OS024-0006
IODP proposal for Bend-Fault Hydrology in the Old Incoming Plate (H-ODIN) using CHIKYU: Scientific objectives and drilling site & strategy

Thursday, 10 December 2020
Poster
Tomoaki Morishita1, Gou Fujie2, Shigeaki Ono3, Takanori Kagoshima4, Jason Phipps Morgan5, Marianne Conin6, Akira Ijiri7, Benoit Ildefonse8, Tsuyoshi Ishikawa9, Ikuo Katayama10, Peter B Kelemen11, Junichiro Kuroda3, Yohey Suzuki12, Damon A H Teagle13, Alexis S Templeton14, Tomohiro Toki15, Kohtaro Ujiie16, Asuka Yamaguchi17 and Makoto Yamano18, (1)Kanazawa University, Course in Earth and Planetary Science, Kanazawa, Japan, (2)Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan, (3)JAMSTEC, Yokosuka, Japan, (4)Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan, (5)Royal Holloway, Runnymede, United Kingdom, (6)Laboratoire GeoRessources (UMR 7359, Université de Lorraine, CNRS, CREGU), Nancy, France, (7)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kochi Institute for Core Sample Research, Kanagawa, Japan, (8)Géosciences Montpellier, Univ Montpellier, CNRS, Univ Antilles, Montpellier, France, (9)JAMSTEC, Nankoku, Kochi, Japan, (10)Hiroshima Univ, Hiroshima, Japan, (11)Lamont Doherty Earth Observatory, Columbia University, Palisades, NY, United States, (12)University of Tokyo, Department of Earth and Planetary Science, Tokyo, Japan, (13)University of Southampton, School of Ocean & Earth Science, National Oceanography Centre Southampton, Southampton, United Kingdom, (14)University of Colorado at Boulder, Geological Sciences, Boulder, CO, United States, (15)Univ. of the Ryukyus, Okinawa, Japan, (16)University of Tsukuba, Tsukuba, Japan, (17)University of Tokyo, Kashiwa, Japan, (18)University of Tokyo, Earthquake Research Institute, Bunkyo-ku, Japan
Abstract:
It has been generally accepted that extensive hydration due to plate bending-induced normal faults (bend-faults hereafter) occurs in the region between trench and outer rise (outer rise) (e.g, Ranero et al., Nature, 2003; Key et al., EPSL, 2012, Fujie et al., GRL, 2013). Investigating several subduction zones with various conditions is crucial to expand our knowledge of bend-fault hydration processes. The northwest Pacific (NW Pacific) region is one of the world oldest, thus coldest, and is therefore the end-member to study bend-fault hydration. Water circulation and hydration through the bend-faults in the NW Pacific region are supported by extensive geophysical survey: (1) Horst and graben structures formed by bend-faulting (Nakanishi, Springer, 2011) (2) Large bend-fault earthquakes (M>7) , (3) Detailed Vp/Vs variations within the incoming plate (Fujie et al., Nature Comm, 2018), (4) The local stress state is likely to have changed significantly after the 2011 Tohoku Earthquake (Obana et al., Geophys. Jour. Inst., 2019), and (5) Anomalously high heat flow (Yamano et al., EPSL, 2014). In addition, intraplate normal-faulting (i.e., bend-fault) earthquake in the outer rise occurred within a day to 37 years after the plate-interface earthquakes. Both types of earthquakes caused tsunamis that caused massive damage along the coast of northeastern Japan. We must be aware of the possibility of the future outer rise earthquake (e.g. Lay et al. EPS, 2011). We are likely be in a rare phase between a giant megathrust event and its potential outer-rise doublet. In order to address (a) hydration processes and their extents along bend-faults, (b) geophysical, chemical and structural properties of the bend-faults, (c) outer rise earthquake and development of horst-graben structure, and (d) lithospheric biosphere: its living conditions and sustainability, we will analyze in-situ physical properties and lithofacies that will be best obtained by ocean drilling in the NW Pacific region. Two drill sites are absolute minimum requirement (fault along sediment and basement, fault within basement).
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