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Structure and lithology of the Japan Trench subduction plate boundary fault
Author(s) -
Kirkpatrick James D.,
Rowe Christie D.,
Ujiie Kohtaro,
Moore J. Casey,
Regalla Christine,
Remitti Francesca,
Toy Virginia,
WolfsonSchwehr Monica,
Kameda Jun,
Bose Santanu,
Chester Frederick M.
Publication year - 2015
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2014tc003695
Subject(s) - geology , trench , seismology , subduction , slip (aerodynamics) , plate tectonics , lithology , décollement , fault (geology) , drilling , convergent boundary , petrology , tectonics , oceanic crust , chemistry , organic chemistry , layer (electronics) , mechanical engineering , physics , engineering , thermodynamics
The 2011 M w 9.0 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.