Attitude analysis on the sunken Samho Brother vessel

Abstract

In October 2005, the Samho Brother, a 90 m long chemical tanker ship, sank 74 m deep in the Taiwan Strait off the Hsinchu coast. The ship was transporting benzene and marine fuel. In April 2009, an attitude survey of the sunken ship was conducted to prevent further environmental damage that may arise from chemical spillage. The survey used multi-beam echo sounders and side-scan sonar systems. However, attitude estimations using multi-beam data only gave the vessel's laying angle, with large variations, at around 14° roll direction. This value was suspicious because 1.5° footprints of multi-beam echoes were too large for deep and acoustic waves that could easily bounce on the wreckage. With detailed mapping using the side-scan sonar approach, different sonographs of the sunken vessel were obtained from different scanning attitudes and angles standing more than 10 m above the seafloor. In this study, an estimation of target heights was demonstrated to determine the correct procedures in handling side-scan sonar schemes. It is proposed that the Samho Brother had transversely rotated; its port was at an upward position relative to its side, which was lying on the seafloor. It lies horizontally along the keel direction, but the surface of the hold (deck) level is tilted 18° vertically to the west.

Acknowledgements

We wish to thank GAS's team members, C.I. Chou, W.G. Liu, S.I. Wu and C.S. Chou, for conducting fieldwork and collecting side-scan sonar and multi-beam bathymetric data. GAS commissioned Saipem Singapore Pte. Ltd. (Saipem) to provide information on the vessel's attitude for their cleaning plan. We thank the representatives of Global Aqua Survey Ltd. (GAS) for their generous provision of survey data. The authors especially wish to thank M.L. Lee and K.H. Sheh of GAS for their help in processing multi-beam and side-scan data. Jesman Chou has excellent skills in computer drawing; she completed the illustration in figure 21. Jinnee Chou helped in modifying some figures. We gratefully acknowledge their contributions. The authors deeply appreciate John Perry Fish for his help in betterment of the language to improve the quality of this article.