TrekGEO > Geology of Japan > Faults

Japanese page



Tectonic lines


Sediments are accreted to continents via faults in an arc-trench system. Tectonic lines are defined by the faults determining the upper and the lower boundaries of an accretionary complex. Distribution of accretionary complexes are modified by secondary faults as the result of surrounding plate movements. There are also numerous smaller faults in blocks formed by larger tectonic lines and faults. The shallow parts of large faults shallower than 10 km depth (less than 0.3 GPa, less than 300 degree) are crushing belts composed of cataclasites (fault breccia, fault gauge), and the deep parts of them deeper than 10 km are composed of mylonites (pseudotachylite, ultramylonite).


There are 3 types of fautls: tectonic lines determining arrangements of accretinary complexes, secondary faults modifying distribution of accretionary complexes, and numerous smaller faults.

Tectonic lines determining arrangements of accretionary complexes are as follows:

Black: Nagato-Hida marginal tectonic line, Green: Ishigaki-Kuga tectonic line, Orange: Median tectonic line, and Yellow: Butsuzo tectonic line, Light blue: Hidaka thrust,

where Osayama-Omi tectonic line overlaps Nagato-Hida marginal tectonic line.

Secondary faults modifying distribution of accretionary complexes are:

Pink: Itoigawa-Shizuoka tectonic line (Fossa magna), Blue: Tanakura tectonic line,

Itoigawa-Shizuoka tectonic line are interpreted as a transform fault in a plate at the boundary between North American plate and Eurasian plate.

Red: Kozu-Matsuda fault (Kannawa fault) is considered as the plate boundary between Eurasian plate and Philippine sea plate.


  • Numerous small faults
  • Kozu-Matsuda fault (Kannawa fault)
  • Hidata thrust
  • Tanakura Tectonic Line (TTL)
  • Itoigawa-Shizuoka Tectonic Line
  • Butsuzo Tectonic Line (BTL)
  • Median Tectonic Line (MTL)
  • Ishigaki-Kuga Tectonic Line (I-KTL)
  • Osayama-Omi Tectonic Line (O-OTL)
  • Nagato-Hida marginal T.L. (Mg-HmTL)

Geological Settings

Copyright (c) 2016 NariNari, All Rights Reserved.