Hidden Fault Scarp Inferred from Gravity Analysis and Disaster Belt of the 1995 Hyogo-Ken Nanbu Earthquake

  • Shigeki Kobayashi
  • Shigeo Yoshida
  • Shuhei Okubo
  • Ryuichi Shichi
  • Toshihiko Shimamoto
  • Teruyuki Kato
Conference paper
Part of the International Association of Geodesy Symposia book series (IAG SYMPOSIA, volume 117)

Abstract

Dense gravity measurements were carried out together with the GPS positioning along five survey lines across the Rokko fault system. The subsurface structure relevant to the 1995 Hyogo-ken Nanbu earthquake was inferred from the Bouguer anomaly. A hidden fault was discovered on the southwestward extension of the Koyo fault underneath the sedimentary layer. The extension runs just on the edge of the earthquake disaster belt. The thickness of the sedimentary layer was estimated to decrease gradually toward the mountain side. The wedge-like structure of the soft layer and the hidden fault scarp under the Kobe plain may serve as a focusing lens of seismic rays during the earthquake.

Keywords

Cretaceous Mountain Side Geophysics Kato Body Wave 

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References

  1. Endo, H., S. Watanabe, M. Makino, A. Urabe, H. Aso, Y. Koreishi and T. Ejiri, Seismic reflection survey of Ashiyagawa survey line in Ashiya city, Hyogo Pref., Japan, Bull. Geol. Surv. Japan, 47, 79–94, 1996 (in Japanese).Google Scholar
  2. Gravity Research Group in Southwest Japan, A Bouguer gravity anomaly map in Central Japan, Rept. Geol. Surv. Japan, 280, 29–36, 1994.Google Scholar
  3. Hashimoto, M., Geophysical image of the 1995 Hyogoken-Nanbu earthquake, Kokudochiriin Jihou, 83, 6–14, 1995 (in Japanese).Google Scholar
  4. Huzita, K., T. Kasama, M. Hirano, T. Shinoda, and M. Tanaka, Geogoly and geomorphology of the Rokko area, Kinki District, Japan, J. Geosci. Osaka Univ., 14, 71–124, 1971.Google Scholar
  5. Kamae,K., and K. Irikura, A fault rupture model of the 1995 Hyogoken Nanbu earthquake (M,=7.2) estimated by the empirical Green’s function method, J. Natural Disaster Sci., 16, 31–40, 1995.Google Scholar
  6. Kikuchi, M., Source process of the 1995 Hyogoken-nanbu earthquake. Preliminary analysis of teleseismic body waves, Chishitsu News (Geological News), 486, 12–15, 1995 (in Japanese).Google Scholar
  7. Kobayashi, S., S. Yoshida, S. Okubo, R. Shichi, T. Shimamoto and T. Kato, Two-dimensional analysis of gravity anomaly across the Rokko fault system, J Phys. Earth, 44, 357–372, 1996.CrossRefGoogle Scholar
  8. Motosaka, M. and M. Nagano, Analytical study on amplification characteristics of ground motions taking account of irregular bedrock structure in Kobe city, Soil and basement, 43, 15–20, 1995 (in Japanese).Google Scholar
  9. Nakata, T., K. Yomogida, J. Okada, T. Sakamoto, K. Asahi, and N. Chida, Surface fault ruptures associated with the 1995 Hyogoken-Nanbu earthquake, J. Geogr., 104, 127–142, 1995 (in Japanese with English abstract).CrossRefGoogle Scholar
  10. Pitarka, A., K. Irikura, T. Iwata, and T. Kagawa, Basin structure effects in the Kobe area inferred from the modeling of ground motions from two aftershocks of the January 17, 1995 Hyogoken-nanbu earthquake, J. Phys. Earth, 44, 563–576, 1996.CrossRefGoogle Scholar
  11. Shichi, R. and H. Aoki, Gravity anomaly around the focal region of the Hyogoken-Nanbu earthquake, Chikyuu Monthly, supplement 13, 129–134, 1995 (in Japanese).Google Scholar
  12. Shimamoto, T., Mystery of ‘earthquake disaster belt’, Kagaku (Science), 65, 195–198, 1995 (in Japanese).Google Scholar
  13. Talwani, M., J. Lamar Worzel, and M. Landisman, Rapid gravity computations for two-dimensional bodies with application to the Mendocino submarine fracture zone, J. Geophys. Res., 64, 49–59, 1959.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Shigeki Kobayashi
    • 1
  • Shigeo Yoshida
    • 1
  • Shuhei Okubo
    • 1
  • Ryuichi Shichi
    • 2
  • Toshihiko Shimamoto
    • 1
  • Teruyuki Kato
    • 1
  1. 1.Earthquake Research InstituteThe University of TokyoBunkyo-ku, Tokyo 113Japan
  2. 2.Department of Earth and Planetary Sciences, School of ScienceNagoya UniversityFuro-cho, Chikusa-ku, NagoyaJapan

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