Investigation of low-frequency earthquake/tremor in shallow portion of subduction zone: Marine earthquake observation in the Cascadia subuction zone

• Project/Area Number: 23253005
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 海外学術
• Research Field: Solid earth and planetary physics
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: KODAIRA Shuichi 独立行政法人海洋研究開発機構, 地震津波海域観測研究開発センター, 研究開発センター長 (80250421)
• Co-Investigator(Renkei-kenkyūsha): OBANA Koichiro 独立行政法人海洋研究開発機構, 地震津波海域観測研究開発センター, 主任研究員 (10359200) ; TAKAHASHI Narumi 独立行政法人海洋研究開発機構, 地震津波海域観測研究開発センター, 研究開発センター長代理 (70359131) ; MIURA Seiichi 独立行政法人海洋研究開発機構, 地震津波海域観測研究開発センター, グループリーダー (00371724) ; TAKAHASHI Tsutomu 独立行政法人海洋研究開発機構, 地震津波海域観測研究開発センター, 主任研究員 (90435842) ; YAMAMOTO Yojiro 独立行政法人海洋研究開発機構, 地震津波海域観測研究開発センター, 研究員 (10540859) ; SUETSUGU Daisuke 独立行政法人海洋研究開発機構, 地球内部ダイナミクス研究分野, 分野長 (20359178)
• Project Period (FY): 2011-04-01 – 2015-03-31
• Project Status: Completed (Fiscal Year 2014)
• Budget Amount: ¥50,700,000 (Direct Cost: ¥39,000,000、Indirect Cost: ¥11,700,000); Fiscal Year 2014: ¥7,410,000 (Direct Cost: ¥5,700,000、Indirect Cost: ¥1,710,000); Fiscal Year 2013: ¥12,220,000 (Direct Cost: ¥9,400,000、Indirect Cost: ¥2,820,000); Fiscal Year 2012: ¥29,900,000 (Direct Cost: ¥23,000,000、Indirect Cost: ¥6,900,000); Fiscal Year 2011: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
• Keywords: 地震 / 津波 / カスカディア地震発生帯 / 低周波地震 / 沈み込み帯 / スローな地震 / 海洋地殻 / 地震観測

Outline of Final Research Achievements

Cascadia margin is a seismogenic subduction zone with a history of the repeated occurrence of megathrust earthquakes. The Cascadia subduction zone has many similarities with the Nankai subduction zone. We conducted earthquake observation using ocean bottom seismographs as a comparable study between Cascadia and Nankai subduction seismogenic zones. Our results show that during the observation period most of the offshore seismicity occurred in the subducting plate along the Nootka fault zone. Otherwise seismicity was extremely low, with no earthquakes located along the shallow, seismogenic part of the Cascadia megathrust. The lack of interplate seismicity may indicate complete healing and locking of the megathrust over three centuries after the great earthquake of 1700 and a somewhat lower degree of structure heterogeneity.

Research Products

• [Journal Article] Earthquake Activity in Northern Cascadia Subduction Zone Off Vancouver Island Revealed by Ocean‐Bottom Seismograph Observations (2015)
  • Author(s): Obana, K., Scherwath, M., Yamamoto, Y., Kodaira, S., Wang, K., Spence, G., Riedel, M., and Kao, H.
  • Journal Title: Bull. Seismol. Soc. Am Volume: 105 Issue: 1 Pages: 489-495
  • DOI: 10.1785/0120140095
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Seafloor seismometers monitor northern Cascadia earthquakes (2011)
  • Author(s): Scherwath
  • Journal Title: EOS, Transactions American Geophysical Union Volume: 92 Issue: 47 Pages: 421-440
  • DOI: 10.1029/2011eo470001
  • Peer Reviewed
• [Presentation] SeaJade:カナダ・カスカディア地震発生帯における海底地震観測 (2015)
  • Author(s): 尾鼻浩一郎・小平秀一・山本揚二朗・高橋努・利根川貴志，Kelin Wang, Michael Riedel, Honn Kao, Martin Scherwath, George Spence, Jesse Hutchinson, Ayodeji Paul Kuponiyi, 寺田育正・西條暁里
  • Organizer: Blue Earth’15
  • Place of Presentation: 東京海洋大学品川キャンパス、東京都港区
  • Year and Date: 2015-03-20
• [Presentation] Ps変換波を用いたカスカディア沈み込み帯における海底堆積物の異方性構造の推定 (2014)
  • Author(s): 利根川 貴志, 尾鼻 浩一郎, 山本 揚二朗, 小 平 秀一
  • Organizer: 日本地震学会2014年秋季大会
  • Place of Presentation: 新潟市朱鷺メッセ, 新潟県新潟市
  • Year and Date: 2014-11-26
• [Presentation] SeaJade Earthquake Observations in Cascadia Subduction Zone off Vancouver Island (2014)
  • Author(s): Koichiro Obana, Shuichi Kodaira, Yojiro Yamamoto, Tsutomu Takahashi, Kelin Wang, Michael Riedel, Honn Kao, Martin Scherwath, George Spence, Jesse Hutchinson, Ayodeji Paul Kuponiyi, Michael Bostock
  • Organizer: IRIS Amphibious Array Facility Workshop
  • Place of Presentation: Snowbird, UT, United States
  • Year and Date: 2014-10-24
• [Presentation] Shear wave anisotropy within marine sediments in the Cascadia subduction zone derived from Ps converted waves (2014)
  • Author(s): Takashi Tonegawa, Koichiro Obana, Yojiro Yamamoto, Shuichi Kodaira, Kelin Wang, Michael Riedel, Honn Kao, George Spence
  • Organizer: IRIS Amphibious Array Facility Workshop
  • Place of Presentation: Snowbird, UT, United States
  • Year and Date: 2014-10-24
• [Presentation] Northern Cascadia Seismicity From Ocean Floor Observations - Campaign and Permanent Seismic Experiments (2013)
  • Author(s): Heesemann, M, Scherwath, M, Kodaira, S, Obana, K, Yamamoto, Y, Spence, G, Riedel, M, Rogers, G C,Wang, K, McGuire, J J
  • Organizer: Fall Meeting, AGU
  • Place of Presentation: San Francisco, CA, USA
  • Year and Date: 2013-12-10
• [Presentation] Seismic Structures Beneath the Deformation Front of the Northern Cascadia Subduction Zone: Preliminary Results from the SeaJade Project (2013)
  • Author(s): Hutchinson, J A, Kao, H, Obana, K, Spence, G
  • Organizer: Fall Meeting, AGU
  • Place of Presentation: San Francisco, CA, USA
  • Year and Date: 2013-12-10
• [Presentation] Northern Cascadia Seismicity From Ocean Floor Observations ― Campaign and Permanent Seismic Experiments
  • Author(s): Heesemann, M, Scherwath, M, Kodaira, S, Obana, K, Yamamoto, Y, Spence, G D, Riedel, M, Rogers, G C, Wang, K, McGuire, J J
  • Organizer: 2013 Fall Meeting, AGU
  • Place of Presentation: Moscone Center,San Francisco,USA
• [Presentation] Seismic Structures Beneath the Deformation Front of the Northern Cascadia Subduction Zone: Preliminary Results from the SeaJade Project
  • Author(s): Hutchinson, J A*, Kao, H, Obana, K, Spence, G D
  • Organizer: 2013 Fall Meeting, AGU
  • Place of Presentation: Moscone Center,San Francisco,USA