Basic study on the estimation method of burrows on the seafloor using ultrasound

There have been concerns about the effects of ocean energy facilities on pollution, including chemical, water contamination, and noise. Aquatic environmental measurements have been conducted to assess the effect. However, the effect under the seafloor remains unknown due to the lack of an efficient method for surveying a wide area. The marine environment is affected by the burrows formed by organisms living on the seafloor. Therefore, it is important to understand the morphologies of their burrows from the viewpoint of marine environmental conservation. In addition, the benthic organisms in the burrow can be identified by their burrow because a burrow morphology varies depending on the benthic organisms form it. In this study, we investigated an efficient method for estimating the length and diameter of the burrow using broadband ultrasonic waves. The model experiment and the acoustic simulation using the finite-difference time-domain method (FDTD) were comparatively performed to verify the possibility of estimating the tube length and diameter. It was confirmed that the tube length was estimated with a relative error of about 3 to 6% for acrylic and PVC tube models.