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A real-time observation network of ocean-bottom-seismometers deployed at the Sagami trough subduction zone, central Japan

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Abstract

We installed a real-time operating regional observation network of Ocean-Bottom-Seismometers, connected to an electro-optical fiber communication cable, at the Sagami trough subduction zone, just south of the Tokyo metropolitan area, central Japan. The network, called ETMC, has six seismic observation sites at approximately 20 km spacing. In addition, there are three tsunami observation sites along the ETMC network to monitor the propagation process of tsunamis around the Sagami trough region.

The on-line data from the ETMC has been improving the detection capability of smaller-magnitude earthquakes even at areas close to the margin of the trough. The ETMC data analyzing system, which has a function of real-time digital filtering for each seismic channel, can read the arrival times of P- and S-waves precisely, constraining well the automatic on-line hypocenter locations. The network has been providing useful information regarding the bending and downgoing process of the Philippine sea plate at the Sagami trough subduction zone.

The pressure sensors of the installed network have a detection capability of tsunami wave trains with an amplitude of less than 1 cm. For example, the sensors recorded the full time history of tsunami wave trains, with mm order resolution, originating from a ‘tsunami earthquake’ with 5.7 MW and the tsunami magnitude of 7.5 occurred near Tori Shima (Tori Is.) of the Izu-Bonin Is. arc on September 4, 1996. The maximum amplitude of the tsunami signals on the trough-floor was approximately 1 cm (P-P), in contrast with approximately 20 cm (0-P) at a coastal site on Izu-Oshima, near the trough. Also, the pressure sensors observed tsunamis due to a large tsunami earthquake (7.1 MW) at the northern New Guinea, on July 17, 1998.

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References

  • Eguchi, T., Fujinawa Y., Matsuzaki T. and Aoyagi M.: 1986, ‘New Pop-up Type Ocean Bottom Seismometer’, Mar. Geophys. Res. 8, 187–199.

    Google Scholar 

  • Eguchi, T., Fujinawa Y. and Ukawa M.: 1987, ‘Microearthquakes and Tectonics Around an Outer Rise: the Zenisu Ridge, Japan’, Phys. Earth Planet. Inter. 48, 47–63.

    Google Scholar 

  • Eguchi, T. and Fujinawa Y.: 1991, ‘New projects with on-line sea-bottom cable observation system for monitoring crustal activity in off-shore areas by the National Research Institute Earth Science and Disaster Prevention’, The Kaiyo Monthly 23, 321–328 (in Japanese).

    Google Scholar 

  • Jeffreys, S. H. and Bullen, K. E.: Seismological Tables, British Assn. Advans., Gray-Milne Trust.

  • Kanamori H.: 1971, ‘Faulting of the great kanto earthquake of 1923 as revealed by seismological data’, Bull. Earthquake Res. Inst. 49, 13–18.

    Google Scholar 

  • Kanamori H.: 1972, ‘Mechanisms of Tsunami earthquakes’, Phys. Earth Planet. Inter. 6, 346–359.

    Google Scholar 

  • Kanamori, H., Ekstrom G., Dziewonski A., Barker J. S. and Sipkin S. A.: 1993, ‘Seismic radiation by magma injection: an anomalous seismic event near Tori Shima, Japan’, J. Geophys. Res. 98,B4, 6511–6522.

    Google Scholar 

  • Matsu'ura, M, Iwasaki T., Suzuki Y. and Sato R.: 1980, ‘Statical and dynamical study on faulting mechanism of the 1923 Kanto earthquake’, J. Phys. Earth 28, 119–143.

    Google Scholar 

  • Seismology and volcanology research division, Meteorological research institute (MRI), Japan: 1980, ‘Permanent ocean-bottom seismograph observation system’, Technical Reports of the Meteorological Research Institute, No. 4, p. 233 (in Japanese).

    Google Scholar 

  • Ukawa, M., Eguchi T. and Fujinawa Y.: 1989, ‘Seismicity survey with pop-up type OBS array in the western part of Sagami Bay’, J. Phys. Earth 37, 31–54.

    Google Scholar 

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Eguchi, T., Fujinawa, Y., Fujita, E. et al. A real-time observation network of ocean-bottom-seismometers deployed at the Sagami trough subduction zone, central Japan. Marine Geophysical Researches 20, 73–94 (1998). https://doi.org/10.1023/A:1004334021329

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  • DOI: https://doi.org/10.1023/A:1004334021329

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