[S-CG55] Oceanic plate as inputs to subduction zone and the subduction initiation

Thu. May 28, 2026 9:00 AM - 10:30 AM Convention Hall (CH-B) (International Conference Hall, Makuhari Messe)

Chairperson:Ishizuka Osamu(Geological Survey of Japan, AIST), Akamatsu Yuya(Japan Agency for Marine-Earth Science and Technology), Zhang Jin(Texas A&M University College Station)

This session focuses on two main topics: the oceanic plate as inputs to the subduction zone and the processes that initiate subduction. Subduction of oceanic plate drives various geodynamic phenomena, such as magma generation and fault formation, triggering volcanic and earthquake activity at subduction zones. Scales and distributions of such subduction zone-phenomena are controlled by physicochemical properties of subducting oceanic plates. In addition, oceanic plate-subduction processes transport surface materials such as water and carbon into the deep interior of Earth, playing an important role in global geochemical cycles. Physicochemical properties of oceanic plates as "subduction inputs" reflect their evolutionary histories from their formation at mid-ocean ridges until subduction at trenches. These characteristics are further modified by processes associated with plate bending prior to subduction, including fault development and petit-spot volcanism. Subduction initiation and the subsequent development of oceanic island arcs are poorly understood and remain an important unresolved problem in plate tectonics. Recent efforts to investigate geological record of subduction initiation along oceanic arcs and ophiolite have significantly improved understanding of processes associated with subduction initiation. This has also prompted extensive study utilizing tomography and numerical modeling to investigate requirements for the plate to subduct, and reconstruct tectonics for subduction initiation. We welcome contributions from a broad range of earth science (geophysics, geochemistry, geology, petrology, drilling science, and so on) discussing topics related to the nature of the subduction initiation of oceanic plate and their role as inputs to subduction zones.

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9:00 AM - 9:15 AM

[SCG55-01] Crustal composition of the continental overriding plate at the IBM subduction initiation: Constraints from the Gagua Ridge

*Kenichiro Tani¹, Osamu Ishizuka², Kyoko Okino³, Hayato Ueda⁴, Yumiko Harigane², Chih-Chieh Su⁵, Ta-Wei Hsu⁵, KH-23-10 shipboard scientists (1. Department of Science, National Museum of Nature and Science, 2. Geological Survey of Japan/AIST, 3. AORI, University of Tokyo, 4. Niigata University, 5. Institute of Oceanography, National Taiwan University)

9:15 AM - 9:30 AM

[SCG55-02] Heterogeneity of mantle source beneath the West Philippine Basin: Evidence from whole-rock and mineralogical data

*Mori Kouki¹, Osamu Ishizuka², Yuji Ichiyama¹ (1. Chiba university, 2. Geological Survey of Japan, AIST)

9:30 AM - 9:45 AM

[SCG55-03] Ridge collision sculpts forearc segmentation: 3D seismic view from the eastern Nankai Trough

*Gaku Kimura¹, Kazuya Shiraishi¹, Yasuyuki Nakamura¹, Gou Fujie¹, Paul Caesar. M. Flores¹ (1. Japan Agency for Marine-Earth Science and Technology)

9:45 AM - 10:00 AM

[SCG55-04] A machine learning framework for seismic facies mapping of sediment input in subduction zones using reflection amplitudes from 2D profiles: a case study in the Nankai Trough, Japan

*Paul Caesar Mason Flores¹, Gou Fujie¹, Kazuya Shiraishi¹, Yasuyuki Nakamura¹, Gaku Kimura¹, Jun Su¹, Ryoichiro Agata¹, Shuichi Kodaira¹ (1. Japan Agency for Marine-Earth Science and Technology)

10:00 AM - 10:15 AM

[SCG55-05] Heat flow distribution on the Nankai Trough floor: Correlation with the basement structure of the subducting Shikoku Basin

*Makoto Yamano¹, Yoshifumi Kawada², Yasuyuki Nakamura³, Kazuya Shiraishi³ (1. Atmosphere and Ocean Research Institute, The University of Tokyo, 2. Graduate School of Science, The University of Tokyo, 3. Research Institute for Marine Geodynamics, JAMSTEC)

10:15 AM - 10:30 AM

[SCG55-06] Early-stage structural evolution of the subducting Pacific Plate off Nemuro, Hokkaido, revealed by dense-OBS and MCS seismic imaging

*Ryosuke Azuma¹, Gou Fujie², Ryota Hino¹, Shuichi Kodaira² (1. Recearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, 2. Japan Agency for Marine-Earth Science and Technology)

Session information