Unified Understanding of Slow and Regular Earthquakes from Nonequilibrium Physics Point of View

• Project Area: Science of slow earthquakes
• Project/Area Number: 16H06478
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: Osaka University (2018-2020); The University of Tokyo (2016-2017)
• Principal Investigator: 波多野 恭弘 大阪大学, 理学研究科, 教授 (20360414)
• Co-Investigator(Kenkyū-buntansha): 住野 豊 東京理科大学, 理学部第一部応用物理学科, 准教授 (00518384) ; 鈴木 岳人 青山学院大学, 理工学部, 助教 (10451874) ; 山口 哲生 九州大学, 工学研究院, 准教授 (20466783)
• Project Period (FY): 2016-06-30 – 2021-03-31
• Project Status: Granted (Fiscal Year 2020)
• Budget Amount: ¥94,380,000 (Direct Cost: ¥72,600,000、Indirect Cost: ¥21,780,000); Fiscal Year 2020: ¥19,890,000 (Direct Cost: ¥15,300,000、Indirect Cost: ¥4,590,000); Fiscal Year 2019: ¥18,200,000 (Direct Cost: ¥14,000,000、Indirect Cost: ¥4,200,000); Fiscal Year 2018: ¥15,860,000 (Direct Cost: ¥12,200,000、Indirect Cost: ¥3,660,000); Fiscal Year 2017: ¥16,510,000 (Direct Cost: ¥12,700,000、Indirect Cost: ¥3,810,000); Fiscal Year 2016: ¥23,920,000 (Direct Cost: ¥18,400,000、Indirect Cost: ¥5,520,000)
• Keywords: スロー地震 / 摩擦不安定性 / 非平衡物理 / 非線形動力学 / ソフトマター物理 / 地震 / 摩擦 / ゲル / 粘弾性 / ソフトマター物理学 / レオロジー

Outline of Annual Research Achievements

1) 弾性体や流体を用いたアナログ実験　不均一な断層面における地震活動をモデル化するため、ゲル表面に複数のアスペリティを配置した摩擦実験を行った。その結果、本震の核生成過程として、微動を伴うゆっくりすべりが発生することを見出した。加えて、微動の継続時間が系の駆動速度に対して単調に減少することも確認した。これらの結果は数値計算でも再現されており、速度に対して非単調な摩擦構成則および法線応力の不均一性によって説明されることが明らかとなった．
流体系モデリングでは、混合することで紐状ミセルを生成しゲル化する溶液二種類を用いた実験を行った。まず溶液Aを薄い平行平板内に導入し、その後で溶液Bを中心より注入すると、注入した溶液Bの先端がゲル化する実験系が構築できる。こうした系では注入がもたらす流動とゲル化が結合することで多様な時空ダイナミクスが生まれる。ここでは、セルに予め岩盤中の構造を模擬した規則格子構造を導入しその影響を調べた。その結果、直進的に枝が進行する場合があり、その実現条件を見いだした。このことは簡単な数理モデルでも再現出来た。
2) プレート境界の数理モデル構築と解析　動的地震滑り過程における摩擦発熱による流体の高圧化、及び、空隙生成による流体の減圧化をモデル化し、初期滑り速度と最終滑り量の間に冪的な関係式が成り立つことを示した。この関係式における指数1/2は普遍的であり、空隙発展則の詳細には依存しないことは特筆される。具体的なモデルを仮定して数値計算してみると、初期滑り速度のずれが最終滑り量のずれに大きく拡大されるケースもあることが確認された。これは最終的な地震サイズの予測不能性を示唆するので、意義深い結果である。ここで得られた解析的成果はLotka-Volterra系の特別な場合などにも適用可能であることから、地震現象の理解にとどまらない意義を持つ。

