JpGU-AGU Joint Meeting 2026

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[E] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG63] Uncovering stress accumulation and fault strengthening of megathrust earthquakes

Mon. May 25, 2026 9:00 AM - 10:30 AM 301A (International Conference Hall, Makuhari Messe)

Chairperson:Kodaira Shuichi(Japan Agency for Marine-Earth Science and Technology), Ujiie Kohtaro(Faculty of Life and Environmental Sciences, University of Tsukuba), Regalla Christine(Northern Arizona University)

In the 2011 Tohoku-Oki Earthquake, large fault slips exceeding 50 meters were observed near the trench axis, an area previously thought to experience stable sliding or aseismic slip during an earthquake cycle. Various methods, including geophysical surveys, observations, ocean drilling, experiments, and simulations, have been employed to clarify the mechanisms behind these shallow, large fault slips. However, the state of fault locking before and between earthquakes - critical to understanding fault slip - remains unclear. To answer this question based on data from the Tohoku-Oki and inland earthquakes, as well as theoretical and model studies, two contrasting hypotheses have been proposed: one suggests that mechanical locking in the shallow part of the plate boundary rapidly progresses after an earthquake, while the other posits that the shallow part remains mechanically unlocked throughout an earthquake cycle. A unified view on this issue has not yet been established. This session aims to address the fundamental problem in the earthquake generation process: how fault strength recovers and stress accumulates along the source fault of a subduction seismogenic zone. We also hope to use the session as an opportunity to share new knowledge about the geophysical and geological structure of the source faults of megathrust earthquakes, and their spatial variation along and across the subduction zone. We invite research presentations from a wide range of fields, including geophysics, geodesy, geology, petrology, geochemistry, drilling science, and both model and theoretical researches, with a focus on subduction seismogenic zones worldwide.

9:00 AM - 9:15 AM

[SCG63-01] Taking the Temperature of the Japan Trench Megathrust: Successful Recovery and Redeployment of Site C0019 Observatories

★Invited Papers

*Patrick M Fulton1, Jamie Kirkpatrick2, C. Nur Schuba3, Huiyun Guo4, Lena Maeda5, Natsumi Okutsu5, Sean Toczko5, Nobu Eguchi5, Noriaki Sakurai5, Tomokazu Saruhashi5, Keita Akiyama5, Masanori Kyo5, Takahiro Yokoyama5, IODP Expedition 405 Scientists6 (1. Dept. of Earth and Atmospheric Sciences, Cornell University, 2. Dept. of Geological Sciences and Engineering, University of Nevada Reno, 3. Bureau or Economic Geology, University of Texas at Austin, 4. Division of Geological and Planetary Sciences, California Institute of Technology, 5. Institute for Marine-Earth Exploration and Engineering (MarE3), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 6. https://publications.iodp.org/proceedings/405/405title.html#staff)

9:15 AM - 9:30 AM

[SCG63-02] Evolution of magnetic fabric in sediments associated with initial subduction processes across the Japan Trench (IODP Expedition 405)

*Takeru Yoshimoto1, Taizo Uchida2, Toshiya Kanamatsu3, Sara Satolli4, Derya Gürer10, Yuzuru Yamamoto1, Kohtaro Ujiie5, Marianne Conin6, Patrick Fulton7, Jamie Kirkpatrick8, Christine Regalla9, Shuichi Kodaira3 (1. Kobe University, 2. Kochi University, 3. JAMSTEC, 4. University of Chieti-Pescara, 5. University of Tsukuba, 6. University of Lorraine, 7. Cornell University, 8. University of Nevada, Reno, 9. Northern Arizona University, 10. Heidelberg University)

10:00 AM - 10:15 AM

[SCG63-05] Trench-parallel fluid migration and its transient discharge in a cold subduction zone decoded by geochemistry of subducted cherts

*Hanaya Okuda1, Hitomi Mizuno2, Takashi Sano3, Akira Ijiri4,1, Minoru Ikehara5, Wataru Tanikawa1, Asuka Yamaguchi2 (1. Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 2. Atmosphere and Ocean Research Institute, University of Tokyo, 3. Department of Science, National Museum of Nature and Science, 4. Graduate School of Maritime Sciences, Kobe University, 5. Marine Core Research Institute, Kochi University)

10:15 AM - 10:30 AM

[SCG63-06] Numerical transport modeling of near-fault geochemical anomalies at IODP Site C0019, Japan Trench

★Invited Papers

*Junli Zhang1, Tsuyoshi Ishikawa2, Troy Rasbury3, Chijun Sun4 (1. MARUM–Center for Marine Environmental Sciences, University of Bremen, 2. Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 3. Department of Geosciences, FIRST, Stony Brook University, 4. Department of Earth and Planetary Sciences, University of California Davis)

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