Structure and lithology of the Japan Trench subduction plate boundary fault

James D. Kirkpatrick, Christie D. Rowe, Kohtaro Ujiie, J. Casey Moore, Christine Regalla, Francesca Remitti, Virginia Toy, Monica Wolfson-Schwehr, Jun Kameda, Santanu Bose, Frederick M. Chester

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

The 2011 Mw9.0 Tohoku-oki earthquake ruptured to the trench with maximum coseismic slip located on the shallow portion of the plate boundary fault. To investigate the conditions and physical processes that promoted slip to the trench, Integrated Ocean Drilling Program Expedition 343/343T sailed 1 year after the earthquake and drilled into the plate boundary ∼7 km landward of the trench, in the region of maximum slip. Core analyses show that the plate boundary décollement is localized onto an interval of smectite-rich, pelagic clay. Subsidiary structures are present in both the upper and lower plates, which define a fault zone ∼5-15m thick. Fault rocks recovered from within the clay-rich interval contain a pervasive scaly fabric defined by anastomosing, polished, and lineated surfaces with two predominant orientations. The scaly fabric is crosscut in several places by discrete contacts across which the scaly fabric is truncated and rotated, or different rocks are juxtaposed. These contacts are inferred to be faults. The plate boundary décollement therefore contains structures resulting from both distributed and localized deformation. We infer that the formation of both of these types of structures is controlled by the frictional properties of the clay: the distributed scaly fabric formed at low strain rates associated with velocity-strengthening frictional behavior, and the localized faults formed at high strain rates characterized by velocity-weakening behavior. The presence of multiple discrete faults resulting from seismic slip within the décollement suggests that rupture to the trench may be characteristic of this margin.

Original languageEnglish (US)
Pages (from-to)53-69
Number of pages17
JournalTectonics
Volume34
Issue number1
DOIs
StatePublished - Jan 1 2015
Externally publishedYes

Keywords

  • aseismic creep
  • conditional stability
  • décollement
  • Japan Trench
  • JFAST
  • seismic slip

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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