The effects of thermomechanical heterogeneities in island arc crust on time-dependent preeruptive stresses and the failure of an andesitic reservoir

J. Gottsmann*, H. Odbert

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

16 Citations (Scopus)

Abstract

Using ground deformation data from Soufrière Hills volcano (SHV), we present results from numerical modeling of the temperature- and time-dependent stress evolution in a mechanically heterogeneous crust prior to reservoir failure and renewed eruptive activity. The best fit models do not allow us to discriminate between a magmatic plumbing system consisting of either a single vertically elongated reservoir or a series of stacked reservoirs. A prolate reservoir geometry with volumes between 50 and 100 km3, reservoir pressure changes between 4 and 7 MPa, and reservoir volume changes between 0.03 and 0.04 km3 with magma compressibility between 4 × 10−11 and 1 × 10−9 Pa−1 provide plausible thermomechanical model parameters to explain the deformation time series; around an order of magnitude less overpressure than is generally inferred from homogeneous, elastic crustal models. Reservoir failure is predicted to occur at the crest of the reservoir except for reservoirs with highly compressible magma ( Pa) for which subhorizontal sill formation is predicted upon reservoir failure. Introducing a deep-crustal hot zone modulates the partitioning of strains into the hotter underlying crust and results in a further reduction in overpressure estimates to values of around 1–2 MPa upon reservoir failure. Deduced volume fluxes are consistent with constraints from thermal modeling of active subvolcanic systems and imply dynamic failure of a compressible magma mush column feeding eruptions at SHV. Our interpretation of the results is that the combined thermomechanical effects of a deep-crustal hot zone and hot encasing rocks around a midcrustal andesitic reservoir fundamentally alter the time-dependent subsurface stress and strain partitioning upon reservoir priming. These effects substantially influence surface strains recorded by volcano geodetic monitoring.
Original languageEnglish
Pages (from-to)4626-4639
Number of pages14
JournalJournal of Geophysical Research: Solid Earth
Volume119
Issue number6
Early online date6 Jun 2014
DOIs
Publication statusPublished - Jun 2014

Keywords

  • magma
  • ground deformation
  • modeling
  • FEM
  • hot zone

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