High resolution seismic imaging of the ocean structure using a small volume airgun source array in the Gulf of Cadiz.
Résumé
A small volume (117 cu‐inch) seismic source producing signal predominantly in the 150–200 Hz frequency window was used during the GO calibration experiment in the Gulf of Cadiz (April–May 2007). The data show the small scale (<10 m in the z direction) internal structure of the ocean. High‐resolution images display seismic reflectors that often appear as distinct, horizontal, short (∼a few hundred meters to a few km long) segments, lying at different depths, while low‐resolution (∼20 to 30 Hz) display long, horizontal reflectors (∼a few tens of km), sometimes linked by short, apparently “dipping” segments. The present data suggest that this apparent dipping effect is due to the insufficient separation power (∼λ/4) of the low resolution data. Improving high resolution acquisition systems hence appears to be a critical challenge to understand the seismic response of the ocean.