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Slow slip in the focal region of the anticipated Tokai earthquake following the seismo-volcanic event in the northern Izu Islands in 2000

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Transient crustal deformation occurred in the regions of Kanto and Tokai during the seismo-volcanic event in the northern Izu Islands in 2000. In our investigation of the observed deformation, we constructed an optimum-source model of the event between Miyake and Kozu Islands. We then made an inversion analysis of the differences between the observed displacement field and the calculated displacement field from the optimum model, assuming that the differences were caused by the changes in the interplate coupling beneath the Tokai region. From the inversion analysis of data for each of three-month periods, May to August, June to September, and July to October, we found decreased interplate coupling in the early stages of the 2000 event. In the first stage, either a slow slip or a temporary suspension of the plate subduction occurred in the focal region of the anticipated Tokai earthquake. The area then extended to the west and, finally, a slow slip exceeded the secular convergence velocity on the plate interface near Lake Hamana in the fall of 2000. We believe this ongoing slow slip began in August or early September 2000.


  1. Furuya, M., S. Okubo, W. Sun, Y. Tanaka, J. Oikawa, H. Watanabe, and T. Maekawa, Spatiotemporal Gravity Changes at Miyakejima Volcano, Japan: Caldera Collapse, Explosive Eruptions and Magma Movement, J. Geophys. Res., 108(B4), 2219, doi:10.1029/2002JB001989, 2003.

  2. Hatanaka, Y., T. Iizuka, M. Sawada, A. Yamagiwa, Y. Kikuta, J. M. Johnson, and C. Rocken, Improvement of the Analysis Strategy of GEONET, Bull. Geograph. Surv. Inst., 49, 11–37, 2003.

  3. Japan Meteorological Agency, Recent seismic activity in the Miyakejima and Niijima-Kozushima region, Japan—the largest earthquake swarm ever recorded, Earth Planets Space, 52, i–viii, 2000.

  4. Kaidzu, M., Dose velocity field in 1999 really represent standard secular field?, Prog. Abst. Geod. Soc. Jpn., P-14, 2003 (in Japanese).

  5. Kaidzu, M., T. Nishimura, M. Murakami, S. Ozawa, T. Sagiya, H. Yarai, and T. Imakiire, Crustal deformation associated with crustal activities in the northern Izu-islands area during the summer, 2000, Earth Planets Space, 52, ix–xviii, 2000.

  6. Kobayashi, A., T. Yamamoto, H. Takayama, and A. Yoshida, Crustal deformation in the Chubu-Kanto region at and after the 2000 seismic and volcanic activity around the northern Izu islands, J. Geodetic Soc. Japan, 49, 121–133, 2003 (in Japanese with English abstract).

  7. Matsu’ura, M. and Y. Hasegawa, A maximum likelihood approach to nonlinear inversion under constraints, Phys. Earth Planet. Inter., 47, 179–187, 1987.

  8. Miyazaki, S., Y. Hatanaka, T. Sagiya, and T. Tada, The nationwide GPS array as an Earth observation system, Bull. Geograph. Surv. Inst., 44, 11–22, 1998.

  9. Murakami, M. and S. Miyazaki, Periodicity of strain accumulation detected by permanent GPS array: Possible relationship to seasonality of measure earthquakes’ occurrence, Geophys. Res. Lett., 28, 2983–2986, 2001.

  10. Nishimura, T., S. Ozawa, M. Murakami, T. Sagiya, T. Tada, M. Kaidzu, and M. Ukawa, Crustal deformation caused by magma migration in the northern Izu islands, Japan, Geophys. Res. Lett., 28, 3745–3748, 2001.

  11. Ozawa, S., M. Murakami, M. Kaidzu, T. Tada, T. Sagiya, H. Hatanaka, H. Yarai, and T. Nishimura, Detection and monitoring of ongoing aseismic slip in the Tokai region, central Japan, Science, 298, 1009–1012, 2002.

  12. Ozawa, S., S. Miyazaki, T. Nishimura, M. Murakami, M. Kaidzu, T. Imakiire, and X. Ji, Creep, dike intrusion, and magma chamber deflation model for the 2000 Miyake eruption and the Izu islands earthquakes, J. Geophys. Res., 109, B02410, doi:10.1029/2003JB00260, 2004.

  13. Sagiya, T., Interplate coupling in the Tokai district, Central Japan, deduced from continuous GPS data, Geophys. Res. Lett., 26, 2315–2318, 1999.

  14. Sakai, S., T. Yamada, S. Ide, M. Mochizuki, H. Shiobara, T. Urabe, N. Hirata, M. Shinohara, T. Kanazawa, A. Nishizawa, G. Fujie, and H. Mikada, Magma migration from the point of view of seismic activity in the volcanism of Miyake-jima Island in 2000, J. Geog., 110, 145–155, 2001 (in Japanese with English abstract).

  15. Sasai, Y., M. Uyeshima, J. Zlotnicki, H. Utada, T. Kagiyama, T. Hashimoto, and Y. Takahashi, Magnetic and electric field observations during the 2000 activity of Miyake-jima volcano, Central Japan, Earth. Planet. Sci. Lett., 203, 769–777, 2002.

  16. Savage, J. C., A dislocation model of strain accumulation and release at a subduction zone, J. Geophys. Res., 88, 4984–4996, 1983.

  17. Wessel, P. and W. H. F. Smith, New version of the Generic Mapping Tools released, EOS Trans., AGU, 76, 329, 1995.

  18. Yabuki, T. and M. Matsu’ura, Geodetic data inversion using a Bayesian information criterion for spatial distribution of fault slip, Geophys. J. Int., 109, 363–375, 1992.

  19. Yamamoto, T., Temporal and spatial changes of annual variation pattern of GEONET coordinate data, Japan Earth and Planetary Science Joint Meeting, D58-004, 2002.

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Correspondence to Akio Kobayashi.

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Kobayashi, A., Yoshida, A., Yamamoto, T. et al. Slow slip in the focal region of the anticipated Tokai earthquake following the seismo-volcanic event in the northern Izu Islands in 2000. Earth Planet Sp 57, 507–513 (2005) doi:10.1186/BF03352584

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Key words

  • Tokai region
  • slow slip
  • interplate coupling
  • crustal deformation