Seismic Reflexion Surveying from Inland Waterways

Abstract

THE continuous seismic profiler is in common use for investigating the geological strata beneath the sea bed. We have developed a new use for this instrument—namely, to obtain a continuous reflexion profile of the geological strata on land by operating the instrument in a shallow inland waterway, the Grand Union Canal. The chief difficulty in seismic reflexion surveying on the ground itself is that of continuous and easy movement, but this is effectively overcome by using an inland waterway. The acoustic source, a spark in this instance, is effectively coupled to the ground by the water and a towed pressuresensitive hydrophone eliminates the complications of surface and shear waves. With a spark acoustic source at a rapid repetition rate, the peak acoustic pressure in the canal water is low and damage to fish and other wildlife is thus avoided. Careful observation of the canal during the experiment discovered no signs of damage to wildlife.