High-resolution marine reflection profiling for engineering and environmental purposes. Part A: Acquiring analogue seismic signals

Abstract This paper discusses the digitizing of analogue seismic signals. It is assumed that they have been acquired with adequate attention to signal-to-noise ratio. It is explained how the analogue signals must be amplified and filtered prior to digitization in order to match the available digital resolution and the intended digitization rate. The casuality of seismic signals is seen to present some difficulties when specifying a bandwidth for the high-cut anti-aliasing filter. The direct use of seismic power spectra is demonstrated to be highly subjective in this regard. An objective method of calculating practical bandwidths for causal signals is derived. The method is applied to the signature of a common type of seismic source. The result indicates a sampling rate that seems to be close to the minimum rate required to describe the signature. The influence of processing techniques that broaden signal bandwidth is examined and leads to a conclusion that intended processing procedures can be as important as source bandwidth for determining sampling rate. Published spectral characteristicsand calculated bandwidths are tabulated with suggested sampling rates for a variety of source types.