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2001 Fiscal Year Final Research Report Summary

Study on detailed rupture processes and generation mechanism of strong ground motions by dense array observations in an earthquake swarm area

Research Project

Project/Area Number 10490010
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field 広領域
Research InstitutionThe University of Tokyo

Principal Investigator

KOKETSU Kazuki  Earthquake Research Institute, The University of Tokyo, Associate Professor, 地震研究所, 助教授 (90134634)

Co-Investigator(Kenkyū-buntansha) YAMANAKA Yoshiko  Earthquake Research Institute, The University of Tokyo, Research Associate, 地震研究所, 助手 (30262083)
FURUMURA Takeshi  Earthquake Research Institute, The University of Tokyo, Associate Professor, 地震研究所, 助教授 (80241404)
KIKUCHI Masayuki  Earthquake Research Institute, The University of Tokyo, Professor, 地震研究所, 教授 (20046147)
TAKEO Minoru  Earthquake Research Institute, The University of Tokyo, Professor, 地震研究所, 助教授 (00197279)
IDE Satoshi  Earthquake Research Institute, The University of Tokyo, Research Associate, 地震研究所, 助手 (90292713)
Project Period (FY) 1998 – 2001
Keywordsearthquake swarm / strong motion observation / earthquake rupture process / underground structure / 強振動
Research Abstract

For investigating detailed rupture processes and generation mechanism of strong ground motions, we deployed a dense strong-motion observation array in the off-Ito area of the Izu peninsula region, where earthquake swarm activities were repeated and another one can be expected during the term of this project. However, any activity has not yer occurred in these four years after the previous swarm from March to June 1998, and so we also carried out mobile observations in the northern Izu islands region, where the eruption of Miyakejima induced a swarm of earthquakes in 2000. They brought us a huge dataset of strong motion records for many middle-size earthquakes including thirty-one M5 events and five M6 events.
For the off-Ito area of the Izu peninsula region, we analyze the strong motion records observed at 384 stations in the Kanto basin for the 1998 Izu Toho Oki earthquake (M5.7) immediately before the project term. Such a strike-slip event in Izu or the Sagami bay as this earthquake often generates dominant surface waves called Love waves for rather long-period strong motions in the Kanto basion, and their generation and propagation are controlled by the three-dimensional structure of the basin. We then carry out moment tensor inversions and tomographic analyzes for the observed seismograms from the earthquake swarm induced by the Miyakejima eruption. Spatio-temporal variations in the earthquake source mechanism are found in the seismically active zone, and the three-dimensional attenuation structure in the zone is also derived from the spectral amplitudes of the observed records. The analysis of the seismic motions associated with the caldera collapse indicates slow inflation and some phenomenon represented by a single force beneath the crater.

  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [Publications] 菊地正幸, 山中佳子, 纐纈一起: "三宅島2000年噴火活動に伴う長周期地震のメカニズムとその解釈"地学雑誌. 110. 204-216 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 古村孝志, 纐纈一起, 坂上実, 山中佳子, 高橋正義: "2000年伊豆諸島群発地震における式根島の震度異常と地盤増幅特性"地震2. 54. 299-308 (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Koketsu, K., M.Kikuchi: "Propagation of seismic ground motion in the Kanto basin, Japan"Science. 288. 1237-1239 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Afnimar, K.Koketsu: "Finite-difference traveltime calculation for head waves traveling along an irregular interface"Geophysical Journal International. 143. 729-734 (2000)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Koketsu, K., T.Furumura: "Imaging earthquake fault rupture and simulating seismic ground motion"Leading Edge. 18. 1414-1416 (1999)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Kikuchi, M., Y. Yamanaka and K. Koketsu: "Source process of long-period seismic pulses associated with the 2000 eruption of Miyake-jima volcano, and its implications"Journal of Geography. 110. 204-216 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Furumura, T., K. Koketsu, M. Sakaue, Y. Yamanaka and M. Takahashi: "Seismic intensity anomalies due to strong site amplification of ground motion at the Shikine-jima during the earthquake swarm at Izu Islands in 2000"Zisin 2. 54. 229-308 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Koketsu, K. and M. Kikuch: "Propagation of seismic ground motion in the Kanto basin, Japan"Science. 288. 1237-1239 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Afnimar and K. Koketsu: "Finite-difference traveltime calculation for head waves traveling along an irregular interface"Geophysical Journal International. 143. 729-734 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Koketsu, K. and T. Furumura: "Imaging earthquake fault rupture and simulating seismic ground motion"Leading Edge. 18. 1414-1416 (1999)

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

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Published: 2003-09-17  

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