SHALLOW-WATER SUB-BOTTOM SEISMIC INVESTIGATION: A MULTI-FREQUENCY APPROACH

Abstract

Continuous seismic profiling is a geophysical method widely used in shallow-water geological and geotechnical investigations. Although other geophysical techniques, e.g., electric, electromagnetic, and potential methods, can also assist in investigating these environments, they do not produce adequate data to support engineering projects from a quantitative perspective. A guide for selecting the technique or techniques that can meet the objectives of the survey with optimum data is still lacking. Wrong procedures can still be found in this professional and research field in Brazil and elsewhere as regards the selection of acoustic sources that produce the best results or solutions for different underwater projects. This article aims at contributing to the discussion on the performance of seismic sources in shallow-water surveys. It concludes that the best final product is obtained by using multifrequency acoustics systems simultaneously. Operating multiple seismic sources at the same time can yield both good resolution and good penetration, thereby meeting all the needs of any given underwater engineering survey, e.g., dams, ports, pipelines, bridges, tunnels, offshore wind farms, basic geology and archeology surveys, dredging projects, and investigations of silting processes in rivers and water reservoirs.