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Imaging heterogeneous velocity structures and complex aftershock distributions in the source region of the 2007 Niigataken Chuetsu-oki Earthquake by a dense seismic observation


The velocity structure and accurate aftershock distributions in the source region of the 2007 Niigataken Chuetsu-oki Earthquake (thrust type) are obtained by inverting the arrival times from 848 aftershocks observed by a dense seismic network deployed immediately after the mainshock (8 h later). Both the detailed velocity structure and the accurate aftershock distribution show lateral heterogeneity along the fault strike. In the northeast area, aftershocks are aligned along both the NW- and SE-dipping planes. These planes are conjugate to each other. The mainshock hypocenter is located close to the bottom of an approximately 50° NW-dipping plane, which indicates that the mainshock rupture could have initiated on the NW-dipping plane. The high-V p body beneath this aftershock alignment shows a convex upward shape. In contrast, from the center to the southwest area, most of the aftershocks are aligned along SE-dipping planes. The high-V p body beneath this aftershock alignment shows a convex downward shape. Based on these results, we suggest that the crustal structure in the source region is divided into two segments by a boundary zone situated between the northeast and southwest areas. It should be noted that this segment boundary zone is coincident with the complex aftershock zone where numerous conjugate fault planes exist. We propose that the mainshock rupture initiated near the bottom of the NW-dipping fault plane and ran to the southwest, then transferred at the segment boundary zone which has numerous conjugate fault planes to the SE-dipping plane.


  1. Aochi, H. and E. Fukuyama, Three-dimensional nonplanar simulation of the 1992 Landers earthquake, J. Geophys. Res., 107(B2), 2035, 10. 1029/2000JB000061, 2002.

  2. Aoki, Y., M. Furuya, and T. Kato, Coseismic deformation due to the 2007 Chuetsu-oki earthquake (Mw = 6.8), Earth Planets Space, 60, this issue, 1075–1080, 2008.

  3. Chiarabba, C., A. Amato, and M. Meghraoui, Tomographic images of the EI Asnam fault zone and the evolution of a seismogenic thrust-related fold, J. Geophys. Res., 102, 24485–24498, 1997.

  4. Geological Survey of Japan, AIST, Geological map of Japan, CD-ROM Version, Digital Geoscience Map G-3, 2002.

  5. Hirata, N. and M. Matsu’ura, Maximum-likelihood estimation of hypocenter with origin time eliminated using nonlinear inversion technique, Phys. Earth Planet. Inter., 47, 50–61, 1987.

  6. Hirata, N., H. Sato, S. Sakai, A. Kato, and E. Kurashimo, Fault system of the 2004 Mid Niigata Prefecture Earthquake and its aftershocks, Landslides, 2, 153–157, 2005.

  7. Horikawa, H., Earthquake doublet in Kagoshima, Japan: Rupture of asperities in a stress shadow, Bull. Seismol. Soc. Am., 91, 112–127, 2001.

  8. Kato, A., S. Sakai, N. Hirata, E. Kurashimo, T. Iidaka, T. Iwasaki, and T. Kanazawa, Imaging the seismic structure and stress field in the source region of the 2004 mid-Niigata prefecture earthquake: Structural zones of weakness and seismogenic stress concentration by ductile flow, J. Geophys. Res., 111, B08308, doi:10.1029/2005JB004016, 2006.

  9. Kato, A., S. Sakai, T. Iidaka, T. Iwasaki, E. Kurashimo, T. Igarashi, N. Hirata, T. Kanazawa, and Group for the aftershock observations of the 2007 Noto Hanto Earthquake, Three-dimensional velocity structure in the source region of the Noto Hanto Earthquake in 2007 imaged by a dense seismic observation, Earth Planets Space, 60, 105–110, 2008.

  10. Koketsu, K., H. Miyake, and K. Hikima, Source Inversion for the 2007 Chuetsu-oki, Japan, Earthquake: A Case of Difficulty Determining the Source Fault Plane, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract, S54A-05, 2007.

