Western Baltic, Kattegat (RV Gunnar Thorson cruise spring 2003)
and Aarhus Bay (MS Line spring/summer 2003)

Seismics performed by GEUS:

Chirp Sonar

Sparker

Single channel GeoSpark 200 (Design Projects, UK) - low frequency/low resolution/high penetration profiles with a centre frequency of 800-1200 Hz giving a penetration of 50-100 m. The pulse emitter consists of 200 electrodes inside water-filled tubings and generates gas bubbles by sudden spark formation during electrical pulses drawing up to 1 kJ s^-1. As the gas bubbles subsequently implode, a bang is generated. For the 2003-Kattegat survey a sampling frequency of 8 or 10 kHz and a pulse transmitted with a sweep time of 0.2 ms have been used. The vertical resolution was up to 0.5 m. The streamer used was a Design Projects 8 element streamer with a cable length of 2.8 m. Sparker and streamer were towed just below the water surface besides the ship. Data were collected using the Delph Elics Seismic acquisition software and stored on dual 80 GB mobile HD.

Boomer

230-1 Uniboom (EG&G, USA) The katamaran-shaped flotation enables the instrument to be towed just below the water surface. The boomer generates sound pulses by two metal plates collapsing against each other, driven by an electromagnet. Reflected sound frequencies of 0.6-2.5 kHz are recorded by the streamer hydrophones, thus providing lower penetration but somewhat higher depth resolution than the sparker. Software and data storage similar to the sparker.

Side-scan sonar

Ship-mounted instruments on RV Gunnar Thorson:

Echo sounder

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