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

ゲル摩擦実験における2019年度の目標は、摩擦面の凸凹を成形して不安定挙動と安定挙動の境界領域を実験装置で十分実現可能な値に設定した上で、本震の核生成過程のダイナミクスを再現することであった。この目標は達成でき、その結果として微動的な発振を伴うゆっくりすべりを発見できたことは当初の計画以上の進展と言える。この現象に関して簡単な数理モデルを構築し、数値計算を行なって実験と良い一致が得られたことも高く評価できる。
流体実験においては、レオロジーがもたらす対称性の破れ（パターン形成）を実験的に見出し、その機構を数理的に解明することを目標としていた。ここでは、混合することで紐状ミセルを生成しゲル化する溶液二種類を用いるという実験的工夫を行うことで、新奇なパターン動力学を見出すことができた。簡単な場合については数理的な解明もできたため、計画通りの成果を挙げたということができる。
数理モデルにおいては、多孔質媒質中の流体移動についての考察を深めるために乱流のk-εモデルを導入・解析し、一定の成果を得たが、スロー地震、特に観測研究に対する意義は検討を継続する必要がある。それと並行して、摩擦発熱と空隙生成モデルに実際の岩石から得られた空隙率等の値を導入することで、通常の地震とゆっくり地震の両方が起こり得ることを示せたのは、本課題の目標である「通常の地震とスロー地震の統一的な理解」へ大きく近づいたと言える。

Strategy for Future Research Activity

これまでに引き続き、法線応力の不均一性が地震発生過程に及ぼす影響について、ゲルや流体を用いたアナログ実験、及び、数理モデルを用いて調査する。ゲル実験においては法線応力が空間的に増加する場合も考慮して地震発生サイクルを模擬した実験を行う。これは沈み込み帯の大域的応力場に対応させる意図がある。その際、ひずみ場と応力場だけでなく、すべり速度などの動的な物理量を精密に計測することで、地震発生メカニズムの解明に取り組む。
スロー地震においては岩盤中の水の移動が重要とされる。このダイナミクスを実験室で詳細に調べる観点から、狭いセル中に溶液を注入する実験も行いたい。具体的には、系に不純物（粒子）を意図的に導入することで媒質中の不均一性をモデル化し、誘起される不安定性を調べる。

