Strike-slip motion of a mega-splay fault system in the Nankai oblique subduction zone
Abstract
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.
- Publication:
-
Earth, Planets and Space
- Pub Date:
- December 2014
- DOI:
- 10.1186/1880-5981-66-120
- Bibcode:
- 2014EP&S...66..120T
- Keywords:
-
- Strike-slip fault;
- Mega-splay fault;
- Nankai Trough;
- Oblique subduction;
- Stress boundary