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Strike-slip motion of a mega-splay fault system in the Nankai oblique subduction zone

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The Paper of Assoc. Prof. Takeshi Tsuji (Principal Investigator, CO2 Storage Research DivisionI²CNER) and his collaborators was published online in “Earth, Planets and Space.

 

■ Summary

We evaluated the influence of the trench-parallel component of plate motion on the active fault system within the Nankai accretionary wedge from reflection seismic profiles, high-resolution seafloor bathymetry, and deep-towed sub-bottom profiles. Our study demonstrated that a large portion of the trench-parallel component of oblique plate subduction is released by strike-slip motion along a fault located just landward of and merging down-dip with a mega-splay fault. The shallow portion of the splay fault system, forming a flower structure, seems to accommodate dominant strike-slip motion, while most of the dip-slip motion could propagate to the trenchward décollement. Numerous fractures developed around the strike-slip fault release overpressured pore fluid trapped beneath the mega-splay fault. The well-developed fractures could be related to the change in stress orientation within the accretionary wedge. Therefore, the strike-slip fault located at the boundary between the inner and outer wedges is a key structure controlling the stress state (including pore pressure) within the accretionary prism. In addition, the strike-slip motion contributes to enhancing the continuous mega-splay fault system (outer ridge), which extends for approximately 200 km parallel to the Nankai Trough.

 

■ Paper

Title: Strike-slip motion of a mega-splay fault system in the Nankai oblique subduction zone

Authors: Takeshi Tsuji, Juichiro Ashi and Yasutaka Ikeda

DOI: 10.1186/1880-5981-66-120

Publication Date: September 19, 2014