Open Access

A dense GPS observation immediately after the 2004 mid-Niigata prefecture earthquake

  • Hiroaki Takahashi19Email author,
  • Takeshi Matsushima29,
  • Teruyuki Kato39,
  • Akira Takeuchi49,
  • Teruhiro Yamaguchi19,
  • Yuhki Kohno29,
  • Takeshi Katagi29,
  • Jun’ichi Fukuda39,
  • Kazuya Hatamoto49,
  • Ryousuke Doke49,
  • Yuki Matsu’ura49 and
  • Minoru Kasahara19
Earth, Planets and Space201457:BF03351844

Received: 15 February 2005

Accepted: 30 June 2005

Published: 20 June 2014


To investigate the postseismic crustal deformation associated with the 2004 mid-Niigata prefecture earthquake (M6.8), we newly started GPS observation to fill a gap of the nationwide continuous GPS network. Our GPS sites were mainly distributed in the focal region without permanent GPS site, and succeeded in obtaining the postseismic deformation. Coseismic displacements of two aftershocks were clearly detected because of immediate observation. Estimated fault parameters of the aftershock (M5.9) on November 8 occurring just beneath our GPS network indicated that geodetic data could be explained by either east- or west-dipping fault model inferred from detailed aftershock data. Moreover, clear postseismic deformation, which could be characterized by a logarithmic decay function, was observed. This signal probably suggests possible aseismic slip. Our results indicated that dense GPS observation could give important and interesting data to clarify the properties of shallow inland middle-size earthquakes.

Key words

The 2004 mid-Niigata prefecture earthquakeGPSpostseismic deformationfault modelaseismic slip