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Imaging of S-wave reflectors in and around the hypocentral area of the 2004 mid Niigata Prefecture Earthquake (M6.8)


An S-wave reflector is considered to relate to the existence of liquid in the seismogenic zone of the crust, which plays an important role in understanding the mechanism of earthquakes. We studied a distribution of S-wave reflectors in and around the hypocentral zone of the 2004 mid Niigata Prefecture Earthquake (M6.8). The earthquake was followed by several aftershocks that were greater than M6. Moreover, the aftershocks were not only located on the fault plane of the main shock but also on conjugate fault planes and on a parallel plane to that of the main shock. In order to discuss the relationship between this complex activity and the crustal heterogeneities, we analyzed the seismograms observed at the seismic stations in this region. Normal moveout processing (NMO) was applied to the data of the aftershock. Several S-wave reflectors could be identified from the NMO sections for every station. In particular, relatively strong S-wave reflectors exist in the lower crust at a depth of approximately 20-25 km in the middle part of the aftershock region. Additionally, reflectors were found beneath the fault planes of the main shock and the largest aftershock. This suggests a possibility of the correlation of the crustal heterogeneities to the occurrence of an earthquake.


  1. Kato, A., E. Kurashimo, N. Hirata, T. Iwasaki, and T. Kanazawa, Imaging the source region of the 2004 Mid-Niigata prefecture earthquake and the evolution of a seismogenic thrust-related fold, Geophys. Res. Lett., 2005 (in press).

  2. Korenaga, M., S. Matsumoto, Y. Iio, T. Matsushima, K. Uehira, and T. Shibutani, Three dimensional velocity structure around aftershock area of the 2004 mid Niigata prefecture earthquake (M6.8) by the Double-Difference tomography, Earth Planets Space, 57, 429–433, 2005.

  3. Matsumoto, S., K. Obara, and A. Hasegawa, Imaging P-wave scatterer distribution in the focal area of 1995 M7.2 Hyogo-ken Nanbu (Kobe) Earthquake, Geophys. Res. Lett., 25, 9, 1439–1442, 1998.

  4. Matsumoto, S., K. Obara, N. Kimura, and M. Nakamura, Imaging P-wave scatterer distribution around the focal area of the 2000 Western Tottori Earthquake (Mw6.6), Zisin, 2, 55, 229–232, 2002 (in Japanese).

  5. Miyazawa, M., J. Mori, Y. Iio, T. Shibutani, S. Matsumoto, H. Katao, S. Ohmi, and K. Nishigami, Triggering Sequence by Static Stress Changes of Large aftershocks of the Niigata-Chuetsu, Japan Earthquake, Earth Planets Space, 2005 (submitted).

  6. Okada, T., N. Umino, T. Matsuzawa, J. Nakajima, N. Uchida, T. Nakayama, S. Hirahara, T. Sato, S. Hori, T. Kono, Y. Yabe, K. Ariyoshi, S. Gamage, J. Shimizu, J. Suganomata, S. Kita, S. Yui, M. Arao, S. Hondo, T. Mizukami, H. Tsushima, T. Yaginuma, A. Hasegawa, Y. Asano, H. Zhang, and C. Thurber, Aftershock distribution and 3D seismic velocity structure in and around the focal area of the 2004 mid Niigata prefecture earthquake obtained by applying double-difference tomography to dense temporary seismic network data, Earth Planets Space, 57, 435–440, 2005.

  7. Shibutani, T., Y. Iio, S. Matsumoto, H. Katao, T. Matsushima, S. Ohmi, F. Takeuchi, K. Uehira, K. Nishigami, B. Enescu, I. Hirose, Y. Kano, Y. Kohno, M. Korenaga, Y. Mamada, M. Miyazawa, K. Tatsumi, T. Ueno, H. Wada, and Y. Yukutake, Aftershock distribution of the 2004 Mid Niigata Prefecture Earthquake derived from a combined analysis of temporary online observations and permanent observations, Earth Planets Space, 57, this issue, 545–549, 2005.

  8. Wada, H., T. Mikumo, and M. Koizumi, Seismicity and focal mechanism of local earthquakes along the Atotsugawafault and in the northern Hida region, Zisin, 2, 32, 3, 281–296, 1979.

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Correspondence to Satoshi Matsumoto.

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Matsumoto, S., Iio, Y., Matsushima, T. et al. Imaging of S-wave reflectors in and around the hypocentral area of the 2004 mid Niigata Prefecture Earthquake (M6.8). Earth Planet Sp 57, 557–561 (2005).

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Key words

  • Inhomogeneity
  • reflector
  • mid Niigata
  • crustal structure