcanology and Geothermal Research
Volume390
DOIs
Publication statusPublished - 15 Jan 2020

Bibliographical note

Funding Information:
This review has benefitted from the many engaging conversations the first and second authors have had at conferences and meetings in the last years. The first and second authors also acknowledge an Erskine Fellowship at the University of Canterbury awarded to the first author, which kick-started the idea for this paper. The first author additionally thanks Thierry Reuschl? and Bertrand Renaudi?. The second author acknowledges New Zealand Ministry of Business, Innovation and Employment Catalyst grant UOCX1508 ?Energy Straight from Magma?. The experimental data presented in this study are, for the most part, unpublished data that were collected during mechanical studies performed in collaboration with many scientists. Although non-exhaustive, we thank Nick Varley, Yan Lavall?e, Fr?d?ric Dondin, Ben Kennedy, Yoshitaka Nara, Alexandra Kushnir, Sergio Vinciguerra, Kelly Russell, Salvatore Martino, and Gian Marco Marmoni. The basalt from Krafla was exported with permission from the Icelandic Institute of Natural History (and we thank Holly Unwin for organising permission). Kelly Russell, Martin Harris, Stephan Kolzenberg, and particularly Amy Ryan are thanked for their help in furnishing the laboratory with the samples from Chaos Crags. The constructive comments of Agust Gudmundsson and an anonymous reviewer helped improve this manuscript.

Funding Information:
This review has benefitted from the many engaging conversations the first and second authors have had at conferences and meetings in the last years. The first and second authors also acknowledge an Erskine Fellowship at the University of Canterbury awarded to the first author, which kick-started the idea for this paper. The first author additionally thanks Thierry Reuschlé and Bertrand Renaudié. The second author acknowledges New Zealand Ministry of Business, Innovation and Employment Catalyst grant UOCX1508 “Energy Straight from Magma”. The experimental data presented in this study are, for the most part, unpublished data that were collected during mechanical studies performed in collaboration with many scientists. Although non-exhaustive, we thank Nick Varley, Yan Lavallée, Frédéric Dondin, Ben Kennedy, Yoshitaka Nara, Alexandra Kushnir, Sergio Vinciguerra, Kelly Russell, Salvatore Martino, and Gian Marco Marmoni. The basalt from Krafla was exported with permission from the Icelandic Institute of Natural History (and we thank Holly Unwin for organising permission). Kelly Russell, Martin Harris, Stephan Kolzenberg, and particularly Amy Ryan are thanked for their help in furnishing the laboratory with the samples from Chaos Crags. The constructive comments of Agust Gudmundsson and an anonymous reviewer helped improve this manuscript.

Publisher Copyright:
© 2019 Elsevier B.V.

Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

Keywords

  • Elastic half-space
  • Elastic moduli
  • Mogi
  • Upscaling
  • Volcanic rock
  • Young's modulus

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