Pore pressure distribution of a mega-splay fault system in the Nankai trough subduction zone: Insight into up-dip extent of the seismogenic zone

Takeshi Tsuji, Rie Kamei, R. Gerhard Pratt

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

We use the pore pressure distribution predicted from a waveform tomography (WT) velocity model to interpret the evolution of the mega-splay fault system in the Nankai Trough off Kumano, Japan. To map pore pressure around the mega-splay fault and plate boundary décollement, we integrate the high-resolution WT velocities with laboratory data and borehole well log data using rock physics theory. The predicted pore pressure distribution shows that high pore pressures (close to lithostatic pressure) along the footwall of the mega-splay fault extend seaward to the trough region, and the normalized pore pressure ratio is nearly constant over that extent. This continuity of the overpressured zone indicates that a coseismic rupture can potentially propagate nearly to the trough axis. We interpret a high-pressure belt within an accretionary wedge on the landward side of the present mega-splay fault as evidence of the ancient mega-splay fault. Because the ancient mega-splay fault soles into the active mega-splay fault, the active mega-splay fault may function as a basal detachment fault and is directly connected to the seaward plate boundary décollement.

Original languageEnglish
Pages (from-to)165-178
Number of pages14
JournalEarth and Planetary Science Letters
Volume396
DOIs
Publication statusPublished - Jan 1 2014

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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