Electrokinetic contributions to self-potential signals from magmatic stressing

Fee Arens*, Joachim Gottsmann, Karen Strehlow, James Hickey, Geoff Kilgour

*Corresponding author for this work

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

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Abstract

Pre-eruptive electrical signals at active volcanoes are generally interpreted in terms of electrokinetic processes. Spatio-temporal self-potential (SP) signals can be caused by strain-induced fluid flow in volcanic aquifers, however, previous studies lack the quantitative assessments of these phenomena and the underpinning poroelastic responses. Here we use Finite-Element Analysis to study poroelastic responses induced by subsurface stressing from sill and dike sources by jointly solving for ground displacements, pore pressure and SP signals. We evaluate the influence of pressure source orientation on the poroelastic response in two different volcanic aquifers (pyroclastic and lava flow) to provide insights on emergent geodetic and SP signals and their sensitivity to governing parameters. Strain-induced SP amplitudes deduced from a reference parameter set vary in both aquifer models and are of negative polarity (-0.35 mV and -22.6 mV) for a pressurized dike and of positive polarity (+4 mV and +20 mV) for a pressurized sill. Importantly, we find uniquely different SP and ground displacement patterns from either sill or dike intrusions. Our study shows that SP signals are highly sensitive to the subsurface Young's modulus, streaming potential coupling coefficient and electrical conductivity of the poroelastic domains. For the set of parameters tested, the dike model predicts SP amplitudes of up to -947 mV which are broadly representative of recorded amplitudes from active volcanoes. Our study demonstrates that electrokinetic processes reflect magma-induced stress and strain variations and highlights the potential of joint geodetic and SP studies to gain new insights on causes of volcanic unrest.
Original languageEnglish
Article numbere2020GC009388
Number of pages21
JournalGeochemistry, Geophysics, Geosystems
Volume21
Issue number12
Early online date11 Nov 2020
DOIs
Publication statusPublished - 10 Dec 2020

Keywords

  • electrical self-potential as indicator of volcanic unrest
  • ground deformation
  • numerical modeling
  • poroelasticity
  • volcanic unrest

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