Scale dependence of in-situ permeability measurements in the Nankai accretionary prism: The role of fractures

David F. Boutt, Demian Saffer, Mai Linh Doan, Weiren Lin, Takatoshi Ito, Yasuyuki Kano, Peter Flemings, Lisa C. McNeill, Timothy Byrne, Nicholas W. Hayman, Kyaw Thu Moe

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Abstract

Modeling studies suggest that fluid permeability is an important control on the maintenance and distribution of pore fluid pressures at subduction zones generated through tectonic loading. Yet, to date, few data are available to constrain permeability of these materials, at appropriate scales. During IODP Expedition 319, downhole measurements of permeability within the uppermost accretionary wedge offshore SW Japan were made using a dual-packer device to isolate 1m sections of borehole at a depth of 1500m below sea floor. Analyses of pressure transients using numerical models suggest a range of in-situ fluid permeabilities (5E-15-9E-17m2). These values are significantly higher than those measured on core samples (2E-19m2). Borehole imagery and cores suggests the presence of multiple open fractures at this depth of measurement. These observations suggest that open permeable natural fractures at modest fracture densities could be important contributors to overall prism permeability structure at these scales.

Original languageEnglish (US)
Article numberL07302
JournalGeophysical Research Letters
Volume39
Issue number7
DOIs
StatePublished - Apr 1 2012

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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    Boutt, D. F., Saffer, D., Doan, M. L., Lin, W., Ito, T., Kano, Y., Flemings, P., McNeill, L. C., Byrne, T., Hayman, N. W., & Moe, K. T. (2012). Scale dependence of in-situ permeability measurements in the Nankai accretionary prism: The role of fractures. Geophysical Research Letters, 39(7), [L07302]. https://doi.org/10.1029/2012GL051216