Accession Number : ADA112708

Title :   Some Approaches to the Analysis and Interpretation of Wide-Angle Bottom Loss Data.

Descriptive Note : Technical rept.,


Personal Author(s) : Ingram,Gregory D

Full Text :

Report Date : 15 Feb 1982

Pagination or Media Count : 204

Abstract : Some approaches are developed to analyze and interpret wide angle bottom loss data in terms of ocean sediment acoustic properties. After a brief review of bottom loss data collection and the state-of-the-art knowledge of relevant ocean bottom properties, a filter description of the acoustic signal is developed illustrating the effects of the source waveform and ghosts on travel time versus grazing angle plots. It is shown that these effects can be identified and that, in general, they severely distort the ocean bottom impulse response. The autocorrelation and power cepstrum are examined for their usefulness in extracting geoacoustic information from the multiple bottom bounce data. The autocorrelation is initially preferred due to several reasons having to do with the fact that it has the superposition property with respect to convolution: (1) the shape of events are more interpretable in terms of the phase of the time components, (2) the amplitudes of events are more predictable, and (3) the effects of coherent noise are more recognizable. An impulse response estimate was obtained from the data by using a least squares method to deconvolve an (n-1) bottom bounce waveform from an (n) bottom bounce waveform. Application of the autocorrelation, power capstrum, and deconvolution techniques to real data obtained in a turbidite province indicated that bottom loss in the region was largely controlled by a single reflector and refracted energy.

Descriptors :   *Acoustic signals , *Ocean bottom , *Bottom loss , *Systems analysis , *Least squares method , Wide angles , Waveforms , Response , Travel time , Autocorrelation , Plotting , Bottom bounce , Estimates , Sediments , Data acquisition , Filters , Multiple operation , Noise , Coherence , Grazing

Subject Categories : Statistics and Probability
      Air Breathing Engines(unconventional)

Distribution Statement : APPROVED FOR PUBLIC RELEASE