Research Products

• [Int'l Joint Research] Ecole Normale Superieure/Universite de Paris(フランス)
• [Int'l Joint Research] Ecole Normale Superieure/University Paris Diderot(フランス)
• [Journal Article] Topology and Toughening of Sparse Elastic Networks (2020)
  • Author(s): Yamaguchi Tetsuo、Onoue Yudai、Sawae Yoshinori
  • Journal Title: Physical Review Letters Volume: 124 Issue: 6 Pages: 68002-68002
  • DOI: 10.1103/physrevlett.124.068002
  • Peer Reviewed
• [Journal Article] Two Floating Camphor Particles Interacting through the Lateral Capillary Force (2020)
  • Author(s): Hirose Yuhei、Yasugahira Yusuke、Okamoto Mamoru、Koyano Yuki、Kitahata Hiroyuki、Nagayama Masaharu、Sumino Yutaka
  • Journal Title: Journal of the Physical Society of Japan Volume: 89 Issue: 7 Pages: 074004-074004
  • DOI: 10.7566/jpsj.89.074004
  • NAID: 40022283350
  • Peer Reviewed
• [Journal Article] Universal Relaxation Dynamics of Sphere Packings below Jamming (2020)
  • Author(s): Ikeda Atsushi、Kawasaki Takeshi、Berthier Ludovic、Saitoh Kuniyasu、Hatano Takahiro
  • Journal Title: Physical Review Letters Volume: 124 Issue: 5 Pages: 1-6
  • DOI: 10.1103/physrevlett.124.058001
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Stress Relaxation above and below the Jamming Transition (2020)
  • Author(s): Saitoh Kuniyasu、Hatano Takahiro、Ikeda Atsushi、Tighe Brian P.
  • Journal Title: Physical Review Letters Volume: 124 Issue: 11 Pages: 1-5
  • DOI: 10.1103/physrevlett.124.118001
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Surface Effect on Frictional Properties for Thin Hydrogel Films of Poly(vinyl ether) (2019)
  • Author(s): Itagaki Nozomi、Kawaguchi Daisuke、Oda Yukari、Nemoto Fumiya、Yamada Norifumi L.、Yamaguchi Tetsuo、Tanaka Keiji
  • Journal Title: Macromolecules Volume: 52 Issue: 24 Pages: 9632-9638
  • DOI: 10.1021/acs.macromol.9b01786
  • Peer Reviewed / Open Access
• [Journal Article] Patterning defects in high-speed reverse offset printing: lessons from contact dynamics (2019)
  • Author(s): Kusaka Yasuyuki、Mizukami Makoto、Yamaguchi Tetsuo、Fukuda Nobuko、Ushijima Hirobumi
  • Journal Title: Journal of Micromechanics and Microengineering Volume: 29 Issue: 4 Pages: 045001-045001
  • DOI: 10.1088/1361-6439/ab024b
  • Peer Reviewed / Open Access
• [Journal Article] Sensitivity of Acoustic Emission Triggering to Small Pore Pressure Cycling Perturbations During Brittle Creep (2019)
  • Author(s): Chanard K.、Nicolas A.、Hatano T.、Petrelis F.、Latour S.、Vinciguerra S.、Schubnel A.
  • Journal Title: Geophysical Research Letters Volume: 46 Issue: 13 Pages: 7414-7423
  • DOI: 10.1029/2019gl082093
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Macroscopic Steady Slippage and Creep Motion in a System with Velocity-Dependent Friction Stress (2019)
  • Author(s): Suzuki, T., & Matsukawa, H
  • Journal Title: Journal of the Physical Society of Japan Volume: 88 Issue: 11 Pages: 114402-114402
  • DOI: 10.7566/jpsj.88.114402
  • Peer Reviewed / Open Access
• [Journal Article] Longer migration and spontaneous decay of aseismic slip pulse caused by fault roughness (2019)
  • Author(s): So Ozawa, Takahiro Hatano, Nobuki Kame
  • Journal Title: Geophys. Res. Lett. Volume: 46 Issue: 2 Pages: 1-8
  • DOI: 10.1029/2018gl081465
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Rheology of Cohesive Granular Particles under Constant Pressure (2018)
  • Author(s): Yamaguchi Yuta、Takada Satoshi、Hatano Takahiro
  • Journal Title: Journal of the Physical Society of Japan Volume: 87 Issue: 9 Pages: 094802-094802
  • DOI: 10.7566/jpsj.87.094802
  • NAID: 210000134971
  • Peer Reviewed
• [Journal Article] Relaxation Dynamics of a Granular Pile on a Vertically Vibrating Plate (2018)
  • Author(s): Tsuji Daisuke、Otsuki Michio、Katsuragi Hiroaki
  • Journal Title: Physical Review Letters Volume: 120 Issue: 12 Pages: 1-4
  • DOI: 10.1103/physrevlett.120.128001
  • Peer Reviewed / Open Access
• [Journal Article] Contrasting Roles of Water at Sliding Interfaces between Silicon-Based Materials: First-Principles Molecular Dynamics Sliding Simulations (2018)
