Date of Award

Winter 1980

Project Type


Program or Major


Degree Name

Doctor of Philosophy


An underwater antenna consisting of an acoustic paraboloid reflector with a 12 kHz transducer mounted at its focus was designed and built for remote sensing of the subbottom {1}. Surveys taken with the 3 degree half-power beamwidth projector operating in a 1/2 ms pulsed mode indicated horizontal and vertical resolutions of less than 1 m with penetration into the sediments of up to 20 m at 20 m of depth. The image detail was substantially increased over that taken with a conventional 30 degree profiler.

The data was interpreted using a physical model of the subbottom consisting of plane parallel layers of variable impedance overlying those of monotonically increasing impedance to a basement of granite {2,3}. A signal processing technique, extracting both phase and amplitude information of the acoustic echos, was used to simulate the data. The magnitude and phase angle of the boundary reflection coefficients were calculated allowing determination of positive or negative changes in the characteristic acoustic impedance of the respective layers. Relative impedance profiles, plotted over a region where facsimile graphs indicated a continuous subbottom layer, showed a consistent decrease of impedance at that depth before increasing again as expected.