Skip to main content

Spatiotemporal distribution of very-low frequency earthquakes in Tokachi-oki near the junction of the Kuril and Japan trenches revealed by using array signal processing


We have developed a signal-processing method for array data recorded at densely and widely distributed tiltmeter stations in Japan and analyzed the data recorded during the last 5 years. Filtered seismograms were analyzed to detect coherent seismic waves and estimate the epicenters. In order to identify very-low frequency earthquakes (VLFEs) with only low-frequency energies only, we selected only events not listed in the earthquake catalogue provided by the Japan Meteorological Agency from all of the detected events. The epicenters of the obtained VLFEs were estimated to be distributed not only along the Nankai Trough, where the events occurred on the reverse faults in the well-developed accretionary prism, but also in Tokachi-oki without accretion. This result suggests that even in such a region, VLFEs can occur on a shallower portion of the plate boundary than the seismogenic region of ordinary earthquakes and/or in a deformed area of the overriding plate along the subduction zone without accretion.


  • Dominguez, S., S. E. Lallemand, J. Malavieille, and R. von Huene, Upper plate deformation associated with seamount subduction, Tectonophysics, 293, 207–224, 1998.

    Article  Google Scholar 

  • Earthquake Research Committee, Long-term evaluation of earthquakes along the Kuril trench,, The Headquarters for Earthquake Research Promotion, 2003.

    Google Scholar 

  • Ito, Y. and K. Obara, Dynamic deformation of the accretionary prism excites very low frequency earthquakes, Geophys. Res. Lett., 33, L02311, doi:10.1029/2005GL025270, 2006.

    Google Scholar 

  • Ito, Y., H. Matsubayashi, H. Kimura, T. Matsumoto, Y. Asano, and S. Sekiguchi, Spatial distribution for moment tensor solutions of the 2003 Tokachi-oki earthquake (Mw = 7.9) and aftershocks, Earth Planets Space, 56, 301–306, 2004.

    Article  Google Scholar 

  • Ito, Y., K. Obara, K. Shiomi, S. Sekine, and H. Hirose, Slow earthquakes coincident with episodic tremors and slow slip events, Science, 315, 503–506, 2007.

    Article  Google Scholar 

  • Miyazaki, S., P. Segall, J. Fukuda, and T. Kato, Space-time distribution of afterslip following the 2003 Tokachi-oki earthquake: Implications for variations in fault zone frictional properties, Geophys. Res. Lett., 31, L06623, doi:10.1029/2003GL019410, 2004.

    Google Scholar 

  • Moore, G., T. Shipley, P. Stoffa, D. Karig, A. Taira, S. Kuramoto, H. Tokuyama, and K. Suyehiro, Structure of the Nankai Trough accretionary zone from multichannel seismic reflection data, J. Geophys. Res., 95, 8753–8765, 1990.

    Article  Google Scholar 

  • Neidell, N. S. and M. T. Taner, Semblance and other coherency measures for multichannel data, Geophysics, 36, 482–497, 1971.

    Article  Google Scholar 

  • Obara, K., Nonvolcanic deep tremor associated with subduction in southwest Japan, Science, 296, 1679–1681, 2002.

    Article  Google Scholar 

  • Obara, K. and Y. Ito, Very low frequency earthquakes excited by the 2004 off the Kii peninsula earthquakes: A dynamic deformation process in the large accretionary prism, Earth Planets Space, 57, 321–326, 2005.

    Article  Google Scholar 

  • Obara, K., Y. Haryu, Y. Ito, and K. Shiomi, Low frequency events occurred during the sequence of aftershock activity of the 2003 Tokachi-Oki earthquake; a dynamic process of the tectonic erosion by subducted seamount, Earth Planets Space, 56, 347–351, 2004.

    Article  Google Scholar 

  • Obara, K., K. Kasahara, S. Hori, and Y. Okada, A densely distributed high-sensitivity seismograph network in Japan: Hi-net by National Research Institute for Earth Science and Disaster Prevention, Rev. Sci. Inst., 76, 021301, doi:10.1063/1.1854197, 2005.

    Article  Google Scholar 

  • Park, J. O., T. Tsuru, S. Kodaira, P. R. Cummins, and Y. Kaneda, Splay fault branching along the Nankai subduction zone, Science, 297, 1157–1160, 2002.

    Article  Google Scholar 

  • Press, W. H., S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery, Numerical recipes: The art of scientific computing FORTRAN version, 702 pp., Cambridge Univ. Press, Cambridge, 1989.

    Google Scholar 

  • Scholz, C. H., Earthquakes and friction laws, Nature, 391, 37–42, 1998.

    Article  Google Scholar 

  • von Huene, R. and R. Culotta, Tectonic erosion at the front of the Japan Trench convergent margin, Tectonophysics, 160, 75–90, 1989.

    Article  Google Scholar 

  • Wessel, P. and W. H. F. Smith, New, improved version of the Generic Mapping Tools released, Eos Trans. AGU, 79, 579, 1998.

    Article  Google Scholar 

  • Yagi, Y., Source rupture process of the 2003 Tokachi-oki earthquake determined by joint inversion of teleseismic body wave and strong ground motion data, Earth Planets Space, 56, 311–316, 2004.

    Article  Google Scholar 

  • Yamazaki, T. and Y. Okamura, Subducting seamounts and deformation of overriding forearc wedges around Japan, Tectonophysics, 160, 207–229, 1989.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Youichi Asano.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit

Reprints and permissions

About this article

Cite this article

Asano, Y., Obara, K. & Ito, Y. Spatiotemporal distribution of very-low frequency earthquakes in Tokachi-oki near the junction of the Kuril and Japan trenches revealed by using array signal processing. Earth Planet Sp 60, 871–875 (2008).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Key words