Elucidate a tidal phenomenon to improve the mid-term risk evaluation for the occurence of large thrust-type earthquakes

• Project/Area Number: 15K17746
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: The University of Tokyo
• Principal Investigator: Tanaka Yoshiyuki 東京大学, 大学院理学系研究科(理学部), 准教授 (90508350)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2017: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000); Fiscal Year 2016: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000); Fiscal Year 2015: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
• Keywords: スロースリップ / 潮汐 / 海溝型地震 / 地殻変動 / 重力

Outline of Final Research Achievements

An 8.85-year periodicity associated with the lunar orbital motion is seen in the occurrence time of historical large earthquakes with M>7.5 over eastern Japan. However, why such a weak tide triggers earthquakes has not been known. In this study, we found a mechanism that can explain how the effect of a slow, weak tide is enhanced. We confirmed that decadal variations in the ocean and crustal fluid flow, when combined with short-period stronger tides, accelerates/decelerates the plate subduction speed near the source region of mega-thrust earthquakes, resulting in the change of the probability of earthquake occurrence.

Academic Significance and Societal Importance of the Research Achievements

海溝型大地震の発生時期の確率的な見積もりには、３０年以内に何十パーセントという表現がよく用いられる。本研究は、潮汐が地震を誘発するメカニズムを明らかにすることで、地震がより起きやすい時期、起きにくい時期を数年の時間スケールで見積もることのできる中期予測の手法を切り開くものである。本研究の結果は、例えば、海洋変動の一例である黒潮大蛇行を予測することで、その後の地震発生確率の変動をある程度予測することが可能になることを示唆している。

