Seafloor Acoustic Ranging and the Effect of Temperature Variation
Although acoustic ranging of a resolution of 1 cm at a baseline length of several kilometers is now an attainable target, correction for temperature variations remains to be a serious problem. A seafloor experiment was carried out to estimate how accurately the effect of temperature variation on the sound velocity can be corrected from the temperature data observed at both ends of the baseline. The water temperature on the shallow (about 1400 m) seafloor of Sagami Bay, Central Japan, showed tidal variation of about 0.2 °C, which corresponds to the acoustic range of about 1 m at the baseline length of 1.5 km. Although temperature variations at both ends were considerably different from each other, the effect on the acoustic ranging could be corrected with r.m.s. residuals of 7 cm. The residuals are caused by short-term fluctuations, and the correction can be better for longterm variations. If temperature on the deep seafloor is more stable by one order, measurement of 1 cm at a baseline length of several kilometers can be a reasonable target.
KeywordsQuartz Subduction Geophysics Subduction Zone
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