Comparison of High-Resolution Seismic Methods for Determining Seabed Velocities in Shallow Water

摘要

The ability to resolve both seismic velocity of the seabed in shallow water and lateral variability of these measured velocities using four conventional seismic methods is compared. The methods differ in the ease and efficiency in which the field data are collected and interpreted, and in the resolution of the velocity of the seabed they provide. Narrow-aperture refraction studies provide limited constraints due to the frequent absence of first-arriving sediment refractions in the narrow portion of the wave field that is sampled. Wide-aperture refraction experiments using ocean bottom seismometers provide high resolution of both the compressional- and shear-wave velocities of the seabed but are time consuming to perform and to interpret. Narrow-aperture multichannel reflection data are easily collected, and are ideal for areal mapping of sedimentary sequences, but resolution of seismic velocities is low unless the aperture of the multichannel streamer is several water depths in length. Wide-aperture multichannel reflection prolifing generally provides the highest resolution in velocity in all geoacoustic environments, including those which provide little or no precritical reflected energy and little dispersion of the acoustic normal modes.