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

2014 Fiscal Year Final Research Report

• 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
• Keywords: 地震 / 津波 / カスカディア地震発生帯 / 低周波地震

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.

Free Research Field

固体地球惑星物理学