  • Author(s): Y. Ootani, J. Xu, T. Hatano, M. Kubo
  • Journal Title: J. Phys. Chem. C Volume: 122 Issue: 19 Pages: 10459-10467
  • DOI: 10.1021/acs.jpcc.8b01953
  • Peer Reviewed
• [Journal Article] Creeplike behavior in athermal threshold dynamics: Effects of disorder and stress (2018)
  • Author(s): Roy Subhadeep、Hatano Takahiro
  • Journal Title: Physical Review E Volume: 97 Issue: 6 Pages: 062149-062149
  • DOI: 10.1103/physreve.97.062149
  • Peer Reviewed
• [Journal Article] Simple statistics for complex Earthquake time distributions (2018)
  • Author(s): Matcharashvili Teimuraz、Hatano Takahiro、Chelidze Tamaz、Zhukova Natalia
  • Journal Title: Nonlinear Processes in Geophysics Volume: 25 Issue: 3 Pages: 497-510
  • DOI: 10.5194/npg-25-497-2018
  • Peer Reviewed
• [Journal Article] Geological implication of grain-size segregation in dense granular matter (2018)
  • Author(s): Itoh Ryo、Hatano Takahiro
  • Journal Title: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences Volume: 377 Issue: 2136 Pages: 20170390-20170390
  • DOI: 10.1098/rsta.2017.0390
  • Peer Reviewed
• [Journal Article] Temporal gravity anomalies observed in the Tokai area and a possible relationship with slow slips (2018)
  • Author(s): Tanaka, Y., T. Suzuki, Y. Imanishi, S. Okubo, X. Zhang, M. Ando, A. Watanabe, M. Saka, C. Kato, S. Oomori, and Y. Hiraoka
  • Journal Title: Earth, Planets and Space Volume: 70 Issue: 1 Pages: 25-32
  • DOI: 10.1186/s40623-018-0797-5
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] The Third Law of Earthquake Statistics? (2017)
  • Author(s): Takahiro Hatano
  • Journal Title: JPSJ News Comments 14, 03 (2017) Volume: 14 Pages: 03-03
  • DOI: 10.7566/jpsjnc.14.03
  • Open Access
• [Journal Article] Sign Flip in the Casimir Force for Interacting Fermion Systems (2017)
  • Author(s): Antonino Flachi, Muneto Nitta, Satoshi Takada, Ryosuke Yoshii
  • Journal Title: Phys.Rev.Lett. Volume: 119 Issue: 3 Pages: 031601-031601
  • DOI: 10.1103/physrevlett.119.031601
  • Peer Reviewed
• [Journal Article] Kinetic theory of discontinuous shear thickening (2017)
  • Author(s): Hisao Hayakawa and Satoshi Takada
  • Journal Title: EPJ Web of Conferences Volume: 140 Pages: 09003-09003
  • DOI: 10.1051/epjconf/201714009003
  • Peer Reviewed / Open Access
• [Journal Article] Kinetic theory of shear thickening for a moderately dense gas-solid suspension: From discontinuous thickening to continuous thickening (2017)
  • Author(s): Hisao Hayakawa, Satoshi Takada, and Vicente Garzo
  • Journal Title: Physical Review E Volume: 96 Issue: 4 Pages: 042903-042903
  • DOI: 10.1103/physreve.96.042903
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Relationship between the size of a camphor-driven rotor and its angular velocity (2017)
  • Author(s): Yuki Koyano, Marian Gryciuk, Paulina Skrobanska, Maciej Malecki, Yutaka Sumino, Hiroyuki Kitahata, and Jerzy Gorecki
  • Journal Title: Physical Review E Volume: 96 Issue: 1 Pages: 012609-012609
  • DOI: 10.1103/physreve.96.012609
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Importance of Adaptive Multimode Lubrication Mechanism in Natural Synovial Joints (2017)
  • Author(s): T. Murakami, S. Yarimitsu, N. Sakai, K. Nakashima, T. Yamaguchi, Y. Sawae
  • Journal Title: Tribology International Volume: 印刷中 Pages: 306-315
  • DOI: 10.1016/j.triboint.2016.12.052
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Superior lubrication mechanism in poly(vinyl alcohol) hybrid gel as artificial cartilage (2017)
  • Author(s): Murakami Teruo、Yarimitsu Seido、Sakai Nobuo、Nakashima Kazuhiro、Yamaguchi Tetsuo、Sawae Yoshinori、Suzuki Atsushi
  • Journal Title: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology Volume: 231 Issue: 9 Pages: 1160-1170
  • DOI: 10.1177/1350650117712881
  • Peer Reviewed
• [Journal Article] The Influence of Proteins and Speed on Friction and Adsorption of Metal/UHMWPE Contact Pair (2017)
