A fundamental aspect of the ADRIASEISMIC-09 cruise was the tight integration of classical physical oceanography measurements with the seismic reflection images of water structure. This requires a fast seismic data processing strategy so the seismic data are assessed for optimum locations for CTD casts. The processing of seismic data for oceanography poses a number of major challenges over and above those required for more conventional imaging of the sub-surface. This extra processing work is partly compensated by the relatively simple average sound-speed within the water column. Also this was the first attempt to capture seismic images of water structure in water depths of less than 400-500m which required testing of optimal seismic source/receiver configurations. All the relevant information for the acquisition is presented in the Appendix 6.1. The source was set up as tuned array of Sercel's GI-GUNs, mainly in the 'Harmonic' 45+45 cu.in. configuration, being powered at 140-150 bar compressed air delivered by a 2500 l/min I25 model by BAUER. The array was fired and synchronized by ISMAR's GUN SYNCHRONIZER [Masini and Ligi(1995)]. The RS-232 firing pulse, converted to TTL or Contact Closure by an external circuit, was provided by the PDS-2000 navigation system on programmed distances along the planned routes.
The seismic recording equipment employed (by Sercel) is summarized here below: Seal Recording System (Sys 5), NAS drives, Esqc QA, FSK/Digimain bird controller, 96 channel Digital Streamer, 8 actives, 2 head stretches, 50 m tow leader, passive tail buoy, Digicourse cable levelers.
IMPORTANT NOTE: A fixed delay of 10ms was applied to the TB for the gun synchronization, plus 10-11 ms accounting for the opening of valves and shuttles, i.e. actual shot time is espected to appear some 20 ms after TB.
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