HR: 1340h
AN: T33D-0595    [Abstracts]
TI: An alternate method of measuring seafloor structural orientations: A post-cruise means to boost ROV bottom-time efficiency.
AU: * Popham, C T
EM: pophamc@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Box 200 South Ferry Rd., Narragansett, RI 02882
AU: Pockalny, R A
EM: robp@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Box 200 South Ferry Rd., Narragansett, RI 02882
AU: Larson, R L
EM: rlar@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Box 200 South Ferry Rd., Narragansett, RI 02882
AB: Existing in situ methods of measuring orientations of accretion-related structures on the seafloor with ROVs are time consuming, require bulky instrumentation, and limit the efficiency of near-bottom surveys. As an alternative, we present a method of estimating structural orientation using ROV video that addresses these problems. A simple compass and dip-surface apparatus is used in conjunction with video from the ROV Jason's forward-looking light bar camera. This camera is fixed to the Jason frame and aligned with ROV heading, enabling the compass to be oriented to the environment and strike and dip to be measured directly from screen during or after the ROV lowering. The primary benefit of this method is the ability to obtain a large number of orientations from recorded video without any loss of ROV bottom time. The accuracy of this method is tested using 3D block models of known orientation measured with the same compass apparatus. Our results show a significant but quantifiable bias for shallow and steeply dipping structures, which may be removed from the raw orientation set to obtain measurements of both strike and dip to within approximately 10 degrees. A limitation of this method is that structures striking at high angles to the camera viewing direction are difficult to measure consistently. This technique, however, appears viable if care is taken to view structures parallel to strike. A valuable ground-truth of this method would be to compare orientations measured visually with structures measured with an in situ apparatus such as the Geocompass.
DE: 8038 Regional crustal structure
DE: 8094 Instruments and techniques
DE: 8194 Instruments and techniques
SC: Tectonophysics [T]
MN: Fall Meeting 2005