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2000 Fiscal Year Final Research Report Summary

Seismo-Tectonic Studies on Split Subduction of the Steeply Dipping Plate

Research Project

Project/Area Number 09440161
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 InstitutionKagoshima University

Principal Investigator

KAKUTA Toshiki  Kagoshima University, Faculty of Science, Professor, 理学部, 教授 (40041222)

Co-Investigator(Kenkyū-buntansha) YAKIWARA Hiroshi  Kagoshima University, Faculty of Science, Research Associate, 理学部, 助手 (60295235)
MIYAMACHI Hiroki  Kagoshima University, Faculty of Science, Associate Professor, 理学部, 助教授 (30182041)
GOTO Kazuhiko  Kagoshima University, Faculty of Science, Associate Professor, 理学部, 助教授 (20244220)
Project Period (FY) 1997 – 2000
Keywordssplit subduction / left-lateral strike slip / narrow seismic zone / block boundary of seismicity / Tokara submarine canyon / mantle wedge / Amami Oshima / OBS observation
Research Abstract

The 1997 Northwestern Kagoshima Earthquakes (M6.5, 6.3) suggest a left-lateral strike slip movement due to subduction of the Philippine Sea plate splitted into several blocks ; they occurred in a narrow seismic zone through the crust in South Kyushu with a strike of nearly E-W and a block boundary of seismicity is found on the east extension of the zone in a region of Hyuganada. It is probably another evidence that westward migration of swarm type earthquakes was observed along the zone from January through July, 1995. Then we investigated especially crustal structures along the seismic zone on land and west off Kyushu.
Seismic activity in and around the Tokara submarine canyon, north off Amami Oshima, Ryukyu islands was investigated in detail by deploying not only OBS's but also temporary stations, because a left-lateral tectonic line is geologically supposed along the canyon and because dip angles of the subducting plate are iferred to differ largely on the both sides with each other. From the temporary observation in Amami Oshima, we found crustal earthquakes at depths of 11 to 19km and active earthquakes in a mantle wedge where any earthquakes have never been found in Kyushu except the east region off Tanegashima island. The subducting plate is also estimated at depths of 40-50 km with a low dip angle of about 25° under the island. From the observation of 10 OBS's and 9 land stations deployed aroud the Tokara submarine canyon, any clear difference was, however, not found in dip angle between both sides of the canyon, although some clusters of crustal and intraplate earthquakes were found along the canyon.

  • Research Products

    (4 results)

All Other

All Publications (4 results)

  • [Publications] 宮町宏樹: "1997年鹿児島県北西部地震の臨時余震観測"北大地球物理学研究報告. 61. 85-97 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] MIYAMACHI Hiroki: "Fine structure of aftershock distribution of the 1997 Northwestern Kagoshima Earthquakes with a three-dimensional velocity model."Earth Planets Space. 51. 233-246 (1999)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] MIYAMACHI Hiroki.: "Temporary seismic observation of aftershocks for the 1997 Northwestern Earthquakes in Kagoshima Prefecture"Geophys.Bull.Hokkaido Univ.. 61. 85-97 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] MIYAMACHI Hiroki.: "Fine structure of aftershock distribution of the 1997 Northwestern Kagoshima Earthquakes with a three-dimensional velocity model"Earth Planets Space. 51-4. 233-246 (1999)

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

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Published: 2002-03-26  

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