There has been an ongoing debate for years of how dangerous seismic surveys are with respect tomarine life. Marine seismics is today dominated by airgun technology, where high energy isgenerated by a release of compressed air into the water. The objective of the “Time codedimpulse seismic technique” project is to examine whether a new low energy acoustic source canbe used for seismic purposes. If the method turns out to be successful, the low output energy andcontinuous operation will make the source suitable in environmental sensitive areas. The Lowlevel Acoustic Combustion Source (LACS) is a petrol driven pulsed underwater acoustic source.It operates at a few meters depth, and each shot can be digitally controlled from the surface by acomputer located in the mother vessel. A presentation of the recorded LACS signalcharacteristics, the modulation, the Pseudo Noise coding/decoding principles and field testresults, is given. The importance of using an optimized code with fine resolution and the nearfield recording as correlator sequence was demonstrated. Clear correlation peaks could then beseen from the bottom and sub bottom reflectors.
展开▼
