The Use of Very Low Frequency Acoustics to Probe Ocean Bottom Properties
Abstract
Propagation of VLF sound, particularly in shallow-water environments, is strongly affected by the geoacoustic properties of the ocean bottom. As a result, the 'inverse' process, viz., determination of bottom properties from the behavior of the sound, is not only feasible, but often the only practical procedure. Depending on the circumstances, a significant fraction of waterborne VLF energy may be transferred into the seabed in the form of interface and other seismic waves. Apart from providing an effective propagation path for acoustic energy, these interface waves allow one to obtain information on properties of the seabed, at least to a depth of one or two Scholte wavelengths. These deduced properties include the shear sound speed profile and bottom attenuation. Numerical modelling, using both range-dependent parabolic equation models and full-wave FFP models, coupled with measured data, provides considerable insight into the propagation modes and hence the bottom geoacoustics. In this regard, analysis of dispersion curves and stacked seismograms are particularly informative. Even infrasonic ambient noise carries with it evidence of its interaction with the seabed. Clearly, the propagation of very low frequency sound provides an eminently useful tool for probing the geoacoustic properties of the ocean floor. Underwater acoustics; Sound transmission; SAFARI fast field program. Reprints. (EDC)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1989
- Accession Number
- ADA214178
Entities
People
- Hassan B. Ali
Organizations
- United States Naval Research Laboratory