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Volume 57 Supplement 4

Special Issue: Special Section for the 2004 off the Kii peninsula earthquakes (2)

Double-difference relocations of the 2004 off the Kii peninsula earthquakes

Earth, Planets and Space volume 57, pages 357–362 (2005)Cite this article

Abstract

Two large earthquakes (Mw7.3 and Mw7.5) occurred off-shore of the Kii peninsula (Japan) on 5th September 2004. The insufficient station coverage in the area where the large events and their aftershocks occurred led to significant uncertainty regarding their depth location. By using a double-difference approach, we were able to determine more accurate hypocenter locations and better define the main characteristics of the aftershock distribution. The data we used in this study comprise of about 700 earthquakes recorded by the Japanese Meteorological Agency (JMA) from 5 to 12 September 2004. We assume several depth ranges for the initial double difference earthquake locations and select the solution with the smallest rms residual. The resulting hypocenter distribution has two distinctive features: 1) on average the depths are about 20 km shallower than the initial JMA location and 2) the hypocenters are divided into two groups: one shallow (around 12 km depth) and another deep (around 27 km depth). The epicenters of the relocated events define a finer, more clustered structure compared with the epicentral distribution of JMA. The splitting of the earthquake locations into two depth groups is still observed when using a significantly different velocity structure. Our results of the two depth groups for the hypocenters resemble the independently determined hypocentral distribution from the OBS survey.

References

  • Maeda, N. and H. Watanabe, Mode of activity of microearthquakes—In the case of the middle and northern parts of Kinki District, southwestern Japan, Zisin, 37, 579–598, 1984 (in Japanese).

    Google Scholar 

  • Nakanishi, A., H. Shiobara, R. Hino, K. Mochizuki, T. Sato, J. Kasahara, N. Takahashi, K. Suyehiro, H. Tokuyama, J. Segawa, M. Shinohara, and H. Shimahura, Deep crustal structure of the eastern Nankai Trough and Zenisu Ridge by dense airgun-OBS seismic profiling, Marine Geology, 187, 47–62, 2002.

    Article  Google Scholar 

  • Sakai, S., T. Yamada, M. Shinohara, H. Hagiwara, T. Kanazawa, K. Obana, S. Kodaira, and Y. Kaneda, Urgent aftershock observation of the 2004 off the Kii Peninsula earthquake using ocean bottom seismometers, Earth, Planets Space, 57, this issue, 363–368, 2005.

    Article  Google Scholar 

  • Shinohara, M. T. Yamada, T. Kanazawa, T. Hirata, Y. Kaneda, T. Takanami, H. Mikada, K. Suyehiro, S. Sakai, T. Watanabe, K. Uehira, Y. Murai, N. Takahashi, M. Nishino, K. Mochizuki, T. Sato, E. Araki, R. Hino, K. Uhira, H. Shiobara, H. Shimizu, Aftershock observation of the 2003 Tokachi-oki earthquake by using dense ocean bottom seismometer network, Earth Planets Space, 56, 295–300, 2004a.

    Article  Google Scholar 

  • Shinohara, M., T. Yamada, S. Sakai, T. Kanazawa, K. Obana, S. Kodaira, M. Kinoshita, and Y. Kaneda, Urgent observation of earthquakes occurred off-coast of the Kii peninsula, by using ocean bottom seismometers, 2004 Meeting of the Seismological Society of Japan, book of abstracts (supplementary pages), 2004b.

    Google Scholar 

  • Ueno, H., K. Nakamura, S. Aoki, T. Aketagawa, K. Ohtake, A. Kamiya, D. Nozaka, D. Hasebe, O. Kamigaichi, and H. Hamada, The improvement for precise earthquake location determined by Japan Meteorological Agency (Part 3), 2002 Japan Earth and Planetary Joint Meeting, Tokyo, 2002.

    Google Scholar 

  • Waldhauser, F. and W. L. Ellsworth, A double-difference earthquake location algorithm: method an application to the northern Hayward Fault, California, Bull. Seism. Soc. Am., 80, 1548–1368, 2000.

    Google Scholar 

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Authors and Affiliations

  1. Disaster Prevention Research Institute (DPRI), Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan

    Bogdan Enescu, James Mori & Shiro Ohmi

Authors
  1. Bogdan Enescu
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  2. James Mori
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  3. Shiro Ohmi
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Correspondence to Bogdan Enescu.

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Enescu, B., Mori, J. & Ohmi, S. Double-difference relocations of the 2004 off the Kii peninsula earthquakes. Earth Planet Sp 57, 357–362 (2005). https://doi.org/10.1186/BF03352576

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  • DOI: https://doi.org/10.1186/BF03352576

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