Abstract

The continuous seismic profiling system used at the Woods Hole Oceanographic Institution now has (1) an electrical spark sound source which has a maximum stored energy of 100,000 joules and can produce a variety of acoustic pulses with peak pressures of up to 134 db above 1 dyne/cm 2 , at a repetition period of 10 sec, and which has a conversion efficiency (stored electrical energy to sound energy radiated) of 10 percent, (2) a streamlined and uniformly neutrally buoyant line-hydrophone array with a band-pass of 20 to 1,000 cps, and (3) a matched-filter detector that measures the correlation between the reflected signal and the waveform incident on the sea floor in the same frequency range as the reflection.A source whose sonic output can be varied readily makes possible tailoring the resolution of the system for the best display of features of the oceanic crust of varying vertical size. A large reduction in the self-noise of the detector is achieved through the use of streamlined, stable-towing, line-hydrophone arrays which also discriminate against the noises of the towing vessel. A matched-filter detector gives the maximum signal-to-noise ratio obtainable from a linear filter, and an eight-fold improvement over the rectified amplitude presentation formerly used has been obtained. Reflections from 0.8 sec beneath the sea floor in continental shelf areas have been obtained at ship speeds of eleven knots and from 1.8 sec beneath the sea floor in the deep sea at six knots.

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