• Search Research Projects
  • Search Researchers
  • How to Use
  1. Back to project page

1993 Fiscal Year Final Research Report Summary

A SEISMOLOGICAL STUDY ON THE MAGMA CHAMBER OF UNZEN VOLCANO

Research Project

Project/Area Number 04452066
Research Category

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

Allocation TypeSingle-year Grants
Research Field 固体地球物理学
Research InstitutionKYUSHU UNIVERSITY

Principal Investigator

SHIMIZU Hiroshi  KYUSHU UNIV.F.OF SCI., ASSOCIATE PROFESSOR, 理学部, 助教授 (50178985)

Co-Investigator(Kenkyū-buntansha) OHATA Kazuya  KYUSHU UNIV.F.OF SCI., PROFESSOR, 理学部, 教授 (10037202)
MATSUSHIMA Takeshi  KYUSHU UNIV.F.OF SCI., RESEARCH ASSOCIATE, 理学部, 助手 (40222301)
MATSUWO Norimichi  KYUSHU UNIV.F.OF SCI., RESEARCH ASSOCIATE, 理学部, 助手 (70108645)
UMAKOSHI Kodo  KYUSHU UNIV.F.OF SCI., RESEARCH ASSOCIATE, 理学部, 助手 (30232888)
Project Period (FY) 1992 – 1993
KeywordsUnzen Volcano / Mt. Fugen / Eruption / Seismic activity / Magma chamber / Ascending pass of magma / Lava dome / Low-frequency earthquake
Research Abstract

We tried to reveal the location and movement of magma beneath Unzen Volcano by analyzing volcanic earthquakes.
An earthquake swarm occured near the center of the Chijiwa bay, about 20 km west of Mt. Fugen, about a year before the eruption. The souce region of the swarm moved toward Mt. Fugen, and the eruptive actiity started. One remarkable feature of the hypocenter distribution is the possibility that itis delineating a ring-fault corresponding to the caldera wall in the Chijiwa bay, which suggests the existence of magma chamber beneath the bay. Another notable feature is alignment of hypocenters between the bay and Mt. Fugen, and it may represent the ascending path of magma. Geodetic measurements after the lava dome emergence showed that a depression source located at the lower border of the hypocenter alignment. Furthermore seismic S-waves passing beneath the hypocenter region were strongly attenuated. These are the evidence that supports our model for the magma feeding system of Unzen Volcano.
The pattern of seismicity drastically changed in association with the laba dome emergence. Swarm activity of low-frequency (LF) earthquakes began to occur beneath the summit craters. By contrast, seismic activity around the volcano declined extremely after the dome appearance. This is probably because the excess pressure of magma decreased owing to the lava extrusion. The LF eartquakes were activated before the extrusion of new lobes and during the endogeneous growth of the lava dome. Our seismic observation in the vicinity of the dome revealed that the LF earthquakes were generated by stick-slips of the lava blocks due to magma intrusion into the dome.

  • Research Products

    (14 results)

All Other

All Publications (14 results)

  • [Publications] 大見士朗・清水洋: "雲仙火山とその周辺地域の地震波速度構造" 火山. 37. 133-145 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 大学合同観測班地球物理班(執筆者:清水洋): "雲仙火山1990〜1992年噴火の地球物理観測(その1)" 火山. 37. 209-215 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 清水洋: "雲仙火山モニタリング" 物理探査. 45. 458-466 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 馬越孝道・他: "雲仙火山の地震活動II" 自然災害西部地区部会報論文集. 14. 1-8 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 太田一也: "1990-1992年雲仙岳噴火活動" 地質学雑誌. 99. 835-854 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Kodo UMAKOSHI et al.: "Seismic observations and infrared thermal surveys of the 1990-1993 eruption of Unzen Volcano" Journal of Natural Disaster Science. 15(印刷中). (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Edited by T.Yanagi,H.Okada and K.Ohta: "Unzen Volcano,the 1990-1992 Eruption" 西日本新聞社&九州大学出版会, 137 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] S.Ohmi: "Three dimensional velocity structure in the Unzen volcanic region" J.Volcanol. Soc. Japan. 37. 133-145 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Geophysical Party, Joint University Research Group (Author : H.Shimizu): "Geophysical observation of the 1990-1992 eruption at Unzen Volcano (Part 1)" J.Volcanol. Soc. Japan. 37. 209-215 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Shimizu: "Monitoring of the eruptive activity at Unzen Volcano" BUTSURI-TANSA. 45. 458-466 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Umakoshi: "Seismic Activity of Unzen Volcano II" Western Regional Div. Rep. of Natural Disaster Science. 14. 1-8 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Ohta: "The 1990-1992 eruptive activity at Unzen Volcano" Jour. Geol. Soc. Japan. 99. 835-854 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Umakoshi: "Seismic observations and infrared thermal surveys of the 1990-1993 eruption of Unzen Volcano" Journal of Natural Disaster Science. 15 (in press). (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Edited by T.Yanagi et al: The Nishinippon & Kyushu University. Unzen Volcano the 1990-1992 Eruption, 137 (1992)

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

URL: 

Published: 1995-03-27  

Information User Guide FAQ News Terms of Use Attribution of KAKENHI

Powered by NII kakenhi