Research Products

• [Int'l Joint Research] German Geoscience Center (GFZ)(ドイツ)
• [Int'l Joint Research] Dublin Institute for Advanced Studies(アイルランド)
• [Int'l Joint Research] ドイツ地球科学センター（GFZ)(ドイツ)
• [Journal Article] Surface Loading of a Self-Gravitating, Laterally Heterogeneous Elastic Sphere: Preliminary Result for the 2D Case (2019)
  • Author(s): Tanaka, Y., V. Klemann, and Z. Martinec
  • Journal Title: International Association of Geodesy Symposia Volume: ー Pages: 1-7
  • DOI: 10.1007/1345_2019_62
  • ISBN: 9783030542665, 9783030542672
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] 光格子時計の地震・火山研究応用の可能性を探る (2018)
  • Author(s): 田中愛幸, 黒石裕樹, 香取秀俊
  • Journal Title: 地震ジャーナル Volume: 65 Pages: 36-44
  • NAID: 40021650429
  • Open Access
• [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] Two long-term slow slip events around Tokyo Bay found by GNSS observation during 1996-2011 (2017)
  • Author(s): Tanaka, Y., and S. YABE
  • Journal Title: Earth Planets and Space Volume: 69 Issue: 1 Pages: 43-52
  • DOI: 10.1186/s40623-017-0628-0
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] 重力ポテンシャル差計としての光格子時計の地球物理応用の可能性 (2016)
  • Author(s): 田中愛幸
  • Journal Title: 光学 Volume: 45 Pages: 259-263
  • Peer Reviewed
• [Journal Article] Earthquake potential revealed by tidal influence on earthquake size-frequency statistics (2016)
  • Author(s): Ide, S., S. Yabe, and Y. Tanaka
  • Journal Title: Nature Geoscience Volume: 9 Issue: 11 Pages: 834-837
  • DOI: 10.1038/ngeo2796
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] An estimate of fluctuating plate subduction velocities caused by tidal modulations and decadal variations in the ocean (2015)
  • Author(s): Tanaka Y., S. Yabe and S. Ide
  • Journal Title: Earth Planets and Space Volume: 67 Issue: 1 Pages: 141-151
  • DOI: 10.1186/s40623-015-0311-2
  • Peer Reviewed / Open Access
• [Journal Article] Tidal sensitivity of tectonic tremors in Nankai and Cascadia subduction zones (2015)
  • Author(s): Yabe, S., Y. Tanaka, H. Houston, and S. Ide
  • Journal Title: J. Geophys. Res. Volume: 120 Issue: 11 Pages: 7587-7605
  • DOI: 10.1002/2015jb012250
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Temporal gravity anomalies observed in the Tokai area and a possible relationship with slow slips (2018)
  • Author(s): Yoshiyuki Tanaka, Takehito Suzuki, Yuichi Imanishi, Shuhei Okubo, Xinlin Zhang, Miwako Ando, Atsushi Watanabe, Mamoru Saka, Chiaki Kato, Shuichi Oomori and Yoshifumi Hiraoka
  • Organizer: JpGU-AGU-EGU-AOGS joint meeting
  • Int'l Joint Research
• [Presentation] 光格子時計の測地応用の可能性 (2018)
  • Author(s): 田中愛幸, 黒石祐樹, 香取秀俊
  • Organizer: 日本測地学会第130回講演会
• [Presentation] Effects of laterally heterogeneous elastic structures on surface loading -a preliminary result for a rotationally symmetric spherical earth model (2018)
  • Author(s): Tanaka, Y., V. Klemann, Z. Martinec
  • Organizer: 2018 American Geoiphysical Union Fall Meeting
  • Int'l Joint Research
• [Presentation] A spectral finite-element approach to surface loading of a self-gravitating, laterally heterogeneous elastic sphere -preliminary result for the 2D case (2018)
  • Author(s): Tanaka, Y., V. Klemann, Z. Martinec
  • Organizer: The IX Hotine-Marussi Symposium
  • Int'l Joint Research
• [Presentation] Could decadal variations in the ocean accelerate plate subduction in the Japan Trench before the 2011 M9 Tohoku earthquake? (2017)
  • Author(s): Tanaka, Y. S. Yabe, S. Ide
  • Organizer: JPGU-AGU joint meeting
  • Int'l Joint Research
• [Presentation] Anomalous gravity changes observed during long-term slow slip events and a possible interpretationbased on fluid flow (2017)
  • Author(s): Yoshiyuki Tanaka, Yuichi Imanishi, Shuhei Okubo, Kazunari Nawa, Yoshiaki Tamura, Kenji Yoshida
  • Organizer: IAG-IASPEI joint meeting
  • Int'l Joint Research
• [Presentation] Gravity changes observed during the long-term slow slip events in the Tokai area (2017)
  • Author(s): Yoshiyuki Tanaka, Yuichi Imanishi, Shuhei Okubo, Miwako Ando, Atsushi Watanabe, Kenji Yoshida
  • Organizer: 日本地震学会
• [Presentation] Relativistic geodesy in plate subduction zones -applications to crustal deformation monitoring (2016)
  • Author(s): Tanaka, Y.
  • Organizer: ERATO International workshop: Challenges in Precision Science
  • Place of Presentation: 東京大学（東京都文京区）
  • Year and Date: 2016-01-25
  • Int'l Joint Research / Invited
• [Presentation] 光格子時計を用いた重力ポテンシャル計測の測地学・地震学・火山学への応用の可能性 (2016)
  • Author(s): 田中愛幸
  • Organizer: 地球惑星科学連合2016年度連合大会
  • Place of Presentation: 幕張メッセ（千葉県千葉市）
• [Presentation] 余効変動をGRACEで観測することで粘性の水平不均質を検出できるか？ (2016)
  • Author(s): 田中愛幸
  • Organizer: 日本測地学会
  • Place of Presentation: 奥州市文化会館（岩手県奥州市）
• [Presentation] 1996年から2011年のGNSSデータから明らかになった関東地方の２つの長期的なすべりイベント (2016)
  • Author(s): 田中愛幸・矢部優・井出哲
  • Organizer: 日本地震学会
  • Place of Presentation: 名古屋国際会議場（愛知県名古屋市）
• [Presentation] Long-term slow slip events in the Kanto district in Japan found by GNSS observation during 1996-2011 and relationships with variations in the ocean bottom pressure (2016)
  • Author(s): TANAKA Yoshiyuki, YABE Suguru, IDE Satoshi
  • Organizer: 2016 American Geophysical Union Fall Meeting
  • Place of Presentation: San Francisco (USA)
  • Int'l Joint Research
• [Presentation] Some applications of satellite gravity data to seismological problems in the future (2015)
  • Author(s): Tanaka, Y.
  • Organizer: American Geophysical Union Fall Meeting
  • Place of Presentation: San Francisco (USA)
  • Year and Date: 2015-12-14
  • Int'l Joint Research / Invited
• [Presentation] 衛星重力データを用いて巨大地震の余効変動メカニズムを探る (2015)
  • Author(s): 田中愛幸・長谷川崇・鶴岡弘・Volker Klemann・Zdenek Martinec
  • Organizer: 日本地震学会
  • Place of Presentation: 神戸国際会議場（兵庫県神戸市）
  • Year and Date: 2015-10-26
• [Presentation] 潮汐・非潮汐海洋変動によるプレート沈み込み速度のゆらぎ―東海地方の例 (2015)
  • Author(s): 田中愛幸, 矢部 優, 井出 哲
  • Organizer: 日本測地学会
  • Place of Presentation: 九州大学（福岡県福岡市）
  • Year and Date: 2015-10-14
• [Presentation] Tidal and non-tidal modulations of tremors and great earthquakes (2015)
  • Author(s): Tanaka, Y.
  • Organizer: International workshop on slow earthquakes
  • Place of Presentation: 名古屋大学（愛知県名古屋市）
  • Year and Date: 2015-09-24
  • Int'l Joint Research
• [Presentation] Physical modeling of gravity field variations to explore mechanisms of great earthquakes (2015)
  • Author(s): Tanaka, Y.
  • Organizer: 26th IUGG General Assembly （IAG Guy Bomford Prize commemorative ｌecture）
  • Place of Presentation: Prague, the Czech Republic
  • Year and Date: 2015-06-22
  • Int'l Joint Research / Invited
• [Presentation] Spectral-finite element approach to post-seismic relaxation in a spherical compressible Earth: application to the 2004 Sumatra-Andaman earthquake (2015)
  • Author(s): Tanaka, Y.
  • Organizer: 26th IUGG General Assembly
  • Place of Presentation: Prague, the Czech Republic
  • Year and Date: 2015-06-22
  • Int'l Joint Research
• [Presentation] 潮汐と海洋の長期変動によるプレート沈み込み速度のゆらぎを見積もる (2015)
  • Author(s): 田中 愛幸, 矢部 優, 菊池 亮佑, 井出 哲
  • Organizer: 日本地球惑星科学連合2015年度連合大会
  • Place of Presentation: 幕張メッセ（千葉県千葉市）
  • Year and Date: 2015-05-24
  • Invited