  • Author(s): Necas D.、Sawae Y.、Fujisawa T.、Nakashima K.、Morita T.、Yamaguchi T.、Vrbka M.、Krupka I.、Hartl M.
  • Journal Title: Biotribology Volume: 11 Pages: 51-59
  • DOI: 10.1016/j.biotri.2017.03.003
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Slip Morphology of Elastic Strips on Frictional Rigid Substrates (2017)
  • Author(s): Tomohiko G. Sano, Tetsuo Yamaguchi, and Hirofumi Wada
  • Journal Title: Physical Review Letters Volume: 118 Issue: 17 Pages: 178001-178001
  • DOI: 10.1103/physrevlett.118.178001
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Emergence and seismological implications of phase transition and universality in a system with interaction between thermal pressurization and dilatancy (2017)
  • Author(s): Suzuki, T.
  • Journal Title: Physical Review E Volume: 96 Issue: 2 Pages: 023005-023005
  • DOI: 10.1103/physreve.96.023005
  • Peer Reviewed
• [Journal Article] Homogeneous cooling state of dilute granular gases of charged particles (2017)
  • Author(s): Takada Satoshi、Serero Dan、P?schel Thorsten
  • Journal Title: Physics of Fluids Volume: 29 Issue: 8 Pages: 083303-083303
  • DOI: 10.1063/1.4993620
  • Peer Reviewed
• [Journal Article] Statistical properties of Olami-Feder-Christensen model on Barabasi-Albert scale-free network (2017)
  • Author(s): Hiroki Tanaka, Takahiro Hatano
  • Journal Title: European Physical Journal B Volume: 90 Issue: 12 Pages: 248-248
  • DOI: 10.1140/epjb/e2017-80295-0
  • Peer Reviewed
• [Journal Article] Pattern of a confined chemical garden controlled by injection speed (2017)
  • Author(s): Wagatsuma Shu、Higashi Takuro、Sumino Yutaka、Achiwa Ayumi
  • Journal Title: Physical Review E Volume: 95 Issue: 5 Pages: 1-7
  • DOI: 10.1103/physreve.95.052220
  • Peer Reviewed
• [Journal Article] SUPERIOR LUBRICATION ABILITY AND MINIMAL WEAR OF POLY (VINYL ALCOHOL) HYBRID HYDROGEL AS A NOVEL MATERIAL APPLICATION FOR ARTIFICIAL CARTILAGE (2016)
  • Author(s): T. Murakami, S. Yarimitsu, K. Nakashima, N. Sakai, T. Yamaguchi, and Y. Sawae
  • Journal Title: Bone & Joint Journal Volume: 98 (supp 9) Pages: 65-65
  • Peer Reviewed
• [Journal Article] INFLUENCE OF SYNOVIA CONSTITUENTS ON FRICTION AND WEAR IN ARTIFICIAL HYDROGEL CARTILAGE AS A NOVEL MATERIAL APPLICATION FOR JOINT PROSTHESES (2016)
  • Author(s): T. Murakami, S. Yarimitsu, K. Nakashima, T. Yamaguchi, Y. Sawae, and N. Sakai
  • Journal Title: Bone & Joint Journal Volume: 98 (supp 9) Pages: 59-59
  • Peer Reviewed
• [Journal Article] Solvent effects on the fracture of chemically crosslinked gels (2016)
  • Author(s): Y. Tanaka, R. Shimazaki, S. Yano, G. Yoshida, T. Yamaguchi
  • Journal Title: Soft Matter Volume: 12 Issue: 39 Pages: 8135-8142
  • DOI: 10.1039/c6sm01645f
  • Peer Reviewed
• [Journal Article] Effects of loading angles on stick-slip dynamics of soft sliders (2016)
  • Author(s): T. Yamaguchi, Y. Sawae, S. M. Rubinstein
  • Journal Title: Extreme Mechanics Letters Volume: 9 Pages: 331-335
  • DOI: 10.1016/j.eml.2016.09.008
  • Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
• [Presentation] Crackling noise in sheared granular matter (2017)
  • Author(s): Takahiro Hatano
  • Organizer: FRACMEET - Plasticity and failure in disordered materials
  • Int'l Joint Research / Invited
• [Presentation] Creep-like relaxation in athermal systems (2017)
  • Author(s): Takahiro Hatano
  • Organizer: International workshop on Glasses and Related Nonequilibrium Systems
  • Int'l Joint Research / Invited
• [Presentation] Crackling noise in sheared granular matter (2016)
  • Author(s): Takahiro Hatano
  • Organizer: STATPHYS Kolkata IX
  • Int'l Joint Research / Invited
• [Presentation] Rate and state friction law as derived from atomistic processes at asperities (2016)
  • Author(s): Takahiro Hatano
  • Organizer: ICTAM 2016
  • Int'l Joint Research / Invited
• [Presentation] Rate and State Friction Law and Its Scaling Property (2016)
  • Author(s): Takahiro Hatano
  • Organizer: Tribology - Gordon Research Conference
  • Int'l Joint Research / Invited