2025_programme: Geoacoustic Inversion using Mid-frequency Bottom: Differences from Surficial Sediment Layers

• Day: June 19, Thursday
    Location / Time: C. THALIA at 11:40-12:00
• Last minutes changes: -
• Session: 15. Seabed Acoustics
  Organiser(s): Megan Ballard, Kevin Lee, Nick Chotiros
  Chairperson(s): Nicholas Chotiros
• Lecture: Geoacoustic Inversion using Mid-frequency Bottom: Differences from Surficial Sediment Layers
  Paper ID: 2230
  Author(s): Him Chan Seo, Dong-Gyun Han, Sunhyo Kim, Sungho Cho, Donhyug Kang, Jee Woong Choi
  Presenter: Him Chan Seo
  Abstract: Bottom loss measurements were conducted at two sites with surficial sediments of different thicknesses using 3-10 kHz continuous waves. A transducer (D11, Neptune) was deployed at depths of 20, 30, 40, 50, and 60 m, while the self-recording hydrophones (ic-listen SB2-ETH, Ocean Sonics) were placed at depths of 15, 30, 45, and 60 m. The nominal source-receiver distances were 100, 150, 200, 250, and 300 m. Experiments were performed at two sites, each characterized by a thin mud layer of different thickness; the surficial sediment thicknesses at site 1 and site 2 were estimated to be 6 m and 1 m, respectively, based on a chirp sonar survey. Bottom loss as a function of grazing angle at different frequencies was calculated by comparing the received levels and transmission losses of the direct and bottom paths using the sonar equation. The bottom-loss estimates were then used for geoacoustic inversion via a genetic algorithm. The inversion results at each site were compared with Rayleigh reflection loss predictions. At site 1, the bottom path and sub-bottom path were well separated in time. In contrast, at site 2, the two paths were not separated due to the thin surficial sediment layer. As a result, different geoacoustic inversion approaches were applied to the two sites. The inversion results for site 1 and site 2 will be presented and discussed in relation to the sedimentary characteristics of the sites. \n\nAcknowledgement\nThis research was supported by the Korea Institute of Marine Science & Technology Promotion (KIMST), funded by the Ministry of Oceans and Fisheries, Korea (20210696).\n\n
• Corresponding author: Mr Him Chan Seo
  Affiliation: Hanyang University ERICA
  Country: Korea, Republic of