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Earth, Planets and Space

, Volume 57, Issue 5, pp 411–416 | Cite as

Multi-planar structures in the aftershock distribution of the Mid Niigata prefecture Earthquake in 2004

  • Shigeki AokiEmail author
  • Masaki Nishi
  • Koji Nakamura
  • Tetsuo Hashimoto
  • Sumio Yoshikawa
  • Hidemi M. Ito
Open Access
Letter

Abstract

A shallow destructive inland earthquake of M6.8 occurred on Oct. 23, 2004 (JST) in the middle part of Niigata prefecture, Japan. The aftershock activity was high as compared to those of the other shallow inland earthquakes in Japan. We relocated the sources of the main shock and aftershock activity by adopting the double-difference earthquake location algorithm. The precisely relocated hypocenter distribution shows that there are a doubleplanar structure with a distance 5 km in parallel dipping in WNW with about 50 degrees and a single-planar structure dipping in ESE with about 15 degrees. The upper and lower planes of the double plane began to be formed with the main shock and the largest aftershock of M6.5, respectively, while the ESE dipping plane began to be formed with the 3rd largest aftershock of M6.1. The three planes represent the fault planes of the large events mentioned above. The aftershock distribution is found to be a superposition of the fault planes of the main shock and the large aftershocks. The high aftershock activity is attributed to the formation of the fault planes.

Key words

The Mid Niigata prefecture Earthquake in 2004 aftershock distribution double-planed seismic zone fault plane double-difference earthquake location algorithm 

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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2005

Authors and Affiliations

  • Shigeki Aoki
    • 1
    Email author
  • Masaki Nishi
    • 2
  • Koji Nakamura
    • 2
  • Tetsuo Hashimoto
    • 2
  • Sumio Yoshikawa
    • 1
  • Hidemi M. Ito
    • 2
  1. 1.Seismology and Volcanology Research DepartmentMeteorological Research InstituteTsukuba, IbarakiJapan
  2. 2.Seismological and Volcanological DepartmentJapan Meteorological AgencyTokyoJapan

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