Gas permeability evolution of cataclasite and fault gouge in triaxial compression and implications for changes in fault-zone permeability structure through the earthquake cycle

Shin ichi Uehara, Toshihiko Shimamoto

    Research output: Contribution to journalArticle

    56 Citations (Scopus)

    Abstract

    We report the results of permeability measurements of fault gouge and tonalitic cataclasite from the fault zone of the Median Tectonic Line, Ohshika, central Japan, carried out during triaxial compression tests. The experiments revealed marked effects of deformation on the permeability of the specimens. Permeability of fault gouge decreases rapidly by about two orders of magnitude during initial loading and continues to decrease slowly during further inelastic deformation. The drop in permeability during initial loading is much smaller for cataclasite than for gouge, followed by abrupt increase upon failure, and the overall change in permeability correlates well with change in volumetric strain, i.e., initial, nearly elastic contraction followed by dilatancy upon the initiation of inelastic deformation towards specimen failure. If cemented cataclasite suffers deformation prior to or during an earthquake, a cataclasite zone may change into a conduit for fluid flow. Fault gouge zones, however, are unlikely to switch to very permeable zones upon the initiation of fault slip. Thus, overall permeability structure of a fault may change abruptly prior to or during earthquakes and during the interseismic period. Fault gouge and cataclasite have internal angles of friction of about 36° and 45°, respectively, as is typical for brittle rocks. © 2003 Elsevier B.V. All rights reserved.

    Original languageEnglish
    Pages (from-to)183-195
    Number of pages13
    JournalTectonophysics
    Volume378
    Issue number3-4
    DOIs
    Publication statusPublished - 30 Jan 2004

    Keywords

    • Cataclasite
    • Earthquake
    • Fault gouge
    • Fluid flow
    • Median Tectonic Line
    • Permeability
    • Triaxial deformation

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