  11. Nozu, A., Rupture Process of the 2007 Chuetsu-oki, Niigata, Japan, Earthquake—Waveform Inversion using Empirical Green’s Functions—, Earth Planets Space, 2008 (in press).

  12. Okamura, Y., M. Watanabe, R. Morijiri, and M. Satoh, Rifting and basin inversion in the eastern margin of the Japan Sea, The Island Arc, 4, 166–81, 1995.

  13. Research Group for Active Faults of Japan, Active faults in Japan: Sheet maps and inventories, 437 pp., The University of Tokyo Press, 1991.

  14. Robinson, D. P., C. Henry, S. Das, and J. H. Woodhouse, Simultaneous Rupture Along Two Conjugate Planes of the Wharton Basin Earthquake, Science, 292, 1145–1148, 2001.

  15. Sato, H., The relationship between late Cenozoic tectonic events and stress field and basin development in northeast Japan, J. Geophys. Res., 99, 22261–22274, 1994.

  16. Schaff, P. D., G. H. R. Bokelmann, W. L. Ellsworth, E. Zanzerkia, F. Waldhauser, and G. C. Beroza, Optimizing Correlation Techniques for Improved Earthquake Location, Bull. Seismol. Soc. Am., 94, 705–721, 2004.

  17. Shinohara, M., T. Kanazawa, T. Yamada, K. Nakahigashi, S. Sakai, R. Hino, Y. Murai, A. Yamazaki, K. Obana, Y. Ito, K. Iwakiri, R. Miura, Y. Machida, K. Mochizuki, K. Uehira, M. Tahara, A. Kuwano, S. Amamiya, S. Kodaira, T. Takanami, Y. Kaneda, and T. Iwasaki, Precise aftershock distribution of the 2007 Chuetsu-oki Earthquake obtained by using an ocean bottom seismometer network, Earth Planets Space, 60, this issue, 1121-1126, 2008.

  18. Takeda, T., H. Sato, T. Iwasaki, N. Matsuta, S. Sakai, T. Iidaka, and A. Kato, Crustal structure in the northern Fossa Magna region, central Japan, modeled from refraction/wide-angle reflection data, Earth Planets Space, 56, 1293–1299, 2004.

  19. Takenaka, H., Y. Yamamoto, and H. Yamasaki, High-Resolution Source Imaging of the 2007 Niigataken Chuetsu-oki Earthquake From Dense Strong-Motion Networks: Focus on the First 5 Seconds of the Rupture Process, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract, S31A-0208, 2007.

  20. Thurber, C. H., S. R. Atre, and D. Eberhart-Phillips, Three-dimensional Vp and Vp/Vs structure of the Loma Prieta, California, from local earthquake tomography, Geophys. Res. Lett., 22, 3079–3082, 1995.

  21. Townend, J. and M. D. Zoback, Stress, strain, and mountain building in central Japan, J. Geophys. Res., 111, B03411, doi:10.1029/2005JB003759, 2006.

  22. Wessel, P. and W. H. F. Smith, New version of the generic mapping tools released, Eos Trans. AGU, 76, 329, 1995.

  23. Zhang, H. and C. H. Thurber, Double-difference tomography: The method and its application to the Hayward fault, California, Bull. Seismol. Soc. Am., 93, 1875–1889, 2003.

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Correspondence to Aitaro Kato.

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Kato, A., Sakai, S., Kurashimo, E. et al. Imaging heterogeneous velocity structures and complex aftershock distributions in the source region of the 2007 Niigataken Chuetsu-oki Earthquake by a dense seismic observation. Earth Planet Sp 60, 1111–1116 (2008).

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Key words

  • Tomography
  • the 2007 Niigataken Chuetsu-oki Earthquake
  • aftershocks
  • heterogeneous structures