Skip to main content


A comprehensive model of the deformation process in the Nagamachi-Rifu Fault Zone


A two-dimensional finite element model was constructed along a cross section almost perpendicular to the Nagamachi-Rifu Fault Zone, in order to clarify the stress accumulation process on an intraplate earthquake fault. We explain the surface deformations observed by the dense GPS network and leveling surveys using models with heterogeneities in the crust. These heterogeneities are identified from various geophysical surveys in the region. We found that the observed surface deformations cannot be explained by a model having a weak zone in the upper crust, but can be explained by models having a weak zone in the lower crust. Models having an aseismic fault or fault zone in the lower crust can reproduce the spatial pattern of the observed deformations, but amplitudes predicted by these models are smaller than those observed. The weak zone in the lower crust probably plays an important role in the stress accumulation process on the Nagamachi-Rifu fault zone.


  1. Hibbitt, Karlsson, and Sorensen, Abaqus/Standard User’s Manual, vol. 1 and 2, version 6.2, Hibbitt, Karlsson, and Sorensen Inc., Pawtucket, 2001.

  2. Iio, Y. and Y. Kobayashi, A physical understanding of large intraplate earthquakes, Earth Planets Space, 54, 1001–1004, 2002.

  3. Iio, Y. and Y. Kobayashi, Is the plastic flow uniformly distributed below the seismogenic region?, Tectonophysics, 364, 43–53, 2003.

  4. Iio, Y., T. Sagiya, and Y. Kobayashi, What controls the occurrence of shallow intraplate earthquakes?, Earth Planets Space, 56, this issue, 1077–1086, 2004.

  5. Ikawa, T., T. Kawanaka, S. Kawasaki, A. Hasegawa, N. Umino, A. Nakamura, and H. Ito, Seismic reflection survey of the deep structure of Nagamachi-Rifu fault, Northeastern Japan, Proceedings of International Symposium on Slip and Flow in and below the Seismogenic Region, in Sendai, Japan, 44, 2001.

  6. Imanishi, K., H. Ito, Y. Kuwahara, Y. Mamada, T. Yokokura, N. Kano, K. Yamaguchi, and A. Tanaka, Deep structure of the Nagamachi-Rifu fault deduced from small aperture seismic array observations, Earth Planets Space, 54, 1033–1038, 2002.

  7. Kenner, S. and P. Segall, A mechanical model for intraplate earthquakes: Application to the New Madrid, Science, 289, 2329–2332, 2000.

  8. Komazawa, M. and M. Mishina, Caldera structure inferred from gravity anomalies west of Nagamachi-Rifu Fault, Northeast Japan, Earth Planets Space, 54, 1049–1053, 2002.

  9. Liu, L. and M. D. Zoback, Lithospheric strength and intraplate seismicity in the New Madrid seismic zone, Tectonics, 16, 585–595, 1997.

  10. Melosh, H. J. and A. Raefsky, A simple and efficient method for introducing faults into finite element computations, Bull. Seism. Soc. Am., 71, 1391–1400, 1981.

  11. Nakajima, J., A. Hasegawa, S. Horiuchi, K. Yoshimoto, T. Yoshida, and N. Umino, Three-dimensional seismic velocity structure around the Nagamachi-Rifu fault, northeastern Japan, Tectonophysics, 2004 (submitted).

  12. Nakamura, A., Y. Asano, and A. Hasegawa, Estimation of deep fault geometry of the Nagamachi-Rifu fault from seismic array observations, Earth Planets Space, 54, 1027–1031, 2002.

  13. Nishimura, T., T. Sagiya, and S. Miura, Crustal deformation around the Nagamachi-Rifu fault zone and its vicinity (central Tohoku), northeastern Japan, observed by a continuous GPS network, Zisin, 56, 497–509, 2004 (in Japanese with English abstract).

  14. Ogawa, Y., S. Takakura, and Y. Honkura, Resistivity structure across Itoigawa-Shizuoka tectonic line and its implications for concentrated deformation, Earth Planets Space, 54, 1115–1120, 2002.

  15. Ogawa, Y., M. Mishina, Y. Honkura, K. Takahashi, and S. B. Tank, Resistivity imaging of deep extension of Nagamachi-Rifu Fault, Program and abstracts of the 2004 Joint meeting of earth and planetary sciences, S075–014, 2003.

  16. Research Group for Deep Structure of Nagamachi-Rifu Fault (Umino, N. and A. Hasegawa), Seismic reflection survey in Nagamachi-Rifu fault, Sendai, northeastern Japan, Tohoku Geophys. Journ., 36, 311–356, 2002.

  17. Sato, H., T. Imaizumi, T. Yoshida, H. Ito, and A. Hasegawa, Tectonic evolution and deep to shallow geometry of Nagamachi-Rifu Active Fault System, NE Japan, Earth Planets Space, 54, 1039–1043, 2002.

  18. Sibson, R., Continental fault structure and the shallow earthquake source, J. Geol. Soc. London, 140, 741–767, 1983.

  19. Umino, N., H. Ujikawa, S. Hori, and A. Hasegawa, Distinct S-wave reflectors (bright spots) detected beneath the Nagamachi-Rifu fault, NE Japan, Earth Planets Space, 54, 1021–1026, 2002a.

  20. Umino, N., T. Okada, and A. Hasegawa, Foreshock and aftershock sequence of the 1998 M5.0 Sendai, Northern Japan, earthquake and its implications for earthquake nucleation, Bull. Seismol. Soc. Am., 92, 2465–2477, 2002b.

  21. Yoshimoto, K., T. Okada, and A. Hasegawa, Seismic observation around the Nagamachi-Rifu fault by using semi-broad-band seismometers, Program and abstracts of the 2001 Joint meeting of earth and planetary sciences, Sz-009, 2001.

Download references

Author information

Correspondence to Yoshihisa Iio.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Key words

  • Intraplate earthquake
  • lower crust
  • ductile fault zone
  • stress accumulation
  • plate boundary