Japan Geoscience Union Meeting 2016

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International Session (Oral)

Symbol S (Solid Earth Sciences) » S-TT Technology & Techniques

[S-TT18] Stress geomechanics: observations, modelings and implications

Sun. May 22, 2016 10:45 AM - 12:15 PM 302 (3F)

Convener:*HungYu Wu(Japan Agency for Marine-Earth Science and Technology), Chung-Han Chan(Earth Observatory of Singapore, Nanyang Technological University), Saneatsu Saito(Japan Agency for Marine-Earth Science and Technology), Yoshinori Sanada(Japan Agency for Marine-Earth Science and Technology), Ayumu Miyakawa(Geodynamics Research Group, Institute of Geology and Geoinformation (IGG), Geological Survey of Japan/AIST), Yasuhiro Yamada(Japan Agency for Marine-Earth Science and Technology (JAMSTEC), R&D Center for Ocean Drilling Science (ODS)), Chair:HungYu Wu(Japan Agency for Marine-Earth Science and Technology), Yasuhiro Yamada(Japan Agency for Marine-Earth Science and Technology (JAMSTEC), R&D Center for Ocean Drilling Science (ODS)), Ayumu Miyakawa(Geodynamics Research Group, Institute of Geology and Geoinformation (IGG), Geological Survey of Japan/AIST)

11:00 AM - 11:15 AM

[STT18-08] Spatial distribution of stress state in the NanTroSEIZE transect and a comparison with JFAST at frontal thrust

★Invited papers

*Weiren Lin1, Timothy Byrne2, Masataka Kinoshita3 (1.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 2.Connecticut University, USA, 3.ERI, The University of Tokyo)

Keywords:NanTroSEIZE, JFAST, Stress

To better understand the distribution of three dimensional stress states in the Nankai subduction zone, southwest Japan, we review various stress-related investigations carried out in the first and second stage expeditions of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) by the Integrated Ocean Drilling Program (IODP) and compile the stress data. Overall, the maximum principal stress SIGMA1 in the shallower levels (<~1km) is vertical from near the center of forearc basin to near the trench and; the maximum horizontal stress SHmax (interpreted to be the intermediate principal stress SIGMA2) is generally parallel to the plate convergence vector. The exception to this generalization occurs along the shelf edge of the Nankai margin where SHmax is along strike rather than parallel to the plate convergence vector. Reorientation of the principal stresses at deeper levels (e.g., >~1km below seafloor or in underlying accretionary prism) with s1 becoming horizontal is also suggested at all deeper drilling sites. We also make a comparison of the stress state in the hanging wall of the frontal plate-interface between Site C0006 in the Nankai and Site C0019 in the Japan Trench subduction zone drilled after the 2011 Mw9.0 Tohoku-Oki earthquake. In the Japan Trench, the comparison between stress state before and after the 2011 mega-earthquake shows that the stress changed from compression before the earthquake to extension after the earthquake. As a result of the comparison between the Nankai Trough and Japan Trench, a similar current stress state with trench parallel extension was recognized at both C0006 and C0019 sites.