NATIVE I VLF Signal Analysis. NATIVE I VLF Experiment Data Research and Analysis.
Abstract
During the NATIVE I experiment conducted in the Blake Plateau area, very low frequency (VLF) sound waves transmitted at 7 and 10 Hz from a source towed at a depth of 122 m were sampled over the bottom half of the water column by an 18-element vertical hydrophone array anchored on the bottom (3170 m deep). Analysis included the comparison of measured beam levels with corresponding eigenray and adiabatic normal mode models at short (0.7 km - 20 km) and long (35-60 km) ranges. At short ranges, the VLF measurements and both models were consistent in indicating easily distinguishable direct, bottom, bottom surface, and bottom-surface-bottom interacting arrivals. At longel range, the arrivals typically consisted of three from the surface and three from the bottom, corresponding to two, three, and four bottom interactions. An anomalous bottom loss observed at 30-34 deg at 7 Hz appears to be the result of a slow hydrate layer in the sediment. Except for these angles, VLF bottom loss was low compared to typical values at higher frequency, and consistent with conventional modeled loss calculations for the pre-assessed geoacoustic parameters of the sediment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 20, 1993
- Accession Number
- ADA295099
Entities
People
- Joan C. Lange
- Nancy R. Bedford
- Scott J. Levinson
- Stephen K. Mitchell
Organizations
- University of Texas at Austin