Multi-sensor marine geophysical profiling and digital acquisition using SAS1

Abstract

A digital seismic acquisition and processing system (SAS1) has been developed for high resolution, multi-sensor, marine geophysical surveys to replace conventional analog methods of recording. This system has achieved vertical resolutions of better than 1 metre, with trace separations as close as 0.25 metres. As well as mapping reflections it is an ideal tool for detecting subtle changes in seismic stratigraphy. Seismic traces, high resolution magnetics, bathymetry and electronic navigation data are stored on Exabyte Video 8 cartridges with storage capacities up to 2.2 Gbytes. With data rates between 50 and 150 Mbytes/hour, this storage capacity is essential for the implementation of a practical, low cost system. A complete mapping and seismic processing system has been developed to complement this new high resolution acquisition system. Unsealed and hand-annotated analog field plots have been replaced by edited, scaled and enhanced seismic sections, merged with high resolution magnetics and bathymetry. Maps of the magnetic and bathymetric data can be produced with little delay on completion of the survey. Significant improvements have been achieved with the seismic presentation by careful attention to swell filtering, trace stacking, time variant gain, variable density display and wavelet compression by deconvolution.