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  • Article
  • Open Access

Is the Ryukyu subduction zone in Japan coupled or decoupled? —The necessity of seafloor crustal deformation observation

  • 11Email author,
  • 21,
  • 21,
  • 21,
  • 31 and
  • 31
Earth, Planets and Space200961:BF03352954

  • Received: 19 July 2008
  • Accepted: 3 June 2009
  • Published:


The 2004 Sumatra-Andaman earthquake of Mw 9.3 occurred in a region where a giant earthquake seemed unlikely from the point of view of tectonics. This clearly implies that our current understanding of strain accumulation processes of large earthquakes at subduction zones needs to be reexamined. The Ryukyu subduction zone is one such zone since no large earthquake has been anticipated there for reasons similar those pertaining to the Sumatra-Andaman arc. Based on our analysis of historical earthquakes, plate motion, back-arc spreading, and GPS observation along the Ryukyu trench, we highly recommend monitoring seafloor crustal deformation along this trench to clarify whether a large earthquake (Mw>8) could potentially occur there in the future.

Key words

  • Subduction zones
  • Ryukyu trench
  • decoupled/couple subduction
  • back-arc spreading
  • seafloor crustal deformation