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Fine structure of aftershock distribution of the 1997 Northwestern Kagoshima Earthquakes with a three-dimensional velocity model

Earth, Planets and Space volume 51, pages 233–246 (1999)Cite this article

Abstract

In 1997, two earthquakes (M6.5 and M6.3) occurred in the northwestern part of Kagoshima Prefecture, Japan. We carried out temporary seismic observation to obtain the detailed aftershock distribution. We constructed a 3-D P wave velocity model by inverting the travel times of aftershocks observed at 14 seismic stations in and around the focal area and relocated more than 14,000 aftershocks with the 3-D velocity model.

The general features of the aftershock distribution are as follows: (1) Aftershocks of the first main shock (M6.5) are distributed with a strike of nearly E-W (N100°E) in a vertical plane with a horizontal length of 21 km and a depth range of 2 to 9 km; (2) The second main shock (M6.3) has an ‘L’-shaped aftershock distribution: one plane strikes nearly E-W, which is parallel to the aftershock zone of the first main shock, and the other is a conjugate plane; (3) An obvious seismicity gap of about 3 km wide is found between the aftershock zones striking E-W for the first and second main shocks; (4) The aftershock activities are generally low around the hypocenters of the two main shocks. Our results show that most of aftershocks occurred not in high or low velocity zones, but in intermediate velocity areas. Several vertical linear distributions of aftershocks are also confirmed in the two focal zones striking E-W. These peculiar distributions suggest that the aftershock activity is affected by the underground structural boundaries.

References

  • Crosson, R. S., Crustal structure modeling of earthquake data. 1. Simultaneous least squares estimation of hypocenters and velocity parameters, J. Geophys. Res., 81, 3036–3046, 1976.

    Article  Google Scholar 

  • Hirahara, K., N. Hirata, A. Ikami, H. Miyamachi, and T. Yabuki, et al., Three-dimensional P and S wave velocity structure in the focal region of the 1984 Western Nagano Prefecture Earthquake, J. Phys. Earth, 40, 343–360, 1992.

    Article  Google Scholar 

  • 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.

    Article  Google Scholar 

  • Humphreys, E. and R. W. Clayton, Adaptation of back projection tomography to seismic travel time problems, J. Geophys. Res., 93, 1073–1085, 1988.

    Article  Google Scholar 

  • Imura, R., A. Iwamatsu, and K. Kumamoto, Disasters caused by the 1997 earthquakes at northwestern Kagoshima Prefecture, in General Report on the 1997 Northwestern Kagoshima Prefecture Earthquakes, 59–69, March, 1998 (in Japanese).

  • Inoue, H., Y. Fukao, K. Yanabe, and Y. Ogata, Whole mantle P-wave travel time tomography, Phys. Earth Planet. Inter., 59, 294–328, 1990.

    Article  Google Scholar 

  • Kakuta, T., H. Miyamachi, K. Goto, H. Yakiwara, S. Hirano, S. Fukumitsu, H. Sekitani, K. Kaneko, K. Iwakiri, and C. Shimizu, Large inland seismic activity in the northern part of Satsuma district, in General Report on the 1997 Northwestern Kagoshima Prefecture Earthquakes, 9–20, March, 1998 (in Japanese).

  • Ministry of International Trade and Industry, Report of regional geological survey; Hokusatsu-Kushikino area, 1995 fiscal year, 1–178, 1996 (in Japanese).

  • Miyamachi, H. and T. Moriya, Velocity structure and aftershock distribution of the 1982 Urakawa-oki Earthquake, J. Phys. Earth, 35, 309–326, 1987.

    Article  Google Scholar 

  • Miyamachi, H., K. Iwakiri, T. Tsuno, C. Shimizu, S. Fukumitsu, K. Kaneko, H. Sekitani, T. Kakuta, K. Goto, H. Yakiwara, S. Hirano, T. Matsushima, and H. Shimizu, Temporary seismic observation of aftershocks for the 1977 Northwestern Earthquakes in Kagoshima Prefecture, Geophys. Bull. Hokkaido Univ., 61, 85–98, 1998 (in Japanese with English abstract).

    Google Scholar 

  • Murata, A., Hokusatsu bend and clockwise rotation of the southwest Japan arc, J. Fac Sci., Univ. Tokyo, Sec. II, 21, 333–349, 1987.

    Google Scholar 

  • Thurber, C. H., Earthquake locations and three-dimensional crustal structure in the Coyote lake area, Central California, J. Geophys. Res., 88, 8226–8236, 1983.

    Article  Google Scholar 

  • Um, J. and C. H. Thurber, A fast algorithm for two-point seismic ray tracing, Bull. Seism. Soc. Am., 77, 972–986, 1987.

    Google Scholar 

  • Wessel, P. and W. H. F. Smith, Free software helps map and display data, EOS Trans. Amer Geophys. U, 72, 441, 445–446, 1991.

    Article  Google Scholar 

  • Yoneda, S. and A. Iwamatsu, Stratigraphy and geologic structure of the Shimanto super group in the Hokusatsu district, Kagoshima Prefecture, South Kyushu, Japan, J. Geol. Soc. Japan, 93, No. 2, 881–895, 1987 (in Japanese with English abstract).

    Article  Google Scholar 

  • Zhao, D. and H. Negishi, The 1995 Kobe earthquake: Seismic image of the source zone and its implications for the rupture nucleation, J. Geophys. Res., 103, 9967–9986, 1998.

    Article  Google Scholar 

Download references

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Authors and Affiliations

  1. Faculty of Science, Kagoshima University, Kagoshima, 890-0065, Japan

    Hiroki Miyamachi, Kazuhiro Iwakiri, Hiroshi Yakiwara, Kazuhiko Goto & Toshiki Kakuta

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  1. Hiroki Miyamachi
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  2. Kazuhiro Iwakiri
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  3. Hiroshi Yakiwara
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  4. Kazuhiko Goto
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  5. Toshiki Kakuta
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Correspondence to Hiroki Miyamachi.

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Miyamachi, H., Iwakiri, K., Yakiwara, H. et al. Fine structure of aftershock distribution of the 1997 Northwestern Kagoshima Earthquakes with a three-dimensional velocity model. Earth Planet Sp 51, 233–246 (1999). https://doi.org/10.1186/BF03352227

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