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1992 Fiscal Year Final Research Report Summary

High Resolution and Three-Dimensional Investigation of Crustal Structure of an Island Arc-Toward the Deliberation of Stratified Llthospheric Tectonices(Stratotectonics)

Research Project

Project/Area Number 02102001
Research Category

Grant-in-Aid for Specially Promoted Research

Allocation TypeSingle-year Grants
Research InstitutionUniversity of Tokyo

Principal Investigator

TAIRA Asahiko  Ocean Resarch Institute,Univ.of Tokyo,Professor, 海洋研究所, 教授 (50112272)

Co-Investigator(Kenkyū-buntansha) TOKUYAMA Hidekazu  Ocean Resarch Institute,Univ.of Tokyo,Assistant Professor, 海洋研究所, 助手 (10107451)
SUYEHIRO Kiyoshi  Ocean Resarch Institute,Univ.of Tokyo,Associate Professor, 海洋研究所, 助教授 (20133928)
Project Period (FY) 1990 – 1992
KeywordsIzu-Ogasawara Island Arc / Arc Crustal Structure / Streamer Cable / Ocean Bottom Seismomter / Two-ship seismic Experiment / Tonalite / Rift Zone / Magmatic Underplating
Research Abstract

The investigation conducted in 1992 focused on seismic imaging of deep crustal structure of the Izu-Ogasawara(Bonin) Arc along the latitude 32゚.The field investigation included three vessels: R/V Hakuho-maru and Tansei-maru which belong to Ocean Research Institute of the University of Tokyo and a chartered vessel used for explosive operation. Two ship seismic experiments were conducted. Hakuho-maru being as transmitting ship and Tansei-maru as receiving ship. The experiments enabled us to obtain the data for deeper crustal images. Total fifty ocean bottom seismometers (OBS) were deployed along the line of two-ship seismic experiments. The OBS array recorded various signals including dinamite-generated seismic waves and yielded information on upper mantle seismic velocity structure underneath the island arc crust.
The results of preliminary data processing indicate that the Izu-Ogasawara Island Arc crust at this location is composed of four seismic layers: 1)2-3.5km/sec P-wave velocity layer which is dominantly composed of cover volcanicalastic sequences(Layer A1),2)4-5km/sec layer which is interpreted to be sheeted dike complex(Layer A2),3) 6.1-6.3km/sec layer of the upper crust(Layer A3),4)7.1-7.3km/sec layer which corresponds to the lower crust(Layer a4).Layer A3 is 5km thick under the fore arc region and increases thickness under the central rift zone(7-8km thick). Layer A4 shows relatively uniform thickness: about 8km thick under the fore arc and 7km thick under the central rift zone.
Layer A3 shows a range of seismic velocity typical to "granitic layer". Taking also account that the Tanzawa pluton in the Izu collision zone could well be an exposed example we interpreted Layer A3 as felsic intrusive layer possibly being composed of tonalite and granodiorite. This felsic layer might be derived from remelting of the lower crust mafic layer (including pre-existed oceanic crust ?) Layer A4 is probably composed of underplated mafic-ultra mafic intrusives.

  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] 篠原 雅尚,末広 潔,松田 滋夫,小沢 和男: "DATレコーダを用いたデジタル大容量海底地震計" 海洋調査技術学会誌. 5. (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 平 朝彦,篠原 雅尚,倉本 真一: "北部伊豆・小笠原“島弧-海溝系"" 科学(岩波書店). 62. 335-336 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 徳山 英一: "音で探る海底の姿" 「流れの可視化今・音」,可視化情報学会. 246-247 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Shipboard Scientific Party(in print): "Prelimineary Report of the Hakuho Maru Cruise KH-92-2,the Tansei Maru Cruise KT-92-7 and the Kaiko Maru-5 Cruise,Editor K.Suyehiro" Ocean Res.Inst,Univ.Tokyo, (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] M.Shinohara,K.Suyehirs,S,Matsuda,and K.Ozawa: "Digital recording ocean bottom seismometer using portable digital audio tape recorder." Journal of the Japan Society for Marine Surveys and Technology (in press). (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Taira,M.Shinohara,and S.Kuramoto: ""Island Arc-Trench System"in the northern Izu-Ogasawara Ridge." Kagaku(Iwanami). V.62. P335-336 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Tokuyama: "Seafloor morphology revealed by acoustic survey." Visualization of flow - the change wrought by time. 246-247 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] editor K.Suyehiro: Ocean Research Institute University of Tokyo. Shipboard Scientific Party, Preliminary Report of the Hakuho Maru Cruise KH-92-2, the Tansei Maru Cruise KT-92-7,and the Kaiks-Maru-5 Cruise.,

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1994-03-24  

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