How to Influence the Low Frequency Output of Marine Air-gun Arrays

The low frequency spectral characteristics of signals emitted from marine air-gun arrays are constrained by the source ghost, the response of the air-guns, and the air-gun array design. Both the ghost and the response of air-guns are related to the tow depth(s). This paper examines the total effect of these combined responses. Below ~7 Hz it is difficult to significantly increase the signal levels from marine air-gun arrays, unless the total volume and number of guns fired in each shot is increased significantly compared to current sources. In the frequency band between ~7Hz and ~40Hz, the signal levels can be increased by towing sources deeper. However, towing deeper compromises the mid-part of the seismic band, unless the effect of the ghost can be attenuated.