Anomalous depth dependency of the stress field in the 2007 Noto Hanto, Japan, earthquake: Potential involvement of a deep fluid reservoir

Aitaro Kato, Shinichi Sakai, Takashi Iidaka, Takaya Iwasaki, Eiji Kurashimo, Toshihiro Igarashi, Naoshi Hirata, Toshihiko Kanazawa, Kei Katsumata, Hiroaki Takahashi, Ryo Honda, Takahiro Maeda, Masayoshi Ichiyanagi, Teruhiro Yamaguchi, Masahiro Kosuga, Tomomi Okada, Junichi Nakajima, Shuichiro Hori, Takashi Nakayama, Akira HasegawaToshio Kono, Syuichi Suzuki, Noriko Tsumura, Yoshihiro Hiramatsu, Katsunori Sugaya, Aiko Hayashi, Tetsuya Hirose, Akihiro Sawada, Keisuke Tanaka, Yoshiko Yamanaka, Haruhisa Nakamichi, Takashi Okuda, Yoshihisa Iio, Kin'Ya Nishigami, Masatoshi Miyazawa, Hiroo Wada, Norio Hirano, Hiroshi Katao, Shiro Ohmi, Kiyoshi Ito, Issei Doi, Shunta Noda, Satoshi Matsumoto, Takeshi Matsushima, Atsushi Saiga, Hiroki Miyamachi, Kazutoshi Imanishi, Tetsuya Takeda, Youichi Asano, Yohei Yukutake, Tomotake Ueno, Takuto Maeda, Takanori Matsuzawa, Shutaro Sekine, Makoto Matsubara, Kazushige Obara

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Abstract

We have elucidated depth variations in the stress field associated with the 2007 Noto Hanto, Japan, earthquake by stress tensor inversion using high-quality aftershock data obtained by a dense seismic network. Aftershocks that occurred above 4 km in depth indicated a strike-slip stress regime. By contrast, aftershocks in deeper parts indicated a thrust faulting stress regime. This depth variation in the stress regime correlates well with that in the slip direction derived from a finite source model using geodetic data. Furthermore, the maximum principal stress (σ1) axis was stably oriented approximately W20N down to the depth of the mainshock hypocenter, largely in agreement with the regional stress field, but, below that depth, the σ1 axis had no definite orientation, indicating horizontally isotropic stress. One likely cause of these drastic changes in the stress regime with depth is the buoyant force of a fluid reservoir localized beneath the seismogenic zone.

Original languageEnglish
Article numberL06306
JournalGeophysical Research Letters
Volume38
Issue number6
DOIs
Publication statusPublished - 2011 Mar 1

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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    Kato, A., Sakai, S., Iidaka, T., Iwasaki, T., Kurashimo, E., Igarashi, T., Hirata, N., Kanazawa, T., Katsumata, K., Takahashi, H., Honda, R., Maeda, T., Ichiyanagi, M., Yamaguchi, T., Kosuga, M., Okada, T., Nakajima, J., Hori, S., Nakayama, T., ... Obara, K. (2011). Anomalous depth dependency of the stress field in the 2007 Noto Hanto, Japan, earthquake: Potential involvement of a deep fluid reservoir. Geophysical Research Letters, 38(6), [L06306]. https://doi.org/10.1029/2010GL046413