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Volume 50 Supplement 11-12

Special Issue: Ocean Hemisphere network Project (OHP)

Development of instruments for seafloor geodesy


We have developed systems for measuring differential displacements across a fault zone, and examined their resolutions through seafloor experiments at relatively short baselines. A system for a seafloor extensometer makes use of precise acoustic ranging with a linear pulse compression technique. The system has a resolution better than 1 cm in acoustic ranging over a baseline of at least 1 km. The most critical problem is correction for temperature variations, and we estimate that the effect can be corrected with cm-order accuracy in the case of a deep-sea experiment. We have also examined a leveling system on the seafloor using an array of ocean bottom pressure gauges and an ocean bottom gravimeter to detect differential vertical motion. The system is estimated to have a resolution of several centimeters in vertical displacement. These system will be useful for triangulation and leveling on the seafloor, but we need further studies over a longer baseline and to achieve better long-term stability.


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Correspondence to Hiromi Fujimoto.

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Fujimoto, H., Koizumi, Ki., Osada, Y. et al. Development of instruments for seafloor geodesy. Earth Planet Sp 50, 905–911 (1998).

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  • Crustal Deformation
  • Earth Tide
  • Baseline Length
  • Pseudorandom Noise
  • Ocean Bottom Pressure