2016 年 43 巻 4 号 p. 233-248
The exploration of deposits buried under sea sediment requires high directivity and low attenuation beams. The parametric sub-bottom profiler (PSBP) meets these requirements. Moreover, it is comparatively small and can be easily mounted on autonomous underwater vehicles (AUVs), which are both highly stabile and able to operate close to the target. A new PSBP system for AUVs has been developed for this purpose, and we present recent results from its development. The performance of the PSBP system was estimated using a sonar equation with the Biot–Stoll model, and the results showed that the secondary/primary wave with low/high frequency was valid for measurements under thick/thin sediment. A field test was conducted at Beppu Bay, and a new data-processing method based on the continuous wavelet transform (CWT) was applied to the data. The method increased S/N, and some layers under the sea bottom could be clearly detected in the acoustic data. One example of such data obtained during the sea trials was compared with core data (BP09-3), and the peaks in the acoustic data agreed with the positions of the layers in the core. Thus, the PSBP system will be suitable for exploring buried deposits using AUVs in deep-sea areas.
