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Monitering of submarine crustal activity by ocean acoustic waves and ocean-seismic waves

Research Project

Project/Area Number 10440125
Research Category

Grant-in-Aid for Scientific Research (B).

Allocation TypeSingle-year Grants
Section一般
Research Field 固体地球物理学
Research InstitutionUniversity of Tokyo

Principal Investigator

FUKAO Yoshio  Univ.Tokyo, Earthq.Res.Inst., Professor, 地震研究所, 教授 (10022708)

Co-Investigator(Kenkyū-buntansha) OKAMOTO Taro  Tokyo Institute of Technology, Geophys. Dept., Research Associate, 理学部, 助手 (40270920)
KANAZAWA Toshihiko  Univ.Tokyo, Earthq.Res.Inst., Professor, 地震研究所, 教授 (30114698)
KASAHARA Junzo  Univ.Tokyo, Earthq.Res.Inst., Professor, 地震研究所, 教授 (70012953)
KANJO Kenji  Meteorological Research Inst., Senior Researcher, 気象研究所, 主任研究官
EGUCHI Takao  National Res.Inst.for Earth Sci. & Disaster Prevention, Senior Researcher, 主任研究員
綿田 辰吾  東京大学, 地震研究所, 助手 (30301112)
Project Period (FY) 1998 – 2000
Project Status Completed (Fiscal Year 2000)
Budget Amount *help
¥13,000,000 (Direct Cost: ¥13,000,000)
Fiscal Year 2000: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1999: ¥4,400,000 (Direct Cost: ¥4,400,000)
Fiscal Year 1998: ¥7,000,000 (Direct Cost: ¥7,000,000)
Keywordssubmarine volano / OBS / ocean acoustic waves / seismic waves / 海底 / T-phase
Research Abstract

(1) Study of anomalous submarine earthquakes by ocean acoustic waves
An anomalous submarine earthquake with the CLVD mechanism happened near Torishima Island. We found that this earthquake generated a series of ocean acoustic wave trains. The analysis of the OBS records of these waves lead us to conclude that the crustal deformation associated with the CLVD earthquake squeezed magma fluid in the source region upward, that the ascent of the magma fluid generated volcanic earthquakes whose foci migrated upward progressively, and that these earthquakes generated a series of ocean acoustic wave trains.
(2) Detection of submarine seismic activity by ocean-coupled shear waves
We detected a series of events that generated "T phase-like" waves and found that they were the shallowest submarine seismic activity in a very localized area off Boso, Japan. Our theoretical study indicates that the observed "T-like" waves are the sediment-trapped shear waves coupled with ocean acoustic waves multiplly reflected at the sea surface. We named these waves "ocean-coupled sedimentary shear waves" which should be useful to detect any submarine shallowest activity.
(3) Study of submarine volcanic activity by ocean acoustic waves
The seismograms of OBS cable arrays often record ocean acoustic waves due to submarine volcanic activities. We located the origins of these waves near the northern end of the Mariana volcanic arc. The analysis of these waves indicate that the volcanic activity often starts gradually and stops abruptly and that ocean acoustic waves become more rich in lower-frequency content as the activity becomes more intense. We also detected a semi-diurnal migration of the T-phase origins, which is perhaps an apparent one due to the tidal effect of the velocity structure of the ocean.

Report

(4 results)
  • 2000 Annual Research Report   Final Research Report Summary
  • 1999 Annual Research Report
  • 1998 Annual Research Report
  • Research Products

    (18 results)

All Other

All Publications (18 results)

  • [Publications] Sugioka,H.,Y.Fukao et al.: "Volcanic events associated with an enigmatic submarine eartquake"Geophys.J.Int.. 142. 361-370 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Sugioka,H.,Y.Fukao et al.: "Detection of shallowest submarine seismicity by acoustic-coupled-shear waves"J.Geophys.Res.. (in press). (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Sugioka, H., Y.Fukao et al.: "Volcanic associated with an enigmatic Submarine earthquake"Geophys.J.Int.. 142. 361-370 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Sugioka, H., Y.Fukao et al.: "Detection of shallowest submarine Seismicity by acoustic-coupled-shear waves"J.Geophys.Res.. (in press). (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Sugioka,H.,Y.Fukao et al.: "Volcanic events associated with an enigmatic submarine eartquake"Geophys.J.Int.. 142. 361-370 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] Sugioka,H.,Y.Fukao et al.: "Detection of shallowest submarine seismicity by acoustic-coupled-shear waves"J.Geophys.Res.. (in press). (2001)

    • Related Report
      2000 Annual Research Report
  • [Publications] Nawa,K.N,Suda Y.Fukao et al.: "Incessant excitation of the Earth's free oscillations"Earth Plants Space. 50. 3-8 (1998)

    • Related Report
      1999 Annual Research Report
  • [Publications] Kasahara,J.,T.Sato,H.Utada et al.: "A New approach to real time measurements at Izu-Bonin Trench using TPC-1, dimission telecommuncation cable"Proc. Underwater Technology. 442-447 (1998)

    • Related Report
      1999 Annual Research Report
  • [Publications] Sugioka,H.,Y.Fukao,T.Kanazawa and K.Kanjo: "Volcanic events associated with an enigmatic submarine earthquake"Geophys.J.Int.. (in press). (2000)

    • Related Report
      1999 Annual Research Report
  • [Publications] 綿田辰吾、坪井誠司、深尾良夫: "海半球プロジェクトデータセンター"月刊地球. 20. 205-209 (1998)

    • Related Report
      1999 Annual Research Report
  • [Publications] Eguchi T.,Y.Fujinawa,E.Fujita,S.I.Iwasaki,I..Watabe,and H.Fujiwara: "A Real-Time Observation Network of Ocean-Bottom-Seismometers Deployed at the Sagami Trough Subduction Zone, Central Japan"Mar,Geophys.Res.. 20/2. 70-94 (1998)

    • Related Report
      1999 Annual Research Report
  • [Publications] Okamoto,T.,and H.Takenaka: "A reflection/transmission matrix formulation for seismoacoustic scattering by at irregular fluid-solid interface"Geophysical Journal International. 139. 531-546 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] Suda,N., N.Nawa and Y.Fukao: "Earth's background free oscillations" Science. 279. 2089-2091 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Fukao,Y., E.Fujita, S.Hori and K.Kanjo: "Response of a volcanic conduit to step-like change in magma pressure" Geophys.Res.Lett.25. 105-108 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Nawa,K, K.Suda, Y.Fukao, T.Sato et al.: "Incessant excitation of the Earth's free oscillations" Earth Planets Space. 50. 3-8 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Tajima,F., Y.Fukao, M.Obayashi and T.Sakurai: "Evaluation of slab images in the northwestern Pacific" Earth Planet Space (OHP speical issue). 50. 953-964 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] Obayashi,M.and Y.Fukao: "P and PcP travel time tomography for the core-mantle boundary" J.Geophys.Res.102. 17825-17841 (1997)

    • Related Report
      1998 Annual Research Report
  • [Publications] Nawa,K, Y.Fukao, R.Shichi and Y.Murata: "Inversion of gravity data for the terrain density distribution in southwest Japan" J.Geophys.Res.102. 27703-27719 (1997)

    • Related Report
      1998 Annual Research Report

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Published: 1998-04-01   Modified: 2016-04-21  

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