High-resolution sub-bottom profiling and reverberation mapping using reflection seismology and synthetic aperture techniques

Abstract

Recent experiments in the Atlantic margin have measured the acoustic response of the shallow water environment. A near-surface orthogonal towed array was used to record the response of the environment to broadband (75 Hz to 1.6 kHz) acoustic excitations produced by a piezoelectric source at timed intervals. Approximately 30 km of data were taken. Reflections from the bottom and subbottom layering have been measured yielding information about the layering and sediment properties of the area. The bistatic configuration of the source receiver and source firing position pairs invited the investigation of the reverberation or scattering field over a large coverage area using beamform and aperture enhancement processing. Array dimensions have been extended to 24×24 element and may be increased further. The effective large apertures provide array gain and beam focusing over a 360°×180° region. The combination of synthetic aperture processing and the three-dimensional characteristics of the experimental setup provide excellent resolution and survey rate. Both the water column and subseafloor sediment regions are investigated. Results of the processing of the measured data are presented. [Work supported by ONR.]