New buoy observation system for tsunami and crustal deformation

Narumi Takahashi, Yasuhisa Ishihara, Hiroshi Ochi, Tatsuya Fukuda, Jun’ichiro Tahara, Yosaku Maeda, Motoyuki Kido, Yusaku Ohta, Katsuhiko Mutoh, Gosei Hashimoto, Satoshi Kogure, Yoshiyuki Kaneda

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication.

Original languageEnglish
Pages (from-to)243-253
Number of pages11
JournalMarine Geophysical Research
Volume35
Issue number3
DOIs
Publication statusPublished - 2014

Keywords

  • Buoy
  • Crustal deformation
  • Nankai Trough
  • Slack mooring
  • Tsunami

ASJC Scopus subject areas

  • Oceanography
  • Geophysics
  • Geochemistry and Petrology

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  • Cite this

    Takahashi, N., Ishihara, Y., Ochi, H., Fukuda, T., Tahara, J., Maeda, Y., Kido, M., Ohta, Y., Mutoh, K., Hashimoto, G., Kogure, S., & Kaneda, Y. (2014). New buoy observation system for tsunami and crustal deformation. Marine Geophysical Research, 35(3), 243-253. https://doi.org/10.1007/s11001-014-9235-7