GPS observation of the first month of postseismic crustal deformation associated with the 2003 Tokachi-oki earthquake (MJMA 8.0), off southeastern Hokkaido, Japan

Hiroaki Takahashi, Shigeru Nakao, Noritoshi Okazaki, Junji Koyama, Takeshi Sagiya, Takeo Ito, Fumio Ohya, Kazutoshi Sato, Yasuyoshi Fujita, Manabu Hashimoto, Yoshinobu Hoso, Teruyuki Kato, Takeshi Iinuma, Jun’ichi Fukuda, Takeshi Matsushima, Yuhki Kohno, Minoru Kasahara

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Abstract

To investigate the postseismic crustal deformation associated with the Tokachi-oki earthquake (MJMA=8.0) of 26 September 2003 in Japan Standard Time (JST), off southeastern Hokkaido, Japan, we newly established thirty GPS sites just after the mainshock in the eastern part of Hokkaido. Rapid data analysis for one month after the mainshock clearly indicated postseismic displacements only in the horizontal components. Observed maximum horizontal displacement was 6.6 cm from 28 September to 24 October, 2003. Absence of the vertical suggests that afterslip occurred in and around the coseismic fault rather than at downdip extension. Time series of coordinates are characterized by logarithmic decay functions with 4-11 days relaxation times. This suggests that postseismic deformation was due to afterslip on the fault following the large earthquake.

Original languageEnglish
Pages (from-to)377-382
Number of pages6
Journalearth, planets and space
Volume56
Issue number3
DOIs
Publication statusPublished - Jan 1 2004

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science

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